Monocots: Phylogeny and Systematics

1.1. Introduction: The Place of Monocots in the APG IV System

In the modern system of classification of angiosperms developed by the Angiosperm Phylogeny Group (APG), all flowering plants are divided into several large, well-differentiated clades. The APG IV system (2016) is the result of a synthesis of a huge array of molecular phylogenetic data and represents the most substantiated picture of evolutionary relationships to date (APG IV, 2016).

According to this system, the basal angiosperms, or ANA grade (from the names of the orders included in it: Amborellales, Nymphaeales, Austrobaileyales), represent successive branches that diverged from the common angiosperm stem during the early stages of their evolution (Judd et al., 2018). All remaining flowering plants, taken together, are united in the clade Mesangiospermae — “mesangiosperms,” or “true angiosperms” (APG IV, 2016; Pandey, 2021). It is precisely within this clade that the main division into modern large groups occurs.

Within the mesangiosperms, five main branches are distinguished: Chloranthales, Magnoliids, Monocots, Ceratophyllales, and Eudicots (APG IV, 2016; Pandey, 2021). Monocots occupy a special position among them, being one of the largest and most diverse clades. According to estimates, the number of monocot species exceeds 90,000, and by some data approaches 100,000, which constitutes approximately one quarter of the entire species diversity of flowering plants (Raven Biology of Plants, 2013; Singh, 2019).

Thus, in the modern phylogenetic system, Monocots are not a taxonomic rank (for example, a class or division), but a clade, that is, a group including a common ancestor and all of its descendants (Judd et al., 2018). This is a fundamentally important methodological distinction. Traditional ranks, such as the class Liliopsida (Monocots) in the Cronquist system, were based on morphological characters and did not always reflect true relatedness (Cronquist, 1981; Kubitzki, 1998). Modern systematics, relying on the principle of monophyly, strives to recognize only those groups that correspond to clades.

1.2. Differences from Other Major Groups of Angiosperms

To understand the uniqueness of monocots, it is necessary to clearly define their place among other major groups of angiosperms.

Difference from basal angiosperms (ANA grade): The ANA grade is a group small in species number that has retained many archaic (plesiomorphic) characters. These include, for example, the absence of vessels in Amborella and some water lilies, as well as carpels closed by secretion rather than by fusion (Judd et al., 2018; Pandey, 2021). Monocots, by contrast, possess a set of advanced (apomorphic) characters that define their appearance. They are not “primitive” in an evolutionary sense, but represent a specialized branch.

Difference from eudicots: This is the key comparison, since in the past all angiosperms were divided into two large groups: monocots and dicots. However, modern science has shown that “dicots” are an artificial, paraphyletic group (Judd et al., 2018). This means that the common ancestor of all “dicots” is also the ancestor of monocots, but the latter are not included in the composition of “dicots.” Thus, “dicots” are not a clade.

• Eudicots (tricolpates) are a monophyletic clade that includes the overwhelming majority of former “dicots” (Judd et al., 2018; Pandey, 2021). Their main synapomorphic character is tricolpate pollen (APG IV, 2016; Judd et al., 2018). Monocots differ from eudicots in a whole series of fundamental characters that will be examined in detail in the next chapter. The key ones are: one cotyledon, parallel leaf venation, scattered vascular bundles in the stem, and, as a rule, trimerous flowers (Raven Biology of Plants, 2013; Singh, 2019).

It is important to note that in some respects monocots may resemble certain groups of basal angiosperms. For example, trimerous flowers occur in some representatives of Nymphaeales and Piperales, and scattered vascular bundles occur in water lilies (Kubitzki, 1998; Pandey, 2021). However, these similarities are either the result of parallel evolution or inherited from the common ancestors of all angiosperms, and they do not indicate close relatedness.

1.3. Why Are “Monocots” a Clade Rather Than a Rank?

As already stated, the recognition of monocots as a clade is based on proof of their monophyly. Monophyly means that all monocots descend from one common ancestor, and this ancestor did not give rise to any other group except monocots (Judd et al., 2018). Numerous molecular phylogenetic studies based on analysis of DNA sequences from the nucleus, chloroplasts, and mitochondria unequivocally confirm the monophyly of monocots (Chase et al., 1993; Soltis et al., 2000; Qiu et al., 2006; APG IV, 2016; Zeng et al., 2014).

This means that in a phylogenetic system, where taxa must be monophyletic, “monocots” deserve the status of a separate large clade. Assigning it a formal rank (for example, class) is a matter of convenience and tradition, not biological essence. In the APG system, which strives to avoid excessive hierarchy and emphasizes cladistic structure, rank is not the main thing; the main thing is position on the phylogenetic tree (APG IV, 2016).

Thus, “monocots” are not merely a convenient morphological group, but a real evolutionary branch. Understanding this fact is the foundation for further study of their internal structure and diversity.

1.4. Brief Review of Phylogenetic Position

On the phylogenetic tree of angiosperms, monocots occupy the position of one of the five main branches of mesangiosperms (APG IV, 2016). Their sister group is most likely the clade including Ceratophyllales and Eudicots, or their position remains a subject of debate, since some analyses place them as a sister group to eudicots (Pandey, 2021). However, most modern studies confirm that monocots diverged from the common stem after the divergence of magnoliids and Chloranthales, but before the main radiation of eudicots (APG IV, 2016; Judd et al., 2018).

This position emphasizes their ancient origin. Monocots are thought to have arisen in the Early Cretaceous, possibly about 140–130 million years ago, and since then have undergone significant evolutionary radiation, occupying almost all ecological niches on Earth (Bell et al., 2010; Li et al., 2019; Pandey, 2021). They dominate in herbaceous communities such as meadows, steppes, savannas, and prairies, and play a key role in terrestrial ecosystems.

Thus, monocots represent not merely one of the groups of angiosperms, but a large, ancient, and evolutionarily successful clade, the study of which is of primary importance both for fundamental botany and for applied disciplines related to agriculture. In the next chapter we will dwell in detail on the key characters that define this clade and distinguish it from other groups of plants.

2.1. Introduction: The Search for Synapomorphies

In the previous chapter we established that monocots (Monocots) represent a monophyletic clade, that is, a group including a common ancestor and all of its descendants. However, for the practical work of a systematist and for understanding evolutionary biology, it is not enough simply to state the fact of monophyly. It is necessary to identify those unique characters that arose in the evolution of this particular branch and distinguish it from all other angiosperms. Such characters, inherited from a common ancestor and present in most members of the group, are called synapomorphies (Judd et al., 2018).

The search for synapomorphies is not merely compiling a list of “characteristic traits.” It is a complex process requiring consideration of parallelisms (independent origin of similar characters in different lineages) and reversals (return to the ancestral state). Many characters that were traditionally considered “typical” for monocots turn out to be either not universal or to have arisen independently in different groups (Kubitzki, 1998; Pandey, 2021). In this chapter we will examine the classical morphological characters that long served as the basis for recognizing monocots, evaluate them from the standpoint of modern phylogenetics, and then turn to molecular data, which today play a key role in diagnosing clades.

2.2. Classical Morphological Characters

Traditionally, monocots were contrasted with “dicots” on the basis of a set of easily observed characters. However, as we already know, “dicots” are a paraphyletic group, so such a contrast is incorrect. Nevertheless, these characters are useful for initial acquaintance with the group, if one remembers their relativity. Here are the main ones:

1. One cotyledon. This is perhaps the best-known character, which gave the entire group its name. In the embryo of monocots, only one cotyledonary leaf forms, whereas in eudicots and basal angiosperms there are usually two (Raven Biology of Plants, 2013; Singh, 2019). However, it is important to understand that this is not simply “one cotyledon instead of two.” In monocots, the single cotyledon is often modified into a scutellum — a specialized organ that absorbs nutrients from the endosperm during germination (Raven Biology of Plants, 2013). In eudicots, the two cotyledons often become photosynthetic and storage organs.

2. Parallel leaf venation. Most monocots are characterized by longitudinal, parallel, or arcuate arrangement of veins in the leaf blade. In eudicots, pinnate or palmate (reticulate) venation predominates (Raven Biology of Plants, 2013). However, there are exceptions here as well. For example, in representatives of the order Alismatales (for example, in water plantain — Alisma), the venation may be arcuate but with elements of reticulate venation. In some monocots, such as herb Paris (Paris) or representatives of the genus Smilax, the venation is reticulate, which is the result of a secondary return to the ancestral state associated with adaptation to life in shaded understory (Kubitzki, 1998; Pandey, 2021). Thus, parallel venation is not an absolute but only a predominant character.

3. Scattered vascular bundles in the stem. In the stem of monocots, vascular bundles (xylem and phloem) are arranged irregularly, “scattered” throughout the ground tissue, rather than gathered in a ring, as in most eudicots (Singh, 2019). This is associated with the absence in monocots of cambium — the secondary meristem that provides secondary growth. This type of stem structure is called an atactostele (Raven Biology of Plants, 2013). The absence of cambium is one of the key characters, but here too there are important exceptions, which we will discuss below.

4. Trimerous flowers. Monocot flowers are usually constructed on a trimerous plan: the perianth consists of 3 or 6 (two whorls of 3) tepals, the androecium of 3 or 6 (two whorls of 3) stamens, and the gynoecium of 3 carpels (Raven Biology of Plants, 2013; Singh, 2019). This contrasts sharply with the predominant four- or five-merous plan in eudicots. Flower trimerism is considered one of the key synapomorphies of monocots, although in some basal angiosperms (for example, water lilies) trimerous flowers also occur, which is probably the result of parallel evolution or inherited from common ancestors (Kubitzki, 1998).

5. Absence of cambium and, consequently, absence of true secondary growth. This is one of the fundamental characters determining the appearance of most monocots. The absence of bifacial cambium means that after the completion of primary growth, the stem cannot thicken through the formation of new layers of xylem and phloem (Raven Biology of Plants, 2013). This limits the ability of monocots to form large woody forms. However, as we will see, evolution found workarounds.

2.3. Exceptions and Parallelisms: Why Characters Are Not Absolute

The most interesting part of biology begins with exceptions. They show how evolution “plays” with characters, and why one cannot build a system on only one or two morphological criteria.

• Secondary growth in monocots. Although true cambium is absent in monocots, some groups, such as palms (Arecales) and dragon trees (Asparagales: Asparagaceae), reach considerable sizes. This becomes possible thanks to primary thickening — the activity of the primary meristem, which increases stem diameter before its final formation (Raven Biology of Plants, 2013). In palms, for example, the stem can reach 40–50 meters in height, but its diameter remains relatively constant. In dragon trees and some other monocots, so-called anomalous secondary growth is observed, in which thickening occurs through the activity of atypical meristems not homologous to the cambium of eudicots (Kubitzki, 1998; Pandey, 2021). This is a striking example of parallelism: different groups of monocots independently acquired the ability to thicken the stem, but by different pathways.

• Arborescent forms. Besides palms and dragon trees, arborescent forms occur among bananas (Zingiberales: Musaceae), which form a massive pseudostem from tightly adjacent leaf sheaths (Singh, 2019). This is another example of how monocots circumvent the limitations imposed by the absence of cambium.

• Reduction and simplification. In some groups of monocots, significant simplification of morphology is observed. For example, duckweeds (Araceae: Lemnoideae), which were formerly separated into the family Lemnaceae, are tiny floating plants whose body is often reduced to several fronds 1–2 mm in size (Raven Biology of Plants, 2013; APG IV, 2016). Their flowers are extremely simplified. This is an example of reduction, which may be associated with adaptation to an aquatic lifestyle.

2.4. Molecular Synapomorphies

In light of the above, it becomes obvious that morphological characters, even such fundamental ones as cotyledon number or venation type, are not always reliable for determining clade boundaries. They may be subject to homoplasy (parallelisms and reversals). Therefore, modern systematics increasingly uses molecular data — DNA sequences — for diagnosing clades.

The monophyly of monocots has been confirmed by many molecular phylogenetic studies based on analysis of chloroplast genes (for example, rbcL, matK, ndhF), mitochondrial genes, and nuclear genes (Chase et al., 1993; Soltis et al., 2000; Qiu et al., 2006; APG IV, 2016; Zeng et al., 2014). This means that in the genome of the common ancestor of monocots, unique changes arose (nucleotide substitutions, insertions, deletions) that were inherited by all of their descendants.

One of the most striking molecular synapomorphies is the structure of sieve-element plastids. In all monocots (with rare exceptions, for example, Asarum from the family Aristolochiaceae, which belongs to basal angiosperms), the sieve-element plastids contain so-called cuneate protein crystals. This plastid type is designated P2c (Behnke, 1981; Kubitzki, 1998). In eudicots and most basal angiosperms, sieve-element plastids have a different type (S-type, accumulating starch, or P-type without cuneate crystals). This unique ultrastructural formation arose in the evolution of monocots and is their reliable synapomorphy.

Another important molecular character is the presence of one type of microsporogenesis. In most monocots, simultaneous microsporogenesis is observed, in which tetrads of microspores form after meiosis, and cell walls form only after the second division. In eudicots, by contrast, successive microsporogenesis predominates, when walls form after each division (Kubitzki, 1998; Rudall et al., 1997). However, as with morphological characters, there are exceptions here: in some “lower” Asparagales (for example, in Hypoxidaceae), the successive type is observed, which is probably plesiomorphic for monocots as a whole, while the simultaneous type arose later (Kubitzki, 1998).

2.5. Characters Associated with Life Form

One of the key aspects distinguishing monocots is the predominance of herbaceous forms. The overwhelming majority of monocots are herbs, although among them there are also secondarily woody forms. The common ancestor of monocots is thought to have been a herbaceous plant (Pandey, 2021). This distinguishes them from eudicots, among which woody forms are much more common.

The absence of cambium and the herbaceous habit are closely linked. The loss of cambium in the ancestors of monocots was probably associated with a transition to an aquatic or semi-aquatic lifestyle, which made it possible to dispense with the need for the powerful mechanical support provided by secondary wood (Kubitzki, 1998). This hypothesis of the “aquatic origin” of monocots is finding increasing support in molecular data, which place such aquatic and semi-aquatic groups as Acorales and Alismatales at the base of the monocot clade (APG IV, 2016; Pandey, 2021).

2.6. Conclusion

Thus, monocots are a clade characterized by a unique combination of characters. The classical morphological characters (one cotyledon, parallel venation, trimerous flowers, scattered bundles, absence of cambium) are for the most part synapomorphies, but they are subject to homoplasy and are not always reliable for diagnosis. Molecular data, such as the structure of sieve-element plastids (P2c type) and features of microsporogenesis, provide more reliable criteria for defining this clade.

It is important to understand that the “typical” appearance of a monocot is a herbaceous plant with parallel venation and trimerous flowers. However, evolution within this clade has led to the appearance of very different forms: from the tiny duckweed to giant palms and bananas, from submerged aquatic grasses to epiphytes. It is precisely this diversity, based on a single evolutionary “foundation,” that makes monocots one of the most fascinating and important groups to study. In the next chapter we will turn to the internal structure of this clade — its main orders and their phylogenetic relationships.

3.1. Introduction: The Backbone of Monocot Phylogeny

In the previous chapters we established that monocots represent a monophyletic clade characterized by a unique set of characters. Now our task is to understand the internal structure of this clade. Which groups are included in it? How are they related to one another? Which group is the most ancient, and which is the most recent? Answers to these questions are provided by phylogeny — the evolutionary history of the group, reconstructed on the basis of molecular and morphological data.

Modern phylogenetic studies based on analysis of DNA sequences from the nucleus, chloroplasts, and mitochondria have made it possible to construct a fairly reliable picture of relationships within monocots (Chase et al., 1995; Soltis et al., 2000; Qiu et al., 2006; Givnish et al., 2010; APG IV, 2016). This picture is constantly being refined, but its main contours are already clear.

According to these data, monocots are divided into several large, successively branching groups, which we call orders. It is important to understand that orders in a phylogenetic system are not merely convenient “shelves” for families, but real evolutionary branches characterized by common origin and a set of synapomorphies (Judd et al., 2018). The sequence of order divergence reflects the sequence of evolutionary events: the earlier an order diverged from the common stem, the more characters it shares with the ancestral form and the fewer with advanced groups.

In simplified form, the phylogenetic tree of monocots can be represented as a sequence of branchings. At the base of the clade are several orders small in species number that have retained many archaic traits. Then follows a large branch uniting Liliales and Asparagales, and the tree is completed by Commelinids — a group including the most advanced and diverse orders, such as Poales and Zingiberales (APG IV, 2016; Pandey, 2021).

3.2. Basal Orders: Acorales and Alismatales

The first to diverge from the common monocot stem are the orders Acorales and Alismatales. Their basal position means that they are sister groups to all remaining monocots taken together (APG IV, 2016). In other words, they represent the most ancient surviving branches of monocots.

• Acorales. This order includes the single family Acoraceae with the single genus Acorus (sweet flag). Sweet flag is a perennial herbaceous plant inhabiting wet places and shores of water bodies. Its flowers are small, gathered in a spadix, and its leaves have a sword-shaped form (Kubitzki, 1998; Singh, 2019). For a long time sweet flag was placed in the family Araceae (Arales), but molecular data showed that it represents a separate, very ancient branch of monocots that has retained a number of unique characters, including cellular endosperm (whereas in most other monocots the endosperm is nuclear) and unusual pollen structure (Kubitzki, 1998; Pandey, 2021). The position of Acorales at the base of the monocot clade is confirmed by analysis of sequences of the rbcL gene and other markers (Duvall et al., 1993; Chase et al., 1995).

• Alismatales. This is the second order to diverge, but it includes a much larger number of species. Alismatales are predominantly aquatic and semi-aquatic plants. The order includes such well-known families as Alismataceae (water-plantain family), Araceae (arum family), Hydrocharitaceae (frogbit family), Potamogetonaceae (pondweed family), Zosteraceae (eelgrass family), and others (APG IV, 2016). Many representatives of this order are fully submerged or floating plants. It is in this order that we see the greatest diversity of life forms — from giant aroids (for example, Amorphophallus with its enormous inflorescence) to tiny duckweeds (Lemna, Wolffia*), which were formerly separated into the family Lemnaceae but are now included in Araceae (APG IV, 2016; Singh, 2019).

The basal position of Acorales and Alismatales has important evolutionary significance. It confirms the aquatic origin hypothesis of monocots, according to which the ancestors of monocots were aquatic or semi-aquatic plants, and only later did their descendants colonize land (Kubitzki, 1998; Pandey, 2021). In addition, study of these orders helps to understand which characters were present in the common ancestor of monocots. For example, the presence of trimerous flowers in Alismatales and Acorales confirms that trimerism was ancestral for the entire clade.

3.3. Orders of Uncertain Position: Petrosaviales

After the divergence of Acorales and Alismatales, the next branch, apparently, is the order Petrosaviales. This order includes the single family Petrosaviaceae with two genera (Petrosavia and Japonolirion). These are small herbaceous plants inhabiting shaded forests, often mycoheterotrophic (that is, obtaining nutrients through fungal hyphae rather than through photosynthesis) (APG IV, 2016; Pandey, 2021). The position of Petrosaviales on the phylogenetic tree long remained unclear. Some studies placed them at the base of the monocot clade, others closer to Liliales. Modern data, however, indicate that this is a separate ancient branch that diverged after Alismatales but before the separation of the main groups Lilianae and Commelinids (APG IV, 2016). In the APG IV system, Petrosaviales are considered an order of uncertain position within monocots.

3.4. Lilianae: Liliales, Asparagales, and Dioscoreales

The next large group unites the orders Liliales, Asparagales, and Dioscoreales. This clade, often called Lilianae (or “lilioid monocots”), is characterized by a number of common characters, including the presence of perigonal nectaries (nectaries located on the tepals) and often simultaneous microsporogenesis (Kubitzki, 1998; Chase et al., 1995). However, clear morphological synapomorphies for this group are few, and its monophyly is mainly confirmed by molecular data (APG IV, 2016).

• Dioscoreales. This order includes the families Dioscoreaceae (yam family), Nartheciaceae, Burmanniaceae, and Taccaceae (APG IV, 2016). The best-known representative is yam (Dioscorea), which includes the yam — an important food crop in tropical countries (Singh, 2019). Dioscoreales are most often lianas with tubers or rhizomes. Their leaves may have reticulate venation, which is a reversal to the ancestral state. Flowers are usually unisexual, and plants are dioecious. The position of Dioscoreales in monocot phylogeny long remained a subject of debate. They were previously considered basal monocots because of similarity to some “dicots” (for example, the presence of reticulate venation and tubers). However, molecular data place them in the clade Lilianae, closer to Liliales and Asparagales (Chase et al., 1995; APG IV, 2016).

• Liliales. This order includes such well-known families as Liliaceae (lily family), Colchicaceae (autumn crocus family), Melanthiaceae (bunchflower family), Smilacaceae (greenbrier family), and Alstroemeriaceae (Alstroemeria family) (APG IV, 2016; Singh, 2019). Lilies are herbaceous plants with bulbs or rhizomes, with large, often brightly colored flowers. Typical examples are the lily (Lilium) or tulip (Tulipa). It is important to note that in the modern system Liliaceae is understood narrowly, unlike in the old Cronquist system, where this family was “composite” and included many genera now assigned to other families and even orders (Cronquist, 1981; APG IV, 2016). For example, onion (Allium) and asparagus (Asparagus) are now placed in Asparagales, and autumn crocus (Colchicum) in Colchicaceae. Liliales are characterized by the presence of perigonal nectaries and often extrorse anthers (anthers dehiscing outward) (Kubitzki, 1998).

• Asparagales. This is the largest order in the clade Lilianae and one of the largest among all monocots. It includes such important families as Orchidaceae (orchid family), Asparagaceae (asparagus family), Amaryllidaceae (amaryllis family), Alliaceae (onion family), Iridaceae (iris family), Asphodelaceae (asphodel family), and Hyacinthaceae (hyacinth family) (APG IV, 2016; Singh, 2019). Asparagales demonstrate enormous diversity of life forms — from terrestrial herbs to epiphytes (orchids) and arborescent forms (dragon trees, yuccas). The key synapomorphy of this order is the presence of phytomelanin — a black pigment deposited in the seed coat, giving seeds a black color (Kubitzki, 1998; Pandey, 2021). This is why seeds of asparagus, onion, amaryllis, and orchids are usually black. Asparagales are also characterized by successive microsporogenesis (in contrast to Liliales, where it is simultaneous), although this rule has exceptions (Rudall et al., 1997). Orchids (Orchidaceae) — the largest family of flowering plants, numbering more than 25,000 species. They are characterized by extremely specialized flowers, often with a labellum and pollinia (sticky masses of pollen), as well as mycorrhiza, necessary for seed germination (Singh, 2019; Pandey, 2021).

3.5. Commelinids: Arecales, Commelinales, Zingiberales, and Poales

The phylogenetic tree of monocots is completed by the large clade Commelinids. This group is characterized by a number of unique biochemical and anatomical characters, including the presence of ferulic acid in cell walls, silica bodies in the epidermis, and epicuticular waxes of a special type (Kubitzki, 1998; APG IV, 2016). Commelinids include four orders: Arecales, Commelinales, Zingiberales, and Poales.

• Arecales. This order includes the single family Arecaceae (palms). Palms are woody plants with a massive, often unbranched trunk and large fan-shaped or pinnate leaves gathered in a crown (Singh, 2019). Palms are distributed in the tropics and subtropics and have enormous economic importance (coconut palm, oil palm, date palm). Despite their woody appearance, palms do not have true cambium; their trunk thickens through primary thickening (Raven Biology of Plants, 2013). Palms are one of the most easily recognized groups of monocots, and their monophyly is not in doubt.

• Commelinales. This order includes the families Commelinaceae (spiderwort family), Haemodoraceae (bloodwort family), Pontederiaceae (pickerelweed family), and Philydraceae (APG IV, 2016). Commelinaceae are herbaceous plants with succulent stems and characteristic flowers, often with two large bright petals and one smaller one (Singh, 2019). An example is spiderwort (Tradescantia) or dayflower (Commelina). Pontederiaceae are aquatic plants, such as water hyacinth (Eichhornia), which has become an invasive species in many regions of the world.

• Zingiberales. This order unites such families as Zingiberaceae (ginger family), Musaceae (banana family), Cannaceae (canna family), Marantaceae (arrowroot family), and Strelitziaceae (bird-of-paradise family) (APG IV, 2016; Singh, 2019). Zingiberaceae are aromatic herbs with underground rhizomes, including ginger (Zingiber), turmeric (Curcuma), and cardamom (Elettaria). Musaceae are large herbaceous plants with a massive pseudostem formed from leaf sheaths. Their fruits — bananas — are an important food crop. Cannaceae and Marantaceae are ornamental plants with beautiful leaves and flowers. Zingiberales are characterized by zygomorphic flowers and often reduction of the androecium to one fertile stamen (Singh, 2019).

• Poales. This is the largest order of monocots and one of the largest orders of flowering plants. It includes the families Poaceae (grasses), Cyperaceae (sedge family), Juncaceae (rush family), Bromeliaceae (bromeliad family), Typhaceae (cattail family), and many others (APG IV, 2016; Singh, 2019). Grasses are undoubtedly the most important group of plants for humanity, including all major cereal crops: wheat, rice, maize, barley, oats, rye, sorghum, and millet. Sedges and rushes are often wind-pollinated plants of wet habitats. Bromeliads are epiphytes of tropical forests, including pineapple (Ananas comosus). Poales are characterized by reduction of flowers, wind pollination (in many groups), and the presence of silicified cells in the epidermis (Kubitzki, 1998; Singh, 2019). It is in this order that the family Poaceae is found, which will be examined in detail in the next chapter.

3.6. Conclusion: The Overall Picture of Monocot Phylogeny

Thus, the phylogeny of monocots represents a sequence of branchings reflecting their evolutionary history. At the base of the clade are Acorales and Alismatales — predominantly aquatic and semi-aquatic plants that have retained a number of archaic characters. Next follows Petrosaviales, whose position remains uncertain. Then a large group branches off — Lilianae, including Dioscoreales, Liliales, and Asparagales. The tree is completed by Commelinids — a group uniting Arecales, Commelinales, Zingiberales, and Poales.

This scheme is important not only for understanding evolution but also for practical systematics. Knowing the phylogeny, we can predict plant properties. For example, if we know that onion (Allium) and asparagus (Asparagus) belong to Asparagales, we can expect their seeds to be black (due to phytomelanin) and their microsporogenesis to be successive. If we know that banana (Musa) and ginger (Zingiber) belong to Zingiberales, we can expect their flowers to be zygomorphic and their androecium reduced.

Thus, phylogeny is not merely an abstract scheme, but a working tool allowing orientation in the enormous diversity of monocots. In the next chapter we will dwell in more detail on economically important groups of monocots in order to understand how their phylogenetic position is connected with their practical use.

4.1. Introduction: From Phylogeny to Practice

In the previous chapter we examined the phylogenetic structure of monocots and became acquainted with their main orders. Now the time has come to answer the key question: what significance do these orders have for humans and agriculture? The answer lies in the field of economic botany — the discipline studying the use of plants by humans. Knowledge of phylogeny allows us not merely to list useful plants, but also to understand why they possess certain properties and to predict where to look for new useful species.

Monocots play a colossal role in human life. Suffice it to say that all major cereal crops — wheat, rice, maize, barley, oats, rye, sorghum, and millet — belong to one family, Poaceae (grasses), in the order Poales (Singh, 2019). However, as we will see, the economic importance of monocots is far from exhausted by grasses. They give us vegetables, fruits, spices, sugars, fibers, medicines, and ornamental plants. In this chapter we will examine the most important economic groups of monocots in the order of their phylogenetic relatedness, beginning with the most basal and ending with the most advanced.

4.2. Poales: Grasses and More

The order Poales is undoubtedly the most important order of monocots from the standpoint of agriculture. However, as we already know from the previous chapter, Poales is not only grasses. This order includes several families, each of which has its own economic importance.

• Poaceae (grasses). This family deserves separate detailed consideration, and a significant part of this chapter will be devoted to it. Here we note only that Poaceae are the source of all major cereal crops, as well as sugarcane, forage grasses, and bamboo (Singh, 2019). Grasses dominate agricultural production due to their high productivity, the nutritive value of their grain, and their ability to be easily cultivated in the most diverse climatic conditions (Connor et al., 2011).

• Cyperaceae (sedges). Sedges are predominantly herbaceous plants of wet habitats. They do not have the same agricultural importance as grasses, but some species are used by humans. For example, Cyperus papyrus (papyrus) in antiquity served as material for making paper, and Cyperus esculentus (chufa, tiger nut) forms edible tubers that are used as food (Singh, 2019). Some sedges are used as forage plants and for weaving (Raven Biology of Plants, 2013).

• Typhaceae (cattails). Cattails (Typha) are aquatic and marsh plants with characteristic cylindrical inflorescences. Their rhizomes and young shoots are edible, and their leaves are used for weaving and as roofing material (Singh, 2019). Cattails also play an important ecological role in water purification, absorbing excess nutrients.

• Bromeliaceae (bromeliads). This family includes pineapple (Ananas comosus) — an important tropical fruit crop. Pineapple is a multiple fruit formed from fused berries and the inflorescence axis (Singh, 2019). Many bromeliads (for example, Tillandsia) are epiphytes and are grown as ornamental plants (Raven Biology of Plants, 2013).

• Juncaceae (rushes). Rushes (Juncus) and wood-rushes (Luzula) are herbaceous plants externally resembling grasses and sedges. They do not have great economic importance, but are used for weaving baskets, mats, and as bedding for livestock (Singh, 2019).

• Eriocaulaceae (pipeworts). Representatives of this family, such as Eriocaulon and Syngonanthus, are often used in floristry for making dried bouquets (Singh, 2019). Some species are used in folk medicine.

Thus, Poales is not only grasses, but a whole spectrum of plants used in various spheres — from paper production to ornamental horticulture. However, it is grasses that define the appearance of modern agriculture, and we will return to them in the following chapters.

4.3. Asparagales: Vegetables, Spices, Medicines, and Ornamental Plants

The order Asparagales is the second most important order of monocots for humans after Poales. It includes several families, each of which gives us important food, medicinal, and ornamental plants.

• Alliaceae (onion family). This family includes the genus Allium, to which belong onion (Allium cepa), garlic (Allium sativum), leek (Allium porrum), shallot (Allium ascalonicum), wild garlic (Allium ursinum), and many others (Singh, 2019). Alliums are among the most important vegetable and flavoring crops used throughout the world. Their characteristic odor and taste are due to sulfur-containing compounds such as allyl sulfides (Pandey, 2021). Onion and garlic also possess antimicrobial properties and are widely used in folk medicine (Singh, 2019).

• Asparagaceae (asparagus family). This family in the modern sense includes many genera that were formerly assigned to different families. The best-known representative is asparagus (Asparagus officinalis), whose young shoots are eaten (Singh, 2019). This same family includes ornamental plants such as lily of the valley (Convallaria majalis), Solomon's seal (Polygonatum), hosta (Hosta), snake plant (Sansevieria), and dracaena (Dracaena) (APG IV, 2016). Some species are used as medicinal plants.

• Amaryllidaceae (amaryllis family). This family includes many ornamental plants with large, bright flowers: amaryllis (Amaryllis), narcissus (Narcissus), snowdrop (Galanthus), clivia (Clivia), hippeastrum (Hippeastrum), and crinum (Crinum) (Singh, 2019). Many amaryllids contain alkaloids that can be toxic, but some are used in medicine. For example, Galanthus contains galanthamine, used in the treatment of Alzheimer's disease (Pandey, 2021).

• Iridaceae (iris family). This family includes such ornamental plants as iris (Iris), gladiolus (Gladiolus), saffron crocus (Crocus), freesia (Freesia), and blue-eyed grass (Sisyrinchium) (Singh, 2019). The most important economic plant of this family is saffron (Crocus sativus), from whose stigmas the famous spice saffron is obtained. Saffron is the most expensive spice in the world, since obtaining 1 kg requires about 150,000 flowers (Singh, 2019). Iridaceae are also used as ornamental plants in gardens and parks.

• Asphodelaceae (asphodel family). This family includes aloe (Aloe), asphodel (Asphodelus), red hot poker (Kniphofia), and others (APG IV, 2016). Aloe is a succulent plant whose sap is widely used in medicine and cosmetics due to its wound-healing and anti-inflammatory properties (Singh, 2019). Some aloe species are used for fiber production.

• Orchidaceae (orchids). This is the largest family of flowering plants, numbering more than 25,000 species (Singh, 2019). Orchids are predominantly ornamental plants, but among them there are also economically important species. The best-known example is vanilla (Vanilla planifolia), from whose fruits vanillin is obtained — a popular spice and flavoring (Pandey, 2021). Orchids are also used in medicine and perfumery. Many species are threatened with extinction due to habitat destruction and illegal collecting.

• Hyacinthaceae (hyacinth family). This family includes hyacinth (Hyacinthus), grape hyacinth (Muscari), squill (Scilla), star-of-Bethlehem (Ornithogalum), and other ornamental plants (Singh, 2019). Some species are used in folk medicine.

Thus, Asparagales are not only vegetables and spices, but also important ornamental and medicinal plants. Alliums and asparagus play a key role in human nutrition, while amaryllids, irises, and orchids play a role in ornamental horticulture and pharmaceuticals.

4.4. Zingiberales: Spices, Fruits, and Ornamental Plants

The order Zingiberales includes several families of enormous economic importance in tropical and subtropical countries.

• Zingiberaceae (ginger family). This family is the source of the most important spices: ginger (Zingiber officinale), turmeric (Curcuma longa), cardamom (Elettaria cardamomum), and galangal (Alpinia galanga) (Singh, 2019). Ginger and turmeric are used not only as spices but also in medicine. Turmeric contains curcumin — a substance with anti-inflammatory and antioxidant properties (Pandey, 2021). Some zingiberaleans (for example, Hedychium) are grown as ornamental plants.

• Musaceae (banana family). This family includes banana (Musa) and enset (Ensete). Banana is one of the most important fruit crops in the world and also an important food source in tropical countries (Singh, 2019). Banana fruits are eaten fresh and are also used to prepare various dishes. Plantain (cooking banana) requires heat treatment and is an important food product in many countries. From banana fibers, textile fiber — Manila hemp — is obtained (Raven Biology of Plants, 2013).

• Cannaceae (canna family). This family includes the genus Canna, many species of which are grown as ornamental plants. Indian shot (Canna indica) is used for starch production (Singh, 2019).

• Marantaceae (arrowroot family). This family includes ornamental plants with beautiful leaves, such as arrowroot (Maranta) and calathea (Calathea). From the rhizomes of arrowroot, arrowroot starch is obtained, used in dietary nutrition (Singh, 2019).

• Strelitziaceae (bird-of-paradise family). This family includes Strelitzia (Strelitzia), or “bird of paradise,” and the traveler's palm (Ravenala madagascariensis), which are grown as ornamental plants (APG IV, 2016).

Thus, Zingiberales are spices, fruits, starch, and ornamental plants. Many representatives of this order are important for tropical agriculture.

4.5. Arecales: Palms — A Source of Food, Oils, and Fiber

The order Arecales includes the single family Arecaceae (palms). Palms are one of the most important groups of tropical plants. They provide humans with food, oils, fibers, construction materials, and much more (Singh, 2019).

• Coconut palm (Cocos nucifera). This is perhaps the best-known economic plant of the family. The coconut is a drupe with a hard endocarp and edible endosperm. From the fresh endosperm, coconut milk is obtained; from the dried endosperm, copra is obtained, from which coconut oil is pressed (Singh, 2019). Coconut palm leaves are used for weaving, the trunk as construction material, and from the fibers of the mesocarp, coir is obtained — a coarse fiber for making carpets and mats (Raven Biology of Plants, 2013).

• Oil palm (Elaeis guineensis). This is the most important source of palm oil, which is used in the food industry, cosmetics, and biodiesel production. Palm oil is one of the most widespread vegetable oils in the world (Singh, 2019).

• Date palm (Phoenix dactylifera). The fruits of the date palm — dates — are an important food product in the countries of the Middle East and North Africa. Dates are rich in sugars and are used both fresh and dried (Singh, 2019).

• Sugar palm (Arenga pinnata). From the inflorescences of this palm, a sweet sap is obtained, which is used to produce sugar and palm wine (Singh, 2019).

• Rattan (Calamus). These are lianas from the palm family, whose stems are used for the production of furniture and woven articles. Rattan is an important export commodity in the countries of Southeast Asia (Singh, 2019).

• Sago palm (Metroxylon sagu). From the pith of the trunk of this palm, sago is obtained — a starchy product used as food in some regions (Singh, 2019).

Thus, palms are a source of food, oils, fibers, construction materials, and ornamental elements. Their importance for tropical countries is difficult to overestimate.

4.6. Alismatales: Aquatic Vegetables and Ornamental Plants

The order Alismatales includes predominantly aquatic and semi-aquatic plants. The economic importance of this order is not as great as that of Poales or Asparagales, but some representatives are used by humans.

• Alismataceae (water-plantain family). Some species of water plantain (Alisma) and arrowhead (Sagittaria) are edible. The tubers of arrowhead (Sagittaria sagittifolia) are eaten in China and Japan (Singh, 2019). These plants are also grown as ornamentals for decorating water bodies.

• Araceae (arum family). This family includes such important food plants as taro (Colocasia esculenta), Xanthosoma (Xanthosoma), and Amorphophallus (Amorphophallus). Taro tubers are an important source of starch in tropical countries (Singh, 2019). Some aroids (for example, Monstera, Philodendron, Anthurium) are grown as ornamental plants. Duckweeds (Lemna, Wolffia), formerly separated into a separate family, are used as livestock feed and in wastewater treatment (Raven Biology of Plants, 2013).

• Hydrocharitaceae (frogbit family). This family includes aquatic plants, some of which are used in aquarium keeping (for example, Elodea, Vallisneria). Some species have become invasive (for example, Hydrilla verticillata) (Singh, 2019).

• Potamogetonaceae (pondweed family). Pondweeds (Potamogeton) are aquatic plants that serve as food for waterfowl and fish. Some species are used in aquaria (Singh, 2019).

Thus, Alismatales are, first of all, a source of aquatic vegetables (taro, arrowhead) and ornamental plants for aquaria and water bodies.

4.7. Liliales: Ornamental Plants and Medicinal Raw Material

The order Liliales includes several families of economic importance, primarily as ornamental plants.

• Liliaceae (lily family). This family includes such well-known ornamental plants as lily (Lilium), tulip (Tulipa), fritillary (Fritillaria), and Gagea (Gagea) (Singh, 2019). Tulips and lilies are among the most popular ornamental plants in the world. Some species are used in medicine.

• Colchicaceae (autumn crocus family). Autumn crocus (Colchicum) contains colchicine — an alkaloid used in medicine for treating gout, as well as in breeding for obtaining polyploid plants (Singh, 2019). However, colchicine is very toxic.

• Melanthiaceae (bunchflower family). This family includes Veratrum (Veratrum), which contains alkaloids used in medicine and as an insecticide (Singh, 2019). Some species (for example, Trillium) are grown as ornamental plants.

• Smilacaceae (greenbrier family). Smilax (Smilax) are lianas, some species of which are used to obtain sarsaparilla — a medicinal raw material and flavoring (Singh, 2019).

Thus, Liliales are, first of all, ornamental plants (lilies, tulips) and sources of medicinal raw material (colchicine, Veratrum).

4.8. Conclusion: Monocots Are Not Only Grasses

Summing up, we can confidently say that the economic importance of monocots is enormous and multifaceted. Undoubtedly, Poales (and especially Poaceae) occupy first place in importance for humanity, providing us with basic food products — grain, sugar, as well as feed for livestock. However, as we have seen, the economic importance of monocots is far from exhausted by grasses.

Asparagales give us vegetables (onion, garlic, asparagus), spices (saffron), medicines (aloe, galanthamine), and ornamental plants (orchids, narcissi, irises). Zingiberales are spices (ginger, turmeric, cardamom), fruits (bananas), and starch (arrowroot). Arecales are palms, a source of food (coconuts, dates), oils (palm oil), fibers (coir, rattan), and construction materials. Alismatales are aquatic vegetables (taro, arrowhead) and ornamental plants for aquaria. Liliales are ornamental plants (lilies, tulips) and medicinal raw material (colchicine).

Thus, monocots are not only “our daily bread,” but also a source of diverse products, materials, and medicines. Understanding the phylogeny of monocots allows us to systematize this knowledge and predict where to look for new useful plants. In the next chapter we will dwell in more detail on the practical importance of individual orders and on the identification characters of the most important economic groups.

5.1. Introduction: From Theory to Practice

In the previous chapters we examined the phylogenetic structure of monocots and their economic importance as a whole. Now the time has come to systematize this knowledge and turn to practical aspects. In this chapter we will dwell in detail on the role played by individual orders of monocots in human life and, what is especially important for specialists in the agricultural sphere, we will learn to distinguish the most important economic groups by identification characters.

Knowledge of phylogeny and identification characters is not merely an academic exercise. In the practical activity of an agronomist, plant breeder, or plant protection specialist, the ability to quickly and accurately identify a plant is of primary importance. The methods of its cultivation, harvesting, storage, and processing depend on which family a plant belongs to. In addition, understanding relatedness allows one to predict potential pests and diseases, as well as to find wild relatives of crop plants for breeding.

We will examine the practical importance of monocots by categories of use: food, forage, technical, medicinal, and ornamental. Then we will turn to the identification characters of the most important groups and analyze concrete examples.

5.2. Food Plants

The food importance of monocots is enormous. It is they that provide humanity with its main sources of energy and protein.

• Poales. Grasses (Poaceae) are the foundation of human nutrition. Wheat (Triticum aestivum), rice (Oryza sativa), maize (Zea mays), barley (Hordeum vulgare), oats (Avena sativa), rye (Secale cereale), sorghum (Sorghum bicolor), and millet (Panicum miliaceum, Setaria italica) provide more than half of all calories consumed by humans (Singh, 2019; Connor et al., 2011). Sugarcane (Saccharum officinarum) is the main source of sugar in the world (Singh, 2019). Bamboo (subfamily Bambusoideae) provides edible young shoots that are widely used in Asian cuisine (Raven Biology of Plants, 2013). Among other families of the order Poales, note should be made of Bromeliaceae, to which pineapple (Ananas comosus) belongs — an important tropical fruit crop (Singh, 2019).

• Asparagales. Alliaceae are the source of the most important vegetable and flavoring crops: onion (Allium cepa), garlic (Allium sativum), leek (Allium porrum), shallot (Allium ascalonicum), and wild garlic (Allium ursinum) (Singh, 2019). Asparagaceae provide asparagus (Asparagus officinalis), whose young shoots are eaten. Iridaceae are the source of saffron (Crocus sativus), the most expensive spice in the world, obtained from the stigmas of flowers (Singh, 2019).

• Zingiberales. Musaceae provide bananas and plantains (Musa spp.) — the most important fruit and vegetable crops of the tropics. Zingiberaceae are the source of spices: ginger (Zingiber officinale), turmeric (Curcuma longa), cardamom (Elettaria cardamomum), and galangal (Alpinia galanga) (Singh, 2019). Marantaceae provide arrowroot — starch from the rhizomes of arrowroot (Maranta arundinacea), used in dietary nutrition (Singh, 2019).

• Arecales. Palms (Arecaceae) are the source of coconuts (Cocos nucifera), dates (Phoenix dactylifera), palm oil (Elaeis guineensis), and sago (Metroxylon sagu) (Singh, 2019). Coconut milk and copra, dates, and palm oil are important food products in many tropical countries.

• Alismatales. Araceae provide taro (Colocasia esculenta), Xanthosoma (Xanthosoma), and Amorphophallus (Amorphophallus), whose tubers are rich in starch and are used as food in the tropics (Singh, 2019). Alismataceae — arrowhead (Sagittaria sagittifolia), whose tubers are edible (Singh, 2019).

• Dioscoreales. Dioscoreaceae — yam (Dioscorea spp.), an important starch-bearing crop in tropical countries (Singh, 2019).

Thus, the food diversity of monocots is not limited to grasses. Alliums, asparagus, bananas, gingers, palms, and aroids play an enormous role in human nutrition in different regions of the world.

5.3. Forage Plants

The forage importance of monocots is also very great. The main forage crops belong to the order Poales.

• Poaceae. Grasses are the foundation of the forage base of animal husbandry. Perennial and annual grasses such as timothy (Phleum pratense), fescue (Festuca), cocksfoot (Dactylis glomerata), brome (Bromus), and ryegrass (Lolium) are used for hayfields and pastures (Connor et al., 2011). Maize (Zea mays) and sorghum (Sorghum) are grown for silage and green fodder. Hay, straw, and silage are all products of grass processing.

• Other orders. Some sedges (Cyperaceae) and rushes (Juncaceae) are used as bedding for livestock or as roughage (Singh, 2019). Cattails (Typhaceae) can be used as livestock feed in some regions.

The forage importance of monocots is difficult to overestimate, since it is grasses that form the basis of the diet of herbivorous animals.

5.4. Technical Plants

The technical use of monocots is diverse. They provide fibers, construction materials, paper raw material, dyes, and much more.

• Poales. Bamboo (Bambusoideae) is a universal material for construction, furniture, paper production, utensils, and musical instruments (Raven Biology of Plants, 2013). Sugarcane (Saccharum officinarum) is used for sugar and bioethanol production (Singh, 2019). Straw of grasses is used for weaving, paper production, and fuel.

• Arecales. Palms provide rattan (Calamus) for furniture, coir (fiber from the coconut mesocarp) for carpets and mats, and palm oil for technical purposes (Singh, 2019). Palm wood is used in construction.

• Asparagales. Aloe (Aloe) provides fiber (sisal), and Sansevieria (Sansevieria) provides coarse fiber for ropes and cords (Singh, 2019). Dracaena (Dracaena) is a source of the resin “dragon's blood,” used as a dye and varnish.

• Zingiberales. Banana (Musa textilis) provides Manila hemp — a strong fiber for ropes and cords (Raven Biology of Plants, 2013).

• Alismatales. Cattail (Typha) is used for weaving baskets, mats, and as roofing material (Singh, 2019). Sedges (Cyperaceae) are also used for weaving.

• Liliales. Smilax (Smilax) is a source of sarsaparilla, used in perfumery and medicine (Singh, 2019).

Thus, the technical importance of monocots covers a wide spectrum from paper and furniture production to the obtaining of fibers and dyes.

5.5. Medicinal Plants

Many monocots possess medicinal properties.

• Asparagales. Aloe (Aloe vera) is a wound-healing and anti-inflammatory remedy (Singh, 2019). Lily of the valley (Convallaria majalis) contains cardiac glycosides. Snowdrop (Galanthus) is a source of galanthamine, used in Alzheimer's disease (Pandey, 2021). Amaryllidaceae contain alkaloids, some of which are used in medicine.

• Liliales. Autumn crocus (Colchicum) is a source of colchicine, used to treat gout and in breeding for obtaining polyploids (Singh, 2019). Veratrum (Veratrum) contains alkaloids used in medicine and as an insecticide.

• Poales. Maize stigmas (Zea mays) are used as a diuretic. Couch grass (Elymus repens) is used in folk medicine. Oats (Avena sativa) are a dietary and tonic remedy.

• Zingiberales. Ginger (Zingiber officinale) and turmeric (Curcuma longa) possess anti-inflammatory and antioxidant properties (Pandey, 2021).

• Arecales. Palm oil is rich in vitamins; coconut oil is used in cosmetics and medicine.

• Alismatales. Sweet flag (Acorus calamus) is a medicinal plant used for stomach diseases (Singh, 2019).

The medicinal importance of monocots is great, and many of them are sources of valuable pharmacological preparations.

5.6. Ornamental Plants

Monocots are perhaps the most important group of ornamental plants in the world.

• Asparagales. Orchids (Orchidaceae) are the largest family of flowering plants, many species of which are among the most valuable ornamental plants (Singh, 2019). Irises (Iris), gladioli (Gladiolus), narcissi (Narcissus), hyacinths (Hyacinthus), amaryllis (Amaryllis), hostas (Hosta), dracaenas (Dracaena), yuccas (Yucca), and sansevierias (Sansevieria) are all representatives of Asparagales widely used in horticulture and landscaping.

• Liliales. Lilies (Lilium), tulips (Tulipa), fritillaries (Fritillaria), and trilliums (Trillium) are among the most popular ornamental plants (Singh, 2019).

• Zingiberales. Cannas (Canna), marantas (Maranta), calatheas (Calathea), strelitzias (Strelitzia), globbas (Globba), and hedychiums (Hedychium) are ornamental plants of the tropics and subtropics (Singh, 2019).

• Arecales. Palms (Arecaceae) are the most important ornamental plants for tropical and subtropical landscaping.

• Poales. Lawn grasses (bluegrass, fescue, ryegrass), ornamental grasses (miscanthus, feather grass), and bromeliads (Tillandsia, pineapple) are widely used in landscape design (Raven Biology of Plants, 2013).

• Alismatales. Aquarium plants (Elodea, Vallisneria, pondweeds), aroids (Monstera, Philodendron, Anthurium) are popular in indoor floriculture (Singh, 2019).

The ornamental importance of monocots is enormous, and they occupy a leading place in world floriculture.

5.7. Identification Characters of the Most Important Groups

For specialists in the agricultural sphere, it is important to be able to distinguish the main economic groups of monocots. Let us examine the key identification characters.

5.8. Conclusion

The practical importance of monocots is multifaceted. They provide humanity with food products, forage, technical raw materials, medicines, and ornamental plants. The ability to distinguish the most important economic groups by identification characters is a necessary skill for specialists in the agricultural sphere. Knowledge of the phylogeny and biology of these plants allows one not only to identify them correctly, but also to use them effectively, as well as to predict their properties and potential problems. In the next chapter we will dwell in more detail on understanding that grasses are only one branch of monocots, and we will discuss the evolutionary depth of this group.

6.1. Introduction: Overcoming “Grass-Centrism”

In the previous chapters we examined in detail the phylogeny of monocots and their economic importance. We have become convinced that the order Poales, and especially the family Poaceae (grasses), play a colossal role in providing humanity with food. Wheat, rice, maize, barley, oats, rye, sorghum, millet, and sugarcane all belong to grasses, and their contribution to the world food balance is difficult to overestimate (Connor et al., 2011; Singh, 2019).

However, precisely because of this enormous importance, there exists the danger of “grass-centrism” — an unconscious reduction of the entire diversity of monocots (and even of all economic botany) to grasses. Such a view is not only factually incorrect but also impoverishes our understanding of plant evolution and practical use. The purpose of this chapter is to show that grasses represent only one, although very important, branch on the enormous evolutionary tree of monocots. We will discuss the share of Poales in agriculture, but we will emphasize that it is not absolute. We will examine other economically important groups that provide spices, fruits, vegetables, oils, fibers, medicines, and ornamental plants. And finally, we will discuss the evolutionary depth of monocots, which arose very early and occupied the most diverse ecological niches.

6.2. The Share of Poales in Agriculture: Enormous, but Not Absolute

Let us begin with facts. According to the UN Food and Agriculture Organization (FAO), cereal crops occupy about half of all cultivated area in the world (Connor et al., 2011). Wheat, rice, and maize — the three main food crops — provide more than 50% of the calories in the human diet (Connor et al., 2011; Singh, 2019). Sugarcane is the main source of sugar. Grasses are also the foundation of the forage base for animal husbandry.

However, if we look at the species diversity of agricultural plants, the picture will be different. Of the approximately 300,000 species of flowering plants, humans cultivate about 2,500 species, of which only about 150 have substantial economic importance (Singh, 2019). Among these 150 species, grasses occupy an important but not exclusive place. For example, in tropical countries a significant part of the diet is provided by root crops (sweet potato, yam, taro), fruits (banana, pineapple, coconut), vegetables (onion, garlic, asparagus), and legumes, which do not belong to grasses.

Moreover, if we consider world production by crops, then after cereals come roots and tubers (potato, cassava, sweet potato), sugar crops (sugarcane and sugar beet), oilseeds (soybean, rapeseed, sunflower), and vegetables (Connor et al., 2011). Among them, monocots are represented not only by grasses but also by palms (oil palm, coconut palm), bananas, alliums, and aroids (taro).

Thus, although Poales occupy first place in production volume and sown area, their share in the diversity of used plants and in the nutritional value of the diet is not absolute. Other orders of monocots make a substantial contribution to the food security of humanity.

6.3. Other Economically Important Groups: Spices, Fruits, Vegetables, Oils, Fibers

Let us systematize the contribution of other orders of monocots to human economic activity.

• Spices. The order Zingiberales gives us ginger, turmeric, cardamom, and galangal (Zingiberaceae). The order Asparagales — saffron (Iridaceae), garlic, and onion (Alliaceae). The order Laurales (not belonging to monocots, but for context) — laurel and cinnamon. Among monocots, it is precisely Zingiberales and Asparagales that are the main sources of spices (Singh, 2019; Pandey, 2021).

• Fruits. Bananas and plantains (Musaceae, Zingiberales) are the most important tropical fruits. Pineapple (Bromeliaceae, Poales) is another example, but already from the order Poales, which shows that even within this order there are not only grasses. Coconut (Arecaceae, Arecales) is a source of food and drink. Dates (Arecaceae) are an important food product in arid regions (Singh, 2019).

• Vegetables. Alliums (Alliaceae, Asparagales) — onion, garlic, leek, shallot. Asparagaceae — asparagus. Araceae (Araceae, Alismatales) — taro, Xanthosoma, Amorphophallus. Dioscoreaceae (Dioscoreaceae, Dioscoreales) — yam. These crops play an enormous role in nutrition, especially in tropical and subtropical countries (Singh, 2019).

• Oils. Oil palm (Arecaceae, Arecales) is the most important source of palm oil, one of the most widespread vegetable oils in the world. Coconut oil (Arecaceae) is also widely used in food and for technical purposes (Singh, 2019). Among grasses, only maize yields a significant amount of oil (germ oil), but palm oil exceeds maize oil in production volume.

• Fibers. Cotton (Malvaceae, Eudicots) is the main plant fiber, but among monocots there are also important fiber crops: Manila hemp (Musa textilis, Musaceae, Zingiberales), sisal (Agave sisalana, Asparagaceae, Asparagales), rattan (Calamus, Arecaceae, Arecales), and coir (Cocos nucifera, Arecaceae). These fibers are used for the production of ropes, cords, carpets, furniture, and much more (Singh, 2019; Raven Biology of Plants, 2013).

• Medicines. Aloe (Asparagaceae, Asparagales) is a wound-healing and anti-inflammatory remedy. Colchicine (Colchicaceae, Liliales) is a medicine for gout and a tool in breeding. Galanthamine (Amaryllidaceae, Asparagales) is a preparation for treating Alzheimer's disease. Curcumin (Zingiberaceae, Zingiberales) is an anti-inflammatory remedy. Sweet flag (Acoraceae, Acorales) is a medicinal plant (Singh, 2019; Pandey, 2021).

• Ornamental plants. Orchids (Orchidaceae, Asparagales) are the largest family of flowering plants, many species of which are among the most valuable ornamental plants. Lilies, tulips (Liliaceae, Liliales), irises, gladioli (Iridaceae, Asparagales), narcissi, amaryllis (Amaryllidaceae, Asparagales), palms (Arecaceae, Arecales), cannas, marantas (Zingiberales), and aquarium plants (Alismatales) are all representatives of different orders of monocots widely used in horticulture and landscaping (Singh, 2019; Raven Biology of Plants, 2013).

As we see, the economic importance of monocots is far from exhausted by grasses. Spices, fruits, vegetables, oils, fibers, medicines, and ornamental plants all make their contribution to the economy and well-being of humanity.

6.4. Evolutionary Depth: Monocots Arose Early and Occupied Different Niches

It is important to understand that monocots are not simply “grass” that we see in meadows and fields. This is an ancient evolutionary line that arose, by various estimates, in the Early Cretaceous, about 140–130 million years ago (Bell et al., 2010; Li et al., 2019; Pandey, 2021). During this time, monocots have undergone an enormous path of evolution and have occupied practically all possible ecological niches on Earth.

• Aquatic and semi-aquatic habitats. The basal orders Acorales and Alismatales are predominantly aquatic and marsh plants. Sweet flag (Acorus) grows along the shores of water bodies; water plantain (Alisma), arrowhead (Sagittaria), pondweed (Potamogeton), and eelgrass (Zostera) are aquatic plants. It was probably from the aquatic environment that the evolution of monocots began (Kubitzki, 1998; Pandey, 2021).

• Terrestrial herbaceous communities. Grasses (Poaceae) and sedges (Cyperaceae) dominate in steppes, prairies, savannas, meadows, and tundras. They form the appearance of these ecosystems and are the basis of food chains (Connor et al., 2011; Singh, 2019).

• Tropical forests. Palms (Arecaceae) are a characteristic element of tropical forests. Bananas (Musaceae) and gingers (Zingiberaceae) grow in the understory of humid tropical forests. Orchids (Orchidaceae) are epiphytes living on tree branches. Bromeliads (Bromeliaceae) are also often epiphytes (Raven Biology of Plants, 2013; Singh, 2019).

• Arid (desert) habitats. Agaves (Agave), yuccas (Yucca), and aloes (Aloe) are succulent plants adapted to life in dry conditions. They store water in leaves and have a thick cuticle to reduce evaporation (Singh, 2019; Pandey, 2021).

• Epiphytic lifestyle. Many orchids, bromeliads, and some aroids (for example, Monstera) are epiphytes. They grow on other plants, using them as support but not parasitizing them (Raven Biology of Plants, 2013).

• Parasitism and mycoheterotrophy. Some monocots (for example, Petrosavia, Burmannia) are mycoheterotrophs — they obtain nutrients through fungal hyphae rather than through photosynthesis. Others (for example, Cuscuta from the order Solanales, but among monocots — Cassytha from Lauraceae, which does not belong to monocots, but for context) are parasites. Among monocots there are also parasitic forms, for example, some Burmanniaceae (Kubitzki, 1998; Pandey, 2021).

• Arborescent forms. Palms (Arecaceae), dracaenas (Asparagaceae), and bananas (Musaceae) are arborescent monocots that, despite the absence of cambium, reach considerable sizes thanks to primary or anomalous secondary thickening (Raven Biology of Plants, 2013; Singh, 2019).

Thus, monocots are not simply “grasses.” This is an enormous, ancient, and ecologically diverse group that includes aquatic, terrestrial, epiphytic, succulent, arborescent, and even parasitic forms. Their evolutionary history numbers more than 100 million years, and during this time they have occupied practically all possible niches on our planet.

6.5. Why This Matters for the Agricultural Sphere

Understanding that grasses are only one branch of monocots has important practical significance for specialists in the agricultural sphere.

First, it helps to predict properties of plants. Knowing the phylogenetic position of a crop, we can assume what relatives it may have, what pests and diseases threaten it, and what breeding methods will be effective. For example, if we know that onion and garlic belong to Alliaceae (Asparagales), we can expect that their wild relatives may also be sources of sulfur-containing compounds with antimicrobial properties.

Second, it helps to find new useful plants. The phylogenetic approach allows targeted searches for relatives of already known crop plants in the wild. For example, if we are looking for new sources of starch, we can pay attention to wild species of Dioscorea (Dioscoreales) that have not yet been domesticated.

Third, it helps to understand limitations. The absence of cambium in monocots limits their ability to undergo secondary growth, which is important to take into account when cultivating arborescent monocots (palms, dracaenas). Knowledge of physiological features associated with phylogeny allows optimization of agricultural practices.

Fourth, it helps to conserve biodiversity. Understanding that monocots are not only grasses but also many other groups is important for developing strategies for conserving rare and endangered species, many of which have potential economic value.

6.6. Conclusion

Thus, grasses are only one, although very important, branch on the evolutionary tree of monocots. Their share in agriculture is enormous, but not absolute. Other orders of monocots provide spices, fruits, vegetables, oils, fibers, medicines, and ornamental plants. Monocots arose very early in angiosperm evolution and over millions of years occupied the most diverse ecological niches — from aquatic depths to deserts and tropical forests. Understanding this diversity and its phylogenetic basis is of enormous importance for the agricultural sphere, allowing prediction of plant properties, discovery of new relatives of crops, optimization of agricultural practices, and conservation of biodiversity.

In the next chapter we will sum up and discuss how knowledge of monocot phylogeny can be used to solve practical problems in agriculture and related fields.

Excellent, let us finish. Here is the seventh and final chapter, written in accordance with your requirements.

7.1. Summary: What We Have Learned About Monocots

We have completed our review of one of the largest and most significant clades of flowering plants — the monocots (Monocots). Let us look back and systematize the knowledge obtained in the previous chapters.

In the first chapter we established that monocots represent a monophyletic clade, that is, a group including a common ancestor and all of its descendants (Judd et al., 2018). In the APG IV system, monocots occupy the position of one of the five main branches of mesangiosperms, along with Chloranthales, Magnoliids, Ceratophyllales, and Eudicots (APG IV, 2016; Pandey, 2021). We emphasized that “monocots” are not a taxonomic rank but an evolutionary branch, which is fundamentally important for understanding their place in the plant system.

In the second chapter we examined the key characters of monocots. The classical morphological characters — one cotyledon, parallel venation, scattered vascular bundles, trimerous flowers, absence of cambium — are for the most part synapomorphies, but are subject to homoplasy (Kubitzki, 1998; Raven Biology of Plants, 2013). We discussed exceptions: secondary growth in palms and dracaenas, arborescent forms of bananas, reduction in duckweeds. Molecular data, such as the structure of sieve-element plastids (P2c type) and features of microsporogenesis, provide more reliable criteria for defining the clade (Behnke, 1981; Rudall et al., 1997).

In the third chapter we analyzed the phylogeny and major orders of monocots. We traced the sequence of branchings from the basal Acorales and Alismatales through Petrosaviales and Lilianae (Dioscoreales, Liliales, Asparagales) to Commelinids (Arecales, Commelinales, Zingiberales, Poales) (APG IV, 2016; Givnish et al., 2010). This scheme reflects the evolutionary history of the group and serves as the basis for understanding its internal structure.

In the fourth and fifth chapters we dwelled in detail on the economic importance of monocots. We saw that they provide humanity with food products, forage, technical raw materials, medicines, and ornamental plants (Singh, 2019; Connor et al., 2011). We examined the food, forage, technical, medicinal, and ornamental importance of individual orders, and also discussed the identification characters of the most important economic groups — how to distinguish a grass from a sedge, onion from garlic, banana from plantain.

In the sixth chapter we overcame “grass-centrism” and showed that grasses are only one branch on the enormous evolutionary tree of monocots. We discussed the share of Poales in agriculture, which is enormous but not absolute, and examined the contribution of other orders to the production of spices, fruits, vegetables, oils, fibers, medicines, and ornamental plants. We also emphasized the evolutionary depth of monocots, which arose early and occupied the most diverse ecological niches (Bell et al., 2010; Li et al., 2019; Pandey, 2021).

7.2. Monocots: A Large and Diverse Clade

Monocots are one of the largest clades of flowering plants, numbering more than 90,000 species, which constitutes approximately one quarter of the entire species diversity of angiosperms (Raven Biology of Plants, 2013; Singh, 2019). They are distributed throughout the world — from tropical forests to Arctic tundras, from aquatic depths to deserts. They dominate in herbaceous communities — steppes, prairies, savannas, meadows — and play a key role in terrestrial ecosystems.

Diversity of life forms of monocots is striking. Among them there are:

• Aquatic plants (Acorales, Alismatales) — sweet flag, water plantain, pondweed, eelgrass.
• Terrestrial grasses (Poales) — grasses, sedges, rushes.
• Epiphytes (Asparagales, Poales) — orchids, bromeliads.
• Succulents (Asparagales) — aloes, agaves, yuccas.
• Arborescent forms (Arecales, Asparagales, Zingiberales) — palms, dracaenas, bananas.
• Lianas (Dioscoreales, Liliales) — Dioscorea, Smilax.
• Mycoheterotrophs (Petrosaviales, Dioscoreales) — Petrosavia, Burmannia.
• Parasites (some Dioscoreales) — representatives of Burmanniaceae.

This diversity is the result of long evolution that began more than 100 million years ago and continues to this day. Monocots are not simply “grass,” but an enormous and diverse group that occupies a key place in the Earth's biosphere.

7.3. Knowledge of Phylogeny Allows Predicting Properties and Finding Relatives of Crop Plants

One of the main practical conclusions of our course is that knowledge of phylogeny has enormous applied significance. The phylogenetic tree is not an abstract scheme, but a working tool that allows one to:

1. Predict properties of plants. Knowing the phylogenetic position of a crop, we can assume what relatives it may have, what pests and diseases threaten it, and what breeding methods will be effective. For example, if we know that onion and garlic belong to Alliaceae (Asparagales), we can expect that their wild relatives may also be sources of sulfur-containing compounds with antimicrobial properties (Singh, 2019; Pandey, 2021).

2. Find new relatives of crop plants. The phylogenetic approach allows targeted searches for relatives of already known crop plants in the wild. For example, if we are looking for new sources of starch, we can pay attention to wild species of Dioscorea (Dioscoreales) that have not yet been domesticated (Singh, 2019). If we are looking for new ornamental plants, we can study wild species of Orchidaceae (Asparagales), which may possess unique flowers.

3. Understand limitations. The absence of cambium in monocots limits their ability to undergo secondary growth, which is important to take into account when cultivating arborescent monocots (palms, dracaenas). Knowledge of physiological features associated with phylogeny allows optimization of agricultural practices (Raven Biology of Plants, 2013).

4. Conserve biodiversity. Understanding that monocots are not only grasses but also many other groups is important for developing strategies for conserving rare and endangered species, many of which have potential economic value (Pandey, 2021).

5. Develop breeding strategies. Knowledge of phylogenetic relationships between cultivated and wild species allows planning crosses and transferring genes for resistance to diseases and pests from wild relatives into cultivated varieties (Connor et al., 2011).

7.4. The Agricultural Importance of Monocots Is Not Limited to Grasses

We have repeatedly emphasized this thesis throughout the course, and now the time has come to formulate it definitively. The agricultural importance of monocots is not limited to grasses. Yes, Poales (and especially Poaceae) occupy first place in production volume and sown area. Yes, wheat, rice, and maize are the foundation of humanity's food security. But:

• Asparagales give us vegetables (onion, garlic, asparagus), spices (saffron), medicines (aloe, galanthamine), and ornamental plants (orchids, narcissi, irises, tulips).
• Zingiberales are spices (ginger, turmeric, cardamom), fruits (bananas), starch (arrowroot), and ornamental plants (cannas, marantas, strelitzias).
• Arecales are palms, a source of food (coconuts, dates), oils (palm oil), fibers (coir, rattan), and construction materials.
• Alismatales are aquatic vegetables (taro, arrowhead) and ornamental plants for aquaria.
• Liliales are ornamental plants (lilies, tulips) and medicinal raw material (colchicine).
• Dioscoreales are yams, an important starch-bearing crop of the tropics.

Thus, monocots are not only “our daily bread,” but also a source of diverse products, materials, and medicines. Understanding this diversity and its phylogenetic basis is of enormous importance for the agricultural sphere.

7.5. Prospects for Further Research

Science does not stand still, and our knowledge of monocots continues to be refined. What prospects open before researchers?

1. Refinement of phylogeny. Despite enormous progress, some nodes of the phylogenetic tree of monocots remain unresolved. For example, the position of Petrosaviales, relationships between the main clades of Lilianae, and the position of Chloranthales relative to monocots — these questions require further research using new molecular markers and more complete taxon sampling (APG IV, 2016; Zeng et al., 2014).

2. Genome studies. Sequencing of monocot genomes opens new possibilities for understanding their evolution and breeding. The genomes of rice, maize, wheat, banana, and palm have already been sequenced, but many other crops await their turn. Comparative genomics allows identification of genes responsible for economically valuable traits and their use in breeding (Pandey, 2021).

3. Development of new crops. Many wild monocots possess valuable properties but have not yet been domesticated. For example, some species of Dioscorea, Amorphophallus, and Xanthosoma may become new starch-bearing crops. Some orchids may be sources of new medicinal compounds. The search for and domestication of new plants is an important task for ensuring food security under climate change (Singh, 2019).

4. Biodiversity conservation. Many monocots are threatened with extinction due to habitat destruction, climate change, and illegal collecting. Developing strategies for conserving these species is an important task for preserving global biodiversity (Pandey, 2021).

5. Data integration. Modern systematics requires integration of morphological, molecular, paleontological, and ecological data. Only an integrated approach allows construction of the most complete and reliable picture of monocot evolution (Judd et al., 2018).

7.6. Final Summary

Let us summarize the entire course.

Monocots are a monophyletic clade of flowering plants characterized by a set of unique characters, the main ones being one cotyledon, parallel venation, scattered vascular bundles, trimerous flowers, and absence of cambium. Molecular synapomorphies, such as the P2c type of sieve-element plastids, confirm the monophyly of this group.

The phylogeny of monocots represents a sequence of branchings from the basal Acorales and Alismatales through Petrosaviales and Lilianae to Commelinids. This scheme reflects the evolutionary history of the group and serves as the basis for understanding its internal structure.

The economic importance of monocots is enormous and multifaceted. They provide humanity with food products (grasses, vegetables, fruits, starch), forage, technical raw materials (fibers, construction materials), medicines, and ornamental plants. Grasses are only one, although very important, branch on the evolutionary tree of monocots. Other orders — Asparagales, Zingiberales, Arecales, Alismatales, Liliales, Dioscoreales — make a substantial contribution to food security and the economy.

Knowledge of phylogeny allows prediction of plant properties, discovery of new relatives of crops, optimization of agricultural practices, conservation of biodiversity, and development of breeding strategies. The phylogenetic approach is not merely an academic exercise, but a working tool for specialists in the agricultural sphere.

The future of research is connected with refinement of phylogeny, genome sequencing, development of new crops, biodiversity conservation, and integration of data from different fields of biology.