Origin and Early Evolution of Angiosperms

1.1. Scale of the Group and Its Importance for Humanity

Angiosperms, or flowering plants (Angiospermae, Magnoliophyta), are the most numerous and diverse group of extant higher plants. According to modern estimates, the number of described angiosperm species ranges from 295,383 (Christenhusz, Byng, 2016) to 369,400 (Kew Report, 2016), and by some estimates reaches 450,000 species (Raven Biology of Plants, 2013). For comparison, the total number of species of all other higher plants — bryophytes, lycophytes, horsetails, ferns, and gymnosperms — taken together is significantly lower than this figure. Angiosperms make up about 90% of all modern terrestrial flora and dominate in virtually all terrestrial ecosystems — from tropical rainforests to Arctic tundra, from freshwater swamps to deserts (Judd et al., 2018).

In the context of the discipline “Systematics and Taxonomy of Agrosphere Organisms,” it is important to emphasize that angiosperms are not merely the dominant group of wild flora, but also the foundation of modern agriculture. All major food crops, with rare exceptions (for example, cycads are not used as food), belong to angiosperms. Grasses (Poaceae) — wheat, rice, maize, barley, oats, rye, sorghum — provide more than 50% of the calories in the human diet (Judd et al., 2018). Legumes (Fabaceae) are the second most important source of plant protein. Solanaceae provide potato, tomato, pepper, and eggplant. Cucurbitaceae — cucumbers, pumpkins, melons, watermelons. Rosaceae — apples, pears, plums, cherries, peaches, raspberries, strawberries. Asteraceae — sunflower, lettuce, Jerusalem artichoke. Brassicaceae — cabbage, turnip, mustard, rapeseed. Apiaceae — carrot, parsley, dill, coriander. Amaryllidaceae, subfamily Allioideae — onion, garlic. Arecaceae — coconut palm, date palm, oil palm. It is no exaggeration to say that the agrosphere in its modern form would be impossible without angiosperms (Pandey, 2021).

Besides their food value, angiosperms provide humanity with wood, fibers (cotton, flax, jute, hemp, ramie), medicinal substances (morphine from poppy, quinine from cinchona, atropine from belladonna, digitalis from foxglove, reserpine from Rauvolfia, taxol from yew — although yew is a gymnosperm, many alkaloids originate from angiosperms), rubber (Hevea), resins, essential oils, dyes, narcotics, stimulants (coffee, tea, cocoa), and countless other products (Simpson, 2010). In agronomic practice, knowledge of angiosperm systematics is necessary for identifying cultivated and weed plants, for searching for wild relatives of crops with valuable traits (disease resistance, drought tolerance, product quality), and for understanding phylogenetic relationships between crops and their wild relatives, which underlies modern breeding and genetic engineering (Judd et al., 2018).

1.2. The Question of Angiosperm Origin: When and from Whom?

The origin of angiosperms is one of the most intriguing and long-unresolved problems of evolutionary biology. Charles Darwin, in a letter to Joseph Dalton Hooker dated 22 July 1879, called the sudden appearance and rapid spread of angiosperms in the fossil record an “abominable mystery” (Darwin, Seward, 1903; cited in Pandey, 2021). Indeed, in Cretaceous deposits (approximately 140–100 million years ago), angiosperms appear almost “immediately” in great diversity, which for a long time seemed inexplicable from the standpoint of a gradual evolutionary process.

Modern molecular phylogenetic and paleobotanical data have largely clarified this picture, although many details remain a matter of debate. According to modern estimates based on the analysis of large molecular datasets calibrated by fossils, the divergence of the angiosperm crown group (that is, the last common ancestor of all modern flowering plants and all its descendants) occurred in the Late Triassic–Early Jurassic, approximately 209–187 million years ago (Li et al., 2019; cited in Pandey, 2021). This is substantially older than the oldest undisputed angiosperm macrofossils, which date to the Early Cretaceous (about 140 million years ago). This gap between molecular estimates and paleontological data has been called the “Jurassic angiosperm gap” (Pandey, 2021). It may be explained both by the incompleteness of the fossil record and by possible systematic errors of molecular clocks associated with uneven rates of molecular evolution (Beaulieu et al., 2015; cited in Judd et al., 2018).

As for the ancestral group, modern concepts exclude the origin of angiosperms from any of the currently living groups of gymnosperms. Morphological cladistic analyses including fossil taxa consistently place a number of extinct groups — the so-called “seed ferns” (pteridosperms), as well as Bennettitales, Caytoniales, Glossopteridales, and Pentoxylales — on the angiosperm stem lineage (Doyle, Donoghue, 1986; Doyle, 2006; Hilton, Bateman, 2006; cited in Judd et al., 2018). This means that the closest relatives of angiosperms among gymnosperms most likely became extinct and are known only from fossil remains. Among these groups, Caytoniales — an extinct order whose representatives had cupules (cup-shaped structures) surrounding ovules, which is considered a possible homology with the angiosperm ovary — are of greatest interest as possible ancestral forms (Doyle, 2008; cited in Pandey, 2021). Bennettitales, externally resembling cycads but having bisexual “flower-like” strobili, are also considered possible close relatives of angiosperms, although most cladistic analyses do not confirm their direct relationship (Doyle, 1998; cited in Pandey, 2021).

It is important to emphasize that angiosperms are monophyletic, that is, they descend from a single common ancestor. This is confirmed both by morphological synapomorphies (shared derived traits) and by numerous molecular data (Qiu et al., 1999; Soltis et al., 2000, 2011; Graham, Iles, 2009; cited in Judd et al., 2018). Thus, the question of angiosperm origin is a question about the nature and appearance of their last common ancestor and about the lineage that led to them.

1.3. A Brief History of Study: From Darwin to Molecular Phylogeny

The history of studying the origin and early evolution of angiosperms spans more than a century and a half and reflects the development of systematic methodology as a whole. As already mentioned, Darwin was aware of the problem of the sudden appearance of angiosperms in the fossil record and considered it difficult to explain from the standpoint of gradualism. In the late 19th and early 20th centuries, two main hypotheses of flower origin dominated: the Pseudanthial theory and the Euanthial theory (Pandey, 2021).

The pseudanthial theory, developed by Engler and his followers, asserted that the flower originated from a complex strobilus (cone) of gymnosperms through reduction and clustering. According to this theory, the simplest flowers — unisexual, without a perianth, gathered in inflorescences — were considered the most primitive. This theory dominated in the late 19th and early 20th centuries and influenced the classifications of Engler and Prantl (Engler, Prantl, 1887–1915; cited in Singh, 2019).

The euanthial theory, proposed by Arber and Parkin (Arber, Parkin, 1907) and supported by Bessey (Bessey, 1915), by contrast, asserted that the flower originated from a bisexual strobilus similar to those of Bennettitales, with numerous spirally arranged micro- and megasporophylls. According to this theory, the most primitive were large bisexual flowers with numerous spirally arranged parts, as in Magnoliaceae. This theory subsequently became dominant and formed the basis of the classifications of Cronquist, Takhtajan, Dahlgren, and Thorne (Cronquist, 1981, 1988; Takhtajan, 1997; Dahlgren, 1989; Thorne, 2007; cited in Singh, 2019).

In the second half of the 20th century, the development of the cladistic method (Hennig, 1966) and its application to morphological data made it possible to move from intuitive phylogenetic schemes to rigorous analyses. Morphological cladistic analyses including both extant and fossil taxa confirmed the monophyly of angiosperms but revealed the inconsistency of many traditional ideas about the directions of evolution (Doyle, Donoghue, 1986; Kenrick, Crane, 1997; Doyle, 1998; cited in Judd et al., 2018).

Beginning in the 1990s, molecular phylogenetic data — first for individual genes, then for multigene and whole-genome datasets — radically changed our understanding of angiosperm relationships. The first molecular analyses revealed that Amborella trichopoda — an endemic of New Caledonia — represents the most basal branch of modern angiosperms, followed by Nymphaeales (water lilies) and Austrobaileyales (Qiu et al., 1999; Soltis et al., 1999; Mathews, Donoghue, 1999; Parkinson et al., 1999; cited in Judd et al., 2018). These three lineages, collectively known as the ANA-grade (Amborellales, Nymphaeales, Austrobaileyales), or formerly the ANITA-grade, occupy successive basal positions on the angiosperm phylogenetic tree. This discovery became possible thanks to the application of maximum likelihood and Bayesian analysis to large molecular datasets, which made it possible to overcome problems associated with long branches and incomplete sampling (Soltis et al., 2004; Qiu et al., 2006; cited in Judd et al., 2018).

In parallel, paleobotanical research developed. Finds of well-preserved Early Cretaceous flowers, such as Archaefructus from China (Sun et al., 2002; Friis et al., 2003), as well as numerous finds of flowers, fruits, and seeds from Cretaceous deposits, have significantly refined the picture of early angiosperm diversification (Friis et al., 2011; cited in Judd et al., 2018). However, the interpretation of these finds — especially such problematic genera as Archaefructus — remains a matter of debate. For example, Archaefructus has been interpreted either as a primitive bisexual flower with an elongated axis or as an inflorescence of reduced unisexual flowers (Sun et al., 2002; Friis et al., 2003; Doyle, 2008; cited in Pandey, 2021).

The culmination of the development of angiosperm systematics was the creation of the Angiosperm Phylogeny Group (APG) — an international group of botanists that since 1998 has published consensus classifications based primarily on molecular phylogenetic data. APG I (1998), APG II (2003), APG III (2009), and APG IV (2016) successively refined and stabilized the angiosperm system, recognizing only monophyletic groups (APG IV, 2016; cited in Pandey, 2021). The APG IV system is currently the generally accepted basis of modern flowering plant systematics, including in agricultural sciences.

Thus, the history of angiosperm study has traveled from speculative theories of the 19th century through cladistic analysis of morphological data of the 20th century to the modern molecular phylogenetic system, which is constantly being refined and improved. Understanding this history is important for correctly interpreting the modern system and for realizing that systematics is a dynamically developing science, not a static set of names.

2.1. Flower

Flower is a determinate (growth-limited) shoot bearing sporophylls: microsporophylls (stamens) and megasporophylls (carpels). It is the presence of a flower that distinguishes angiosperms from all other seed plants. A flower usually consists of four types of appendages arranged on a shortened axis — the receptacle (receptaculum). From outside to inside are located: sepals (calyx), petals (corolla), stamens (androecium), and carpels (gynoecium). Sepals and petals together form the perianth (perianthium) and perform protective and attractive functions (Raven et al., 2013; Judd et al., 2018).

From an evolutionary point of view, the flower is a modified bisexual strobilus (cone) in which sterilization of part of the sporophylls and their differentiation into perianth and fertile elements occurred. This concept, known as the Euanthial theory, is currently generally accepted (Arber, Parkin, 1907; Bessey, 1915; cited in Pandey, 2021). According to this theory, flowers with numerous spirally arranged parts, as in modern Magnoliaceae, are considered the most primitive (Judd et al., 2018).

The angiosperm flower is characterized by a number of key features:

• Bisexuality (hermaphroditism): most flowers contain both stamens and carpels, which ensures the possibility of self-pollination and increases reproductive efficiency (Rudall, 2013).
• Enclosed container for ovules: carpels close, forming an ovary, inside which ovules develop. This distinguishes angiosperms from gymnosperms, in which ovules lie openly on megasporophylls (Doyle, 2013).
• Stigma: a specialized surface at the top of the carpel that captures pollen. The presence of a stigma is a key adaptation to entomophily and anemophily, ensuring selectivity during pollen grain germination (Rudall, 2013).
• Reduction in the number of parts and their fixation: unlike many gymnosperms, in angiosperms the number of flower parts is often fixed (for example, 3, 4, or 5), which is associated with strict genetic regulation (ABC model) (Coen, Meyerowitz, 1991; cited in Rudall, 2013).

In angiosperm systematics, flower structure is the most important source of characters. The number of parts, their arrangement (spiral or cyclic), fusion (connation) and adnation, ovary position (superior, inferior), symmetry (actinomorphic, zygomorphic) — all these are used to delimit large clades (APG IV, 2016; Judd et al., 2018).

From an agronomic point of view, the flower is the organ on which the yield of fruits and seeds depends. Knowledge of flowering biology, pollination and fertilization is necessary for breeding, seed production, and yield management (Pandey, 2021).

2.2. Fruit

Fruit is a modified ovary (or group of ovaries) of angiosperms, developing after fertilization and containing seeds. The fruit is formed from the ovary wall (pericarp), which may differentiate into exocarp (outer layer), mesocarp (middle), and endocarp (inner). Sometimes other parts of the flower (for example, the receptacle, perianth) also participate in fruit formation; then they are called false fruits or accessory fruits (for example, apple, strawberry) (Judd et al., 2018; Raven et al., 2013).

The evolutionary significance of the fruit lies in protecting seeds and dispersing them. Fruits provide:

• Protection from unfavorable conditions and consumption by animals before seed maturation.
• Dissemination — dispersal of seeds by wind, water, animals, self-dispersal. This promotes species dispersal and reduces competition between seedlings (Pandey, 2021).

The diversity of fruits is enormous: dry and fleshy, dehiscent and indehiscent, one-seeded and many-seeded. In systematics, fruit type is often used to characterize families and orders. For example, the legume (Fabaceae), capsule (Papaveraceae), silique (Brassicaceae), berry (Solanaceae), drupe (Rosaceae), caryopsis (Poaceae) are important diagnostic characters (APG IV, 2016).

The agricultural importance of fruits is difficult to overestimate: they are the main product of crop production — grain, beans, nuts, fruits, berries, vegetables. Fruit breeding is aimed at improving taste, keeping quality, transportability, and disease resistance (Simpson, 2010).

2.3. Double Fertilization

Double fertilization is a unique feature of angiosperms (and some Gnetales, but in the latter it does not lead to endosperm formation). The essence of the process: two sperm cells penetrate into the embryo sac (female gametophyte). One of them fuses with the egg cell, forming a diploid zygote, from which the embryo develops. The second sperm fuses with the central cell (containing two polar nuclei), forming a triploid (or another ploidy level) primary endosperm cell. This process was discovered by S. G. Navashin in 1898 (Navashin, 1898; cited in Lersten, 2004).

Double fertilization has enormous evolutionary significance. It provides:

• Rapid formation of nutritive tissue (endosperm) only after fertilization, which saves plant resources.
• Genetic determination of the endosperm: it receives one set of chromosomes from the father and two from the mother (in most cases), which may influence seed development.
• Synchronization of embryo development and nutritive tissue (Becker et al., 2025).

In systematics, double fertilization is considered a key aromorphosis determining the monophyly of angiosperms. However, the mechanisms of its regulation (for example, the involvement of EC1, HAP2, DMP genes) are studied in the context of evolutionary developmental biology (Becker et al., 2025).

For agronomy, understanding double fertilization is important for seed production, since disruptions of this process lead to sterility or defective seed (Lersten, 2004).

2.4. Endosperm

Endosperm is the nutritive tissue formed as a result of double fertilization. In most angiosperms it is triploid (3n), but in some basal groups (Nymphaeales, Austrobaileyales) it is diploid (2n). Endosperm may be nuclear, cellular, or helobial in its developmental type (Lersten, 2004).

The function of the endosperm is to supply nutrients to the developing embryo and, in some cases, the seedling. In many cultivated plants, the endosperm makes up the main part of the seed and is the main food product for humans: wheat, rice, maize, barley — their endosperm is rich in starch and proteins. In others (legumes, cucurbits), the endosperm is consumed by the embryo before seed maturation, and reserve substances are deposited in the cotyledons (Judd et al., 2018).

Evolutionarily, the endosperm represents a unique innovation, since in gymnosperms the nutritive tissue is the female gametophyte (haploid), whereas in angiosperms it is a new type of tissue arising after fertilization. This allows the plant not to spend resources on forming nutritive tissue until fertilization occurs (Raven et al., 2013).

In systematics, the presence of endosperm and its type are used to delimit large taxa. For example, in monocots the endosperm is usually well developed, while in many dicots it may be absent (Judd et al., 2018).

2.5. Vessels in the Xylem

Vessels are specialized water-conducting elements of the xylem, consisting of vessel elements connected by perforation plates. Unlike tracheids (which are present in gymnosperms and some angiosperms), vessels provide more efficient water transport due to through openings between vessel elements. This allows rapid conduction of large volumes of water and promotes better adaptation to arid conditions (Doyle, 2013).

Vessels arose within angiosperms, probably repeatedly. In basal groups (Amborella, Nymphaeales, some Winteraceae) vessels are absent, and water is conducted only by tracheids. In Austrobaileyales and most other angiosperms, vessels are present. Secondary loss of vessels is known in some groups (for example, Winteraceae) (Judd et al., 2018).

The evolutionary significance of vessels lies in increasing the efficiency of water transport, which allowed angiosperms to occupy drier habitats and reach larger sizes. In systematics, the presence or absence of vessels and the type of perforation plates (scalariform, simple) are used to characterize families and genera (Doyle, 2013).

From an agronomic point of view, vessels are important for understanding plant water regime, resistance to drought, and lodging. Breeding for efficiency of the water-conducting system is one direction of adaptive breeding (Pandey, 2021).

2.6. Reduction of the Gametophyte

One of the most striking features of angiosperms is the extremely reduced gametophyte. In gymnosperms, the female gametophyte (primary endosperm) is a multicellular tissue, and the male gametophyte is a pollen grain that may contain several cells. In angiosperms, the female gametophyte (embryo sac) usually consists of only 7 cells and 8 nuclei (Polygonum type), and the male gametophyte consists of 2–3 cells (vegetative cell and two sperm cells) (Lersten, 2004).

Such reduction became possible due to:

• Endosporic development: the megaspore does not leave the megasporangium but germinates inside it.
• Absence of archegonia: archegonia are not formed in angiosperms; the egg cell forms directly in the embryo sac.
• Rapid fertilization: the pollen tube delivers sperm cells directly to the egg cell, which eliminates the need for motile spermatozoids and water (Raven et al., 2013).

The reduction of the gametophyte has enormous adaptive significance: it accelerates the reproductive cycle, reduces dependence on water, and allows efficient use of resources. In systematics, the structure of the embryo sac (number of nuclei, cells) is an important character for delimiting basal groups. For example, in Amborella the embryo sac has 9 nuclei and 8 cells, in Nymphaeales — 4 nuclei and 4 cells, in most others — 8 nuclei and 7 cells (Friedman, 2006; cited in Judd et al., 2018).

For agronomy, understanding gametophyte development is important for seed production and biotechnology, since disruptions in embryo sac formation lead to sterility (Becker et al., 2025).

2.7. Other Important Aromorphoses

In addition to those listed, the key innovations of angiosperms include:

• Bitegmic ovules: presence of two integuments (outer and inner) around the nucellus. This is characteristic of most angiosperms, although in some groups the number of integuments is reduced to one (Judd et al., 2018).
• Closed carpels: fusion of carpel margins, leading to the formation of an ovary. This provides protection for ovules and creates conditions for selective pollen germination (Doyle, 2013).
• Paracytic stomata: a characteristic type of stomatal apparatus, often found in angiosperms (Rudall, 2013).
• Presence of columellae in pollen exine: a sporopollenin-containing pollen wall with columnar structures (columellae), which increases resistance to damage and improves adhesion to the stigma (Doyle, 2013).

These traits, together with those listed above, form the unique morphological “appearance” of angiosperms, which makes it easy to distinguish them from gymnosperms.

3.1. General Characteristics of the ANA-grade

The term “ANA-grade” (formerly ANITA-grade) comes from the first letters of the names of three orders: Amborellales, Nymphaeales, and Austrobaileyales. These three lineages successively separate from the base of the angiosperm phylogenetic tree, with Amborellales occupying the most basal position — either alone or together with Nymphaeales (Mathews, Donoghue, 1999; Qiu et al., 1999; Soltis et al., 1999; Parkinson et al., 1999; cited in Judd et al., 2018). All other angiosperms, including magnoliids, monocots, and eudicots, are united in the clade Mesangiospermae (APG IV, 2016; Cantino et al., 2007; cited in Judd et al., 2018).

It is important to emphasize that the ANA-grade is not a clade in the strict sense (that is, not a monophyletic group), but a grade, or a sequence of basal branching events. This means that Amborellales, Nymphaeales, and Austrobaileyales do not form a single group, but represent successive branches departing from the angiosperm stem. Therefore, in the APG IV system they are not united into a formal taxon, but are considered as three separate orders located at the base of the system (APG IV, 2016).

The basal angiosperm lineages have retained a number of archaic traits that were lost or modified in more advanced groups. Such traits include:

• Absence of vessels in the xylem (in Amborella and most Nymphaeales) (Feild et al., 2000; Schneider et al., 1995; cited in Judd et al., 2018).
• Ascidiate (pitcher-shaped) carpels whose margins close by secretion rather than postgenital fusion (Endress, Igersheim, 2000; cited in Judd et al., 2018).
• Multicellular or weakly reduced female gametophytes (Friedman, 2006; Friedman, Ryerson, 2009; cited in Judd et al., 2018).
• Presence of essential oils in specialized cells (in Austrobaileyales and some Nymphaeales) (Judd et al., 2018).
• Undifferentiated perianth (in Amborella and many Nymphaeales) (Endress, Doyle, 2009; cited in Judd et al., 2018).

The study of these groups is of enormous importance for reconstructing the appearance of the last common ancestor of angiosperms. Morphological traits common to all three basal lineages were with high probability also present in this ancestor. Such traits include, for example, an undifferentiated perianth, numerous spirally arranged stamens and carpels, and the absence of vessels (Doyle, Endress, 2000; Endress, Doyle, 2009; Sauquet et al., 2017; cited in Judd et al., 2018).

3.2. Order Amborellales

The order Amborellales includes a single family Amborellaceae with a single genus and species — Amborella trichopoda Baill. It is an endemic of New Caledonia, growing in the understory of humid mountain forests (Judd et al., 2018; Pandey, 2021). Amborella trichopoda is a small evergreen shrub or small tree with distichously arranged leaves without stipules. Leaf blades are entire or slightly toothed, with pinnate venation. The plant is dioecious: male and female flowers are located on different individuals (Endress, Igersheim, 2000; cited in Judd et al., 2018).

The flowers of Amborella are small, with an undifferentiated perianth consisting of 5–13 spirally arranged tepals. Male flowers have 12–22 (up to 100) stamens arranged in 3–5 whorls; stamens are ribbon-shaped, with undifferentiated filament and connective. Female flowers have 5–8 free carpels arranged in one whorl; carpels are ascidiate, their margins close by secretion, the stigma is sessile, with two expanded lobes. There is one ovule, pendulous, hemianatropous (Endress, Igersheim, 2000; cited in Judd et al., 2018).

The fruit is an aggregate drupe consisting of several small drupes with pitted stones containing resinous substances. Seeds have abundant endosperm and a very small embryo (Judd et al., 2018; Pandey, 2021).

From a systematic point of view, Amborella is unique in a number of traits:

• Absence of vessels in the xylem: water is conducted only by tracheids (Feild et al., 2000; cited in Judd et al., 2018).
• Granular pollen exine without tectum — a unique trait among angiosperms (Sampson, 1993; Hesse, 2001; cited in Doyle, 2013).
• Female gametophyte consists of 8 cells and 9 nuclei (unlike the typical 7 cells and 8 nuclei), with three synergids instead of two (Friedman, 2006; Friedman, Ryerson, 2009; cited in Judd et al., 2018).
• Presence of staminodes in female flowers, indicating origin from a bisexual ancestor (Endress, Igersheim, 2000; cited in Judd et al., 2018).

These traits make Amborella a key object for understanding the early evolution of angiosperms. Molecular analyses using many genes and complete genomes consistently place Amborella at the base of the angiosperm phylogenetic tree (Qiu et al., 1999; Soltis et al., 1999; Mathews, Donoghue, 1999; Parkinson et al., 1999; Soltis et al., 2011; cited in Judd et al., 2018). However, some analyses, especially those based on mitochondrial genes, place Amborella together with Nymphaeales in one clade (Barkman et al., 2000; Xi et al., 2014; cited in Judd et al., 2018). This question remains a matter of debate, but in the APG IV system the order Amborellales is considered the most basal lineage of angiosperms (APG IV, 2016).

Amborella has no economic importance, but its study is of enormous theoretical value for understanding the evolution of the flower, fruit, and life cycle of angiosperms (Pandey, 2021).

3.3. Order Nymphaeales

The order Nymphaeales includes three families: Hydatellaceae, Cabombaceae, and Nymphaeaceae. The total number of species is about 75–90 (APG IV, 2016; Judd et al., 2018). All representatives of the order are aquatic or semiaquatic herbaceous plants, distributed worldwide but most diverse in tropical and subtropical regions (Kubitzki, 1993; Schneider, Williamson, 1993; cited in Kubitzki, 1993).

3.4. Order Austrobaileyales

The order Austrobaileyales includes three families: Austrobaileyaceae, Trimeniaceae, and Schisandraceae (including Illiciaceae). The total number of species is about 100 (APG IV, 2016; Judd et al., 2018). Representatives of the order are woody plants distributed in tropical and subtropical regions of Asia, Australia, and America.

3.5. Significance of Basal Lineages for Understanding Angiosperm Evolution

The basal angiosperm lineages — Amborellales, Nymphaeales, and Austrobaileyales — are of enormous importance for reconstructing ancestral states and understanding the early evolution of flowering plants. A comprehensive analysis of morphological, anatomical, embryological, and molecular traits of these groups allows the following conclusions:

1. The ancestral angiosperm flower was probably small or medium-sized, bisexual, actinomorphic, with an undifferentiated perianth, numerous spirally arranged stamens and carpels (Endress, Doyle, 2009; Sauquet et al., 2017; cited in Judd et al., 2018). The presence of staminodes in female flowers of Amborella indicates that the ancestral flower was bisexual, and unisexuality arose secondarily (Endress, Igersheim, 2000; cited in Judd et al., 2018).

2. Ancestral carpels were ascidiate (pitcher-shaped), with margins closing by secretion rather than postgenital fusion. This carpel type is preserved in Amborellales, Nymphaeales, and Austrobaileyales, but was replaced by plicate carpels in Mesangiospermae (Endress, Igersheim, 2000; Doyle, Endress, 2000; cited in Judd et al., 2018).

3. The ancestral female gametophyte was probably four-celled (as in Nymphaeales) or nine-nucleate (as in Amborella). The typical eight-nucleate embryo sac (Polygonum type) arose later, in Mesangiospermae (Friedman, 2006; Friedman et al., 2003; Williams, Friedman, 2004; cited in Judd et al., 2018).

4. The absence of vessels in Amborella and most Nymphaeales indicates that ancestral angiosperms were vesselless, and vessels arose later within Mesangiospermae (Feild et al., 2000; Schneider et al., 1995; cited in Judd et al., 2018).

5. The presence of essential oils in Austrobaileyales and some Nymphaeales is considered an ancestral trait inherited from the common ancestor of angiosperms (Judd et al., 2018).

6. Dioecy in Amborella and some Nymphaeales is probably a secondary state, since the ancestral flower was bisexual (Endress, Igersheim, 2000; cited in Judd et al., 2018).

These conclusions are important not only for systematics but also for evolutionary developmental biology (evo-devo), since they allow reconstruction of the evolution of genetic mechanisms controlling flower development (ABC model) (Coen, Meyerowitz, 1991; cited in Rudall, 2013).

3.6. Economic Importance of Basal Lineages

Despite the fact that basal angiosperm lineages are few in number and do not play a dominant role in modern flora, some of their species have economic importance:

• Nymphaeaceae: Nymphaea, Nuphar, Victoria — ornamental aquatic plants widely cultivated in ponds and aquaria. Seeds and rhizomes of some species are eaten. Nymphaea and Nuphar are used in folk medicine (Pandey, 2021; Judd et al., 2018).
• Cabombaceae: Cabomba — a popular aquarium plant (Pandey, 2021).
• Schisandraceae: Illicium verum — a source of spice (star anise). Schisandra chinensis — a medicinal plant. Illicium floridanum and other species — ornamental shrubs (Pandey, 2021; Judd et al., 2018).
• Hydatellaceae: no economic importance, but of great scientific interest (Saarela et al., 2007; cited in Judd et al., 2018).

In agronomic practice, knowledge of basal lineages is important for understanding the evolution of cultivated plants and their wild relatives. For example, studying disease and pest resistance in wild species of Nymphaeaceae and Schisandraceae may be useful for breeding (Pandey, 2021).

4.1. General Characteristics of Magnoliids

Magnoliids are predominantly woody plants: trees, shrubs, or lianas, less often herbs (some Piperales). Leaves are usually alternate, simple, with pinnate venation, often leathery, without stipules (or with rudimentary stipules). Many representatives are characterized by the presence of essential oils in specialized cells (idioblasts), which gives leaves and other organs a characteristic aroma (Judd et al., 2018; Kubitzki, 1993).

Flowers of magnoliids are usually large, bisexual or unisexual, with numerous spirally arranged parts. Perianth is often undifferentiated (consisting of tepals), less often differentiated into calyx and corolla. Stamens are usually numerous, ribbon-shaped, with poorly expressed filament and connective. Carpels are usually free, less often fused, often ascidiate or plicate. Ovary superior (Judd et al., 2018; Endress, Doyle, 2009).

Ovules are usually anatropous, bitegmic, with abundant endosperm. Fruits are diverse: aggregate follicles, berries, drupes, nuts (Judd et al., 2018).

From a systematic point of view, magnoliids are characterized by a number of plesiomorphic (archaic) traits:

• Spiral arrangement of flower parts (especially in Magnoliales).
• Numerous free carpels.
• Ribbon-shaped stamens with undifferentiated filament and connective.
• Absence of vessels (in some Winteraceae) or presence of primitive vessels with scalariform perforations (Judd et al., 2018; Doyle, 2013).
• Presence of essential oils (Judd et al., 2018).

However, these traits are not exclusively “primitive” — they are preserved in magnoliids but were lost or modified in more advanced groups. It is important to emphasize that magnoliids are a monophyletic group confirmed by molecular data (Qiu et al., 1999; Soltis et al., 2000, 2011; cited in Judd et al., 2018).

4.2. Order Magnoliales

Magnoliales is the largest order of magnoliids, including 6 families and about 2,840 species (APG IV, 2016; Judd et al., 2018). The most important families: Magnoliaceae, Annonaceae, Myristicaceae, Degeneriaceae, Himantandraceae, and Eupomatiaceae.

4.3. Order Laurales

Laurales is the second largest order of magnoliids, including 7 families and about 3,400 species. The most important families: Lauraceae, Calycanthaceae, Monimiaceae, Siparunaceae, Gomortegaceae, Atherospermataceae, and Hernandiaceae (APG IV, 2016; Judd et al., 2018).

4.4. Order Piperales

Piperales is an order of magnoliids including 3–5 families and about 4,000 species. The most important families: Piperaceae, Saururaceae, and Aristolochiaceae. They are distributed mainly in tropical and subtropical regions, but some species also occur in temperate zones (APG IV, 2016; Judd et al., 2018).

4.5. Order Canellales

Canellales is a small order of magnoliids including 2 families: Winteraceae and Canellaceae. The total number of species is about 90–100. They are distributed in tropical and subtropical regions of the Southern Hemisphere (APG IV, 2016; Judd et al., 2018).

4.6. Significance of Magnoliids for Understanding Angiosperm Evolution

Magnoliids occupy a key position in the angiosperm system because they have retained a number of archaic traits that were lost or modified in more advanced groups. The study of magnoliids allows reconstruction of ancestral states for many traits:

1. Flower: magnoliids demonstrate a wide spectrum of flower structure — from large bisexual flowers with numerous spirally arranged parts (Magnoliaceae) to small unisexual flowers without perianth (Piperaceae). This allows tracing evolutionary trends in flower structure (Endress, Doyle, 2009; cited in Judd et al., 2018).

2. Carpels: in magnoliids there are both ascidiate (pitcher-shaped) and plicate (folded) carpels. This is important for understanding the evolution of the ovary and fruit (Endress, Igersheim, 2000; cited in Judd et al., 2018).

3. Vessels: the presence or absence of vessels in different magnoliid groups (for example, absence in Winteraceae) allows study of the evolution of the water-conducting system (Doyle, 2013).

4. Essential oils: the presence of essential oils in most magnoliids indicates that this trait was present in ancestral angiosperms (Judd et al., 2018).

5. Symbiosis with fungi: many magnoliids form mycorrhizae, which is important for understanding the evolution of symbiotic relationships (Judd et al., 2018).

4.7. Economic Importance of Magnoliids

Magnoliids, despite their relatively small number of species compared with eudicots and monocots, include a number of important economic plants:

• Spices: nutmeg (Myristica fragrans), cinnamon (Cinnamomum verum), camphor (C. camphora), bay leaf (Laurus nobilis), black pepper (Piper nigrum), star anise (Illicium verum) (Pandey, 2021).
• Fruit crops: avocado (Persea americana), cherimoya (Annona cherimola), sugar apple (A. squamosa), soursop (A. muricata) (Pandey, 2021).
• Medicinal plants: Chinese schisandra (Schisandra chinensis), kava (Piper methysticum), some Aristolochia species (Pandey, 2021).
• Ornamental plants: magnolias (Magnolia spp.), tulip tree (Liriodendron tulipifera), sweetshrub (Calycanthus), wintersweet (Chimonanthus), many Peperomia species (Pandey, 2021).
• Timber: Liriodendron tulipifera, some Magnolia, Ocotea, Nectandra, Cinnamomum species (Pandey, 2021).
• Perfumery: ylang-ylang (Cananga odorata), some Chimonanthus species (Pandey, 2021).

5.1. History of the APG System

The prerequisites for the creation of the APG system arose in the 1990s, when the accumulation of molecular data — first for individual genes (rbcL, 18S rDNA, atpB), then for multigene datasets — made it possible to reveal phylogenetic relationships that often contradicted traditional morphological classifications (Chase et al., 1993; Soltis et al., 2000; cited in Judd et al., 2018). In 1998, a group of botanists united in the Angiosperm Phylogeny Group published the first consensus classification (APG I), based primarily on molecular data (APG, 1998; cited in Pandey, 2021). This classification recognized 462 families and 40 orders, but did not assign formal ranks to large clades such as monocots and eudicots (APG, 1998).

APG II (2003) refined the system by introducing a “bracketed” system for families of uncertain status, which allowed authors to choose between narrow and broad circumscriptions of families (APG II, 2003; cited in Pandey, 2021). APG III (2009) abandoned the bracketed system, adopting broader family circumscriptions, and significantly reduced the number of unplaced families (APG III, 2009; cited in Pandey, 2021). APG IV (2016) added five new orders (Boraginales, Dilleniales, Icacinales, Metteniusales, and Vahliales), recognized two additional informal clades — superrosids and superasterids — and finally stabilized the system, which currently includes 64 orders and 416 families (APG IV, 2016; cited in Pandey, 2021).

5.2. General Scheme of APG IV

The APG IV system is organized hierarchically, but without formal ranks above the order. Large clades are designated by informal names that have no nomenclatural status but are widely used in the literature (APG IV, 2016; Judd et al., 2018). The general scheme of APG IV is as follows:

1. Basal Angiosperms — ANA-grade:

• Amborellales
• Nymphaeales
• Austrobaileyales

2. Magnoliids:

• Canellales
• Piperales
• Laurales
• Magnoliales

3. Chloranthales — an order of uncertain position, probably sister to magnoliids or to all the rest of Mesangiospermae (APG IV, 2016).

4. Monocots:

• Acorales
• Alismatales
• Petrosaviales
• Dioscoreales
• Pandanales
• Liliales
• Asparagales
• Arecales
• Commelinales
• Zingiberales
• Poales

5. Probable sister to Eudicots:

• Ceratophyllales

6. Eudicots:

1) Basal eudicots:

• Ranunculales
• Proteales
• Trochodendrales
• Buxales
• Core eudicots:
• Gunnerales
• Dilleniales
• Superrosids
• Superasterids

7. Superrosids:

1) Saxifragales

2) Rosids:

• Vitales
• Fabids (Zygophyllales, Celastrales, Oxalidales, Malpighiales, Fabales, Rosales, Fagales, Cucurbitales)
• Malvids (Geraniales, Myrtales, Crossosomatales, Picramniales, Huerteales, Sapindales, Malvales, Brassicales)

8. Superasterids:

1) Berberidopsidales

2) Santalales

3) Caryophyllales

4) Asterids:

• Cornales
• Ericales
• Lamiids (Garryales, Gentianales, Boraginales, Vahliales, Solanales, Lamiales)
• Campanulids (Aquifoliales, Asterales, Escalloniales, Bruniales, Paracryphiales, Dipsacales, Apiales)

This scheme reflects the sequence of divergence of the main angiosperm lineages, starting from basal groups and ending with large eudicot clades — rosids and asterids (APG IV, 2016; Judd et al., 2018).

5.3. Basal Angiosperms

Basal angiosperms, or ANA-grade, include three orders: Amborellales, Nymphaeales, and Austrobaileyales. These groups occupy successive basal positions on the angiosperm phylogenetic tree and have retained a number of archaic traits (APG IV, 2016; Judd et al., 2018). We examined them in detail in Chapter 3, so here we will only briefly recall:

• Amborellales: a monotypic order with the single species Amborella trichopoda, endemic to New Caledonia. Absence of vessels, undifferentiated perianth, spiral arrangement of flower parts (Judd et al., 2018).
• Nymphaeales: aquatic herbs including water lilies, yellow water lilies, Victoria lilies, etc. Ascidiate carpels, four-celled female gametophyte, absence of vessels in most (Judd et al., 2018).
• Austrobaileyales: woody plants including Austrobaileya, Trimenia, Illicium, Schisandra, Kadsura. Presence of essential oils, spiral arrangement of flower parts, ascidiate carpels (Judd et al., 2018).

5.4. Magnoliids

Magnoliids are a clade including four orders: Canellales, Piperales, Laurales, and Magnoliales. We examined them in detail in Chapter 4. Magnoliids are characterized by a number of archaic traits: spiral arrangement of flower parts, numerous free carpels, ribbon-shaped stamens, essential oils. Among them are important economic plants: spices (nutmeg, cinnamon, black pepper), fruit crops (avocado, cherimoya), medicinal plants (schisandra, kava), and ornamentals (magnolias, tulip tree) (APG IV, 2016; Judd et al., 2018; Pandey, 2021).

5.5. Chloranthales

Chloranthales is an order including the single family Chloranthaceae with 4 genera and about 75 species. These plants are distributed in tropical and subtropical regions. Chloranthaceae are characterized by aromatic opposite leaves, small flowers without perianth or with a rudimentary perianth, often unisexual, gathered in spikes or heads (Judd et al., 2018; Pandey, 2021).

The position of Chloranthales in the APG IV system remains uncertain. Molecular data place them either as a sister group to magnoliids or as a sister group to all the rest of Mesangiospermae (APG IV, 2016; Qiu et al., 2005; Soltis et al., 2011; cited in Judd et al., 2018). In APG IV, Chloranthales are considered an independent lineage not assigned to any of the large clades (APG IV, 2016).

5.6. Monocots

Monocots are a large clade of angiosperms including about 60,000–78,000 species, which constitutes approximately 20–25% of all flowering plants (APG IV, 2016; Judd et al., 2018). Monocots are characterized by a number of synapomorphies: one cotyledon, parallel leaf venation, trimerous flowers, scattered vascular bundles in the stem, absence of secondary growth (in most), and atypical stomatal development (Pandey, 2021).

In the APG IV system, monocots include 11 orders grouped into three main clades (APG IV, 2016; Judd et al., 2018):

1. Alismatid monocots — an early divergent group:

• Acorales
• Alismatales

2. Lilioid monocots:

• Petrosaviales
• Dioscoreales
• Pandanales
• Liliales
• Asparagales

3. Commelinids:

• Arecales
• Commelinales
• Zingiberales
• Poales

Among monocots are the most important agricultural crops: grasses (wheat, rice, maize, barley, oats, rye, sorghum), palms (coconut, date, oil), bananas, ginger, orchids, lilies, alliums, asparagus, pineapples (Pandey, 2021).

5.7. Ceratophyllales

Ceratophyllales is an order including the single family Ceratophyllaceae with one genus Ceratophyllum (6 species). These are submerged aquatic herbs without roots, with whorled dissected leaves and small unisexual flowers without perianth. Fruit is a spiny nutlet (Judd et al., 2018; Pandey, 2021).

The position of Ceratophyllales in the APG IV system is “probable sister to Eudicots.” Molecular data indicate that Ceratophyllum may be a sister group either to eudicots or to monocots, or occupy a position between them (APG IV, 2016; Qiu et al., 2005; Soltis et al., 2011; cited in Judd et al., 2018). In APG IV, Ceratophyllales are considered a separate order not assigned to any of the large clades, but located immediately before eudicots (APG IV, 2016).

5.8. Eudicots

Eudicots are the largest clade of angiosperms, including about 200,000 species, which constitutes approximately 75% of all flowering plants (APG IV, 2016; Judd et al., 2018). Eudicots are characterized by the presence of tricolpate pollen, which is their main synapomorphy (Doyle, 2005; cited in Judd et al., 2018). Other traits: differentiated perianth, cyclic arrangement of flower parts, usually 4- or 5-merous flowers, presence of vessels with simple perforations (Judd et al., 2018).

In the APG IV system, eudicots are divided into basal eudicots and core eudicots (APG IV, 2016; Judd et al., 2018).

5.9. Superrosids

Superrosids are a large clade including Saxifragales and Rosids (APG IV, 2016; Judd et al., 2018).

5.10. Superasterids

Superasterids are a large clade including Berberidopsidales, Santalales, Caryophyllales, and Asterids (APG IV, 2016; Judd et al., 2018).

5.11. Why APG IV Is Accepted by Agricultural Science

The APG IV system has a number of advantages over traditional classifications that make it especially valuable for agricultural science:

1. Monophyly: APG IV recognizes only monophyletic groups, which ensures the predictive power of the classification. If two species belong to the same clade, they are more likely to possess similar traits important for breeding (disease resistance, product quality, responsiveness to fertilizers) (Judd et al., 2018).

2. Phylogenetic basis: APG IV is based on molecular phylogenetic data that reflect real evolutionary relationships. This allows targeted search for wild relatives of cultivated plants with valuable traits (Pandey, 2021).

3. Stability: despite periodic updates, APG IV represents a stable system widely used in scientific literature, databases, and herbaria (APG IV, 2016).

4. Practicality: APG IV includes all known families and orders of angiosperms, which makes it convenient for plant identification and work with herbarium collections (Judd et al., 2018).

5. Integration with molecular data: APG IV is easily integrated with molecular genetic research, which is important for modern breeding and biotechnology (Pandey, 2021).

6.1. Main Elements of a Phylogenetic Tree

A phylogenetic tree consists of two main elements: nodes and branches, or edges (Pandey, 2021). Nodes are branching points where one lineage splits into two or more daughter lineages. Terminal nodes, or leaves, are located at the ends of the tree and represent modern taxa (species, genera, families, orders). Internal nodes represent hypothetical ancestors that existed in the past and from which daughter lineages originated. Branches connect nodes and represent evolutionary lineages along which changes accumulated (Pandey, 2021).

It is important to understand that internal nodes are not real organisms that can be observed — they are statistical reconstructions based on comparison of traits of modern taxa and fossil remains (Judd et al., 2018). The more data (molecular, morphological, paleontological) used to construct the tree, the more reliable the reconstruction. In the APG IV system, the tree is built primarily on the basis of molecular data — DNA sequences from three genomes (nuclear, chloroplast, and mitochondrial), which ensures high statistical support for most nodes (APG IV, 2016; Soltis et al., 2011; cited in Judd et al., 2018).

6.2. Branching Order and Relative Time of Divergence

The branching order on a phylogenetic tree reflects the sequence of lineage divergence. The closer a node is to the base of the tree, the earlier the divergence occurred; the closer to the top, the later (Pandey, 2021). For example, on the APG IV tree, basal angiosperms (Amborellales, Nymphaeales, Austrobaileyales) occupy the lowest branches, which means that these lineages separated from the common angiosperm stem earlier than magnoliids, monocots, or eudicots (APG IV, 2016; Judd et al., 2018).

However, it is important to emphasize that a phylogenetic tree is not a “ladder of progress.” Basal lineages are not “more primitive” or “less evolved” than advanced ones — they simply separated from the common ancestor earlier and have since evolved independently, accumulating their own traits (Judd et al., 2018). For example, Amborella trichopoda is not a “living fossil,” but a modern species that has gone through its own evolutionary path; its lineage simply separated from other angiosperms very early (Doyle, 2013).

In phylogenetics, a distinction is made between cladograms and phylograms. A cladogram shows only the branching order, without indicating branch lengths; a phylogram has branch lengths proportional to the number of accumulated changes (Pandey, 2021). In the APG IV system, cladograms are usually used, since branch lengths may vary depending on the genes used and analytical methods (Judd et al., 2018).

6.3. Monophyly, Paraphyly, and Polyphyly

To correctly read a phylogenetic tree, it is necessary to understand the difference between monophyletic, paraphyletic, and polyphyletic groups (Judd et al., 2018).

A monophyletic group (clade) is a group including the last common ancestor and all its descendants. Monophyletic groups are distinguished on a tree by a single “cut” — they correspond to an entire branch and all its ramifications. Only monophyletic groups are recognized in the APG IV system (APG IV, 2016; Judd et al., 2018).

A paraphyletic group is a group including the last common ancestor but not all its descendants. For example, the traditional “dicots” (Dicotyledoneae) are a paraphyletic group, since they include the common ancestor of all angiosperms but do not include monocots, which also descend from this ancestor (Judd et al., 2018). Paraphyletic groups are not recognized in APG IV, although their names may be used in an informal context (for example, “dicots” in quotation marks).

A polyphyletic group is a group including descendants of different ancestors, that is, not having a common ancestor that would be unique to this group. For example, the traditional family Liliaceae in the broad sense (including lilies, alliums, asparagus, aloe, hyacinths, and many others) turned out to be polyphyletic, since its representatives descend from different ancestors within Asparagales and Liliales (APG IV, 2016; Judd et al., 2018; Pandey, 2021).

6.4. How Orders and Families Are Grouped in APG IV

In the APG IV system, orders and families are grouped into large clades designated by informal names: Basal Angiosperms, Magnoliids, Monocots, Eudicots, Superrosids, Superasterids, Rosids, Asterids, Fabids, Malvids, Lamiids, Campanulids (APG IV, 2016; Judd et al., 2018). These names have no nomenclatural status (that is, they do not follow the rules of the International Code of Nomenclature for algae, fungi, and plants), but are widely used for convenience (APG IV, 2016; Cantino et al., 2007; cited in Judd et al., 2018).

Each order in APG IV represents a monophyletic group, that is, a clade that includes a common ancestor and all its descendants. For example, the order Rosales includes all families descending from the common ancestor of Rosales, and only them (APG IV, 2016). Families within orders are also monophyletic, although in some cases their circumscription has been revised compared with traditional classifications (Judd et al., 2018).

It is important to understand that orders in APG IV are not ranked by “level of advancement” — all of them are modern clades existing at present. For example, the order Nymphaeales (basal angiosperms) and the order Asterales (asterids) are two modern clades that simply separated from the common stem at different times (Judd et al., 2018).

6.5. Why Some Traditional Families Turned Out to Be Polyphyletic

One of the most important results of molecular phylogenetic studies was the discovery that many traditional families, distinguished on the basis of morphological traits, turned out to be polyphyletic or paraphyletic. This led to their division into several monophyletic families in the APG IV system (APG IV, 2016; Judd et al., 2018; Pandey, 2021).

6.6. Practical Use of the APG IV Phylogenetic Tree in Agronomy

The APG IV phylogenetic tree is not merely a theoretical scheme, but a working tool for the agronomist, breeder, and biologist. Let us consider the main directions of its practical use.

6.7. Limitations and Caveats in Reading a Phylogenetic Tree

Despite their enormous value, the APG IV phylogenetic tree has a number of limitations that must be taken into account (Judd et al., 2018).

1. Incompleteness of data: the tree is built on the basis of modern taxa and does not include extinct groups that may occupy an intermediate position. This may distort the reconstruction of ancestral states (Doyle, 2013).

2. Statistical uncertainty: some nodes of the tree have low statistical support (bootstrap < 70%, posterior probability < 0.95), which means that the branching order at these nodes may change when new data are added (Pandey, 2021).

3. Gene trees vs. species trees: a tree built from one gene may differ from a tree built from another gene due to incomplete lineage sorting, hybridization, or horizontal gene transfer (Pandey, 2021). The APG IV system uses a consensus of many genes, but even it may not reflect the true species history.

4. Morphological convergence: some morphological traits may arise independently in different lineages (homoplasy), which may be misleading when interpreting the tree (Judd et al., 2018).

5. Rank conventions: APG IV does not use formal ranks above the order, which may create inconvenience for some practical tasks (for example, when compiling floras or identification keys) (APG IV, 2016; Judd et al., 2018).

6. Dynamism of the system: the APG system continues to develop, and new versions may change the position of some taxa. It is necessary to follow updates (APG IV, 2016; Stevens, 2001 onwards; cited in Judd et al., 2018).

7.1. Angiosperms — the Result of Long Evolution and Key Innovations

Modern molecular phylogenetic and paleobotanical data indicate that the divergence of the angiosperm crown group occurred in the Late Triassic–Early Jurassic, approximately 209–187 million years ago (Li et al., 2019; cited in Pandey, 2021). This conclusion is substantially older than the oldest undisputed macrofossils of flowering plants, which creates the so-called “Jurassic gap” (Pandey, 2021). Despite the incompleteness of the fossil record, it is clear that angiosperms underwent a long period of early evolution before reaching modern diversity.

The key aromorphoses of angiosperms — flower, fruit, double fertilization, endosperm, vessels in the xylem, and radical reduction of the gametophyte — formed a unique morphophysiological “archetype” that ensured this group’s unprecedented evolutionary success (Doyle, 2013; Rudall, 2013). The flower as a determinate shoot with sporophylls, the enclosed container for ovules (ovary), double fertilization with the formation of triploid endosperm, an efficient water-conducting system of vessels, and an extremely reduced gametophyte — all these traits together allowed angiosperms to rapidly colonize diverse habitats, shorten the reproductive cycle, and reduce dependence on water (Judd et al., 2018; Becker et al., 2025).

It is important to emphasize that these innovations did not arise simultaneously and are not present in full set in all modern groups. Basal lineages have retained a number of archaic features, and some advanced groups have secondarily lost certain traits (for example, vessels in Winteraceae or endosperm in some orchids). Nevertheless, it is precisely the combination of these innovations that determined the dominance of angiosperms in the modern biosphere and their central position in the agrosphere (Pandey, 2021).

7.2. Basal Lineages and Magnoliids: Archaic Traits and Economic Importance

The basal angiosperm lineages — Amborellales, Nymphaeales, and Austrobaileyales — occupy successive basal positions on the phylogenetic tree and have retained a number of plesiomorphic traits: ascidiate carpels, undifferentiated perianth, spiral arrangement of flower parts, absence of vessels in Amborella and most Nymphaeales, and multicellular or weakly reduced female gametophytes (Endress, Igersheim, 2000; Friedman, 2006; Judd et al., 2018). The study of these groups is of key importance for reconstructing the ancestral appearance of angiosperms and understanding the early stages of evolution of the flower, fruit, and life cycle (Sauquet et al., 2017; Endress, Doyle, 2009).

Magnoliids (Magnoliidae) are the next large clade, including the orders Magnoliales, Laurales, Piperales, and Canellales. They also have retained many archaic traits: spiral arrangement of flower parts, numerous free carpels, ribbon-shaped stamens, essential oils (Judd et al., 2018). Among magnoliids there are important economic plants: spices (nutmeg, cinnamon, black pepper, star anise), fruit crops (avocado, cherimoya, sugar apple), medicinal plants (Chinese schisandra, kava), ornamentals (magnolias, tulip tree, sweetshrub, wintersweet), and sources of timber (Pandey, 2021). Thus, basal lineages and magnoliids, despite their relatively small number of species, make a noticeable contribution to the agrosphere and are of enormous theoretical importance for systematics and evolutionary biology.

7.3. APG IV as a Working Tool for the Modern Agronomist and Biologist

The APG IV system (2016) is a modern phylogenetic classification of angiosperms that recognizes only monophyletic groups and reflects evolutionary relationships revealed on the basis of molecular data. It includes 64 orders and 416 families and organizes them into large informal clades: Basal Angiosperms, Magnoliids, Chloranthales, Monocots, Ceratophyllales, Eudicots, Superrosids, Superasterids, Rosids, Asterids, Fabids, Malvids, Lamiids, Campanulids (APG IV, 2016; Judd et al., 2018).

For the agronomist and biologist, APG IV is not merely a theoretical scheme, but a working tool. It allows one to:

• Identify plants using modern identification keys and databases built on a phylogenetic basis (Judd et al., 2018).
• Search for wild relatives of cultivated plants — donors of valuable traits (disease resistance, drought tolerance, product quality) (Pandey, 2021).
• Understand the evolution of economically valuable traits, such as C4 photosynthesis, tuber formation, symbiosis with nitrogen-fixing bacteria, accumulation of alkaloids and essential oils (Judd et al., 2018; Pandey, 2021).
• Predict resistance to diseases and pests based on phylogenetic relationships (Pandey, 2021).
• Work with herbarium collections and databases using a stable and generally accepted system (APG IV, 2016).

At the same time, it is necessary to remember the limitations of the system: it is dynamic, some nodes have low statistical support, and the phylogenetic tree does not replace morphological diagnostics (Judd et al., 2018; Pandey, 2021). Nevertheless, APG IV is currently the most substantiated and practically applicable classification of angiosperms.

7.4. Prospects and Concluding Remarks

Angiosperm systematics continues to develop. The integration of genomics, evolutionary developmental biology (evo-devo), paleobotany, and comparative morphology allows refinement of phylogenetic reconstructions and better understanding of the mechanisms of evolutionary innovations (Becker et al., 2025; Doyle, 2013). Projects such as the Open Tree of Life and the Angiosperm Phylogeny Website (Stevens, 2001 onwards) provide continuous updating of the classification and access to data for researchers worldwide (Pandey, 2021).

For agricultural education and science, it is important that students and specialists master the modern phylogenetic system, understand its principles, and are able to use it in practical work. Angiosperms remain an “abominable mystery” in the details of their early evolution, but the general structure of their phylogenetic tree and key aromorphoses are now known well enough to serve as a reliable basis for further research (Darwin, Seward, 1903; cited in Pandey, 2021).

Thus, angiosperms are the result of long evolution and key innovations; basal lineages and magnoliids have retained archaic traits, but among them there are important crops; APG IV is a working tool for the modern agronomist and biologist. Systematics is a dynamic science, and its development will continue, opening new horizons for understanding and using the plant world.