Periodization of Plant Ontogeny
The life of every plant, from the emergence of the zygote to natural death, is a complex, orderly process unfolding over time. This process is called ontogeny (from Greek ὄντος — being and γένεσις — origin). Ontogeny encompasses all successive changes of the organism: growth, differentiation of tissues and organs, formation of reproductive structures, ageing, and death (Gatsuk et al. 1980; Yakovlev et al. 2008). For ease of study and practical use, this continuous process is subdivided into discrete stages, or age states — such a classification is called periodization of ontogeny.
Periodization of plant ontogeny is a scientifically based division of an individual’s development from fertilization (or from the moment of separation from the mother plant during vegetative propagation) until death into qualitatively distinct time intervals, each characterized by a specific set of morphological, anatomical, and physiological traits. In agronomy, such periodization allows precise determination of crop development phases (e.g., tillering, stem elongation, flowering), prediction of harvest dates, and informed application of fertilizers and plant protection products (Kruglova 2023).
The development of detailed periodization of ontogeny has a long history. Several approaches have emerged in global science. In the Russian school (T.A. Rabotnova, A.A. Uranov, I.G. Serebryakov), the main focus was on the age states of individuals within a population, distinguishing latent (seed), pregenerative (seedlings, juvenile, immature, virginile plants), generative (young, mature, old generative individuals), and postgenerative (subsenile, senile) periods (Gatsuk et al. 1980). This approach, described in the classic work “Age states of plants of various growth forms” (Gatsuk et al. 1980), proved universal for herbaceous perennials, shrubs, and trees. In Western literature, the similar concept is referred to as “life stages”, with emphasis often placed on phenological phases (e.g., the BBCH scale) and developmental program switching (Batygina & Vasilyeva 2003; Kruglova 2023).
It is important to emphasize that ontogeny periodization reflects not only chronological age but also the biological age of the organism — its current state determined by structural and functional rearrangements (Gatsuk et al. 1980). Under favorable conditions, a plant may pass through all stages faster; under stress, it may be delayed or return to earlier stages (e.g., formation of adventitious buds on roots of senile individuals).
From an evolutionary perspective, ontogeny periodization is closely linked with the alternation of generations and the increasing complexity of life cycles. In higher plants, evolution saw the gradual dominance of the sporophyte (asexual diploid generation) over the gametophyte (sexual haploid) (Yakovlev et al., 2008). At the same time, the duration of the embryonic period increased, specialized organs of vegetative reproduction formed, and adaptations for surviving unfavorable seasons (seed dormancy, winter buds) emerged. These evolutionary acquisitions are reflected in modern ontogeny: different life forms (trees, shrubs, perennial and annual herbs) vary in the set and duration of age states, but the general logic of successive “youth – maturity – senescence” remains (Gatsuk et al. 1980).
In this article, we will consider the basic principles for distinguishing stages of ontogeny, the criteria for their delimitation (morphological, anatomical, physiological), provide a detailed characterization of plant age states according to Rabotnova–Serebryakov, and discuss the concept of population age structure. Since the UniversityAgro.ru project has already published individual articles on the embryonic, juvenile, virginile, generative, and senile stages, here we will give only a general scheme and indicate key diagnostic features, referring the reader to the relevant materials for in-depth study.
