The problem how plants as a sessile organisms survive in the varying environment, including adverse changes remains one of the most urgent of modern biology, especially in connection with forecasts of climate global change and increased man-made pressure.
We discussed the available views about numerous types of plant life strategies and mechanisms of competition and coexistence in plant communities in the light of an adaptive essence of phenotypic plasticity and its ecological significance.
In our opinion, 1) types of plant adaptive life strategies characterize only biological and ecological traits of species (cenotic types) in modern phytocenoses. Under the changes of environmental factors of natural or anthropogenic origin, plants of different cenotic types reveal phenotypic plasticity, similar in general terms, to adapt and survive in new conditions. Under the strategy of life (a life cycle), we understand the immanent ability of all living organisms to propagation, that is, the implementation of the “reproductive imperative” –- leaving offspring and preserving a species. Epigenetic systems contribute substantially in plant plasticity and adaptation to the environment due to their ability to vegetative propagation, annual growth of perennial plants (presumably clones), and apomictic propagation – adventitious embryony and apospory; 2) interrelations of sessile and autotrophic organisms eliminate competition for resources. Plants product the organic matter from water and carbon dioxide thanks to energy of sun light and a green pigment chlorophyll. Thus, plants are the first link that combines inorganic and organic worlds and underlies the further trophic chains of heterotrophic organisms in the biosphere; 3) inorganic resources needed for photosynthesis and respiration as sun light, carbon dioxide and oxygen in atmosphere are unlimited. Water and bioelements are available to all sessile components of the phytocenosis. Sunlight intensity is really different on the open area, above the canopy and under the canopy of trees. But each habitat in nature with different sunlight intensity and spectrum is occupied by plant species which the photosynthetic apparatus adapted to these conditions and works effectively; 4) coexistence (facilitation, complementarity) of species, not competing for resources, is the main mode of complicated interrelations of plants in modern phytocenoses, which exist throughout the history of mankind. Coexistence of plants in phytocenoses is conditioned by the biological peculiarities of cenotic types, namely by differences in life (morphological) forms and types of root systems, duration of ontogenesis, reproduction systems, sequence of seasonal development as well as the level of adaptive phenotypic plasticity in response to various environmental changes – climatic, seasonal and meteorological. Range of plasticity reflects the ecological and biological peculiarities of the species that make phytocenoses, their different attitude to the environment, and to each other. Just coexistence of species different on biology and ecology provides stability of phytocenoses and, thus, stability of the plant cover on Earth; 5) Restriction ideas about plant competition for resources will increase attention to other aspects of plant relationships as the basis of their coexistence in natural communities.