Shoot-Formation Model as a Basis for Adaptations of Flowering Plants

Abstract

This study describes the biomorphology of plants living under variable watering conditions. Its outcome expands the concept of a modular organization as a constructive and representative approach to comparative-morphological analysis and unraveling the ways of biomorph evolution. The structural organization of biomorphs growing in sites composed of gradients of humidification stability (from floodplain meadows to coasts, water cuts, and beaches) is examined on a base of systemic and complementary approaches. Model plant species—Solanum ulcamara, Thalictrum simplex, Lysimachia vulgaris, Lycopus europaeus, Stellaria palustris Persicaria amphibia, and Erysimum cheiranthoides—are studied. It is determined that acceleration in the vegetative and generative spheres entails the appearance of monocarps in the hygrophilic evolutional line. It is shown that the ontogenesis of individuals of seed and vegetative origin is reduced to a single fruiting, and the specificity of the shoot-formation model is preserved in plants of all the considered biotopes. Such a specific sign is identified as the internode elongation in the shoots located in the substrate, in the supersubstrate parts under flooding, in grass rags, or in dense grass under low light. Another sign is a sympodial growth by formation of the replacement shoots. On the model species, it is determined that plant adaptability is supported by the changes in individual structural elements of the monocarpic shoots; the structural and functional zonation of the monocarpic shoots determines the autonomization of the individual’s parts. Our results confirm the idea that the monocarpic shoot and the system formed on its basis belong to the category of axes of an herbaceous plant as part of an architectural unit (in terms of D. Barthelemy and Y. Caraglio). Our data make it possible to conclude that reservoir settlement with flowering plants is possible for long-shoot long-rhizome grasses and subshrub vines. Two evolutional directions are possible: (1) the emergence of monocarpic annuals and (2) the emergence of short-lived and annual plants of vegetative origin associated with the formation of acentric and clearly polycentric stolon-forming and root-shoot biomorphs.