Ecological Morphology of Proto-Epiphyte Fern Lemmaphyllum microphyllum C. Presl and Its Relation to the Adaptogenesis.

A study of the ecological morphology of plants is a necessary condition in solving a number of fundamental and applied problems of ecology, botany, geography, and physiology of plants when monitoring global and regional environments, as well as the problems of selecting and introducing plants. This approach is successfully used to study flowering plants of different botanical and geographical zones. At the same time, ferns usually fall outside of the field of interest of botanists. The aim of this study is to investigate a photosynthetic apparatus of sporophytes of proto-epiphyte fern Lemmaphyllum microphyllum at different cell organization levels and determine the ways it adapts to environmental conditions. The morphology and structure of a photosynthetic apparatus of plants are analyzed using a Siams Mesoplant laboratory complex. This equipment makes it possible to analyze L. microphyllum at the level of fronds, mesophyll cells, and plastid apparatus, as well as obtain parameters such as the specific surface density of fronds, the number of cells per frond unit area, the number of chloroplasts per cell, the frond thickness, the surface area and volume of chloroplasts, the cell area and volume, etc. We have found that the fern uses different organs and functions for adapting to habitats on tree trunks and branches and on humus-free flat rock surfaces. Adaptations to the light and humidity conditions are characterized by the maximum manifestations in its morphology and anatomy. Such adaptations include the maximum light interception and light excess protection, as well as both the minimization of water losses and the ability to excrete water. They are manifested at different organizational levels and include combinations of xero-, meso-, helio-, and sciomorphic traits, allowing the species to form stable populations in coenoses. In the case of frond-area reduction, the optimum compensatory strategy includes the development of a water-retaining capacity of cells and tissues (succulentization) based on the polyfunctionality of a chlorenchyma, as well as the improvement of conductive xylem elements due to the appearance of vessels. These characteristics do not solve the problem of long-term dehydration, since they provide only a tolerance to short-term water deficiency. For this reason, such ferns can be called cryptic succulents or subsucculents. [ABSTRACT FROM AUTHOR]