Adaptive Features of Leaf Structure in Plants of Different Ecological Groups

It is well known that the structure of leaves plays an important role in adaptation, but there are still no accurate structural criteria to indicate ecological characteristics of the species. We have studied parameters of leaves in 100 herbaceous plant species growing in the southern taiga subzone that belong to different ecological groups in relation to irradiance and moisture supply. The results show that leaf area, thickness, and anatomical type are less correlated with ecological characteristics of the species than structural parameters of photosynthetic tissues. In the series shade-loving mesophytes-light-loving hygromesophytes-mesophytes-xeromesophytes-mesoxerophytes, the concentration of cells and chloroplasts in the leaf gradually increases by a factor of up to 7-10, their size decreases two- to threefold, and the ratio of mesophyll surface area to leaf surface area increases four- to fivefold. It is concluded that characteristics of mesophyll are of adaptive significance. A system of characters is proposed for identification of ecological groups of plants growing in the boreal zone.