Comparative anatomy and physiology of minor veins and paraveinal parenchyma in the leaves of dicots.

摘要

Comparative research of leaf minor veins and paraveinal parenchyma by means of LM and TEM started a quarter century ago. As a result, the typology of these tissues and database for 2500 species representing most subclasses, orders and families of dicots were created. It was shown that divergent evolution of vascular system during trees and herbs phylogeny had led to the formation of two models of mesophyll transport ring and two types of minor veins and paraveinal parenchyma correspondingly. Both are equally advances and specialised types. Structural, functional and developmental specificity of them are described as well as the pathways of solute exchange between xylem, phloem and mesophyll. Functionally, these types differ in the role of the symplast and apoplast in xylem unloading and phloem loading: the fluxes of transporting ring are oppositively compartmentate. The distribution of both types and their evolutionary precursors in the system of flowering plants is analysed.