The Role of Extracellular Space (Apoplast) in The Regulation of Physiological Processes in Plants

Abstract

The paper summarizes the results of studies of the role played by the plant leaf extracellular space in the regulation of mesophyll cells water exchange, photosynthesis and export of assimilates to consuming sink organs. When comparing different methods of assessing water exchange rates, the participation of the plasmalemma in the formation of the leaf water potential was shown. Using the in vivo method of extracting the contents of the apoplast, the dynamics of the exit and movement of labeled photosynthetic products through the extracellular space was traced. It was shown that there is a circulation of assimilates in the plant. As the sugars move downwards along the phloem, they partially escape into the extracellular space and are carried away upwards by the transpiration stream, where they re-enter the leaves that have completed growth and are re-exported. This creates a common pool of photosynthetic products, which serves as a test of the balance between photosynthesis and the use of assimilates by consuming organs.