Distribution mechanism and physiological roles of inorganic ion gradient in a leaf

Abstract

Maintenance of inorganic ion environment is essential for keeping life activities. In plants, however, it is remaining to be resolved how inorganic ions are distributed and accumulated in a leaf. Recently we found that each inorganic ion had a unique gradient within a leaf. For example K⁺ and NO^3- contents in the basal tissue of a leaf was much lower than in a tip. PO₄^3- content of the tissue was constant through a whole leaf. The ion gradients of protoplast isolated from different places of a leaf from the bottom to tip are similar to those of tissues. To discuss mechanisms of the formation of inorganic ion gradients we compared expression levels of known ion transporters in a leaf by using realtime-PCR. To resolve the physiological roles of inorganic ion gradients, we investigated activities of photosynthesis by using 2D-PAM.