The role of the intra- and extracellular protons in the photosynthetic response induced by the variation potential in pea seedlings

Local burning induces generation and propagation of variation potential (VP) in higher plants. VP induces transient inactivation of photosynthesis, which is possibly connected with proton signal in plant cell. Analysis of the role of changes in intracellular and extracellular pH in the VP-induced photosynthetic response in pea seedlings was the aim of this work. It was shown that local burning induced VP propagation, which was accompanied with a decrease of intracellular pH and increase of extracellular pH. VP induced photosynthesis inactivation that included an increase in the nonphotochemical fluorescence quenching and a decrease in the CO2 assimilation rate. Analysis of photosynthetic responses under control and low external CO2 concentration and changes in pH showed that there were two components in the responses. The first component appeared as a fast decrease of the CO2 assimilation and increase of nonphotochemical quenching. It depended on the activity of the dark stage of photosynthesis and was connected with apoplast alkalization. The second component was presented as a slow increase of nonphotochemical quenching. It weakly depended on a dark stage and was connected with a decrease of intracellular pH.