Variation potential-induced photosynthetic and respiratory changes increase ATP content in pea leaves

Local damage induces a physiological response in higher plants by means of generation and propagation of variation potential (VP). The response includes changes in photosynthesis and respiration. The aim of the present study was to investigate the effect of these changes on adenosine triphosphate (ATP) content in pea leaves. VP was induced by local heating of the first mature leaf and registered using extracellular and intracellular electrodes. Photosynthesis and respiration were measured using Dual-PAM-100 and GFS-3000. ATP content was determined using a bioluminescence-based ATP determination kit. Two non-stimulated leaves (second and fourth) were investigated. We showed that heating induced VP that propagated into the second mature leaf, but only a slight electrical reaction was registered in the fourth mature leaf. VP-induced inactivation of photosynthesis developed in the second leaf and included two stages: short- and long-term inactivation. Local heating also caused a two-stage increase in ATP content in the second leaf, which was connected with the photosynthetic responses. Changes in photosynthesis and ATP content were not observed in the fourth leaf. The effect of VP on respiration was investigated under dark conditions. We found that variation potential induced short-term activation of respiration in the second leaf. Local heating induced ATP content increase which included only one stage under dark conditions. Changes in ATP and respiration were absent in the fourth leaf under dark conditions. Thus, VP-induced photosynthetic and respiratory changes are likely to increase ATP content in pea leaves.