Mediation of rapid electrical, metabolic, transpirational, and photosynthetic changes by factors released from wounds. III. Measurements of CO2 and H2O flux

By using intact plants from five angiosperm families, shifts in CO2 and H2O exchange have been demonstrated to follow the arrival of a variation potential in unharmed leaves shortly after adjacent leaves are damaged.Whether in the light or dark, the first change is a brief burst of CO2, which may well be due to a sudden breakdown of bicarbonate dissolved in the extracellular solution.In the dark, a rise in metabolic CO2 output becomes evident during the decay of the initial burst, and the output remains elevated for at least several hours.In the light, a biphasic drop in both transpiration and net CO2 uptake is underway before the initial CO2 burst has subsided. Since the decrease in CO2 uptake is larger than the increase in output in the dark, it must be due in part to decreased net photosynthetic CO2 fixation. It is plausible but as yet unproven that the biphasic photosynthetic change is a consequence of the biphasic closure of the stomata. In any case, curtailment of both transpiration and net photosynthesis, like the enhancement of dark metabolism, persists for a number of hours.