Impact of Local Damage on Transpiration of Pea Leaves at Various Air Humidity

Abstract

Local damages induce a wide spectrum of functional responses in intact parts of the plant, including changes in transpiration and CO₂ assimilation, which may be associated with propagating variation potential (VP). In the present work carried out on pea (Pisum sativum L.) plants, an analysis of the influence of local burn leading to generation of VP on transpiration and CO₂ assimilation under conditions of different air humidity was conducted. It was shown that VP induced multiphase changes in these physiological functions in intact pea leaf, including rapid lowering their parameters, slow elevation of them, and prolonged dropping transpiration and assimilation. Analysis of the impact of air humidity on these processes showed that quick and long lowering transpiration was significantly suppressed under the conditions of high humidity, while slowly increasing transpiration hardly depended on air humidity. Dependence of VP-induced CO₂ assimilation response on air humidity exhibited a similar character. Additional correlation analysis of amplitudes of VP-induced transpiration and CO₂ assimilation changes showed that prolonged stomata closing may be the mechanism of long-term lowering assimilation of intact leaves after the action of local burn. In general, it was established that the VP-induced transpiration response is a complex combination of activation and suppression of transpiration, and the contribution of different components to the observed responses depends on air humidity.