Age-dependent changes of photosynthetic responses induced by electrical signals in wheat seedlings

Electrical signals in plants, namely, the action potential (AP) and variation potential (VP) alter the activity of many processes, including photosynthesis. The functional responses induced by electrical signals vary in direction and amplitude, which might be determined by variable conditions of plants prior to stimulation, by the development stage in particular. In this work, the parameters of VP-induced photosynthetic responses were analyzed at various stages of wheat seedling development. Local wounding of the second leaf in wheat plants induced the propagation of VP and altered the activity of photosynthesis at a distance from the wound location. The amplitude of VP was enlarged when the seedling age increased from 11 to 18 days. The VP-induced photosynthetic response changed with age both qualitatively and quantitatively. The amplitude of VP-induced changes in CO2 assimilation and nonphotochemical quenching (NPQ) increased with age, which might be due to the increase in VP amplitude and associated changes in Ca2+ and H+ concentrations. The quantum yield of photosystem II photoreaction was subject to age-dependent changes: the photochemical quantum yield (gamma(PSII)) was found to increase after VP in young leaves, whereas the decline in gamma(PSII) was observed after the VP propagation in mature leaves. The results may explain the diversity of photosynthetic responses caused by the electrical signals.