Local Action of Moderate Heating and Illumination Induces Electrical Signals, Suppresses Photosynthetic Light Reactions, and Increases Drought Tolerance in Wheat Plants

Local actions of stressors induce electrical signals (ESs), influencing photosynthetic processes and probably increasing tolerance to adverse factors in higher plants. However, the participation of well-known depolarization ESs (action potentials and variation potentials) in these responses seems to be rare under natural conditions, particularly in the case of variation potentials, which are induced by extreme stressors (e.g., burning). Earlier, we showed that the local action of moderate heating and illumination can induce low-amplitude hyperpolarization ESs influencing photosynthetic light reactions in wheat plants cultivated in a vegetation room. In the current work, we analyzed ESs and changes in photosynthetic light reactions and drought tolerance that were induced by a combination of moderate heating and illumination in wheat plants cultivated under open-ground conditions. It was shown that the local heating and illumination induced low-amplitude ESs, and the type of signal (depolarization or hyperpolarization) was dependent on distance from the irritated zone and wheat age. Induction of depolarization ESs was not accompanied by photosynthetic changes in plants under favorable conditions or under weak drought. In contrast, the changes were observed after induction of these signals under moderate drought. Increasing drought tolerance was also observed in the last case. Thus, low-amplitude ESs can participate in photosynthetic regulation and increase tolerance to drought in plants cultivated under open-ground conditions.