Local action of moderate heating and illumination induces propagation of hyperpolarization electrical signals in wheat plants

Abstract

Electrical signals (ESs), which are generated in irritated zones of plants and propagate into their non-irritated parts, are hypothesized to be an important mechanism of a plant systemic response on the local action of adverse factors. This hypothesis is supported by influence of ESs on numerous physiological processes including expression of defense genes, production of stress phytohormones, changes in photosynthetic processes and transpiration, stimulation of respiration and others. However, there are several questions, which require solution to support the hypothesis. Particularly, the non-physiological stimuli (e.g., strong heating or burning) are often used for induction of ESs; in contrast, the ES induction under action of physiological stressors with moderate intensities requires additional investigations. Influence of long-term environmental factors on generation and propagation of ESs is also weakly investigated. In the current work, we investigated ESs induced by local action of the moderate heating and illumination in wheat plants under irrigated and drought conditions. It was shown that combination of the moderate heating (40°C) and illumination (blue light, 540 μmol m−2s−1) induced electrical signals which were mainly depolarization electrical signals near the irritation zone and hyperpolarization electrical signals (HESs) on the distance from this zone. The moderate soil drought did not influence HESs; in contrast, the strong soil drought significantly decreased amplitude of HESs. Finally, it was shown that the moderate heating could induce HESs without additional action of illumination. It was hypothesized that both hyperpolarization and depolarization ESs could be caused by the hydraulic wave.

Hyperpolarization electrical signals induced by local action of moderate heating influence photosynthetic light reactions in wheat plants

“…- Could properties of HESs measured in the current work be approximately similar to these properties showed in our previous work ( Yudina et al., 2023 )? Response on this question should additionally support/disprove the HESs participation in the photosynthetic regulation.…”

“…- Could the local action of the blue light only or the local action of the moderate heating only induce changes in NPQ and Ф PSII in wheat plants? It was previously shown ( Yudina et al., 2023 ) that the moderate heating induced HESs, which were similar to HESs caused by the local action of combination of the blue light and moderate heating; in contrast, the blue light induced HESs with decreased amplitudes. It meant that the moderate heating played a key role in the induction of HESs.…”

“…System potential is a long-term HES which can be induced by various irritations (including damages, Lautner et al., 2005 ; Yudina et al., 2022 ) and is based on a transient activation of H + -ATPase ( Zimmermann et al., 2009 ; Zimmermann et al., 2016 ). Earlier, we hypothesized that system potential can be related to propagation of the hydraulic signals with low amplitude, moderate activation of mechanosensitive Ca 2+ channels in the plasma membrane, calcium influx and relatively low increase of the calcium concentration in the cytoplasm which induces the transient activation of H + -ATPase ( Yudina et al., 2022 ; Yudina et al., 2023 ).…”

“…In our previous work ( Yudina et al., 2023 ), we investigated possibility of induction of variation potential under combined local action of moderate heating (40°C) and blue light because this combination can often influence plants under environmental conditions and its action can be local. Our results did not show propagation of variation potentials; however, combined action of the moderate heating and blue light (or the moderate heating only) induced the propagation of HESs, which were classified as system potential.…”

“…To solve this problem, we approximately repeated design of experiments from our previous work ( Yudina et al., 2023 ); however, the current work was focused on influence of the local irritations on NPQ and Ф PSII ; electrical signals were measured in separate experimental series only. The following specific questions were analyzed:…”