Assessment of P700 Redox State of Tomato Plants Under Conjugated Influence of Elevated Temperature and Fusarium Oxysporum Infection by the Method of Differential Absorption Photometry Using Technology of Saturating Light Pulse

Abstract

Using the method of differential absorption photometry and the technology of sequential saturating light pulses of modulated frequency, the kinetics of P700 oxidation/reduction in the leaves of the upper tier of tomato plants was studied under the influence of elevated temperature (40°C, 3 h) and infection with Fusarium oxysporum and their conjugated action. Thermal exposure reduced the level of P700 oxidation, the quantum yield of photochemical reactions of photosystem I (PSI) and increased the non-photochemical energy dissipation on the acceptor side of PSI. At the same time, in heat-treated plants, the contribution of the electron flow catalyzed by ferredoxin-plastoquinone reductase (FQR) decreased and the proportion of cyclic electron transport dependent on the NADH dehydrogenase-like complex (NDH) increased. When plants were infected with the pathogenic fungus Fusarium oxysporum, a decrease in the quantum yield of photochemical reactions of PSI and a significant increase in non-photochemical energy dissipation on the acceptor side of PSI were observed. The conjugated effect of elevated temperature and Fusarium oxysporum enhanced the suppressive effect of both stress factors on the photoinduced oxidation of P700 and activated non-photochemical energy dissipation on both the acceptor and donor sides of PSI. At the same time, the suppression of linear and FQR-dependent cyclic electron flows induced by Fusarium wilt and elevated temperature was compensated by the activation of NDH-dependent electron transport.