High temperature improves photosynthetic electron transport but reduces stomatal conductance in flooded tomato plants

SANCHEZ, LEONARDO; VIDOZ, MARÍA LAURA; MIGNOLLI, FRANCESCO

Congreso; XXXIV Reunión Argentina de Fisiología Vegetal; 2023

The combination of two or more adverse climatic events may have severe effects on crops since the negative consequences of each stress could add up. This work studied the effect of the combination between high temperature and flooding on the photosynthetic adjustments in tomato leaves. Tomato plants of the cv Ailsa Craig were maintained under regular irrigation and flooded conditions and at either an optimal temperature of 25.8 ºC ±1.0 (OT) or high temperature of 35.8 ºC ±2.3 (HT). After six days, stomatal conductance and chlorophyll fluorescence measurements were performed with an SC-1 portable porometer (Meter-group) and a fluorometer (PocketPea, Hansatech). In HT-flooded plants, we observed signs of severe wilting in the apical part, a lower height and more signs of senescence of basal leaves compared to plants flooded at OT. Flooding stress caused a more substantial decrease in stomatal conductance in HT-flooded plants, while no difference in photosystem 2 (PSII) fluorescence parameters was observed in comparison with OT-flooded plants. However, J0RE1/RC, (Electron transport flux until PSI acceptors per PSII), J0RE1/J0ET2 (Efficiency/probability with which an electron from QuinoneB is transferred until PSI acceptors), J0RE1/ JABS (Quantum yield of the electron transport flux until the PSI electron acceptors) and DFtotal (Driving force on absorption basis) were significantly higher in HT than in OT plants, suggesting an enhanced flow of electrons towards the final photosystem I (PSI) acceptor. If, on the one hand, high temperature makes the transfer of electrons along the transport chain more efficient, on the other hand, gas exchange is more severely impaired due to flooding. Therefore, in plants subjected to flooding under high temperatures, the high flow of electrons could exacerbate the risk of photooxidative damage as the limitation of stomatal conductance and CO2 supply might hamper downstream reactions, i.e. the Calvin–Benson cycle.