Acclimation to salinity in halophytic ice plant prevents a decline of linear electron transport

Abstract

Here we verified whether acclimation to the high salinity of Mesembryanthemum crystallinum plants is associated with the intensification of cyclic electron transport (CET). A strong decline in the FR-oxidizable P700 level was revealed in the intact leaves along with the salinity treatment. This effect was however not dependent on the activation of PGR5-PGRL1-dependent CET, as shown by the effects of Antimycin A addition on kinetics of P700 oxidation (measured with infiltrated leaf discs) and on electron transport at PSI (detected with isolated thylakoid membranes). In contrast, activation of this branch of CET was documented in senescing leaves of well-watered controls in concert with activation of plastoquinol oxidase. Dark rise of chlorophyll fluorescence declined during the treatment with water and with salinity, while the temporary NPQ peak during the induction of photosynthesis was strongly reduced due to salinity. Measurements in vitro in the presence of artificial electron acceptor revealed that an acclimation to salinity in M. crystallinum is associated with a better performance of linear electron transport in comparison to water-irrigated controls. We hypothesize, that acclimation to salinity creates a stronger sink for photosynthetic reducing power in comparison to that developed in non-saline conditions.