Limitation of photosynthetic processes in photosystem II in alpine mosses exposed to low temperatures: Response of chlorophyll fluorescence parameters

Abstract

In this study, we evaluated the effects of low and sub-zero temperature on the fast chlorophyll fluorescence transient (OJIP) and OJIP-derived parameters in 4 different mosses: Sphagnum girgensohnii, Polytrichum formosum, Hylocomium splendens and Pleurozium schreberi. The low temperature stress was applied on the mosses for 90 min. at 3 different temperatures (5°C, -1°C and -10°C). To investigate the effects of this stress on the functioning of photosystem II (PS II), the chlorophyll fluorescence measurements were taken at control temperature (22°C) and, after a 90 min. acclimation period, at each experimental temperature. The shape of OJIP curves and chlorophyll fluorescence parameters were found temperature-dependent in all the species. The mosses differed in their sensitivity to the stress but general trends in response to low temperature were similar. The results support the idea that S. girgensohnii is less resistant to low temperature stress than the other species. We were also interested in the K and L steps in OJIPs, representing different disorders caused by low temperature. The K-step was seen in P. formosum and P. schreberi and the L-step in H. splendens and S. girgensohnii.