Comparison of some photoprotection mechanisms of winter and spring leaves of Jasminum fruticans under drought conditions

In this study, the effects of drought on some physiological characteristics of winter and spring leaves of jasmin (Jasminum fruticans L.) were examined in plants grown in pots and treated with or without water stress for 25 days. Our results showed significant difference in pigment content and phenolic metabolism between winter and spring leaves of jasmine during spring season. In this study, winter leaves showed the higher Chlb, carotanoids, total phenol, flavonoids as well as phenylalanine ammonia lyase (PAL) activity, and relative water content (RWC) as compared to spring leaves, indicating winter leaves are sufficient in their capacity for non-photochemical energy dissipation via these mechanisms. However, water stress did not significantly affect these parameters. Drought significantly increased the amount of malondoialdehyde (MDA) and hydrogen peroxide (H2O2) following significant enhancement of peroxidase (POD) activity. However, in winter and spring leaves treated with water stress, decrease in the maximal quantum efficiency of PSII (Fv/Fm) was not statistically significant. In contrary, spring leaves exhibited a significant decrease in the performance index (PIabs) parameter under drought conditions. Notably, the kinetics of the OJIP chlorophyll fluorescence curve exhibited a quicker difference between winter and spring leaves of jasmine under well watered conditions. Thus, photosynthetic apparatus of winter leaves maintained a higher PIabs during spring season, and showed more tolerance to water stress by dissipating excess light energy by carotenoids; and by screening of photoradiation by phenolic compounds.