The role of external polyamines on photosynthetic responses, lipid peroxidation, protein and chlorophyll a content under the UV-A (352nm) stress in Physcia semipinnata

Physcia semipinnata was exposed to UV-A (352nm) and visible light (210, 800 and 2000mW/cm2) for 30min, 1, 2, 24, and 48h to seek the alterations in the PSII photosynthetic quantum yield, in response to radiation. Chlorophyll a fluorescence did not influence exposure to light, 210, 800 and 2000mW/cm2. Significant alterations of the photosynthetic quantum yield ratio occurred in response to increase in UV-A exposure time. The photosynthetic quantum yield ratio decreased in P. semipinnata following exposure to UV-A for 24 and 48h. The thalli of P. semipinnata treated with 1mM polyamine were not influenced during the exposure to UV-A for 24 and 48h. It was also found that exogenously spd added samples had higher chla content than spm and put added samples. In this study, we showed that lipid peroxidation levels between UV-A-treated samples and exogenously polyamine treated samples that were previously exposed to UV-A for 24 and 48h were significantly decreased. This result is the first record to indicate that external polyamines might have some protective role on photosystem II and membrane against UV-A stress.