Photoprotection Mechanisms in wheat Plants under High Light and Cold Temperature Conditions

High light damages photosynthetic machinery, primarily photosystem II (PSII), and causes photoinhibition that can limit plant photosynthetic activity, growth and productivity. To address this issue, we investigated the basic photoprotection mechanisms including ROS scavenging activity and phenolic compounds production in wheat (Triticum aestivum L.), as a C3 plant, after treatment with low temperature (4°C) and high irradiance (450 and 850 μmol m-2 s-1). Results indicated that wheat plants showed more tolerance to low temperature. Increased tolerance in cold-treated plants was achieved through enhancement in antioxidant system activity. Plants treated with light intensity at 850 μmol m-2 s-1 showed the highest level of stress leading to lower maximal quantum yield of photosystem II (PSII) (Fv/Fm) values. In contrast, the light intensity at 450 μmol m-2 s-1 did not reduce significantly the maximal quantum yield of PSII. This may be attributed to the enhancement of catalase (CAT) activity and anthocyanin synthesis (screening of photoradiation in epidermis cells), and consequently further protection of PSII from photodamage.