He–Ne laser illumination ameliorates photochemical impairment in ultraviolet-B stressed-wheat seedlings via detoxifying ROS cytotoxicity

Resumo

The protective effect and physiochemical mechanism of He-Ne laser illumination on photochemical impairment were evaluated by investigating chlorophyll fluorescence characteristics, photochemical activities of two photosystems, reactive oxygen species (ROS) levels and antioxidant enzyme activities in UV-B stressed-wheat (Triticum aestivum L.) seedlings. The results showed that enhanced UV-B stress significantly inhibited plant growth, reduced photosynthetic pigment content and antioxidant enzyme activities, while increased intracellular ROS levels. Meanwhile, UV-B stress also altered chlorophyll fluorescence characteristics and photochemical activities of seedlings. However, He-Ne laser illumination markedly improved photochemical activities and photosynthetic efficiency of two photosystems through detoxifying excessive ROS productions. Illumination with white fluorescent lamps (W), red light (R), or red light, then far-red light (R + FR) had not alleviated the inhibitory effect of UV-B stress on plant growth, suggesting that He-Ne laser illumination might be responsible for UV-B-stressed seedlings due to its regulation for intracellular ROS levels and plant oxidant/antioxidant balance. Furthermore, the laser alone also showed a positive impact on photochemical activities of photosystem I and photosystem II in plants.