Effects of Shading Nets on Reactive Oxygen Species Accumulation, Photosynthetic Changes, and Associated Physiochemical Attributes in Promoting Cold-Induced Damage in Camellia sinensis (L.) Kuntze

Climate change and extreme weather affect tea growing. A competitive tea market needs quick, short-term solutions. This study evaluates the effects of various shade nets under mild and extreme cold stress on tea leaf physiology, photosynthetic alterations, antioxidant activities, and physiochemical characteristics. Tea plants were treated with SD0 (0% non-shading), SD1 (30% shading), SD2 (60% shading), and SD3 (75% shading). The 30%, 60%, and 75% shade nets shielded tea leaves from cold damage and reduced leaf injury during mild and extreme cold conditions compared with SD0% non-shading. Shading regulates photochemical capacity and efficiency and optimizes chlorophyll a and b, chlorophyll, and carotenoid contents. Moreover, carbon and nitrogen increased during mild cold and decreased in extreme cold conditions. Shading promoted antioxidant activity and physiochemical attributes. In fact, under 60% of shade, superoxide dismutase, peroxidase, catalase, and omega-3 alpha-linolenic acid were improved compared with SD0% non-shading during both mild and extreme cold conditions. From these findings, we hypothesized that the effect of different shades played an important role in the protection of tea leaves and alleviated the defense mechanism for “Zhong Cha 102” during exposure to a cold environment.