Seed Priming with Taurine Debilitates Copper Phytotoxic Effects by Maintaining Redox Balance, Ions Homeostasis and Photosynthetic Efficiency in Canola (Brassica napus L.)

Taurine (TRN) plays a paramount function in protecting against reactive oxygen species (ROS), effectively curbing lipid peroxidation in biological membranes. Additionally, TRN plays a pivotal role in the osmoregulation. Nevertheless, there is a gap in understanding the mechanisms through which TRN brings cellular homeostasis and redox balance, upholds glutathione pool, and curtails copper phytotoxic effects. The current investigation was initiated to assess the impact of TRN seed priming (0.5 and 1 mM) as a mitigative approach to counteract the phytotoxic effects of copper stress (50, 100, and 150 μM) on canola (Brassica napus L.) plants. Copper (Cu) toxicity (50, 100, and 150 μM) notably subsided growth attributes, photosystem efficiency, photosynthetic pigments, leaf relative water content, and acquisition of essential nutrients in plants. Plants encountered increased oxidative injury due to a visible surge in ROS (hydrogen peroxide and superoxide radicals), methylglyoxal, lipoxygenase activity, and lipid peroxidation. A profound increase in the activities of enzymatic antioxidants and levels of non-enzymatic compounds was recorded in plants under Cu stress. Taurine priming significantly diminished oxidative injury by promoting the antioxidant system and visibly abated methylglyoxal levels alongside increasing hydrogen sulphide and nitric oxide content. Plants subjected to TRN-priming exhibited a minimal accumulation of Cu content in aerial parts that could have curbed oxidative stress. The mitigation of oxidative stress notably improves electron transport, photosystem II integrity, and energy dissipation mechanisms. Our study conclusively illustrates that TRN-priming is an efficacious strategy for alleviating the detrimental impacts of Cu toxicity on canola plants. Taurine application reduced oxidative damage and Cu buildup inside plant parts to promote growth, chlorophyll content, ROS metabolism, and methylglyoxal detoxification.