Physiological Stability in Poplar Leaves

Without the influence of external factors, the physiological indexes of the mature leaves (functional leaves) of poplar are relatively stable [71 (link)]. The 5th–7th healthy mature leaves of each plant from the four treatment groups were sampled and quickly placed in the ice box. Then, the physiological and biochemical indexes were measured in the laboratory immediately. A total of 0.2 g of each leaf sample was weighted and ground with 1.5 mL of the phosphate buffer. The homogenized liquid was transferred to a 5 mL tube for the determination of malonaldehyde (MDA), hydrogen peroxide (H₂O₂), Superoxide Dismutase (SOD), Catalase (CAT), and Ascorbate peroxidase (APX). The content of MDA was determined using the Thiobarbituric acid method, and the absorption values at 600 nm, 532 nm, and 450 nm wavelengths were recorded [72 (link)]. The contents of H₂O₂, SOD, CAT, and APX were determined with the Hydrogen Peroxide assay kit, Total Superoxide Dismutase (T-SOD) assay kit (Hydroxylamine method), Catalase (CAT) assay kit (Visible light), and Ascorbate peroxidase (APX) test kit (Nanjing Jian cheng Biological Engineering Institute, Nanjing, China), respectively. There were 9 biological replicates and 3 technical replicates for each treatment.