Abstract:

To elucidate the roles of exogenous salicylic acid（SA）and 12-oxo-phytodienoic acid （OPDA）in regulating the antioxidant mechanisms of variegated plants，leaves of different phenotypes of Sinobambusa tootsik f. albostriata were treated with various concentrations of SA，OPDA，and SA + OPDA. The contents of malondialdehyde（MDA），superoxide anion（$\mathrm{O}_2^{\bar{.}}$），as well as the activities of antioxidant enzymes including superoxide dismutase（SOD），peroxidase（POD），catalase（CAT），and antioxidant enzymes involved in the ascorbate-glutathione（AsA-GSH）cycle，were determined. The results showed that treatments with 0.5 mmol · L^-1 SA，30 μmol · L^-1 OPDA，or 0.5 mmol · L^-1 SA + 30 μmol · L^-1 OPDA significantly enhanced the activities of SOD，POD，CAT，and AsA–GSH cycle enzymes in all leaf phenotypes，markedly increased glutathione（GSH）levels，and effectively scavenged the accumulated reactive oxygen species（ROS）. Comparisons among phenotypes further revealed that GSH content in variegated leaves was significantly higher than in fully white or fully green leaves，and that the white sectors of variegated leaves exhibited stronger antioxidant characteristics than the green sectors. This suggests that variegated leaves possess differentiated redox homeostasis during the formation of color sectors，and that the white tissues may elevate non-enzymatic antioxidant capacity to compensate for the oxidative pressure caused by the absence of chloroplasts，thereby contributing to the stability of the variegated pattern. Overall，SA primarily enhances basal cellular antioxidant capacity by rapidly activating antioxidant enzymes and reinforcing the AsA–GSH cycle，whereas OPDA，as an oxylipin signal，tends to modulate lipid peroxidation and stress-responsive pathways. The two signals act in a complementary manner，and their combined application more effectively reduces ROS accumulation，thereby promoting the phenotypic stability of variegated leaves.

Key words: Sinobambusa tootsik f. albostriata, leaf color, hormone crosstalk, antioxidant capacity