Effect of Short-Term High Temperature Stress on the Physiological Characteristics of Phyllostachys edulis Leaves

Under the global warming, frequent extreme heat poses severe threat to subtropical bamboo forest ecosystem. To investigate the physiological response mechanisms of Phyllostachys edulis under short-term high temperature stress, 2-year-old P. edulis seedlings were used as experimental materials under the condition of short-term high-temperature treatments at 35 ℃ and 45 ℃ for 15 minutes, with 25 ℃ as the control, measuring photosynthetic parameters, chlorophyll fluorescence indices, antioxidant enzyme activities (SOD/POD/CAT) and membrane lipid peroxidation (MDA). The results demonstrated that the net photosynthetic rate (Pn) of P. edulis seedlings treated with 35℃ reduced by 10.0%, the maximum fluorescence yield (Fm) and maximum photochemical efficiency (Fv/Fm) decreased by 8.2% and 4.5%, respectively (P<0.05), conversely, stomatal conductance (Gs) and transpiration rate (Tr) increased significantly by 8.5% and 155%, accompanied by the significant elevation of 2.7%, 3.9%, and 47.9% in the activities of POD, SOD and CAT, respectively (P<0.05). Under 45℃ treatment, Pn, Gs, and Fv/Fm decreased by 23.2%, 9.3%, and 13.5%, respectively, the antioxidant enzyme activities declined by 4.0%～12.3% (P<0.01). Meanwhile, intercellular CO₂ concentration and Tr surged by 20.5% and 381%, respectively, with initial fluorescence (Fo) and MDA content rising by 14.9% and 1.8%, separately (P<0.01). Correlation analysis revealed that photosynthetic rate was significantly positively correlated with Fm and Fv/Fm (P<0.05), but negatively correlated with Fo and MDA content (P<0.05) under short-term high temperature stress. The findings above suggest that P. edulis modulates its antioxidant system to cope with short-term high temperature stress, however, the continuously escalating temperatures gives rise to severe damage of the plant’s photosystem II (PSII), antioxidant defense system and membrane integrity, and ultimately causes the possibly irreversible physiological impairment. This study provides theoretical support for climate-resilient management of subtropical bamboo forests.