Abstract: Taking cut flower chrysanthemum ‘Jinba’ as test material, the effects of exogenous Ca²⁺ on its photosynthetic system and antioxidant enzyme activities under high temperature stress were investigated, with the possible action mechanisms of Ca²⁺ discussed. The results showed that under high temperature stress, Ca²⁺ addition greatly inhibited the net photosynthesis rate (P_n) and quantum yield of PSⅡ electron transport (Φ_PSⅡ). After 24 h treatment, the P_n and Φ_PSⅡ were increased by 31.11% and 21.88%, respectively, and the initial fluorescence (F_o) decreased by 13.19%, compare with the control. Ca²⁺ addition also greatly enhanced the activities of SOD, POD and CAT, and thus, the active oxygen was scavenged timely. After 24 h treatment, the MDA accumulation and REC were 29.20% and 35.81% lower than the control, respectively. In conclusion, Ca²⁺ addition could efficiently protect chrysanthemum leaves from the damage in photosynthetic apparatus under shortterm high temperature stress.

Key words: lysosome, pollution, biomarker, lysosomal membrane stability, neutral red retention time.