Dynamic changes of leaf parameters of PSⅡ fluorescence kinetics and fast photosynthetic response curves in Artemisia ordosica

To explore the mechanisms of adaptive physiological and ecological responses of Artemisia ordosica to desert environments, the dynamic changes of the specific leaf area (SLA), leaf nitrogen content (N_mass), photosynthetic physiological parameters of PSⅡ fluorescence kinetics, and fast photosynthetic response curves of A. ordosica during growth periods were analyzed. The results showed that SLA was the highest in August, but decreased significantly in September (P <0.05), and Nmass showed the opposite tendency. The initial fluorescence (F_o), maximum fluorescence (F_m), and maximum photochemistry efficiency (F_v/F_m) of A. ordosica maintained relatively stable values throughout the growth periods. The minimum fluorescence yield (F_o′) and maximum fluorescence yield (F_m′) under stabilization light varied significantly in different growth stages, with the highest values recorded in August and the lowest in September (P < 0.05). The photosynthetic electron transfer quantum efficiency (ΦPSⅡ) and photochemistry quenching (qP) decreased with the increase of light intensity, while the non-photochemical quenching (NPQ) and photosynthetic electron transfer rate (ETR) showed the opposite trend. The ETR and NPQ of the A. ordosica leaves were the highest in September and the lowest in August under the same light intensity. The results indicated that the leaves of A. ordosica had a high ability to regulate light capture and resist photoinhibition as an adaptation to light environmental changes.