Abstract: By using PAM-2000 portable chlorophyll fluorometer and HCM-1000 photosynthesis measurement system, this paper measured the initial fluorescence (F_o), maximal photochemical efficiency of PSII (F_v/F_m), maximal fluorescence (F_m), amount of inactive PSⅡ reaction centers (F_i-F_o), proportion of Q_B-non-reducing PSⅡ reaction centers［(F_i-F_o)/(F_p-F_o)］, and net photosynthetic rate (P_n) of strawberry leaves under conditions of elevated CO₂ (700 μl·L^-1) and ambient CO₂ (390 μl·L^-1) at three levels of nitrogen application (12, 4 and 0.4 mmol·L^-1). The results showed that there was a significant joint effect between CO₂ and N on the photoinhibition of strawberry leaves. Under elevated CO₂ condition, the P_n in treatment 12 mmol N·L^-1 increased by 62.7%, while that in treatments 4 and 0.4 mmol N·L^-1 decreased by 7.4% and 21.3%, respectively. When exposed to high light and subsequently recovered in dark for 4 hours, the strawberry leaves in treatment 12 mmol N·L^-1 showed less changes of F_m and F_v/F_m in elevated CO₂ than in ambient CO₂, while those in treatments 4 and 0.4 mmol N·L^-1 were in adverse, suggesting that for the strawberry leaves in elevated CO₂, nitrogen deficiency could result in an acclimatized decrease of photosynthesis and an increase of photoinhibition.

Key words: Larch plantation, Rhizosphere soil, Organic phosphorus forms, Availability