The photosynthetic performance of two citrus species under long-term aluminum treatment

Abstract

The effect of Al stress on leaf pigment contents, chlorophyll (Chl) a fluorescence transient, and leaf gas exchange of Citrus sinensis and Citrus grandis were investigated in sandy culture with nutrient solution (control) or supplemented by 0.5 mM AlCl3·6H2O (Al toxic) for 54 weeks. We found a significant decline of Chl a, carotenoids (Car), Ch a/b, and Car/Chl (a+b) in C. grandis caused by Al stress. Except the significant increase of Car/Chl (a+b), no remarkable difference was found in C. sinensis. The Al-induced downregulation of CO2 assimilation was related to the imbalance of reduction and oxidation of primary quinone acceptor of PSII in two Citrus species. Compared to C. grandis, increasing ratio of Car/Chl (a+b) for photooxidation protection and decreasing inhibition of electron transfer contributed to electron conversion efficiency maintenance of PSII under Al stress in C. sinensis, a relatively Al-tolerant species.