Effects of Mg2+on spectral characteristics and photosynthetic functions of spinach photosystem II

Abstract: In the present paper we report the results obtained with the photosystem II (PSII) isolated from spinach treated by MgCl2, and studied the effect of Mg2+ on spectral characteristics and photosynthetic functions of PSII. The results showed that Mg2+ treatment at a suitable concentration could significantly increase the absorption intensity of PSII and the intensity ratio of Soret band to Q band of chlorophyll-a. The treatment also elevated the excited peak intensity at 230, 278 and 343nm, and the emitted peak intensity at 304 and 682nm, and the ratio of F 278/F 230, respectively. The results implied that Mg2+ increased absorbance for visible light, improving energy transfer among amino acids within PSII protein complex and accelerating energy transport from tyrosine residue to chlorophyll-a. The photochemical activity and oxygen evolving rate of PSII were also enhanced by Mg2+. This is viewed as evidence that Mg2+ can promote energy transfer and oxygen evolution in PSII of spinach. [Copyright &y& Elsevier]