Influences of calcium deficiency and cerium on the conversion efficiency of light energy of spinach

Chloroplast absorbs light energy and transforms it into electron energy, and then converts it into active chemical energy and stable chemical energy. In the present paper, we investigated the effects of Ce3+, which has the most significant catalytic effects and similar characteristics with Ca2+, on light energy conversion of spinach chloroplasts under Ca2+-deficient stress. The results illuminated that the Hill reaction activity, electron flow both photosystems and photophosphorylation rate of spinach chloroplasts reduced significantly under Ca2+-deficient condition, and activities of Mg2+-ATPase and Ca2+-ATPase on the thylakoid membrane were severely inhibited. Meanwhile, the activity of Rubisco, which is the key enzyme of photosynthetic carbon assimilation, was also prohibited. However, Ce3+ decreased the inhibition of calcium deprivation the electron transport rate, the oxygen evolution rate, the cyclic and noncyclic photophosphorylation, the activities of Mg2+-ATPase, Ca2+-ATPase and Rubisco of spinach chloroplasts. All above implied that Ca2+-depletion could disturb light energy conversion of chloroplasts strongly, which could be reversed by Ce3+.