Effects of cerium on key enzymes of carbon assimilation of spinach under magnesium deficiency.

The mechanism of the fact that cerium improves the photosynthesis of plants under magnesium deficiency is poorly understood. The main aim of the study was to determine the role of cerium in the amelioration of magnesium deficiency effects in CO(2) assimilation of spinach. Spinach plants were cultivated in Hoagland's solution. They were subjected to magnesium deficiency and to cerium chloride administered in the magnesium-present Hoagland's media and magnesium-deficient Hoagland's media. The results showed that the chlorophyll synthesis and oxygen evolution was destroyed, and the activities of Rubisco carboxylasae and Rubisco activase and the expression of Rubisco large subunit (rbcL), Rubisco small subunit (rbcS), and Rubisco activase subunit (rca) were significantly inhibited, then plant growth was inhibited by magnesium deficiency. However, cerium promotes the chlorophyll synthesis, the activities of two key enzymes in CO(2) assimilation, and the expression of rbcL, rbcS, and rca, thus leading to the enhancement of spinach growth under magnesium-deficient conditions.