Cerium relieving the inhibition of photosynthesis and growth of spinach caused by lead

Chloroplasts were isolated from spinach cultured in lead chloride-present, Ce3+-administered, cerium chloride-administered lead chloride-present Hoaglandʹs media or that of Hoaglandʹs media. The experimental study demonstrated the effects of cerium (Ce) on distribution of light energy and photochemical activities of spinach chloroplast grown in lead (Pb)-present media. It was observed that Pb2+ significantly inhibited photosynthesis in spinach, including light absorption, energy transfer from LHCII to photosystem II, excitation energy distribution from photosystem I to photosystem II, and transformation from light energy to electron energy and oxygen evolution of chloroplasts, and decreased spinach growth. However, Ce3+ treatment to Pb2+-present chloroplasts could obviously improve light absorption and excitation energy distribution in both photosystems and increase activity of photochemical reaction and oxygen evolution of chloroplasts. The results suggested that Ce3+ under Pb2+ stress could maintain the stability of chloroplast membrane, and improve photosynthesis of spinach chloroplast, thus promote spinach growth.