The effect of cerium (III) on the chlorophyll formation in spinach

The effect of Ce3+ on the chlorophyll (chl) of spinach was studied in pot culture experiments. The results showed that Ce3+ could obviously stimulate the growth of spinach and increase its chlorophyll contents and photosynthetic rate. It could also improve the PSII formation and enhance its electron transport rate of PSII as well. By inductively coupled plasma-mass spectroscopy and atom absorption spectroscopy methods, it was revealed that the rare-earth-element (REE) distribution pattern in the Ce3+-treated spinach was leaf > root > shoot in Ce3+ contents. The spinach leaves easily absorbed REEs. The Ce3+ contents of chloroplast and chlorophyll of the Ce3+-treated spinach were higher than that of any other rare earth and were much higher than that of the control; it was also suggested that Ce3+ could enter the chloroplast and bind easily to chlorophyll and might replace magnesium to form Ce-chlorophyll. By ultraviolet-visible, Fourier transform infrared, and extended X-ray absorption fine structure (EXAFS) methods, Ce3+-coordinated nitrogen of porphyrin rings with eight coordination numbers and average length of the Ce-N bond of 0.251 nm.