Effects of 4f Electron Characteristics and Alternation Valence of Rare Earths on Photosynthesis: Regulating Distribution of Energy and Activities of Spinach Chloroplast

Chloroplasts were isolated from spinach treated with LaCl3, CeCl3, and NdCl3. Because of owning 4f electron characteristics and alternation valence, Ce treatment presented the highest enhancement in light absorption, energy transfer from LHCⅡ to PSⅡ, excitation energy distribution from PSⅠto PSⅡ, and fluorescence quantum yield around 680 nm. Compared with Ce treatment, Nd treatment resulted in relatively lower enhancement in these physiological indices, as Nd did not have alternation valence. La treatment presented the lowest enhancement, as La did not have either 4f electron or alternation valence. The increase in activities of whole chain electron transport, PSⅡ DCPIP photoreduction, and oxygen evolution of chloroplasts was of the following order: Ce>Nd>La>control. However, the photoreduction activities of spinach PSⅠ almost did not change with La, Ce, or Nd treatments. The results suggested that 4f electron characteristics and alternation valence of rare earths had a close relationship with photosynthesis improvement.