Effect of lanthanide chloride on photosynthesis and dry matter accumulation in tobacco seedlings.

To investigate the physiological effects of rare earth ions, we have studied the effect of LaCl3 on the photosynthetic light reactions in tobacco (Nicotiana tobacum). When treated with 5-20 mg/L LaCl3 in Hoagland solution by water culture, the dry matter accumulation of different parts in tobacco, the content of chlorophyll increased gradually, but decreased when the concentration of LaCl3 was > or = 50 mg/L. The optimum concentration for growth appeared to be about 20 mg/L of LaCl3 in nutrient solution. La3+ promoted the activities of the Hill reaction, Mg2(+)-ATPase, and stimulated the rate of photophosphorylation in chloroplast at low concentrations, but inhibited them at high concentrations. It is concluded that La3+ stimulated the growth of tobacco seedlings and accelerated the photosynthetic light reactions at suitable concentration in vivo.