Cadmium toxicity affects photosynthesis and plant growth at different levels

In this article we discuss and update some of the effects of Cd toxicity on the photosynthetic apparatus in a model crop Lactuca sativa. Seeds of L. sativa were germinated in solutions with 0, 1, 10 and 50 mu M of Cd(NO3)(2) and then transferred to a hydroponic culture medium. After 28 days, the effects of Cd on the photosynthetic apparatus of lettuce were analysed. Exposure of lettuce to 1 mu M Cd(NO3)(2) affected already plant growth (dry biomass), but, did not induce serious damages in the photosynthetic apparatus. However, increasing concentrations of this metal to 10 and 50 mu M promoted a strong reduction of the maximum photochemical efficiency of PSII and an impairment of net CO2 assimilation rate, putatively due to Rubisco activity decrease. This ultimately results in a strong inhibition of plant growth. Nutrient uptake and carbohydrate assimilation were also severely affected by Cd.