The early response of Arabidopsis thaliana to cadmium- and copper-induced stress

To investigate the early (first day) effects of cadmium and copper poisoning, adult plants of thale cress (Arabidopsis thaliana L) were treated with nutrient solution containing 50-100 mu M Cd2+ or Cu2+. The main effect of Cu2+ treatment was a temporary reduction in F-v/F-m with respect to controls, which is suggestive of transient damage to the antenna. By contrast, within 3 h of Cd2+ treatment, leaf chlorophyll and carotenoid contents and photochemical operating efficiency (phi(II)) fell with respect to controls, while q(N) and ETR rose and F-v/F-m remained essentially unaltered. Protein content fell initially and rose within 24 h, and a transient widespread increase in H2O2 production around hour 6 evolved by hour 24 to more intense production around leaf veins when plants were watered with Cd2+. These alterations were not due to induced nutrient deficiency, and are interpreted as suggestive of damage to the biochemical phase of photosynthesis. The loss of pigment, and fall in phi(II) without an accompanying fall in F-v/F-m might be used as early signs of cadmium poisoning. It is assumed that Cu2+ was less harmful than Cd2+ because of its tendency to remain in roots and because, as a fairly abundant essential micronutrient, it is subject to endogenous mechanisms of regulation. (C) 2011 Elsevier B.V. All rights reserved.