Abstract: In order to analyse the adaptation potential of tomato shoots to a sudden increase in Cd concentration, tomato plants (Solanum lycopersicum L.; cultivar Ailsa Craig) were exposed under controlled environmental conditions to a high dose of this heavy metal (250 礛 CdCl2) in nutrient solution for 7 and 14 days. Both root and shoot growth was completely inhibited but all plants remained alive until the end of the treatment. Cell viability remained unaffected but the activity of the unproductive mitochondrial alternative pathway was stimulated by Cd stress at the expense of the cytochrome pathway. Cadmium concentration was higher in roots than in shoots and a decrease in the rate of net Cd translocation was noticed during the second week of stress. Cadmium decreased both leaf conductance (gl) and chlorophyll concentration. Impact on net CO2 assimilation however remained limited and soluble sugars accumulated in leaves. Photochemical efficiency of PSII (Fv/Fm) was not affected despite a decrease in the number of reaction centers and an inhibition of electron transfer to acceptors of PSII. It is concluded that tomato shoot may sustain short term exposure to high doses of cadmium despite growth inhibition. This property implies several physiological strategies linked to both avoidance and tolerance mechanisms.

Key words: cadmium, heavy metals, tomato