Cadmium and copper stress affect seedling growth and enzymatic activities in germinating barley seeds

To assess Cd and Cu phytotoxicity, experiments focusing on germination of barley (Hordeum vulgare L. var. ‘Manel’) seeds were germinated for two days in a solution containing CdCl2 (25, 50 and 100 µM) or CuSO4 (100, 300 and 500 µM) . The growth of radicles and shoots decreased while the water content in stressed seeds remained near control values. A decline in α-amylase, acid phosphatase and alkaline phosphatase activities was also observed in endosperms while β-amylase activity was only slightly modified by heavy-metal treatments. However, Cd and Cu increased lipid peroxydation, enhanced soluble protein and sugar content even at the lowest dose and induced a significant accumulation of proline essentially in radicles. These results suggest that the inhibition of seed germination after exposure to Cd or Cu is not the consequence of reduced water uptake by seed tissues but may be due to a failure in reserve mobilization from the endosperm.