Trend of polyamine changes in the early stages of maize (zea mays L.) growth under cadmium stress

Heavy metals stress (cadmium stress) is one of the most important factors which lead to reduction of plant growth and productivity of agricultural products. One of the plant responses to heavy metal stresses is changes in polyamines contents in plants. Regarding the economic importance of maize, the effects of cadmium stress on seed germination, plant growth parameters and polyamines contents (putrescin, spermidine and spermine) were investigated in 3 days-old seedlings and the roots after 6, 12, 15 and 20 days. Polyamines analysis was performed by HPTLC. The results indicated that cadmium stress in maize is the cause of delay in seed germination and decreased plant growth parameters. Cadmium stress increased the total polyamine content as a result of 35% increase of the putrescine in 3 days-old seedlings. In general, a significant increase of putrescine was observed in the roots of the 6 days-old- and 15 days-old plants under cadmium stress. While the highest amount of spermine and spermidine was in the root of the 12 days-old plants under cadmium stress. Roots of the 15-days-old plant showed the highest content and translocation factor of cadmium. These results suggest that the changes in the amount of polyamines in maize plant under cadmium stress depend on the cadmium absorption by the plant root and the type of polyamines.