Effect of cadmium on growth and concentrations of cadium, ascorbic acid and sulphydryl groups in durum wheat cultivars

By using two durum wheat cultivars (Triticum durum L. cvs. Balcali-85 and C-1252) a nutrient solution experiment was carried out to study i) genotypic variation in cadmium (Cd) tolerance, ii) Cd concentrations in plants, and iii) the role of ascorbic acid and non-protein SH groups (SH: sulphydryl) in Cd tolerance. Plants were grown under controlled climatic conditions for 15 days and subjected to increasing Cd supply (0, 6, 30, 75 and 150 µM). Of the two cultivars, C-1252 showed greater sensitivity to Cd toxicity as judged from the severity of Cd toxicity symptoms on leaves. Increasing Cd supply markedly reduced the shoot and root dry weight of both cultivars, and these decreases were more marked in C-1252. Cd concentrations of plants were strongly increased by enhanced Cd supply, especially in the roots. C-1252 tended to have greater amounts of Cd in the shoots, but lower amounts in the roots than Balcali-85. Ascorbic acid concentrations in the roots and shoots were similarly affected by increasing Cd supply in both cultivars. SH concentrations were similar in the shoots of Balcali-85 and C-1252, and showed a slight increase due to Cd treatments. However, in the roots, Cd supply resulted in dramatic increases in concentrations in the SH groups, particularly in Cd-tolerant Balcali-85. The results indicate that SH-containing compounds (e.g., phytochelatins) and the retention of Cd in the roots are possibly involved in the expression of high Cd tolerance in durum wheat cultivars