Suppression of cadmium concentration in wheat grains by silicon is related to its application rate and cadmium accumulating abilities of cultivars

BACKGROUND: Cadmium concentration in food grains could be minimised through application of beneficial plant nutrients such as silicon. Therefore, the impact of silicon application on immobilisation of Cd in soil and its concentration in low and high shoot-Cd (LSCd and HSCd, respectively) cultivars of wheat were evaluated in a pot experiment. Selected LSCd cultivars (Iqbal-2000 and Lasani-2008) and HSCd cultivars (Inqlab-91 and Sehar-2006) were grown on artificially Cd contaminated soil at 10 mg Cd kg^-1. Three levels of Si (50, 100 and 150 mg kg^-1 soil), applied as calcium silicate (CaSiO₃), were tested. RESULTS: None of the wheat cultivars showed any symptoms of toxicity or growth retardation against applied Cd stress. Silicon applied to Cd-treated plants did not improve root and shoot dry matter; however, it increased grain yield significantly at the highest rate of application (150 mg kg^-1 soil). Similarly, Si application at 150 mg kg^-1 decreased plant available soil Cd without affecting soil pH. Silicon application not only caused a linear decrease in Cd contents of shoots and grains but also decreased its translocation from roots to shoots and grains. Decrease in shoot Cd concentration was higher in HSCd than LSCd cultivars whereas the reverse was true for Cd concentration in grains. CONCLUSION: Si addition decreased Cd concentration in wheat cultivars by causing a decrease in both plant-available soil Cd and its translocation from roots to shoots. Application of Si at 150 mg kg^-1 proved to be an effective level of Si that could significantly lower Cd concentration in wheat grains.