WHEAT GENOTYPES DIFFER IN ZN EFFICIENCY WHEN GROWN IN CHELATE-BUFFERED NUTRIENT SOLUTION

Ten Triticum aestivum and two Triticum turgidum conv, durum genotypes were grown in chelate-buffered nutrient solution at Zn supplies rangin g from deficient to sufficient (free Zn activities from 2 to 200 pM, p Zn from 11.7 to 9.7). The critical level of Zn ion activity in solutio n for healthy growth of wheat plants was around 40 pM. Genotypes diffe red in the growth response: those classified as Zn-efficient suffered less reduction of shoot growth and did not change the rate of root gro wth at a Zn supply quite deficient for Zn-inefficient genotypes. Root growth of Zn-inefficient genotypes increased at deficient Zn supply. T he shoot/root ratio was the most sensitive parameter of Zn efficiency; Zn-efficient genotypes showed less reduction in the ratio when grown at deficient compared to sufficient Zn supply. Classification of wheat genotypes into Zn-efficient and Zn-inefficient groups after screening in chelate-buffered nutrient solution corresponded well with classifi cation obtained in field experiments on Zn-deficient soil.