CHLORSULFURON REDUCES RATES OF ZINC UPTAKE BY WHEAT SEEDLINGS FROM SOLUTION CULTURE

Wheat plants differing in zinc efficiency (Excalibur; Zn-efficient, Ga tcher and Durati; Zn-inefficient) were grown in HEDTA chelate-buffered nutrient solution in controlled conditions and supplied with 0 or 40 mu g chlorsulfuron L-1. Zinc uptake rates of 12-d-old plants were meas ured over 80 or 90 minutes using Zn-65 added to nutrient solutions. In creasing the zinc concentration of the solution increased the rate of zinc uptake, while the percentage of zinc transported to shoots was de creased. Addition of chlorsulfuron to uptake solutions for 90 minutes did not influence rate of zinc uptake or transport of zinc to shoots. Pretreating plants with chlorsulfuron for 5 days decreased zinc uptake rates, but transport to shoots was proportionally increased. Three-da y pretreatment with chlorsulfuron was the minimum required for signifi cant differences in uptake and transport of zinc to occur. Plants expo sed to chlorsulfuron for 3 days required a further 5 days of growth in chlorsulfuron-free solutions before uptake rates recovered to control plant rates. It is concluded that chlorsulfuron deleteriously but rev ersibly affects uptake of zinc across the plasma membrane after prolon ged exposure.