A STUDY ON THE UPTAKE OF TRIVALENT AND HEXAVALENT CHROMIUM BY PADDY (ORYZA-SATIVA) - POSSIBLE CHEMICAL MODIFICATIONS IN RHIZOSPHERE

The uptake and translocation of chromium by paddy (Oryza sativa L. Arb ario) was studied using radiotracers. Chromium was supplied as Cr III and Cr VI through irrigation water and plants were grown in sand and s oil culture. The uptake of chromium for both the oxidation states and culture types was found to increase more or less linearly with the inc rease in chromium concentration though with different slopes. The rate of increase of the uptake when compared to the increase in feed conce ntration indicates that the uptake by roots is mediated possibly throu gh a passive mechanism. For a given concentration of feed, values of c hromium in mu g g(-1) dry matter in shoot and grain did not vary signi ficantly either for different oxidation states of feed chromium or cul ture type. The order of uptake for paddy shows a considerably differen t pattern when compared to onion, maize and groundnut. This has been q ualitatively explained on the basis of the different chemistry of chro mium in the rhizosphere of paddy. The amount of chromium translocated to grain was also considerably less compared to the other three crops.