Simi. R¹, Subin. M.P^1,

The heavy metal chromium (Cr) is considered as one of the most hazardous metal ion which hampers crop productivity by contaminating both soil and water due to higher solubility. The present study evaluated the impact of different levels of hexavalent chromium (Cr^VI) stress on the morphological and physiological growth performance of Amaranthus dubius. The morphological growth parameters such as length of shoot, root and total plant, fresh and dry biomass accumulation, root/shoot ratio and total leaf number and leaf area/plant recorded progressive reduction along with the progressive increase in the Cr^VI stress, with certain exceptions with respect to the length of root and total plant at initial level Cr^VI stress and root/shoot ratio at higher level concentrations. With respect to physiological parameters, 1mg Cr/kg soil treatment caused a stimulatory action on stomatal conductance (g_S), intercellular CO₂ concentration (C_i) and net photosynthetic rate (P_N) while further enhancement in the concentration of Cr^VI is inhibitory in action. The Cr^VI toxicity at higher level stresses of 50mg Cr/kg soil and above has significant deleterious effects and the tolerance index is reduced to 6.1 - 2.9% and inhibition of plant growth enhanced to 93.9 - 97.1% in terms of biomass yield compared to control plants.

Amaranthus dubius, Cr^VI toxicity, physiological and morphological growth