The growth and some physiological responses of rice to Cd toxicity as affected by nitrogen form

Abstract

A hydroponic experiment was conducted to examine the effect of Cd stress on anti-oxidative enzyme activities at heading stage, yield components, root exudation and Cd and N uptake of rice plants grew in different N source i.e. (NH4)2SO4, NH4NO3 and Ca(NO3)2. The results show that the effect of Cd stress on all measured parameters were N source dependent. Cd stress (1 μM) caused a remarkable reduction in grain yield and shoot biomass, an increase in root exudation, glutathione content, Cd concentration and catalase (CAT) and peroxidase (POD) activities of rice plants. In the plants under the control (without Cd addition) N source had no distinctive effect on the above measured parameters, but the differences among the three N forms in these parameters became significant when plants were exposed to Cd stress. Cd stress significantly increased POD and CAT activities, and gultathione content, with Ca(NO3)2-fed plants having the greatest POD and CAT activities and lowest glutathione content, and (NH4)2SO4-fed plants being just opposite. Moreover, organic acid exudation varied also with N form for the Cd-stressed plants. In comparison with other two N forms, (NH4)2SO4,-treated plants had higher grain yield, N concentration and lower Cd concentration in plants. The current results indicated that (NH4)2SO4 is a better fertilizer for use in Cd contaminated soil.