Influence of Cadmium Toxicity on Plant Growth and Nitrogen Uptake in Rice as Affected by Nitrogen Form

ABSTRACT The influence of different nitrogen (N) fertilizers on plant growth, nitrate reductase (NR) activity, and cadmium (Cd) and N accumulation in Cd-stressed rice plants was studied in a hydroponic experiment. There were three N fertilizers, i.e., ammonium sulfate [(NH4)2SO4], ammonium nitrate (NH4NO3), and calcium nitrate [Ca(NO3)2]; and three Cd levels (0, 1, and 5 μ M). The reduction in all plant growth parameters, including photosynthetic rate, chlorophyll content, and fluorescence efficiency became more predominant with the prolonged stress exposure and increased Cd level. There was no significant difference in all these parameters among three N forms when no Cd was added into the culture solution. While for the plants exposed to Cd stress (1 and 5 μ M), the difference was significant among the three N forms. The least inhibition in growth parameters was recorded in (NH4)2SO4-fed plants and the most in Ca(NO3)2-fed plants. Cd stress significantly reduced NR activity and the reduced extent was dep...