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 dependent on N forms, with greatest reduction in Ca(NO₃)₂-fed plants and least in (NH₄)₂SO₄-fed plants. Furthermore, a significant difference was noted among the three N forms in Cd and N concentrations and accumulation under Cd stress, with (NH₄)₂SO₄ plants having less Cd uptake and more N accumulation. The differences in growth parameters, NR activity and Cd and N accumulation among N forms in Cd stressed plants indicate the possibility to alleviate Cd toxicity through reasonable utilization of N form in Cd contaminated soil.

Keywords:

• Nitrogen source
• cadmium
• growth
• photosynthesis
• rice

ACKNOWLEDGMENTS

We are deeply grateful to the Department of Science and Technology of Zhejiang (2005C12024) and Zhejiang Natural Science Foundation (Z304104) for financial support to this research.

Notes

^†Within each column, values followed by the same letter are not significantly different at 95% probability level

^‡representing the significant difference compared with the control (no Cd addition).

^†Within each column, values followed by the same letter are not significantly different at 95% probability level

^‡representing the significant difference compared with the control (no Cd addition).

^†Within each column, values followed by the same letter are not significantly different at 95% probability level

^‡representing the significant difference compared with the control (no Cd addition).

^†Within each column, values followed by the same letter are not significantly different at 95% probability level

^‡representing the significant difference compared with the control (no Cd addition).

^†Within each column, values followed by the same letter are not significantly different at 95% probability level

^‡representing the significant difference compared with the control (no Cd addition).