Effects of N fertilization on root development and activity of water-stressed cotton (Gossypium hirsutum L.) plants
2008
Liu, Rui-Xian | Zhou, Zhi-Guo | Guo, Wen-Qi | Chen, Bing-Lin | Oosterhuis, D. M. (Derrick M)
The objective of this investigation was to study effects of nitrogen on drought resistance in terms of changes in cotton (Gossypium hirsutum L.) root dry matter accumulation, N concentration, antioxidant enzyme activities and root vigor during short-duration water stress (withholding water for 8 days and then permitting to 10 days recover by re-watering). Cotton plants were grown in pots with three N levels (0, 240, and 480kgNha⁻¹). Soil-relative water content decreased with increasing N supply during the soil water stress period, while leaf area, dry matter production and N accumulation were enhanced. The root/shoot ratio and root-N/shoot-N ratio increased with water stress, and were smallest at 240kgNha⁻¹. Application of N increased the activities of peroxidase (POD) and catalase (CAT) of cotton root, but decreased superoxide dismutase (SOD) activity during water stress as well as during recovery. Malondialdehyde (MDA) content was significantly (p <0.05) increased, and was lowest in the 240kgNha⁻¹ N treatment during water stress. At the 10th day after soil re-watering, MDA content of 240kgNha⁻¹ was similar to that of 480kgNha⁻¹, but less than that of 0kgNha⁻¹. The root vigor, which was debased by water stress, was the highest at 240kgNha⁻¹. After soil re-watering, N application promoted root vigor. The trends of net photosynthetic rate were the same as that of root vigor during water stress. These results suggest that appropriate N supply (240kgNha⁻¹ in this investigation) may contribute to drought resistance of cotton plants by adjusting the antioxidant enzyme activities of root, debasing lipid peroxidation and boosting root vigor during short-duration water stress (withholding water for 8 days in this investigation), however, excessive N supply (480kgNha⁻¹) had a deleterious effect on plant drought resistance.
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