Studies on the physiological effects of excess nickel on rice seedlings
Date Issued
2004
Date
2004
Author(s)
Lin, Yu-Ching
DOI
zh-TW
Abstract
The main purposes of this thesis were to investigate (1) the possible mechanism of the accumulation of proline and NH3 in response to excess Ni in detached leaves of rice (Oryza sativa L. cv. Taichung Native 1), (2) the effect of excess Ni on growth and oxidative stress of rice seedling roots, and (3) the effect of excess Ni on reserve mobilization of rice grains during germination. The main results are outlined as follows:
NiSO4 was effective in inducing proline and NH3 accumulation in detached rice leaves under light condition. Excess Ni had no effect on relative water content of detached rice leaves, suggesting that Ni-induced accumulation of proline and NH3 is unlikely due to water deficit. Proline accumulation induced by excess NiSO4 was related to proteolysis, an increase in proline dehydrogenase specific activity, and a decrease in proline utilization. NH3 accumulation induced by excess NiSO4 was related to a decrease in glutamine synthetase activity.
The inhibition of root growth by NiSO4 is closely associated with accumulation of Ni2+ in roots. Ni-inhibited root growth was found to be pH independent. The accumulation of H2O2 and an increase in cell wall peroxidase activity against ferulic acid in NiSO4-treated root might be a mechanism of Ni-inhibited root growth of rice seedlings. The accumulation of lignin and proline was also associated with root growth inhibition caused by NiSO4. H2O2 accumulation in roots induced by NiSO4 was related to an increase in diamine oxidase activity. NiSO4 was effective in increasing the content of malondialdehyde, and activities of superoxide dismutase and ascorbate peroxidase activity.
NiSO4 had no effect on endosperm reserve mobilization of rice grains or dehulled rice grains during germination. Evidence is provided to show that the hull is a barrier against influx of Ni to endosperm. Excess Ni had no effect on the activities of protease and
Subjects
鎳
毒害
幼苗
水稻
rice
seedling
Nickel
Type
thesis
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