| Farmland Cadmium (Cd) pollution has seriously affected crop yield and quality, it also harming people’s health through biological accumulation. Rice is one of the most universal food crops for over half of world’s population, but itself has accumulation characteristics for Cadmium, and the Cadmium enrichment ability was different in two genotypes cultivars. Further study on the response mechanism to Cd stress of two genotypes cultivars has vital significance to cultivate rice varieties which have Cd resistant ability and low accumulation of edible parts. On the basis of Cd tolerant mechanism in different plants and relative research methods, which were summarized in this study, Chuannong you 527 with low and Ⅱ you 838 with high grain Cd accumulation were selected as experiment materials, this paper has systematically studied the physiological response mechanism of rice Cadmium tolerance through study Cadmium toxic effect, the absorption and accumulation of rice to cadmium, rice antioxidant response to Cadmium stress and different forms of Cadmium. Main results for this study are as follows:(1) The effect of Cd stress on rice biomass and Cd content.Research on the effect of cadmium (Cd) on the dry weight overground, the dry weight; underground, root morphology index and Cd content of the two genotypes cultivars was done. The results showed that the Cd showed inhibition for dry matter accumulation and root morphology, Chuannong you 527 was significantly lighter than Ⅱ you 83. Under 25μM Cd concentration treatment, the difference between the dry matter accumulation content and root morphology of Chuannong you 527 and CK was not significant, but that of Ⅱ you 838 were significantly decreased as compared with controls (P< 0.05). In 50～200μM Cd concentration treatment, dry matter accumulation contents and root morphology of the two genotypes cultivars were significantly decreased as compared with controls, the decreasing amplitude of Ⅱ you 838 was significantly higher than Chuannong you 527. From the Cd accumulation contents in roots and shoots of two genotypes cultivars, the roots has intercepted more than 70% of Cd, and the Cd intercept ability of Chuannong you 527 is better than that of Ⅱ you 838.200μM Cd concentration treatment after one week, the content of Chuannong you 527 Cd in roots is 16 times over that of the control, Ⅱ you 838 is 14.22 times over that of the control. Therefore, the Cd tolerance of Chuannongyou 527 was stronger than that of Ⅱ you 838.(2) The oxidative damage induced by Cd stress and its effects on antioxidant system.Cd stress has not only caused serious lipid peroxidation in two different gene types, but also caused the response of the antioxidant system. But the response degree of two genotypes cultivars to Cd stress were different, compared with Chuannong you 527, the lipid peroxidation of lipid peroxidation was more serious and its active oxygen accumulation amounts was also higher in Ⅱ you 838, While the antioxidants contents of GSH and AsA, the ratio of GSH/GSSG to AsA/DHA and the activity of antioxidant enzymes of Ⅱ you 838 were lower than those of Chuannong you 527. It indicates that Ⅱ you 838 with high grain Cd accumulation was was more sensitive to Cd stress and the stress it suffered was more serious, the ability against antioxidant stress of Ⅱ you 838 was also weaker than that of Chuannong you 527. Moreover, the Non-protein Thiols(NPTs) contents in two genotypes cultivars increase and GSH contents decrease with the increase of concentration of exogenous Cd treatment. After Cd treatment for one week and two weeks, the NPTs and GSH contents in root of Chuannong you 527 was significantly higher than that in Ⅱ you 838.(3) Analysis on the Cd forms of different genotypes cultivars under Cd stress.From the analysis on Cd ions to of two genotype cultivars we found that:with the increasing of Cd concentration and treatment time, of the contents of various forms Cd ions within two genotypes cultivars change significantly. The anion state Cd (i.e. mercapto peptides complexed Cd) in the roots of two genotype cultivars rise in the first stage, and then decrease. In the roots of Chuangnongyou 527 without Cd treatment (CK), it only took up 9.78% of the total Cd content, at 50μM Cd concentrations treatment, it increased to the maximum ratio of 35.32%. In the Control of II you 838, anionic Cd merely took up 7.04% (CK treatment) of total Cd content, at 25μM Cd concentrations treatment, Cd concentration reach the highest ratio of 30.96%. It is clear to be seen, the amplification of anionic Cd content in the root of Chuangnongyou 527 was higher than Ⅱ you 838, and appeared an increasing trend under 50μM Cd concentrations treatment. From the changes of cation Cd(Removable cadmium ion), cation Cd in roots of Ⅱ you 838 accounted for total Cd was increased with the increase of Cd concentration treatment, while that in the roots of Chuannong you 527 changes in small ranges. It shows that the root system of Chuannong you 527 have the stronger ability that adsorption and complexation Cd than it of Ⅱ you 838, it also has higher inhibition efficiency to restrain Cd transfer to overground part. |
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