鎘毒害對水稻生育與抗氧化酶的影響及其對鋅、硫和氮素形態(tài)的反應(yīng).pdf

1、Cadmium (Cd) is among the most widespread and toxic pollutants in the surface soil layer. Its toxicity in soil is becoming a severe threat to living organism worldwide.It is one of the main pollutants in paddy fields nea

2、r industrial areas and highly toxic to rice growth and development, and can be easily taken up by rice plants and enter the food chain. Thus, it is necessary to reduce Cd accumulation in rice, which is one of the most fr

3、equently consumed crops not only in China but also in the world.Therefore, precautionary measurements should be done to reduce accumulation of Cd in rice to alleviate the risk of health hazards in response to Cd-polluted

4、 soils.Several strategies have been proposed for the successful management of the Cd-contaminatedagriculturalsoils.Oneapproach,applicableonslightly contaminated soils, is aiming to screen and use low Cd-accumulating geno

5、types of crops. Secondly, the toxic effect of Cd can be decreased by application of proper chemicals and rate of essential nutrients such as Zn, S and N in Cd contaminated soil. Therefore, the selection of plant genotype

6、s with high ability to repress root uptake and shoot transport of Cd is a reasonable approach to alleviate adverse effects of Cd toxicity in crop plants.Hydroponics experiments were conducted in green house of Zhejiang U

7、niversity,Hang Zhou, China during 2002-2004, to study the genotypic variation in tolerance to Cd toxicity and its interaction with Zn, S and N based on the measurement of plant growth parameters, photosynthetic rate and

8、chlorophyll content, biomass accumulation, interacting effect of Zn, S and N on Cd uptake, changes in antioxidative defense system both in roots as well as shoots and lipid peroxidation.Plants were grown under controlled

9、 environmental conditions, and subjected to different Cd concentrations ranging from 0to 5 μM.In the first experiment the effects of Cd toxicity on growth, lipid peroxidation,antioxidant enzymes and Cd accumulation in di

10、fferent plant organs were studied in two rice cultivars, Bing 97252, relatively Cd-tolerant cultivar and Xiushui 63,relatively sensitive one. Plants were exposed to 0, 0.1, 1 and 5 μM Cd. Cd stress inhibited plant height

11、 and chlorophyll content, altered melondialdehyde (MDA)content and activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD). Roots and shoots responded differently to Cd in terms of antioxidant enzym

12、e activity. Generally the activities of SOD, POD and CAT decreased with increase in Cd level, while the activity of MDA increased with increase in Cd level. With the increase in Cd concentration in medium, MDA content in

13、 shoots and roots of Xiushui 63 increased at much higher rate than Bing 97252 at both growth stages. A significant decrease in chlorophyll content, plant height and photosynthetic rate has been noted in higher Cd treatme

14、nt (1 and 5 μM). The accumulation of Cd in roots and shoots increased with Cd levels in medium, Xiushui63 being higher than Bing 97252.The second experiment was conducted to investigate the alleviating effect of Zn on gr

15、owth inhibition and oxidative stress caused Cd toxicity by using the same rice cultivars. The treatments were consisted of three Zn (0, 0.2 and 1 μmol) and three Cd levels (0, 0.1 and 1 μMI). The results showed that addi

16、tion of Zn into medium solution demonstrated the distinct effect of alleviating Cd toxicity, which may be reflected by the significant increase in growth parameters, including plant height and biomass, chlorophyll conten

17、t and photosynthetic rate, and the marked decrease in MDA content and the activities of anti-oxidative enzymes relative to the control (without Zn) when the plants were exposed to Cd stress. However it is noted that Zn i

18、ncreases shoot Cd concentration at higher external Cd level, probably due to the enhancement of Cd translocation from roots to shoots. Therefore further study is necessary to determine the effect of external Zn level on

19、Cd translocation from shoot to grains or grain Cd accumulation before Zn fertilizer is applied to the Cd-contaminated soil for alleviating Cd toxicity on rice or other cereal crops.The third experiment was conducted to i

20、nvestigate the alleviating effect of sulfur(S) on growth inhibition and oxidative stress caused by Cd toxicity. Treatments consisted of all combinations of three S levels (0.2, 0.4 and 0.8 mmol), two Cd levels (0 and 1 μ

21、M) and the same two rice cultivars. In comparison with lower S level (0.2 mmol), higher S levels (0.4 and 0.6 mmol) demonstrated the distinct effect of alleviating Cd toxicity, characterized by the significant increase i

22、n growth parameters, decrease in Cd and MDA content of both roots and shoots. In addition,superoxide dismutase (SOD) activity in the plants varied in tissues, cultivars and Cd treatments. Higher Cd and MDA content was co

23、nsistently accompanied by higher SOD activity, while higher S levels caused the marked increase in glutathione content and reduction in SOD activity, indicating the exact effect of S and glutathione in alleviating oxidat

24、ive stress.The fourth experiment was conducted to determine the influence of N forms on growth, enzymatic activities and Cd and N uptake of Cd-sensitive rice cultivar. The treatments were consisted of two Cd levels (0, a

25、nd 1 μMI) and three N forms(NH4)2SO4, NH4NO3 and Ca(NO3)2. The results show that N forms in absence of Cd has no considerable effect on plant growth parameters and plant biomass, while(NH4)2SO4 significantly decreases th

26、e Cd toxicity compared to NH4NO3 and Ca(NO3)2 fed plants in terms of growth rate and plant biomass. The greatest plant height and tillers number per plant was noted in (NH4)2SO4 fed plants and lowest in Ca(NO3)2 fed plan

27、ts, when Cd was added to the medium. The greatest photosynthetic rate and chlorophyll content was also recorded in (NH4)2SO4 fed plants. Addition of Cd caused a remarkable increase in SOD activity and MDA content of rice

28、 plant, with greatest value in Ca(NO3)2 fed plants, followed by NH4NO3 and (NH4)2SO4fed plants. The N content of rootsand shoots was notably affected by addition of Cd in nutrient solution. In comparison with the control

29、 plants,the N content of roots and shoots was not significantly affected in (NH4)2SO4 fed plants, but a significant decrease in NH4NO3 and Ca(NO3)2 fed plants was observed when plants was subjected to Cd stress. Addition