| Cadmium .which ranks the first grade of so-called "Five Toxicants ", i.e. Cd, Hg, As.Cr and Pb, is the most dangerous carcinogen to human body, and can deposit easily in kidney and bone, leading to crocking up the function of kidney, osteomalacia and bone broken. There was wide area of . agricultural soil heavily contaminated by Cd around China with distribution of eight provinces including Fujian. In soil, Cd distributes mainly in top soil that without deposited by the soil organic compounds, it is easy assimilated by crop root when compared with other four kinds of heavy metals. However, vegetable varieties can accumulate much more Cd in the shoot, the edible part for human . In China, the total vegetable production adds up to 3.45 million tones that ranked the first of the world, and most of the vegetable farming land locates in the suburb area where the highly intensive industries were developed nowadays, the vegetable lands is contaminated universally by heavy metal pollutants. As a result, the edible part of vegetables accumulated Cd with 2-3 folds, 5.2 folds in some extreme case, of the National Sanitary Criteria of Cd content in vegetable product detected in most city market. Economically, it would weaken the competitive vigor internationally due to heavy metal problem of Chinese vegetable industries, it is urgent, therefore, to clear soil heavy metal, as well as to lower Cd residues in vegetable both for human healthy and national economy.In this study, 24 vegetable genotypes from Braccisa genus were explored to screen: (1) Cd-resistance genotypes with the lower cadmium content in shoot which will in turn to develop a breed program of vegetable with highly sanitary quality; and(2) Cd-tolerance genotypes with higher content to be utilized potentially in phytoremediation of Cd contaminated soil. The main results are as following:1. Establishing vegetable aqueoculturing system with minimized error: to raise seedlings and mature plant excluding extraneous heavy metal interference, vermiculite instead of agricultural soil was used in seedling bed and deionized water instead of distilled water was exploited in hydroponics stage. Besides, the cheap materials such as plastic net, perlite and foam were used to fix the plant in hydroponics, to keep dry of root-shoot interval of plant as well. The measures used above could ensure the normal development of plant material and to minimize the errors at most extent.2.The edible part(shoot) of cabbages being a part of Cd accumulation and distribution: cultured by 125 umol.L-1 of Cd. Pb. As, the average Cd content in shoot of 13 cabbage genotypes added up to 373.34 mg.kg-1'( Cd content thresholds of National Sanitary Criteria.TNSC.is 0.20 mg kg-1) which was 6.0 folds of shoot Pb content(62.20 mg.kg-1, TNSC0.40 mg.kg-1) and 13.6 folds shoot As content(27.56 mg.kg'1, TNSC0.70 mg.kg'1) in average respectively. The results showed that Cd was easier assimilated by shoot and had much more negative effect on cabbages' quality than Pb and As did.3.Screening Cd-resistance and tolerance genotypes with low and high Cd contents in shoot of Brassica vegetables: various Cd stressing concentrations were set combining withphysiochemical studies under the stress of heavy metal, the cabbage genotypes "Dr-SHQ" with lowest shoot Cd content( 140.87 mg.kg-1') and "Kt-RBD" with highest shoot Cd content (699.92mg.kg1) were screened among 13 cabbages genotypes under stress of appropriate Cd (50umol.L-1). In this case, shoot Cd content of "Kt-RBD" was 4.96 times of that of "Dr-SHQ", and they were 36.8% and 182.62% of average Cd content of 13 cabbages genotypes respectively. Meanwhile, the Cd tolerance index for these two genotypes were 97.8% and 91.5% correspondingly which indicated that they could grow normally under the Cd stress.4.Detecting the RAPD markers linking with Cd accumulative characterization of testing materials: under Cd stress (50umol.L-1), we gained three PAPD markers linking with Cd accumulation characterization of testing materials, one of which wa...
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