Screening For Wheat With Low Accumulation Of Lead And Relevant Chemical Forms

Field trial was conducted in a piece of farmland different contaminated with heavy metals, to study differences in Pb uptake and agronomic traits among 30 different wheat cultivars, and to inqure about information of Pb transport and accumulation in wheat, give insight on screening for low-Pb-accumulation wheat cultivars. Based on field trial investigation, six wheat cultivars with different characteristics of Pb absorption were selected for study materials. A sand-culture experiment was carried out to research the differences in Pb uptake, subcellular distribution and chemical extraction of Pb among six wheat cultivars under different levels of Pb stress, to provide theoretical support for screening for cultivars of wheat with low Pb accumulation. The main results are shown as follows:1. In site A(mild concentration), cluster analysis showed that Pb accumulation in the wheat cultivars of No.5, 19, 17, 20, 23, 15, 27, 3, 9, 10, 25, 28, 12, 26, 21 were slight, the transfer factor TF grain/ shoots and the transfer factor TFgrain/ root of wheat No.5, 9, 21 and 26 were lower than that of other cultivars.In site B(middle level concentration), cluster analysis showed that Pb accumulation in the wheat cultivars of No.7, 20, 17, 2, 29, 30, 28 were slight, the transfer factor TFgrain/ shoots and the transfer factor TF grain/ root of wheat 2 and 7 were lower than that of other cultivars.2. Pb in the organs of wheat cultivars of the gradient of content:root > shoots > grain. The Pb transfer factor TFgrain/ shoots,TFgrain/ rootand enrichment factor of low-Pb-accumulation was less than high- Pb-accumulation, but The Pb transfer factor TFgrain/ rootof low-Pb-accumulation was slightly less than high- Pb-accumulation suggestting that under the different levels Pb contaminated, the key factors for the low uptake of wheat were lack of ability of Pb transition from shoots to grains and the low Pb content in roots.3. For chemical forms, poorly-soluble Pb lead(i.e. acetic acid and hydrochloric acid extractable) was mainly detected, which accounted for 65.62%-86.82% of the total. The total content of Pb was the lowest to the cultivar D, but the cultivar F was the peak. Under Pb stress, concent of alcohol-extractable together with water-extractable Pb in cultivar D shoots and roots was the lowest. Under the stress of 800 mg·L-1 Pb, in order to avoid the toxicity, the cultivar F try to convert active-Pb into other forms. Under the stress of 100 mg·L-1 Pb, the cultivar D with a strong ability that was the shoots and roots strong activity of Pb converted into less-activity of Pb than other cultivars, in order to improve the tolerance to Pb stress. Under the stress of 800 mg·L-1 Pb, the cultivar D by controlling the amount of absorption to resist Pb toxicity. The ability to regulate the chemical form of Pb of other cultivar substantially between the cultivar D and F.4. For subcellular distribution, Pb was mainly observed in the cell wall and cytoplasm, which accounted for 63.56%-86.30% of the total. Under the stress of 100 mg·L-1 Pb, the cultivar B、C, D, E had a increase in the proportion of the shoots cell wall of Pb than the roots cell wall of Pb, but there was a decrease for the cultivar A and F. Under the stress of 800 mg·L-1 Pb, the proportion of the roots cell wall of Pb of the cultivar A, B, C, D, E were lower than the shoots cell wall of Pb, but for the cultivar F was higher. Thus, under the stress of different concentration of Pb, the cultivar B, C, D, E reduced the content of the shoots cell wall of Pb to resist Pb toxicity, the cultivar F reduced the content of the roots cell wall of Pb to resist Pb toxicity. the cultivar A reduced the content of the shoots cell wall of Pb to resist Pb toxicity under the stress of 100 mg·L-1 Pb and the content of the roots cell wall of Pb to resist Pb toxicity under the stress of 800 mg·L-1 Pb.