Heavy Metals Toxicity To Wheat And Detoxification Of The Amendments

In this study,the wheat varieties with low accumulation of Pb and Cd was screed by pot experiment,and the Pb and Cd toxicity to wheat and the detoxification of the amendments were researched by hydroponic experiment.The growth and physiological indexes of wheat were analyzed,the main results are shown as follows:?1?The content of heavy metals in soil was decreased by mixed clean soil.In order to screen out wheat varieties with low accumulation of Pb and Cd,absorption of grains to heavy metal?cadmium and lead?in 44 wheat varieties were studied by pot experiment.The results showed that the content of lead,cadmium display a marked difference in different wheat varieties.The accumulation of single heavy metal was also difference in different wheat varieties.The content of lead and cadmium in 44 wheat varieties was analysised using the Nemerow synthetic pollution index methods.Levels of accumulation in 44 wheat varieties were divided into high,middle,low through cluster analysis.According to quantity limit standards of lead,cadmium in?The quantity limit to the lead,chromium,cadmium,mercury,selenium,arsenic,copper,zinc in food and product?NY861-2004??,the content of heavy metal in wheat varieties with low accumulation such as cultivar25,cultivar30,cultivar36,cultivar39 showed the low accumulation of cadmium and lead and conformed to safety standards.?2?The germination and growth of wheat under lead and cadmium stress were studied by hydroponic experiment and used two varieties?cultivar36 has low accumulation characteristic and cultivar21 has high accumulation characteristic?.The results showed that:The germination index and seedling growth was inhibited in different concentrations of Pb and Cd,the cultivar36 is higher than the cultivar21.The chlorophyll content is negatively correlated with the heavy metals concentration of the two wheat varieties,the MDA and CMP are positively correlated with the heavy metals concentration,the POD,CAT and SOD increased with increasing concentration but began to decline after up to a certain extent.On the whole,cultivar36 showed the higher tolerance.?3?The subcellular distribution of cultivar36 and cultivar21 under the heavy metals stress were studied,the results show:The root of wheat is the main source of absorption the heavy metals;the accumulation ability of heavy metals in the cell wall is higher than the organelles and cells.The root of the cultivar36 is more than cultivar21 in the accumulation of heavy metals,the mainly reason maybe is the organic matter secreted by the roots can combining heavy metal ions and reduce heavy metal activity.?4?In order to clarify mechanisms of exogenous Ca²⁺on membrane lipid peroxidation and root activity of wheat under Pb stress,effects of exogenous different concentrations Ca²⁺on chlorophyll content,antioxidant enzyme activity,MDA content,cell membrane permeability and root activity in Xinmai 26?grow in 1/2 Hoagland?seedling under Pb stress were studied.Results showed that the addition of exogenous calcium could alleviate the toxicity of lead stress on wheat more effectively.Compared with Pb treatment,the chlorophyll content increased significantly by the addition of exogenous calcium and it was raised by 77.3%in the Ca3 treatment;the MDA content and the level of membrane lipid peroxidation decreased obviously and they were decreased by 29.9%and 24.5%respectively in the Ca3 treatment;the antioxidant enzyme activities showed different situations,the activities of the SOD and CAT increased by 48.5%and 85.6%respectively,while the POD activity decreased by 26.9%in the Ca3 treatment;the root activity of wheat was restored and the recovery rate was 56.2%in the Ca3 treatment.Therefore,the toxicity of lead on wheat could be alleviated when using the CaO?regulate pH?and appropriate CaCl₂.After,the effect of the repair to wheat under high concentration of lead and cadmium when added the silicon and calcium compounds were studied.The experiment results show that:when the amendments were used,wheat growth significantly improved;the chlorophyll content and root activity were increased,the cell membrane permeability decreased in different degrees,and the three main antioxidant enzymes were effectively controlled.