Effect Of Calcium On Cadmium Absorption And Accumulation Of Peanut

As one of the largest heavy metal toxicity, cadmium is a non-essential element ofthe plants and the human body. And as China’s important economic crops and oil crops,its grain accumulate cadmium in the soil with high efficiency and has the adverse effectto human body health and export trade. In this article, the effect and possiblemechanism had been discussed about how the secondary element calcium reducecadmium content of peanut which will provide a new train of thought to reduce thepeanut cadmium absorption. The major results were summarized as follows:1. The relationship between cadmium contents of peanut and contents of exchangeablecalcium in soil in main production area in Shandong Province and the health riskassessment to human health: the cadmium content ranged from0.03to0.18mg·kg^-1,with an average of0.069mg·kg^-1in the soil samples. All the tested samples cadmiumcontent didn’t surpass hygienic quality standard of green peanut kernel issued byMinistry of Agriculture. Similarly, The cadmium content ranged from0.019to0.46mg·kg^-1, with an average of0.14mg·kg^-1. The cadmium content hygienic qualitystandard of green peanut kernel was0.1mg·kg^-1which was published by FAO/WHO.The rate exceeded the quality standard by60.3%in all tested peanut samples. Theaverage content of calcium in the peanut samples is52.8mg·100g-1and cadmiumcontent of peanut have a trend to reduce with the rise of exchangeable calcium contentin soil, while the relevance is very low.12peanut samples exceeded%ADI（100）whichreached20.7%in all tested peanut samples.This may relatively increase the risk fordietary health in the peanut consumer whose cadmium content exceed0.2mg·kg^-1. Themore cadmium content the peanut have, the higher the risk is.2.Effects of calcium on some physiological characteristics and cadmium absorptionunder cadmium pollution of peanut seedlings in hydroponic conditions: A water cultureexperiment was conducted to investigate effects of different calcium treatment on some physiological characteristics and cadmium absorption under cadmium pollution ofpeanut seedlings. The result showed that the height and fresh weight of peanut seedlingsincrease with the with the increasing of the concentration of calcium.And high levels ofcalcium improved the chlorophyll content of Peanut leaf under cadmium pollution. Italso improved the activities of superoxide dismutase（SOD）, peroxidase（POD）, andcatlase（CAT）, root activity and deceased the accumulation of malondialdeyde（MDA）. Itshowed that a certain range of the high calcium can relieve the influence of peanutphysiological properties under cadmium stress. Besides,the content of cadmium in rootof peanut seedlings was higher than that in the ground department. Also with theincrease of calcium, the content of cadmium in peanut root and the ground departmentwere both significantly lower. It meant that calcium and cadmium have a certain degreeof antagonistic action when they got into the peanut.3.Effect of calcium on some physiological characteristics, yield and cadmiumabsorption of different peanut growth period under the condition of pot: A potexperiment was conducted with the cadmium treatment1mg·kg^-1and added15mg·kg^-1calcium at seedling stage, blossom needle under period, fruiting period and matureperiod respectively. Calcium had a certain role in promoting the physiological indexesof the peanut. Calcium was bset for the protective enzyme when it added at seedlingstage. It could reduce the MDA of peanut leaf most at blossom needle under period. Andit could improve the main stem, lateral branch length, total fruit number, fruit rate, fullplant dry weight, root activity, chlorophyll and carotenoid content most at fruitingperiod. In addition, calcium had certain effect on increasing peanut yield and reducingcadmium concentration of peanut kernels at all period treated.4.Mechanism of calcium on cadmium absorption of peanut:（1） Effect of inhibitor on the cadmium uptake of peanut seedling: a hydroponicexperiment was conducted to study the effect of some inhibitor on peanut overgroundand root about Cadmium absorption. Both of Na₃VO₄and Na₃N had some influence onpeanut Cadmium absorption. Both of the inhibitor Na₃VO₄and Na₃N could inhibitCadmium uptake of peanut under the stress of Cadmium of1mg·kg^-1. Na₃VO₄could inhibit Cadmium uptake but Na₃N promoted that under the stress of Cadmium of5mg·kg^-1which showed properly initiative Cadmium uptake in peanut to a certain degree.Ca²⁺ion channel inhibitor LaCl₃decrease the Cadmium uptake of peanut under thestress of Cadmium of1mg·kg^-1which showed a part of Cadmium entered into peanutthrough Ca²⁺ion channel. However LaCl₃boosted Cadmium uptake of peanut under thestress of Cadmium of5mg·kg^-1.（2） Effect of calcium on cadmium bioavailability of soil: the experiment was productedin darkness at25℃. Adding10mg·kg^-1and20mg·kg^-1could increase the cadmiumbioavailability of soil and the former was more obviously than the latter. Both of themgot low and approached the control in20days.