Effect Of Calcium On The Characteristics Of Cadmium Absorption In Rice

In recent years,the situation of cadmium?Cd?pollution in farmland is becoming an increasingly serious issue in China,which has caused great concern for the safe production of rice in cadmium-contaminated areas.In this study,a Cd high-absorption rice variety T705 and a low-absorption variety Xiangzaoxian X24 were used as test materials for hydroponic experiments to study the effects of calcium?Ca?and cadmium?Cd?on cadmium uptake and translocation of rice and seedlings antioxidant enzyme activity.At the same time,four rice genotypes were selected for pot experiment,and study the effects of foliar calcium fertilizer on the inhibition of cadmium accumulation in rice.The main results obtained are as follows:?1?The toxicity of Cd²⁺ to the root system of rice was significantly alleviated by Ca.The addition of 1² mmol·L^-1 Ca²⁺ to the nutrient solution could enhance the tolerance of rice seedlings to Cd stress.Compared with the Cd control group,the biomass of T705 and X24 seedlings supplemented with 1 mmol·L^-1 Ca²⁺ was increased by 68.91% and 116.19%,respectively,and the root tip number,total root length and total root surface area increased by77.29% and 19.4988.06% and 28.107.56% and 3.31%,respectively.After adding 2 mmol·L^-1Ca²⁺,the biomass of the two kinds of rice seedlings increased by 108.93% and 143.58%,respectively,the number of root tips,total root length,and total root surface area increased by106.13%,74.09%,122.99,% and 33.11%,18.55% and 11.19% respectively.The detoxification effect of 2 mmol·L^-1 Ca²⁺ on Cd stress was significantly greater than 1 mmol·L^-1 Ca²⁺.?2?The uptake and transport of Cd in rice seedlings was significantly decreased by Ca.1.0-2.0 mmol·L^-1 Ca²⁺ could significantly reduce Cd content in rice roots and shoots,and reduce the ratio of Cd to shoots in rice roots.As the Ca content increases,the accumulation of Cd decreases.In the nutrient solution containing 1.0 mmol·L^-1 Ca²⁺ and 2.0 mmol·L^-1 Ca²⁺,Ca reduced the Cd in the two rice roots by 7.94% and 22.19%,respectively,resulting in a 9.34%decrease in cadmium in the aerial parts and 18.72%.?3?Ca could significantly alleviate the adverse effects of Cd on the essential elements of rice seedlings' absorption and transport.Cd could also significantly inhibited the accumulation of Mg,K and Zn in rice roots and shoots.The addition of Ca could relieved the inhibition of essential elements by Cd,and significantly increased Mg,K,Zn content in roots of seedlings and the above-ground parts.?4?The Ca content in roots and shoots of high Cd accumulation genotype rice seedlings wassignificantly higher than that of low Cd accumulation genotype rice.When the genotypes were the same,there was a negative correlation between Ca and Cd contents in roots and shoots of seedlings.?5?Ca could significantly relieve the oxidative damage caused by cadmium stress on rice seedlings.Under 0.3 mmol·L^-1 Cd Cl2 stress,POD activity,SOD enzyme and MDA content in rice roots and aerial parts decreased.The addition of 1-2 mmol·L^-1 of exogenous Ca²⁺ in culture medium significantly alleviated the oxidative stress caused by Cd²⁺,which could significantly increased the content of MDA,and decreased the activity of POD and SOD to the control level.?6?Spraying foliar Ca fertilizer could reduced the Cd accumulation in the spike axis,and inhibited the transportation of Cd from the spike axis to grain.A two time's spraying of calcium fertilizer did more effect on cadmium reduction.