Effects Of Physiological Inhibitors On Growth And Cadmium Absorption Of Vegetables In Cd-contaminated Fields

At present,Cadmium（Cd）pollution in cultivated soil is serious,mainly light to moderate widespread pollution,which seriously affects the yield and quality of crops and threatens human health.Physiological inhibitors have the potential to reduce Cd absorption and provide nutrients for plant growth and development.In this study,soil culture pot experiment was used to study the resistance and control of cadmium absorption of spinach in Cd-containmented soil in northern China,and that of tamato in cadmium containnmented soil in southern China,respectively.1.In view of the mild to moderate alkaline Cd contaminated soil in northern China,the effects and possible mechanisms of Cd inhibition of spinach were studied under different dosages of silicon potassium liquid fertilizer（Si-K）and earthworm liquid fertilizer（EW）(30、75、150 kg·ha^-1).The results show that:（1）The application of earthworm liquid fertilizer of 30-75 kg·ha^-1had a good effect on Cd absorption of spinach,and the content of Cd in the ground part was reduced to 2.02 mg·kg^-1at the lowest level,a decrease of 47%,which was still higher than the limit standard of leaf vegetables（0.2ppm）stipulated in the National Standard of Food Safety Limit of Pollutants in Food（GB 2762-2022）,which was mainly achieved by reducing Cd transport from root to shoot.The photosynthetic capacity of spinach leaves was improved by different amounts of earthworm liquid fertilizer（Fv/Fm and Qy increased）.Furthermore,the soil electrical conductivity EC,Ca²⁺/Mg²⁺and soil available potassium content was reduced under the application of EW,while the high dosage had the potential to repair soil,which showed that the content of soil available Cd was significantly reduced.（2）As for Si-K,the exogenous application alleviated Cd toxicity of spinach,which was manifested as decreased Cd content in shoot,improved photosynthesis（increased Fv/Fm and Qy）and improved nutrient absorption（increased N and P contents in shoot）.With the increase of application concentration,the inhibition and control effect of Cd absorption was enhanced,and the inhibition and control effect was the best under high dosage,the content of shoot Cd decreased to 1.97 mg·kg^-1,which decreased by 48%,and the biomass of spinach increased significantly.In addition,the contents of soil EC,Ca²⁺/Mg²⁺and available potassium were decreased by different application rates of Si-K.2.In light to moderate acid Cd contaminated soil in southern China,the effect and mechanism of chemical,amino acid and nano-sized calcium fertilizer(Ca（H₂PO₄）₂,calcium aspartate and nano-hydroxyapatite,3g·L^-1,100 m L·pot^-1)on Cd absorption of two tomato varieties were studied.The results show that:（1）Under different Ca treatments,the Cd content of tomato fruits of the two varieties was reduced to below the control standard of Cd content in edible parts of vegetables（0.05 ppm）.For“Ouguan”,nanometer calcium had the best effect on Cd absorption in tomato fruits,which might reduce Cd accumulation in tomato fruits by increasing Cd retention in stems and leaves.The tomato leaves and fruit Cd accumulation was reduced under the application of Calcium dihydrogen phosphate and calcium aspartate.For“Baiguoqiangfeng”,there was the most significant inhibition effect on Cd in tomato fruits under the application of calcium dihydrogen phosphate,and root,stem and leaf Cd accumulation of which was increased.（2）The tomato leaf photosynthesis was improved under the application of Ca fertilizers,such as the leaf SPAD,Fv/Fo,Fv/Fm and qp was increased,and the NPQ was reduced,and it was processing to the best effect of the improvement under the calcium aspartate treatment,and the improvement of the nano calcium effect was worse than it.The tomato leaf glutamate content,polyphenol content and Ca content was increased under the three Ca fertilizers treatment,among them,the effect of Calcium aspartate treatment was obvious,which was also significantly reduced the leaf K content in variety of“Baiguoqiangfeng”.（3）There was a great difference among tomato varieties,while the improvement effect of Ca was not obvious.The fruit yield of the two varieties was most obviously increased under the calcium dihydrogen phosphate treatment.For tomato fruit quality,the sugar content and sugar-acid ratio of tomato fruits of two varieties was increased under Ca fertilizers treatments,among them,there was the most significant effect under calcium dihydrogen phosphate treatment,and calcium aspartate increased tomato fruit glutamate content best,and nano calcium fertilizer had the best effect on increasing vitamin C content in fruit.