Effects Of Silicon On Yield, Quality And Soil Properties Of Cucumber Under Cadmium Stress

In this experiment,the photosynthesis,antioxidant enzyme system,soil nutrient and enzyme activities,yield and quality,cadmium of cucumber under Cd stress were studied by pot experiment and cucumber(Mix 60).Morphology and the effects of transport,the results indicate:(1)Under Cd stress,the net photosynthetic rate(Pn),stomatal conductance(Gs),transpiration rate(Tr)and total chlorophyll content in cucumber leaves decreased significantly,while intercellular CO2(Ci)increased.The intervention of silicon can significantly increase the values of Pn,Gs,and Tr,and reduce the Ci in the blade.It can be seen that on calcareous soil,silicon can effectively alleviate Cd toxicity and enhance photosynthesis of cucumber leaves.When Cd was applied,the contents of SOD,POD and CAT in cucumber leaves were significantly decreased,and the content of MDA was increased.After application of silicon,the activity of SOD,POD and CAT can be significantly increased,and the MDA value can be lowered.It indicates that silicon can increase the antioxidant enzyme system in cucumber leaves,thus alleviating the toxic effect of Cd on plants.(2)When the concentration of cadmium is low,it has a promoting effect on catalase.The cadmium concentration of 1mg/kg is the most obvious.With the increase of cadmium concentration,it gradually shows inhibition.The urease activity decreases gradually.When the cadmium concentration is 1mg/ At the time of kg,there was no significant change in urease activity,and cadmium toxicity was not significant;phosphatase activity increased first and then decreased.When cadmium concentration was 1 mg/kg,phosphatase activity was the highest,and cadmium had the most obvious effect on phosphatase.There was no significant change in the activity of invertase,indicating that the difference between cadmium and invertase was not significant.It can be seen that the application of a small amount of silicon fertilizer can reduce cadmium toxicity and purify the soil environment in calcareous soil.(3)The addition of exogenous silicon can reduce the content of cadmium in cucumber leaves and fruits,and the higher the amount of silicon added,the lower the cadmium content.The distribution of cadmium in the aboveground part of cucumber is: stem>leaf>fruit,and cadmium in fruit The contentis much lower than the stems and leaves.The application of silicon can significantly increase the value of stem/leaf/cadmium.Therefore,silicon can reduce the relative content of cadmium in fruits.With the addition of exogenous silicon,the total amount of cadmium in the upper part of cucumber is significantly reduced.The addition of silicon and cadmium can be reduced.The cadmium enrichment coefficient of the aboveground parts of cucumber plants,and the more the addition of silicon cadmium,the more the enrichment coefficient of each organ decreased.When cadmium was not added,the cadmium enrichment coefficient of cucumber was >leaf>fruit.When cadmium was added,it was mainly stem>leaf>fruit.Cadmium can reduce the content of alkali nitrogen and available phosphorus in soil.Applying a larger amount of silicon can significantly increase the alkali nitrogen and available phosphorus in the soil,and has little effect on available potassium.Therefore,in cadmium-contaminated soil,the application of silicon can effectively reduce the toxicity of cadmium to cucumber plants and increase the nutrient content of soil.(4)With the increase of silicon application rate,the content of exchangeable cadmium and carbonate-bound cadmium in soil decreased significantly,with the reduction range of 34.93%-67.97%and 44.32%-47.99%,respectively.The ratio of cadmium and carbonate-bound cadmium in the exchangeable state to total cadmium decreases as the amount of silicon applied increases.When treated with low concentration silicon,the content of cadmium in iron-manganese oxidation state decreased significantly,with a decrease of 34.3%-50.1%.When treated with medium and high concentration silicon,the cadmium content of iron-manganese oxidation state increased significantly,with an increase of 12.9%.-19.61%.The proportion of cadmium in the oxidation state of iron and manganese to the total cadmium decreased first and then increased with the increase of silicon application.When treated with low concentration silicon,the content of organic bound and residual cadmium increased significantly,the organic bound state increased by 15.79%-40.66%,and the residual state increased by50%-93.3%;when treated with high concentration silicon,the organic bound state The residual cadmium content was significantly reduced,and the reduction range was 22.63%-40.9% and17.24%-36.36%,respectively.The content of organically bound cadmium and residual cadmium increased first and then decreased with the increase of silicon application.(5)Cd stress has a certain inhibitoryeffect on the growth and development of cucumber.With the increase of Cd concentration,the toxic effect is more obvious.The application of Si can effectively alleviate the toxic effect of Cd stress on cucumber,increase the plant height and fresh weight of cucumber,and promote the growth and development of crops.Overall,cucumbers grew best when the application amount of single Si was 200 mg/ kg.Applying appropriate Si under Cd stress can reducethe nitrate content in cucumber and the Cd content in cucumber fruit,and increase the content of reducing sugar and vitamin C.When the Cd intervention amount is ?3mg/kg and the Si application amount is 100mg/ kg,the Cd content in cucumber fruit has reached the Cd limit index of food safety.