Effect Of Cadmium Stress On Cucumber Seedlings And Response Of Conditioner To Cadmium Speciation In Soil

At present,due to industrial wastewater,acid deposition and unreasonable farmland fertilization measures,the process of soil acidification accelerated,resulting in the solubility of heavy metal ions in soil increased,the effective content increased,mobility increased.Not only poisoning the growth of plants,but also pose a threat to human health.In this experiment,the p H of soil was reduced by adding conditioner,and the change of cadmium form in soil after acidification.To study the influence of soil acidification on cadmium form and validity was investigated,the change of the occurrence form of cadmium transformation rule in acidified soil conditions.It has some significance to reveal the effects of soil acidification on the solubility and release potential of heavy metals.The results are as follows:1 Cadmium stress inhibited cucumber plant height.In the range of cadmium concentration(0³00?mol·L^-1),the Southern China type was higher than the other 4 types when cadmium concentration was used.Medium low cadmium concentration(0⁵0?mol·L^-1)could increase the root volume of cucumber seedlings,and the root growth was inhibited obviously when cadmium concentration was 100³00?mol·L^-1.The activities of antioxidant enzymes?SOD,POD,CAT?of all types of cucumber seedlings showed a trend of increasing first and then decreasing.The POD and CAT activity of Europe and America greenhouse type are lower than others.The content of cadmium in shoots was higher than that in roots when the concentration of cadmium is below 50?mol·L^-1,and that is opposite when the concentration is 100³00?mol·L^-1.When the concentration of cadmium is 300?mol·L^-1,the content of cadmium in shoots of Europe and America processing and North China?was significantly lower than that in other treatments,showed better low accumulation characteristics.2 With the prolongation of culture time,soil acidity conditioner significantly reduced soil p H.To 56 d,the maximum decrease was 1.83 units.Because the conditioner reduces the soil p H,the cadmium speciation in soil was significantly affected,the content of cadmium in soil was reduced,then convert it into exchangeable cadmium.With the increase of dosage of conditioner,the content of Cadmium bound to iron and manganese oxides increased.However,the dosage of conditioner had no significant influence on the cadmium bound to organic matter and residual cadmium.3 The dosage of conditioner 15g·kg^-1 significantly increased the biomass of brassica juncea and promoted the growth of roots and leaves.But the high dosage of conditioner inhibited its growth.The dosage of conditioner 30g·kg^-1 had a significant inhibitory effect on physiological metabolism of brassica juncea.Photosynthetic indexes such as chlorophyll content,net photosynthetic rate and so on,and antioxidant enzyme activities were significantly lower than those of the control.The dosage of conditioner 15g·kg^-1 was not significantly different from that of the control.With the increase of conditioner dosage,the activity of soil unease activity,invertase activity,hydrogen peroxidase activity was inhibited,and the activity of acid phosphmatase activity in soil was promoted,and the difference among treatments was significant.The dosage of conditioner 15g·kg^-1 reduced the content of cadmium in the unit mass of brassica juncea.However,because of the increase of its biomass,the accumulation of cadmium was increased.Compared with the control,an increase of 169.86%.4 The experiment shows that the utilization of the conditioner can transform the cadmium from the latent and non available cadmium into available cadmium,and increase the cadmium absorption capacity of the hyperaccumulator brassica juncea,and reduce the cadmium content in the soil.But the decrease of soil p H lead to increasing the concentration and available content and mobility of heavy metal cadmium ion in soil.Therefore,the influence of soil acidification on transformation and dissolution of cadmium in soil should be paid to more concern.Through effective measures prevent soil acidification,reduce the pollution of heavy metals in soil and vegetables is very important.