Effects Of Cadmium Bioaccumulation On Chinese Flowering Cabbage Brassica Campestris And Herbivorous Insect Spodoptera Litura

Cadmium?Cd?from environment could transfer and accumulate in higher tropic level through soil-vegetable-herbivorous insect,which has toxic effects on organisms.In this paper,a pot experiment was firstly conducted to investigate the effects of different Cd concentrations in soil on growth and Cd accumulation of two Chinese flowering cabbage Brassica campestris hybrids,Lvbao701 and Chicaixin No.4.Secondly,herbivorous insect Spodoptera litura larvae were fed on two kinds of Chinese flowering cabbages that mentioned above to investigate the Cd transfer in soil-vegetable-insect and effects of Cd in cabbages on the survival rate and the food utilization of S.litura.Thirdly,based on the range of Cd concentrations in above Chinese flowering cabbages,S.litura larvae were fed on the standard artificial diets with different Cd concentrations for three consecutive generations to investigate effects of Cd stress on growth and development,food utilization and the Cd accumulation in different tissues of larvae.The main results were as the follows:1.2.5⁵ mg·kg^-1Cd in soil had no significant effect on the agronomic traits?plant height,leaf number,length and width,plant fresh and dry weight?of two Chinese flowering cabbages?Lvbao701 and Chicaixin No.4?,while high Cd concentration(10 mg·kg^-1)had inhibition on them.The content of chorophyll in two Chinese flowering cabbages was significantly lower than control.However,there were no differences of the photosynthesis parameters?Photo,Cond,Ci,and Trmmol?between these treatments and control.When inhibiting effects of Cd stress on two hybrids of Chinese flowering cabbage were compared,the effect of Cd stress on Chicaixin No.4 was more serious in a certain extent.2.2.5⁵ mg·kg^-1 Cd in soil had no toxic effects on Chinese flowering cabbage,but the Cd content in them exceeded the Chinese food security standard(GB18406.1-2001,0.05 mg·kg^-1).When Lvbao701 and Chicaixin No.4 were exposed to Cd,the Cd accumulation in Chicaixin No.4 was significantly higher than that of Lvbao701.Cd accumulations in underground parts of two Chinese flowering cabbages were significantly higher than those in their above-ground part.3.After S.litura larvae feeding on Cd contaminated Chinese flowering cabbages,the survival rate was not affected.However,the food utilization was affected significantly:larvae fed on 10 mg·kg^-1 Cd treated Lvbao701,their relative consumption rate?RCR?,approximate digestibility?AD?was significantly higher than that of control,while efficiency of conversion of ingested food?ECI?,efficiency of conversion of digested food?ECD?and relative growth rate?RGR?was significantly lower than that of control;the ECD and ECI of larvae fed on Cd treated Chicaixin No.4 was significantly lower than that of control.There was a significant difference in the Cd transfer rate from two Chinese flowering cabbages to larvae among different Cd treatments.Cd concentrations in the feces and larvae significantly increased with the increase of Cd concentrations in soil.Cd concentrations in larval gut were significantly higher than other tissues?cuticle,brain,and hemolymph?.Cd accumulation in S.litura larvae feeding on Cd contaminated Chicaixin No.4 was significantly higher than that of the corresponding Lvbao701 treatments.4.After S.litura larvae exposure to artificial diets with different Cd concentrations for the three consecutive generations,the survival rate?larvae survival rate,pupation rate and eclosion rate?was not affected.The period of larvae,pupae and adults significantly extended when the larvae were exposed to 40.6 and 81.2 mg·kg^-1 Cd stress.The period of larvae and pupae was longer and longer with the increase of generations.Significantly higher RCR and AD and lower ECI,ECD and RGR was found in larvae from the 1^st generation under 81.2 mg·kg^-1 Cd stress and larvae from the 2^nd generation under 40.6mg·kg^-1 Cd stress.Larvae RGR significantly raised with the increase of generations.After larvae were exposed to Cd stress,the Cd concentrations in feces significantly increased with the increase of Cd concentrations in the diets.Cd accumulation in the gut was the highest,and that in hemolymph was the lowest.In summary,Cd in the soil can be transported and accumulated in soil-vegetable-insect,which presented toxic effects on the growth and development of Chinese flowering cabbage and S.litura when they were exposed to high Cd stress,which was closely related to Cd content in plants and insect.The growth and development of S.litura larvae were inhibited by high Cd stress,which reflected that the body weight decreased,developmental duration prolonged,RCR and AD raised and ECD,ECI,RGR reduced.The effect degree was closely related to Cd content in larvae.After S.litura larvae were feed on diets with different Cd concentrations for three consecutive generations,a part of Cd could be excreted via feces,and the remaining Cd could be accumulated in the cuticle,gut,head,fat body and hemolymph,while there were significant differences of accumulative ability among different generations and tissues?the highest and lowest one was detected in gut and hemolymph,respectively?.