Study On The Effect Of Single And Combined Toxicity Of Cadmium And Polystyrene Microplastics(PS-MPS) On Chinese Cabbage Pakchoi(Brassica Chinensis L.)

To clarfy the response characteristics of Chinese cabbage pakchoi(Brassica chinensis L.)under the effects of single and combined toxicity of cadmium and polystyrene microplastics(PS-MPs)stress conditions,and provid a theoretical basis and experimental reference for the interpretation of the physiological and ecological mechanism of microplastic pollution and the bioremediation of Cd and microplastic-contaminated soil.Hydroponic experiments were carried out to study the effects of Cd and two particle sizes(100nm and 1000nm)PS-MPs on growth,photosynthetic physiology,antioxidant enzyme activities,nutritional quality,anatomical structure,and canopy temperature in Chinese cabbage pakchoi.The main findings are as follows:1.Cd stress signifcantly inhibited cabbage’s growth and development.When Cd stress was increased,the phenotypic indicators were signifcantly reduced.Meanwhile,Cd stress signifcantly enhanced the oxidative stress response of cabbage,such as the activities of catalase(CAT),superoxide dismutase(SOD),peroxidase(POD),ascorbate peroxidase(APX),and the content of malondialdehyde(MDA)in leaves.Such a change tended to increase fenestrated tissues’ thickness but decrease the thickness of leaf and spongy tissues.Moreover,Cd stress signifcantly increased soluble sugar,protein,and vitamin C contents in leaves as well as the temperature in the plant canopy.Therefore,Cd stress significantly inhibited the growth,development and physical and chemical characteristics of Chinese cabbage pakchoi.2.PS-MPs(100nm and 1000nm)stress significantly inhibited Chinese cabbage pakchoi’s growth and development.When PS-MPs stress was increased,the phenotypic indicators were significantly reduced.Meanwhile,PS-MPs stress significantly enhanced the oxidative stress response of Chinese cabbage pakchoi,such as the activities of CAT,POD,SOD and APX and the content of MDA in leaves.Such a change tended to decrease fenestrated tissues’ thickness and also decrease the thickness of leaf and spongy tissues.Moreover,PS-MPs stress significantly increased the canopy population temperature of Chinese cabbage pakchoi’s leaves.Microplastic stress has obvious inhibitory effect and toxic damage on the growth,development and physical and chemical properties of Chinese cabbage pakchoi.3.Under the combined stress of Cd and PS-MPs,with the increase of Cd concentration(0,20 and 200 μmol·L-1),the growth and development,photosynthetic physiology,antioxidant enzyme activity,nutritional quality,anatomical structure and temperature inhibition effect of canopy population of Chinese cabbage pakchoi increased gradually.However,exogenous PS-MPs(1 mg·L-1)could effectively alleviate the inhibitory effect of Cd stress.However,with the increase of PS-MPs concentration(20 mg·L-1),the effects of PS-MPs on the above-mentioned physical and chemical characteristics of Chinese cabbage pakchoi showed a compound superposition effect with Cd stress,The effects of exogenous PS-MPs and Cd on Chinese cabbage pakchoi showed a compound trend of low promotion(1 mg·L-1)and high inhibition(20 mg·L-1).In conclusion,Cd and PS-MPs could significantly inhibit the growth,physical and chemical properties of Chinese cabbage pakchoi.However,the combined stress of Cd and PS-MPs could effectively alleviate the toxicity of Cd to Chinese cabbage pakchoi at low concentrations(1 mg·L-1)of PS-MPs,PS-MPs at high concentration(20 mg·L-1)combined with Cd showed a compound stress effect,which aggravated the growth and development of Chinese cabbage pakchoi.