Effects Of Din-butyl Phthalate On Growth Stress And Oxidative Damage Of Pakchoi

Phthalate esters（PAEs）,commonly known as phthalates,are a class of phthalate chemicals commonly used in plastic products as plasticizers.Phthalate dibutyl phthalate（DBP）is widely used in daily life and represents a group of phthalates.Due to the characteristics of volatilization and decomposition,DBP is easy to be released into the soil environment,especially in facility agriculture where a large amount of agricultural film is used.DBP can also threaten human health through skin,respiration and food chain transmission.Pakchoi,as a facility vegetable crop widely cultivated and eaten,can easily absorb DBP from the soil environment,thus affecting the quality of vegetables and endangering human health through the food chain.However,the toxic effect of DBP on Pakchoi remains unclear.In this study,the effects of DBP on the growth,physiology,biochemistry and molecular indexes of Pakchoi（Brassica campestris L.）seedlings were investigated through indoor pot experiment,and the toxicity of DBP on Pakchoi was comprehensively evaluated from individual,cellular and molecular levels.The main research results are summarized as follows:（1）The influence of DBP concentration on growth index of Pakchoi was studied.The germination rate,plant height,root length and growth amount decreased obviously with the increase of DBP concentration.Germination rate decreased from 89.67%to 78.83%.The growth trend of biomass and leaf area decreased with DBP concentration increasing.The growth rate decreased with the increase of DBP concentration,which was most obvious on the24th day,from 13.61 mm~2 in the control group to 10.74 mm~2 in the 200 mg/kg group.（2）The effects of different concentrations of DBP on photosynthesis and accumulative substance content of Pakchoi were studied.The concentrations of plant pigments chlorophyll a,b and carotenoids were affected by DBP concentration,and the pigment content decreased with DBP concentration increasing.The contents of chlorophyll a,chlorophyll b and carotenoid were decreased in different concentrations of DBP,and the growth and development of plants were adversely affected.Soluble sugar（TSS）and total protein（TP）were also significantly affected,and the content of TSS was negatively correlated with the concentration of DBP,showing a significant dose-response relationship.The content of TP also decreased under the influence of DBP concentration.（3）The effects of DBP concentration on ROS level,antioxidant enzyme system and proline content of Pakchoi were discussed.The content of hydrogen peroxide（H₂O₂）was positively correlated with DBP concentration,and the content of superoxide anion(·O^2-)also showed an upward trend with the increase of DBP concentration.The increase of H₂O₂ and·O^2-indicated that ROS was increased under the influence of DBP,and the cells in Pakchoi were damaged and their growth and development were affected.SOD and POD were common enzymes in antioxidant system.SOD activity increased first and then decreased with the cycle.The highest activity was found at 200 mg/kg exposure concentration,and POD activity was similar to SOD activity.Proline content was positively correlated with DBP concentration and presented a significant dose-response relationship.（4）The effect of DBP concentration on gene expression level of Pakchoi was determined.Sensitive indexes at biochemical level were screened out by comprehensive biomarker response index analysis of plants,and the sod,pod and cat enzyme activity genes were amplified by real-time fluorescence quantitative PCR on the 24th day to obtain Ct values,and the relative gene expression levels were analyzed as follows:compared with the control group,the expression level at 2,20 and 200 mg/kg was lower than that in the control group,and the expression level decreased with the increase of concentration.Especially in medium and high concentration（20and 200 mg/kg）groups,the expression level decreased more significantly.This study explored its toxicity effects from individual,physiological and biochemical levels to molecular levels,so as to provide reference for the influence of agricultural film mulching on the growth of vegetable crops in practical production,which has research significance.