Toxicity Response Of Cucumber To Dibutyl Phthalate

As the Taiwan Food plasticizer event in2010set off a storm in the world, phthalate which occupies a dominant position in the food plasticizer raised considerable concern. Dibutyl phthalate (DBP) is one kind of plasticizers mainly used in the plastics industry, and also has been in heavy usage in most research works focusing on the effect of phthalic acid ester compounds (Phthalate esters, PAEs) in recent years. In the field of food contact materials, many countries have instituted relevant laws and regulations against the usage of phthalic acid esters materials. As an environmental hormone disruption substance, phthalic acid ester such as dibutyl phthalate ester can interfere with the endocrine system of human and animals under extremely low concentrations, large doses have teratogenic, carcinogenic and mutagenic effect, on the organism. China Environmental Monitoring Station, the U.S. Environmental Protection Agency and the European Union, along with other countries have controlled the compound as one of the priority pollutants in the environment, but so far few studies have been made in its toxicological effects on plants. In order to clarify the toxicological response mechanisms of plants to phthalic acid esters, a test was conducted using the cucumber (cucumis sativus L.) cultivars Jinyan4as the test plant, with four dibutyl phthalate concentrations,30,50,100and200mg-L-1, while Hoagland’s nutrient solution was used in the control group. The germination conditions of cucumber seeds, physiological characteristics of leaves in different sampling periods, fruit yield, nutritional quality and leaf ultrastructure of plants under dibutyl phthalate stress were compare with the control plants grown without DBP. The results showed that:1. cucumber seed germination was influenced by the different DBP concentrationsJinyan No.4seed germination after treatment with different DBP concentrations were subjected to different degrees of germination inhibition. Application of200mg-L-1DBP treatment compared with the control groups showed significant difference. Fresh weight, lateral root number, root length, lateral root length under DBP application were decreased after an initial increase, which reached maximum (p<0.05) at30mg·L-1DBP treatment conditions by increased1.90%,38.30%,11.01%,10.81%compared with the control group. While for germination rate, germination potential, germination index, vigor index, these factors decreased with increasing DBP concentrations compared with the control group at100and200mg·L-1DBP levels (p<0.05), showed a strong inhibitory effect of the DBP appied.2. This study confirms the DBP treatment can lead to damage of cucumber leaves peroxidation and protective enzyme activities.The results of this study on the examined indicators showed that with the extension of DBP processing time, cucumber leaves SOD, APX, CAT and POD have overall activity gradually increased after decreasing trend under different concentrations of DBP, whereas SOD at low DBP concentrations (30and50mg·L-1) gradually increased, showing a higher resistance; while MDA, H2O2contents showed a sharp rise, under high concentrations of DBP (100and200mg·L-1) compared with the control group showing a significant difference (p<0.05).3. At the same time, chlorophyll, proline and reduced/oxidized glutathione content in leaves of cucumber were tested under the treatment of DBP, also confirmed that DBP has toxic effects on the growth of Cucumber.In this study, chlorophyll, reduced glutathione content in cucumber leaves gradually decreased with DBP concentration while the treatment time increased, and reached a significant level (p<0.05); Proline and oxidized glutathione content also increased significantly (p<0.05). All of these changes in the effect of high DBP concentrations (100and200mg·L-1) on the cucumber plants, reflect the plant suffered serious damage.4. The leaves of cucumber ultrastructural observation further confirmed the toxic damage of DBP.Comparing the DBP treatment group with the control group, the chloroplast morphology showed swelling deformation, thylakoid arrangement became disorganized and gradually disintegrated; the internal structure was simple, showing accumulation of starch granules; mitochondrial membrane possessed a certain profile, but showed more obscure, internal fold reduction.5. DBP treatment showed great effect on cucumber fresh fruit weight and nutritional quality.Cucumber fresh fruit weight, the soluble sugar content, Vc content, organic acid were decreased gradually with the increasing of DBP concentration, and soluble sugar increased significantly (p<0.05).