The Defense Response Mechanism Of Wheat To PAEs Pollution

In this paper,we investigated the defense response of wheat to PAEs in fluvo-aquic soil.The biomarkers including photosynthesis,antioxidative enzymes were determined in order to reveal the possible defense mechanism of wheat to PAEs.The results are as follows:（1）Defense response of wheat to DBP and DEHPat physiological levelThe photosynthetic rate（Pn）,maximum photochemical efficiency（Fv/Fm）,electron transfer rate（ETR）,chlorophyll a and total chlorophyll content and biomass of wheat decreased at seedling,jointing and booting stages under DBP and DEHP stress,however intercellular carbon dioxide concentration（Ci）increased and chlorophyll b and stomatal conductance（Gs）in booting did not change significantly.The results showed that the PS Ⅱ reaction center in wheat was damaged,resulting in the decrease of chlorophyll a contento The reduction of Pn caused by the non-stomatal factors and it was reflected in the decrease of biomass.The decrease of wheat biomass was due to the DBP and DEHP interfered the synthesis of enzyme in the Calvin-Benson cycle.（2）Antioxidative defense response of wheat to DBP and DEHP stressThe O₂·-production rate and H₂O₂ content in roots and leaves at seedling,jointing and booting stage increased with the increase of pollutant DBP and DEHP concentration.At the maturity stage,the changes of O₂·-production rate and H₂O₂ content was similar to roots and leaves.The enzyme activity of cytochromes（P450）,superoxide dismutase（SOD）,catalase（CAT）,glutathione peroxidase（GPX）and ascorbate peroxidase（APX）increased firstly and then decreased with the increase of DBP and DEHP concentration at seedling stage.At the jointing and booting stages,the activities of P450,SOD.CAT,GPX and APX in wheat leaves and roots were as well as grains which increased with the increase of DBP and DEHP concentration.The results showed that,roots and leaves of wheat were damaged serviouly with an increase of DBP and DEHP concentration at seedling stage,while the injury gradually reduced at jointing and booting stage.No programmed death（PCD）due to ROS production in wheat grain endosperm cells.Malondialdehyde（MDA）content of wheat in different periods increased with the increase of DBP and DEHP concentrations.Transport and metabolism of DBP and DEHP in wheatThe contents of DBP and DEHP in wheat leaves,roots and grains increased with the increase of DBP and DEHP in different periods.The content of DBP and DEHP in leaves and roots decreased with the growth of wheat.The translocation factor（TF）of DEHP from root to leaf was greater than that of DBP at seedling and jointing stages,while it was the opposite the booting stage.The monoester metabolites of DBP and DEHP were MBP and MEHP,respectively.The content of MBP and MEHP in leaves and roots firstly increased and then decreased with the growth of wheat.The metabolism of DBP and DEHP mainly occured at the jointing and booting stage.The metabolic rate of DEHP in the leaves was higher than that in the roots,while the DBP is the opposite.DBP and its metabolites were more abundant than DEHP in wheat grains under the same DBP and DEHP concentrations.