| As the giant nation of agriculture,China can also be called as the giant nation of pesticides because of the large number of annual consumption of pesticides.Nowadays,"green" chiral herbicides are preferentially introduced into usage for higher efficiency to target-plant and more friendly to non-target organisms and human beings.At the same time,continuous increase of demand and usage of pesticides is bound to lead to increasing the residues of chiral herbicides,whose interactions with organisms result in enantioselectivity for the structural differences between the enantiomers of chiral herbicides and finally,different toxic effects will occur between the target and non-target organisms.The growth of plants are closely related with water,light and nutrient elements.In this study,effects of chiral herbicide dichlorprop(DCPP)on the regulation of micro/macro elements in Arabidopsis thaliana as well as the stomatal behaviors were investigated and related mechanism was also discussed in an enantiomeric level,aiming to provide with new sight and methods for more precise elucidation of the enantioselectivity of chiral herbicide DCPP.The main conclusions of this research are showed as followed.(1)The effect of DCPP on the nitrogen uptake and assimilation,synthesis of amino acids and nitrogen stable isotope fractionation(NSIF)were studied.The(R)-DCPP significantly inhibited the uptake of NO3-but promoted that of NH4+,and enhancement of nitrate reductase activity accompanied by decrease of nitrite reductase activity also occurred in(R)-DCPP-treated groups.However,(S)-DCPP didn't exhibited any regulation effects on the uptake and assimilation of nitrogen except for slightly increasing the uptake of NH4+.Enantioselectivity was also observed in the synthesis of amino acids.Therein,(R)-DCPP inhibited the glutamate acid-glutamine cycle but increased the activity of amination direction in glutamate acid dehydrogenase,which promoted the synthesis of glutamate acid.On the other hand,(S)-DCPP did not significantly affect this process.As for the concentration of various amino acids in A.thaliana,six kinds of amino acid,including glutamate acid and aspartic acid,were affected by DCPP in an enantiomeric manner.Furthermore,different type of nitrogen resource resulted in a significantly different value of NSIF,where the value in NH4+group was much more negative.As for the effect of DCPP,the NSIF value of(R)-DCPP-treated groups was much more negative than those of(S)-DCPP and the control,indicating that NH4+ may mediate the enantioselective toxicity of DCPP to A.thaliana.(2)The inhibitor of P450 enzyme,1-aminobenzotriazole(ABT)itself showed no obvious toxicity to A.thaliana,but the addition of ABT decreased the toxicity of(R)-DCPP but enhanced that of(S)-DCPP and the production of reactive oxygen species(ROS)exhibited similar trends.As for the damage to Acetyl CoA Carboxylase(ACCase),(R)-DCPP was more toxic than(S)-DCPP without ABT.The addition of ABT changed the toxicity of DCPP enantiomers in an opposite direction,indicating the mediation role of P450 in the enantioselectivity of DCPP.In addition,ABT weakened the aggregation of Fe in A.thaliana exposed to(R)-DCPP but intensified that of(S)-DCPP.Combining the correlation between DCPP toxicity and abnormal behavior of Fe,we further demonstrated the important roles of Fe and P450 enzyme in the enantioselectivity of DCPP.(3)As for the behaviors of stomata in A.thaliana,low concentration of DCPP showed no obvious regulation effect.At high concentration,only the herbicidal-active(R)-DCPP significantly enhanced the opening extent of stomata and the(S)-DCPP remained almost same to that of control,namely the enantioselectivity was also observed in the effect of DCPP on the stomatal behaviors.Furthermore,stomatal opening extent was positively correlated with the ROS production under DCPP treatments.Considering that ROS production is one of DCPP action mechanisms,the results provided a new sight and method for evaluation of DCPP enantioselectivity. |
PDF Full Text Request