氟氯吡啶酯是科迪华农业科技有限公司（原美国陶氏益农）开发的一种新型芳基吡啶甲酸类激素型除草剂，用于小麦苗后茎叶处理防除阔叶杂草。氟氯吡啶酯的作用机理尚不明确，为了探究其作用机理，本文选取7种我国长江中下游小麦田重要阔叶杂草，探究氟氯吡啶酯对麦田常见阔叶草的室内毒力，明确其杀草谱。测定了氟氯吡啶酯对猪殃殃IAA、ABA、乙烯等植物激素以及活性氧含量的变化，进一步明确作用机理。研究了决定上述生化指标变化的

基因表达情况，进一步在分子水平揭示其作用机理。明确其作用机理，这或许可以扩大其效用，并帮助解决与其使用相关的问题，延长其使用的寿命。主要结果如下：

1. 氟氯吡啶酯对常见麦田阔叶杂草的杀草谱、作用表型及生长素含量的影响。采用整株生测法测定了氟氯吡啶酯对7种麦田阔叶草的室内毒力。结果表明：氟氯吡啶酯对于猪殃殃、播娘蒿、荠菜、大巢菜表现出很好抑制作用，其GR50和GR90均小于其推荐剂量，对于野老鹳、牛繁缕和野芥菜有一定的抑制作用，其GR50小于其推荐剂量。采用植株水培法测定了氟氯吡啶酯对猪殃殃幼苗生长的影响。结果发现，氟氯吡啶酯可抑制幼苗根部和地上部的生长，与2,4-D，IAA，乙烯利处理的表型一致，表现为地上部鲜重和根长显著减少，且浓度越高，对幼苗生长的抑制作用越强。采用植物生长素(IAA)酶联免疫试剂盒(ELISA)测定氟氯吡啶酯对猪殃殃体内IAA含量的变化情况。锚点结果表明，氟氯吡啶酯能诱导猪殃殃地上及地下部分的IAA含量明显升高，扰乱植物体内生长素的平衡，从而产生生长素过量的症状，抑制植物生长。

2. 氟氯吡啶酯对杂草生长素平衡相关基因表达量的影响。采用实时荧光定量PCR（qRT-PCR）测定了氟氯吡啶酯对猪殃殃体内与IAA合成、轭合和转运相关的8个基因表达量的影响（分别为与IAA合成相关的Gayucca6和Gayucca8；与IAA转运相关的GaABCB1、GaABCB4和GaABCB19，与IAA轭合相关的GaGH3.1、GaGH3.6和GaGH3.9）。锚点结果表明，药剂处理后，Gayucca6和Gayucca8基因在地上部和地下部的表达量都明显下调。而GaGH3.1和GaGH3.6基因在药剂处理后的一段时间，在地上部和地下部的表达都明显上调，GaGH3.9基因则都明显下调。地上部分的GaABCB1基因和地下部分的GaABCB1、GaABCB19基因的表达量明显下调，而GaABCB4基因的表达量明显上升。综上所述，氟氯吡啶酯的作用机理是模拟生长素，扰乱植物体内生长素的平衡，但是这一结果可能是通过多种途径造成的，具体的途径，以及其主次顺序，还需要进一步的研究。

3.采用气相色谱法，测定了氟氯吡啶酯处理后对猪殃殃乙烯和ABA生物合成途径的影响。结果发现，药剂处理后，猪殃殃乙烯合成量和ACC含量增加，ACC合酶和ACC氧化酶活性增强。而猪殃殃体内ABA含量持续上升。采用qRT-PCR进一步测定了乙烯生物合成相关基因GaACS4，GaACS7以及ABA合成相关基因GaNCE

D1的表达量。结果显示药剂处理后GaACS4，GaACS7和GaNCED1的基因表达量明显上升。综上所述，氟氯吡啶酯作用后的植物生长抑制与乙烯合成增加以及ABA积累有很大关系。

4.测定了氟氯吡啶酯处理后猪殃殃体内丙二醇、超氧根阴离子以及过氧化氢含量的变化。结果表明，药剂处理后猪殃殃体内丙二醇、超氧根阴离子以及过氧化氢的含量迅速上升，说明药剂的处理对猪殃殃造成了强烈的氧化胁迫，从而导致植物受到伤害。

综上所述，氟氯吡啶酯的作用机理主要是扰乱植物体内的生长素平衡，导致与植物衰老和死亡相关的乙烯和ABA等植物激素的合成增加，以及活性氧大量积累，导致氧化胁迫，最终导致植物的衰老和死亡。而扰乱植物生长素的平衡，可能是通过多种途径完成的，其中可能包括IAA的合成、代谢和转运，但是具体涉及哪些途径，还需进一步的研究来确定。

Halauxifen-Methyl, a post-shoot herbicide using for controlling broadleaf weeds in wheat field, is a new auxin herbicide developed by Dow Agro Sciences as the first herbicide that be classified as arylpyridinecarboxylic acid. In this study, 7 species of broadleaf weeds which are dominant or regional dominant in wheat fields in China, were collected in our laboratory to explore the laboratory toxicity of halauxifen-methyl on common broadleaf weeds in wheat fields and we selected Galium spurium as the material for the later research. And then, the changes of plant hormones such as IAA, ABA and ethylene, as well as the contents of reactive oxygen species (ROS) in G. were studied, to further reveal the molecular mechanism of halauxifen-methyl. It provides valuable insights into expand its utility and helping to address issues associated with its use, extending its useful life well into the future.

The main results are as follows:

1. The inhibitory spectra of weeds, inhibition of growth and effects on IAA level of halauxifen-methyl. The whole plant bioassay method was used to determine the herbicidal activity of halauxifen-methyl on 7 common broadleaf weeds in wheat fields, and the results showed that halauxifen-methyl remarkable inhibitory effect on Galium spurium, Descurainia sophia, Vicia gigantea, Capsella bursa-pastoris, and a certain inhibitory effect on Geranium carolinianum, Malachium aquaticum, Raphanus raphanistrum. And the effects of different concentrations of halauxifen-methyl on the growth of Galium spurium seedlings were studied by

 using hydroponic method. The results showed that the treatment with halauxifen-methyl can cause growth inhibition of root and shoot, which is consistent with the inhibiting effect of 2,4-D, IAA and ethephon. The fresh weight and root length of shoot were significantly decreased, and exhibited a positive correlation with the concentration of the compounds in general. The IAA content in the above-ground and underground parts after treated with halauxifen-methyl were evaluated by ELISA respectively. The results showed that halauxifen-methyl could induce the content of IAA in the aboveground and underground parts of the sensitive Galium spurium to increase obviously, which disturbed the auxin balance in the plant, thus occurred symptoms of IAA overdose, eventually lead to growth inhibition and plant death.

2. The effects of halauxifen-methyl on the expression of genes related to weed auxin homeostasis were studied by real-time quantitative PCR (qRT-CR) . Eight genes involved in plant endogenous auxin content were identified, in which two genes (Gayucca6, Gayucca8) are responsible for auxin biosynthesis, three genes(GaGH3.1, GaGH3.6, GaGH3.9) are involved in amino acid conjugation for IAA, three genes (GaABCB1，GaABCB4，GaABCB19) are involved in auxin transport. The expression profile of these 8 genes in both aboveground and underground parts of G. were analyzed by qRT-PCR. The results show that the expression of Gayucca6 and Gayucca9 in both aboveground and underground parts of G. declined significantly after treatment with halauxifen-methyl and 2,4-D。On the contrary, the expression of GaGH3.1 and GaGH3.6 in both aboveground and underground parts of G. was induced significantly after treatment. Meanwhile, the expression of GaGH3.9 in both aboveground and underground parts of of Galium spurium was decreased significantly. At the GaABCBs’ transcriptional level, GaABCB1 in the in both aboveground and underground parts and GaABCB19 in the underground parts of the treated G. was significantly lower than the control. Nevertheless, the expression of GaABCB4 in both aboveground and underground parts of G. was significantly increased after treatment. In conclusion, the mode of action of halauxifen-methyl acts as synthetic mimics of IAA at high concentration and disturb the auxin balance in the plant. It is possible to disrupt auxin balance in plants through multiple pathways, however the specific pathways and their priorities, require further study.

3. The effect on the ethylene and ABA biosynthetic pathway after treatment with halauxifen-methyl were measured by Gas chromatography and ELISA respectively. The result show that compared with the control, ethylene synthesis, ACC content, ACC synthase activity and ACC oxidase activity increased in a period of time after the treatment. In addition, the ABA content showed a trend of increasing after treatment with halauxifen-methyl. And then, quantitative analysis of ethylene synthesis related genes(GaACS4, GaACS7) and ABA synthesis related genes(GaNCED1) was measured by qRT-PCR. The result show that the expression of GaACS4, GaACS7 and GaNCED1 was significantly up-regulated after treatment.In conclusion, the inhibition of plant growth by halauxifen-methyl is related to the increase of ethylene synthesis and the accumulation of ABA.

4. The content of H2O2, .O?- and MDA was measured after treatment with halauxifen-methyl and 2,4-D, and their contents show showed an upward trend, suggested that the treatment of halauxifen-methyl and 2,4-D caused damage to the plant and made it suffer oxidative stress.

Based on the above results, it can be concluded that the mode of action of halauxifen-methyl is disturbing the auxin balance in the plant, and then thylene synthesis, ABA content and ROS content increased, eventually leads to plant senescence and death. It is possible to disrupt auxin balance in plants through multiple pathways, such as IAA synthesis, IAA metabolism and IAA transport, however the specific pathways and their priorities, require further study.