The Effect Of Tribenuron-methyl On The Safety Of Different Foxtail Millet Varieties

Tribenuron-methyl is a sulfonylurea herbicide used in wheat fields.Although it is an acetolactate synthase(ALS)inhibitor herbicide,inhibiting photosynthesis of crops may be another action site of the lethal mechanism of such herbicides.Because of different gramineous crops or different varieties of the same crop,such as wheat,corn,rice and foxtail millet,there are differences in its sensitivity.In order to explore the photosynthetic physiological mechanism of tribenuron-methyl on the safety of different foxtail millet varieties.This article studied the effects of different dosages of 10% tribenuron-methyl WP(0 g/hm~2(CK),112.5 g/hm~2(T1),225 g/hm~2(T2,recommended dosage)and 450 g/hm~2(T3))on the photosynthetic pigment content,P700 parameters,chlorophyll fluorescence parameters,energy allocation and utilization,key enzyme activities of carbon assimilation,gas exchange parameters,yield component parameters,and yield of the top 2 leaves of 9 foxtail millet varieties(Jingu 5,Zhangzagu 10,Zhangzagu 13,Jingu 21,Zhonggu 9,Yugu 18,Huangjingu,Jigu 35 and Longgu 39).The main results were as follows:1.The effect of tribenuron-methyl on agronomic characteristics and yield of different foxtail millet varieties(safety).The treatment of 112.5 g/hm~2(T1)tribenuron-methyl basically did not affect the agronomic traits of all the foxtail millet varieties.Seven days after the treatment of 225 g/hm~2(T1)tribenuron-methyl,the plant heights of Jingu 5,Zhangzagu 10,Zhangzagu 13,Jingu 21 and Longgu 39 were significantly inhibited,the leaf area of Zhangzagu 10 and Zhangzagu 13 were significantly reduced,and the inhibitory effect on stem thickness were small.14 days and 21 days after treatment,the plant height and leaf area of Jingu 21 and Yugu 18 were both significantly reduced.The panicle weight of Jingu 5,the panicle weight and panicle grains weight of Yugu 18,and panicle grains weight of Jigu 35 significant decreased.Yield of Yugu 18 and Huangjingu significant decreased.The plant height and leaf area were significantly reduced at the early stage of the treatment of 450 g/hm~2(T1)tribenuron-methyl,21 days after treatment,the plant height and leaf area of Jingu 21,Yugu 18 and Jigu 35 were all significantly reduced.The panicle grains weight and 1000-grain weight of Jingu 5,Yugu 18 and Huangjingu,and the panicle length,panicle thickness,panicle weight,panicle grains weight and yield of Jigu 35 were all significantly reduced.2.The photosynthetic physiological mechanism of tribenuron-methyl on different foxtail millet varieties.The treatment of 112.5 g/hm~2(T1)tribenuron-methyl did not affect the photosynthetic system of foxtail millet varieties.After 21 days of treatment,under the treatment of 225 g/hm~2(T2,the recommended dosage)of tribenuron-methyl,compared with the control,the Y(NO)of all foxtail millet varieties had no significant differences or decreased,and the Y(NPQ)had no significant differences or increased;NADP-MDH,PEPC,PPDK and NADP-ME activities of Zhangzagu 13 and Longgu 39 were all alleviated,and the photosynthetic enzyme activities of the other foxtail millet varieties still had significant differences compared with the control;Compared with the control,the Pn of Zhangzagu 10,Zhangzagu 13,Huangjingu and Longgu 39 were not significantly different,and the photosynthetic pigment content and Pn of other foxtail millet varieties were significantly reduced.Under the treatment of 450 g/hm~2 tribenuron-methyl,compared with control,the photosynthetic fluorescence parameters of Zhangzagu 13 and Longgu 39 had no significant differences basically;the Y(NO)of Yugu 18 and Jingu 21 increased significantly;Y(NPQ)and Ex of Jingu 5,Zhangzagu 10 and Zhonggu 9 were significantly increased,while Y(II),ETR(II),q P,and P were significantly decreased;Y(NA)of Huangjingu and Jingu 21 were increased significantly,while Y(I)and ETR(I)decreased significantly;except for Zhangzagu 13,the activities of other foxtail millet varieties of NADP-MDH,PEPC,PPDK,NADP-ME and Rubisco were basically inhibited to varying degrees;except for Zhangzagu 13 and Longgu 39,the Pn of leaves of other foxtail millet varieties were inhibited.After tribenuron-methyl treatment,the thylakoid structure in the chloroplast structure of foxtail millet leaves dissolved or even disappeard,the lamella arrangement was disordered,the structure was unclear,The lamellas spacing became smaller,thinner or even disappeard;some thylakoids were permanently destroyed;chloroplasts dissolved;cell membrane ruptured;severed separation of plasmoplasm;mitochondria swelled and ruptured.Based on this experimental study,in terms of output impact,the recommended dose of tribenuron-methyl was relatively safe for other foxtail millet varieties(Zhangzagu 10,Zhangzagu 13,Jingu 21,Zhonggu 9,Longgu 39),except that it inhibited the output composition parameters of Jingu 5,Yugu 18,Huangjingu and Jigu 35.One of the reasons for the decline in the yield of some foxtail millet varieties might be that high dose of tribenuron-methyl destroyde the thylakoid structure in the chloroplast structure;This caused a decrease in the photosynthetic pigment content of foxtail millet leaves,hindered electron transfer,unbalanced energy distribution,and the key to carbon assimilation enzyme activities were reduced,thereby influced the smooth progress of photosynthesis.