| Foxtail millet is an important edible crop in northern China and has a high nutritional value.However,the weeds in the field have seriously affected the growth and development of the foxtail millet,and reduced the yield of foxtail millet.Bensulfuron-methyl and pyrazosulfuron are both ultra-efficient sulfonylurea herbicides that have good applications in rice fields,but have rarely been reported in the application of foxtail millet fields.To explore the effects of these two herbicides on the safety and physiological characteristics of foxtail millet,Jingu 21 and Zhangzagu 10 were used as materials,and different usage of herbicides were sprayed at the 3-5 leaf stage.Bensulfuron-methyl and pyrazosulfuron were sampled at 3,7,15,30 days,respectively.The agronomic traits,photosynthetic characteristics,chlorophyll fluorescence parameters,membrane lipid peroxidation degree,protective enzyme system,non-enzymatic system and yield composition of the foxtail millet were studied.The main results are as follows:1.Both these two herbicides reduced the height,leaf area,stem diameter and yield of foxtail millet to different degrees,and the degree of inhibition was relieved 30 days after the treatment.The stem diameter and plant height treated by bensulfuron-methyl was higher than which by pyrazosulfuron.The plant height treated by pyrazosulfuron at the recommended usage(300 g/hm~2)treatment was significantly lower than the control.The recommended usage of bensulfuron-methyl(300 g/hm~2)is relatively safe to foxtail millet,which is not significantly different from the control.The recommended usage of pyrazosulfuron(300 g/hm~2)significantly reduced the yield of foxtail millet,which was relatively unsafe to foxtail millet.2.Under the herbicides stress,the total chlorophyll(Chl(a+b)),chlorophyll a(Chla),chlorophyll b(Chlb)and carotenoid(Car)content of foxtail millet leaves decreased to different degrees,but the carotenoids content(Car).The decrease of the photosynthetic pigments content in foxtail millet leaves leads to the decline of net photosynthetic rate(Pn),maximum photochemical yield(Fv/Fm),apparent photosynthetic electron transfer rate(ETR)and photochemistry of foxtail millet leaves.However,the intercellular CO2 concentration(Ci)and non-photochemical quenching coefficient(q N)after herbicides treatment were increased.3.After foliar application of herbicides,the dynamic balance of reactive oxygen species in the leaves of foxtail millet leaves was destroyed,and the enzymatic antioxidant system and non-enzymatic system of foxtail millet began to work.Antioxidant enzymes in foxtail millet leaves at recommended concentrations(300 g/hm~2): SOD,POD,CAT,APX activities,valley The activity of GR activity was higher than that of the control,indicating that the foxtail millet seedlings can adapt to the herbicide stress by increasing their activity.At high concentrations(1200 g/hm~2),the activity of antioxidant enzymes decreased,beyond the range that it can withstand.At the same time,the MDA content increased,resulting in membrane lipid peroxidation,and the antioxidant capacity of foxtail millet has been severely damaged.At 30 days after the drug,the stress of the foxtail millet was relieved,and the recovery ability of Zhangzagu 10 was higher than that of Jingu 21.In conclusion,pyrisulfuron-methyl significantly reduced the yield of foxtail millet at the recommended usage(300 g/hm~2),while bensulfuron-methyl was relatively safe on foxtail millet at this concentration.Under the stress of two herbicides,the agronomic traits of foxtail millet were reduced to different degrees.The decrease of photosynthetic pigments in foxtail millet leaves leads to the unreasonable distribution and dissipation of light energy,the decrease of net photosynthetic rate,and the photoinhibition in leaves.To reduce the membrane lipid peroxidation caused by reactive oxygen species,foxtail millet forms a defense system composed of enzymatic and non-enzymatic antioxidant substance,and the damage of herbicide on foxtail millet becomes less and less with the growth.Zhangzagu 10 is more resistance to the herbicide than Jingu 21. |
