Effects Of Three Kinds Of Sulfonylurea Herbicides On Physiological Characteristics And Yield Of Millet

Millet was the main forage dual-purpose type drought-resistance crops in northern China, which owned the character of rich nutrition, strong stress resistance and so on; while disease weed was the main limited factor influencing the high and stable yield of millet, millet output reduction reached to about 20% in China due to grass harm, and even to die when it was serious. At present, the production costs of weeding increased, and the production efficiency reduced because herbicides used widely in the large area grain field are few, and the traditional workload by artificial weeding was large. Therefore, in order to examine the effects of sulfonylurea herbicides such as monosulfuron, tribenuron-methyl and Nicosulfuron on physiological characteristics and yield traits during the seedling growth and the whole growth stage of Millet, and screening herbicides and optimum concentration on millet from samples, both safe and efficient. In this experiment, Zhangzagu 10 and Jingu 21 were used as test material to determine the effects on agronomic characteristic, photosynthetic pigment content, photosynthetic index, chlorophyll fluorescence parameters, protection enzyme activity, MDA content and 1000 grain weight, yield in millet by spraying different dose of Monosulfuron, tribenuron methyl and Nicosulfuron on the stem and leaf at the 3-5 leaf stage in millet, and the main experiments results were as follows:The millet plant height and leaf area were restrained by three kinds of sulfonylurea herbicides: little significance of Monosulfuron on the millet plant height was observed after spraying 5 and 15 days, and after 25 days the plant height reduced significantly; no significantly difference on millet leaf area compared with the CK were observed, after 15 days the leaf area reduced significantly and returned to normal levels after 25 days. Compared with CK, the millet plant height and leaf area were inhibited significantly by Tribenuron methyl and Nicosulfuron after 5 days, while after 25 days, the treatments of low dosage of tribenuron methyl gradually were recovered to the normal level, but the high one still influenced the plant height, leaf area significantly ; Millet plant height, leaf area of both two millet cultivar were inhibited seriously by Nicosulfuron just after spraying 5 days, leaf fade and leaf growth was stopped, and even death phenomenon was probably to happen under high doses Nicosulfuron.Photosynthetic pigment content of two millet varieties leaf were reduced by three kinds of sulfonylurea herbicides, and more effects on chlorophyll a compared with chlorophyll b and carotenoids; among which the leaf carotenoids treated with different doses of Monosulfuron were not affected, and along with the development of growth period, the photosynthetic pigment could be recovered to a certain extent.Under the Herbicide stress conditions, the millet leaf net photosynthetic rate, transpiration rate, stomatal conductance value showed lower than the water treatment one, and the intercellular CO2 concentration increased significantly than the CK, which suggested that herbicide stress could be able to decrease the photosynthetic rate of millet, and the consequent non-stomatal factors probably were the main reason of the decline of Millet photosynthetic rate in two millet varieties.With the increase of spraying dosage of three kinds of herbicide, the maximal photochemical efficiency of millet leaves (Fv/Fm), the actual photochemical efficiency (PS â…¡) and photochemical quenching (qP) showed depressed significantly, instead, non-photochemical quenching(NPQ) increased and showed a certain dose-effect relationship, so the results indicated that under herbicide stress conditions, PS â…¡ complex of millet leaf was subject to the damage, the opening degree of PS â…¡ reaction center was reduced, also the activity was weakened, photochemical efficiency was low, the light energy absorbed was released more in the form of heat dissipation, and maybe the increase of NPQ could be seen a kind of self-adjustment mechanism of millet leaves response on herbicide stress.Under different treatments of the herbicide, SOD activity, POD activity and MDA content of the millet leaf were elevated, but membrane lipid peroxidation level was aggravated. Moreover, most POD activeness, SOD activeness and MDA content showed the trend that increased with herbicide spraying dosage increased at first and then decreased in the earlier stage of spraying the herbicide. After spraying 25 days, no significant difference between different herbicide treatments and the water treatment on POD, SOD activeness and MDA content were observed and most value were recovered to normal levels in ZhangzagulO leaf; on the contrary, almost all the value in the Jingu21 under the high-dose treatment still maintained higher level and the significant difference occurred ,which showed that in the drug 25 days or so after that, the effect of herbicide in vivo of millet gradually disappeared and some certain recovery would occur on the millet, especially stronger to a certain extent for Zhangzagu10 compared with Jingu 21 in the recovery ability.Both two Millet varieties showed that yield had in a certain increased under different spraying doses of Monosulfur and that could be manifested by this trend increased firstly and then decreased with the increase of the dose; Specifically, the yield of ZhangzagulO and Jingu 21, respectively, increased by 4.79-13.96%, 2.01-9.72% compared with water treatment; in addition, the changing trend of the yield components were consistent with yield one. Tribenuron methyl changed the panicle type of the millet, and the ear length, ear diameter and spike grain weight decreased gradually with the increase of the doses, moreover, panicle type became short, fine and compact. Low dose of tribenuron methyl treatment improved the yield of millet, but high dose ones reduced grain yield significantly; as for the varieties, yield of Zhangzagu 10 and Jingu 21 compared with the water treatment increased by 1.87-4.83% and 2.02%, respectively. Millet treated with Nicosulfuron stopped growing and even died under a high spraying dose after 5 days; until after 15 days, all millet treated with all different doses were dead.All the factors indicated that Monosulfuron was the safest on Millet, then the tribenuron methyl, and the Nicosulfuron was worst.