| In order to explore the application of defoliant in mung bean,two mung bean varieties(Zhenglv 12 and Jilv 0616-4)were used as materials and four defoliant treatments were set up,namely,CK,ETH,glyphosate and ethephon + glyphosate(ETH+G).By measuring the microstructure of detached cells,physical changes of plant leaves,chlorophyll fluorescence parameters,yield and mechanical harvesting characteristics of leaves with hydrolase activity in detached cell wall of mung bean,the effects of different defoliating agents on physiological regulation and mechanical harvesting characteristics of mung bean leaves were analyzed in order to provide theoretical and technical basis for the popularization and application of defoliant in mung bean production.Under the test results: The main results were as follows:(1)After spraying defoliant,the breakage of detached cells in petiole abscission zone of mung bean appeared earlier than that of the control.The leaves of glyphosate treatment appeared yellowing-falling or withering but not falling earlier than CK treatment,and leaf yellowing and shedding occurred in ETH treatment compared with CK treatment.(2)Spraying defoliant significantly increased polygalacturonase(PG)activity in petiole abscission zone of mung bean.ETH,G and ETH+G treatments of Zhenglv 12 and Jilv 0616-4 significantly increased 165.49% and 65.12%,83.53% and 193.58%,110.59%and 153.73%,respectively,compared with CK treatment.Defoliant inhibited CL activity in petiole of two mung bean varieties.The ETH,G and ETH+G treatments of Zhenglv12 and Jilv 0616-4 decreased compared with CK,11.09% and 3.03%,12.55% and 3.37%,15.88% and 6.48%,respectively.Glyphosate increased PE activity of Zhenglv 12 and decreased PE activity of petiole of Jilv 0616-4,which indicated that there were differences in enzyme activities related to petiole abscission of different mung bean varieties.(3)Defoliant significantly decreased the maximum photochemical efficiency(Fv/Fm),relative chlorophyll content(SPAD),actual photosynthetic rate(Y Ⅱ),net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(Tr)in the leaves of two mung bean varieties,while the quantum ratio of PSII heat dissipation and non-photochemical quenching coefficient increased significantly.The effects of defoliant on the fluorescence characteristics of two mung bean varieties were basically the same with time,in which the non-photochemical quenching coefficient and PS Ⅱ thermal dissipative electron ratio of leaves treated with defoliant were higher than those of CK,indicating that the leaves were damaged by defoliant.On the third day,the net photosynthetic rate of leaves of ETH,G and ETH+G treatments of Zhenglv 12 and Jilv0616-4 decreased by 17.15% and 33.17%,38.11% and 71.76%,74.88% and 29.10%,respectively,compared with CK treatment.The transpiration rate of ETH,G and ETH+G treatments of Zhenglv 12 and Jilv 0616-4 decreased by 19.15% and 35.03%,64.82% and78.73%,37.38% and 70.69%,respectively,compared with CK treatment on the third day,indicating that the photosynthetic efficiency of leaves decreased,the leaf function was gradually inactivated,and the leaf photosynthetic function period ended ahead of schedule.(4)The analysis of yield components showed that defoliant significantly increased the number of pods per plant and the rate of mature pods,but had no significant effect on the weight of 100 seeds and the number of seeds per pod.The yield data of two years showed that ETH and ETH+G had different effects on the yield of two mung bean varieties.The yield of two mung bean varieties was increased by G treatment.In 2021,the yield of Zhenglv 12 and Jilv 0616-4 increased by 20.97% and 72.42% respectively compared with CK,and the yield of Zhenglv 12 and Jilv 0616-4 increased by 41.61%and 6.34% respectively compared with CK in 2022.Three kinds of defoliating agents significantly increased the defoliation rate and mature pod rate,while the stem moisture content of mung bean decreased significantly,so it was more suitable for mechanized harvesting.To sum up,defoliant can reduce the photosynthetic fluorescence characteristics of mung bean leaves,enhance polygalacturonase activity,reduce cellulase activity,cause petiole detachment cell degradation,promote leaf shedding,and accelerate the process of stem dehydration;at the same time,glyphosate can increase the yield by increasing the number of pods per plant and the rate of mature pods in two mung bean varieties.Therefore,it is suggested that in the planting process of Zhenglv 12 and Jilv 0616-4,glyphosate can be sprayed to reduce the working load and harvest loss during mechanized harvest,so as to provide technical support for high yield and high efficiency cultivation of mung bean. |
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