Regulation Effect Of Uniconazole On Growth And Yield Of Adzuki Bean Under Different Nitrogen Levels

Adzuki beans can not only enrich people’s diet structure,but also have a variety of health care functions,and are often used as land and disaster relief crops in production.This study was carried out in the experimental base of the National Grain Engineering Technology Research Center of Heilongjiang Bayi Agricultural University from 2021 to 2022.Zhenzhuhong（small grain variety）and Jihong 352（large grain variety）were selected as test varieties.The adzuki bean materials were cultured by pot method,and three nitrogen levels were set up:low nitrogen(N_0.5-pure N 28.8 kg·hm^-2),medium nitrogen(N₁-pure N 57.6 kg·hm^-2)and high nitrogen(N_1.5-pure N 86.4 kg·hm^-2).On this basis,different concentrations of uniconazole solution(0 mg·L^-1,25 mg·L^-1,50 mg·L^-1)were sprayed at the early flowering stage,and the effects of different concentrations of uniconazole on the morphological characteristics,photosynthetic characteristics,key physiological indexes of carbon and nitrogen metabolism of adzuki bean plants under different nitrogen levels were compared and analyzed.The effects of uniconazole on the growth and yield of adzuki bean under different nitrogen levels were clarified,in order to provide theoretical basis and reference for improving the yield of adzuki bean by spraying uniconazole in production.1.Spraying appropriate concentration of uniconazole at early flowering stage can improve the morphological characteristics of adzuki bean under different nitrogen levels and promote dry matter accumulation.With the increase of nitrogen application level,the root length of the two tested adzuki bean varieties decreased,while the plant height,stem diameter and leaf area increased.On the 40th day after treatment,the dry matter accumulation of stems,leaves,petioles and whole plants of the two tested adzuki bean varieties also increased with the increase of nitrogen application level,but the dry matter accumulation of roots and pods was the highest under medium nitrogen treatment.Spraying 50 mg·L^-1uniconazole at the early flowering stage reduced the plant height of the two tested varieties at different nitrogen levels,increased stem diameter,leaf area and root length,and promoted root,stem,leaf,petiole,pod and whole plant dry matter accumulation.On the 40th day after treatment,spraying 50 mg·L^-1uniconazole at the early flowering stage had a more significant effect on the inhibition of plant height and the promotion of root length and stem diameter of the two tested adzuki bean varieties under low and medium nitrogen conditions than under high nitrogen levels.2.Spraying appropriate concentration of uniconazole at early flowering stage can improve the photosynthetic characteristics of adzuki bean under different nitrogen levels.Compared with medium and high nitrogen treatments,low nitrogen treatment reduced the photosynthesis-related indicators of the two tested adzuki bean varieties.Spraying 25 mg·L^-1and 50 mg·L^-1uniconazole at the early flowering stage increased the key photosynthetic indexes of the two tested adzuki bean varieties under different nitrogen levels,including chlorophyll a,chlorophyll b and total chlorophyll content,as well as net photosynthetic rate,transpiration rate,intercellular CO₂concentration,stomatal conductance,and the effect of 50 mg·L^-1uniconazole treatment was more significant.3.Spraying appropriate concentration of uniconazole at early flowering stage can increase the sugar content and key enzyme activity of sugar metabolism in adzuki bean leaves under different nitrogen levels.Compared with low nitrogen treatment,medium and high nitrogen treatment increased the contents of soluble sugar,sucrose,fructose and the activities of sucrose phosphate synthase and sucrose synthase in the leaves of two adzuki bean varieties to a certain extent.Spraying 25 mg·L^-1and 50 mg·L^-1uniconazole at the early flowering stage promoted the increase of sugar content,sucrose phosphate synthase and sucrose synthase activity in the leaves of the two tested adzuki bean varieties under different nitrogen levels.The effect of 50 mg·L^-1uniconazole treatment on the above indicators was more significant.4.Spraying appropriate concentration of uniconazole can improve the antioxidant enzyme activity of adzuki bean leaves under different nitrogen levels and reduce the content of malondialdehyde.Compared with low nitrogen treatment,medium and high nitrogen treatments increased the activities of superoxide dismutase,peroxidase and catalase in the leaves of the two tested adzuki bean varieties to a certain extent,while the content of malondialdehyde in the leaves decreased first and then increased with the increase of nitrogen application level.Spraying25 mg·L^-1and 50 mg·L^-1uniconazole at the early flowering stage promoted the antioxidant enzyme activities of the leaves of the two tested adzuki bean varieties under different nitrogen levels,and reduced the malondialdehyde content in the leaves.The 50 mg·L^-1uniconazole treatment increased and decreased more.5.Spraying appropriate concentration of uniconazole can promote the activity of key enzymes of nitrogen assimilation in adzuki bean under different nitrogen levels.Compared with low nitrogen treatment,medium and high nitrogen treatment promoted the activity of nitrogen assimilation key enzymes（nitrate reductase,glutamine synthetase,glutamate synthase,glutamate dehydrogenase）in adzuki bean leaves to a certain extent.Spraying 25 mg·L^-1and 50 mg·L^-1uniconazole at the early flowering stage increased the above enzyme activities in the leaves of the two tested adzuki bean varieties to varying degrees,and increased the content of soluble protein and nitrate nitrogen in the leaves.6.Spraying appropriate concentration of uniconazole can significantly regulate the yield components of adzuki bean under different nitrogen levels and increase the yield of adzuki bean.Compared with low nitrogen treatment,medium nitrogen treatment increased the number of pods per plant,grain number per plant,100-grain weight and grain weight per plant of the two tested adzuki bean varieties to a certain extent,while high nitrogen treatment decreased the number of pods per plant and grain number per plant to a certain extent.Spraying 25 mg·L^-1and 50 mg·L^-1uniconazole at the early flowering stage increased the yield composition and yield of the two tested adzuki bean varieties to varying degrees.Compared with no uniconazole treatment（N₁S₀）,the pod number per plant,grain number per plant and 100-grain weight of Zhenzhuhong and Jihong 352 were increased by 4.18%and 4.68%,7.73%and 8.02%,8.19%and 6.92%,respectively,by spraying 50 mg·L^-1uniconazole treatment(N₁S₅₀)under medium nitrogen condition,and the final yield was increased by 15.16%and 9.24%.Comprehensive analysis showed that spraying appropriate concentration of uniconazole under different nitrogen levels could improve the growth of adzuki bean,increase photosynthetic capacity,carbon and nitrogen metabolism related indicators,promote biomass accumulation,and ultimately increase yield.