Research Of The Regulatory Impact Of S-ABA And Mepiquat Chloride On Soybean Development

Soybean(Glycine max(L.)Merr.)constitutes a significant oil crop in China,characterized by its richness in protein,amino acids,fatty acids,and other essential nutrients,making it a highly valuable nutrient source.Presently,China holds the position as the largest global consumer and importer of soybean;however,the current domestic production falls short of meeting consumer demands.Relying extensively on soybean imports over time presents considerable risks and pose a grave threat to China’s food security.Consequently,augmenting soybean production and expanding planting areas have emerged as pressing issues requiring resolution in China.In practical production,the plant growth regulator S-Abscisic acid(S-ABA)serves a dual purpose: enhancing crop stress tolerance and regulating crop growth and development to boost yield.Mepiquat chloride contributes to delaying crop growth,optimizing plant structure,preventing crop lodging,and significantly increasing crop yield.In this study,the soybean variety “He dou12” was subjected to S-ABA and mepiquat chloride sprays during seedling and flowering stages to investigate the impact of various regulator concentrations on photosynthesis,carbon metabolism,nitrogen metabolism,yield composition factors,and soybean quality at different growth stages.The aim was to identify the optimal concentration and ratio for regulating soybean growth and development,enhancing yield,and offering guidance for soybean production.The study’s specific findings are as follows:1.Spraying various concentrations of S-ABA as a single agent during the soybean seedling stage led to increases in fresh weight,root-top ratio,and chlorophyll content both aboveground and underground soybean parts to varying extents.A 4 mg/L concentration of S-ABA spray during the seedling stage demonstrated the most comprehensive promotional effect,fostering the accumulation of photosynthetic substances in soybean stems,leaves,and roots,as well as chlorophyll biosynthesis in leaves.Chlorophyll content reached 1.37 times that of the untreated control,whereas a higher concentration of S-ABA(6 mg/L)facilitated the transport of aboveground assimilates to the root system,increasing root system weight and elevating the root-top ratio.2.During the initial flowering stage of soybean,both S-ABA and mepiquat chloride spray treatments significantly enhance soybean photosynthesis,elevating Rubisco activity and chlorophyll content.Within a specific concentration range,the promotional effect demonstrates an initial increase followed by a decline.A single dose of 6 mg/L S-ABA spray exhibits the most favorable impact,200 mg/L is preferable when spraying a single dose of mepiquat chloride.When the S-ABA concentration remains constant,combining it with 200mg/L mepiquat chloride notably promotes soybean photosynthesis,with 6 mg/L S-ABA having a significant effect on chlorophyll content,Rubisco activity,stomatal conductance,and intercellular carbon dioxide concentration,which are all considerably higher than in the untreated control.3.Regulators also considerably promote carbon and nitrogen metabolism rates in soybeans during the initial flowering period,enhancing the activity of related enzymes.A single dose of 6 mg/L S-ABA spray demonstrates the most comprehensive promotional effect.When spraying a single dose of mepiquat chloride,except for the amino acid and protein content after 20 days of spraying,the promotion effect is better at 200 mg/L.When spraying a mixed agent,the optimal combination for carbon metabolism comprises 6-8 mg/L S-ABA and 200 mg/L mepiquat chloride,while the ideal combination for nitrogen metabolism entails the same concentration of S-ABA and 200 mg/L mepiquat chloride 10 days after regulator application,and 100 mg/L mepiquat chloride 20 days after application.As the growth process progresses,the activities of sucrose synthase and nitrate reductase in soybean leaves increase significantly,leading to a higher protein and amino acid content,while the sucrose content and sucrose phosphate synthase activity decrease.4.The application of S-ABA and mepiquat chloride substantially improves soybean growth,development,and morphological indicators during the initial flowering period.Spraying 6-8 mg/L S-ABA,either alone or combined with mepiquat chloride,effectively controls soybean elongation and increases the number of effective pods and branches.The combination of 6 mg/L S-ABA and 200 mg/L mepiquat chloride offers the best comprehensive effect in controlling soybean elongation and augmenting the effective number of pods and branches.Various regulator concentrations elevate the number of grains per plant and the 100-grain weight of soybeans,ultimately boosting their yield.Among these,the treatment involving 6 mg/L S-ABA and 200 mg/L mepiquat chloride achieves the highest yield at 277.84 kg/mu,with a yield increase rate of 28.42% and a significantly enhanced yield.Simultaneously,spraying S-ABA and mepiquat chloride also raises the crude protein content in soybean seeds,although the impact on crude fat and oil content is not significant.