Effects Of Brassinolide And Spermine Spraying Period On Cottonseed Yield And Seed Vigor

As plant growth-promoting regulators,brassinolide and spermine have important effects on promoting cotton growth and reproductive organ development.To explore the mechanism about brassinolide and spermine with different spraying period improving cottonseed yield and seed vigor,field experiments were conducted in 2016 and 2017 at Dafeng Experimental Station in Dafeng(33°24’N,120°34’E),Jiangsu Province,China.Two cotton cultivars,CCRI-50 and Siyang 822 were used in the experiment.And two regulators(Brassinolide and Spermine,respectively)and three spraying periods(budding stage,initial flowering period and peak flowering period)were set up with spraying water as control.In the pot experiment,we examined the effects of brassinolide and spermine on cottonseed yield and seed vigor.In addition,we analyzed the mechanism about carbon metabolism of functional leaves and cottonseed.The main results are as follows:1.Effects of brassinosteroids and spermine spraying period on cottonseed yield and biomass accumulationBrassinolide and spermine can significantly increase the boll number and cottonseed yield.The most suitable choice is first flowering period increasing the number of bolls by 15.6%-24.1%and 17.8%-26.4%,respectively in 2016 and 2017.We found that spermine can significantly increase seed index and seed number per boll,in addition brassinolide can significantly increase seed number per boll.CCRI-50 has better increase in yield than Siyang822.Spraying brassinolide and spermine was beneficial to the biomass accumulation of cotton,and the effect of spraying at the initial flowering stage was the best,which significantly increased the biomass of cotton boll opening stage,and significantly increased the leaf area index.2.Effects of brassinolide and spermine spraying period on physiological activities of main stem functional leavesSpraying treatment at the initial flowering stage can significantly improve the activity of the main stem leaves of cotton.We found that the SPAD value and sucrose content of the main stem functional leaves of 31 days post anthesis are increased,on the contrary,the starch content is reduced.Leaf superoxide dismutase and peroxidase activity significantly increased with reducing the malondialdehyde content.3.Effects of brassinolide and spermine spraying period on the vigor and physiological metabolism of cotton seedsSpraying brassinolide and spermine is beneficial to the improvement of seed vigor of cotton,initial flowering stage is the best choice,increaseing seedling fresh weight and germination indexis main cause.It was found that the influence mechanism of brassinolide and spermine on the physiological process of cottonseed was not consistent.Brassinolide can increase the content of sucrose and hexose in two varieties of cotton,increase the activity of sucrose synthase and alkaline invertase of two varieties,increase the maximum accumulation rate of fat and the activity of PEPC and DGAT,thereby increasing cotton kernel fat content,increase catalase and peroxidase activity,reduce malondialdehyde content;spermine increased sucrose content of two varieties of cotton kernels,reduced starch content,increased alkaline invertase activity,and prolonged rapid fat accumulation Duration and increase of PEPC and DGAT activity,thereby increasing cotton kernel fat content,increasing catalase and superoxide dismutase activity,reducing MDA content.In conclusion,spraying Brassinolide and spermine at the beginning of flowering could increase cotton yield and seed vigor.After spraying treatment,the physiological activity of cotton main stem functional leaves increased,as well as the activity of cotton kernel enzymes in carbon metabolism and antioxidant metabolism increased,the accumulation of fat increased and the damage of reactive oxygen species was alleviated.