Effect Of Exogenous Brassinosteroids On Yield And Quality Of Sugar Beet(Beta Vulgaris L.)

Plant growth regulators,as the application of high and new technology,were listed in China's " Outline for Development of Agricultural Science and Technology " in 2001,and have become one of the national key research topics.Brassinosteroids(BRs)have been widely used in crop production as a plant growth regulator essential for the normal growth and development of plants.In order to clarify the regulation effect of brassinosteroids on sugar beet yield and sugar content,based on the results of our research group on the molecular mechanism of sugar content and root tuber growth in sugar beet,four kinds of BRs were spraying on sugar beet at the two key speed-growth stages(refer to foliage and root,respectively)aiming to select the suitable BRs types,concentration and spraying time to regulate the tuber growth and sucrose accumulation,and provide new chemical control technology and theoretical basis for improving sugar beet yield and sugar content.The main results are as follows:(1)The optimum concentration of BRs had a significant effect on the yield and quality of sugar beet.The treatment for highest yield was 24-Epibrassinolide with 1 concentration applied during the foliage speed-growth period,which increased by 6.48%compared to CK.The treatment for highest sugar content was 24-Epibrassinolide with 2 concentration applied during the period of root growth and sucrose accumulation,which could significantly increase the sugar content by 1.33 degrees compared with CK.(2)The suitable concentration of BRs treatment had significant effect on the growth of sugar beet.When spraying 24-Epibrassinolide with 1 concentration during the foliage speed-growth period,the plant height of Sugar beet was 59.54 cm and the leaf area index was 6.91,which was beneficial to the increase of beet yield.When 24-Epibrassinolide was sprayed with 2 concentration during the root growth and sucrose accumulation period,the root/shoot ratio of dry weight was 4.32,the root/shoot ratio of fresh weight was 2.90,and the dry matter accumulation of root was 293.60 g/plant,which was conducive to increasing sugar content and sugar yield.(3)The optimum concentration of BRs had a significant effect on the physiological metabolism of sugar beet.Spraying 24-Epibrassinolide with 1 concentration during the foliage speed-growth period could increase xylan endoglycosidase activity,SPAD value and net photosynthetic rate of by 32.84%,4.02%and 5.22%respectively compared with CK.Spraying brassinolide with 1 concentration could significantly increase the soluble protein content during period of root growth and sucrose accumulation which were 2.19%and 1.27 g/plant/d higher than CK,respectively.