Effects Of Sugar On The Adventitious Roots Growth And Development Of Seedlings In Lotus(Nelumbo Nucifera Gaertn.)

Nelumbo nucifera Gaertn is a perennial aquatic herb plant which belongs to the lotus genus Nymphaeaceae,and at the same time,it is also the largest in cultivated area and important exported aquatic vegetable in China.The enlarged rhizome is the main edible organ of lotus root with rich nutrition and economic value,so it is very popular.Two kinds of roots is existed in lotus root system such as principal root and adventitious root.The principle root of lotus is undeveloped,so the formation of adventitious roots directly affects the development process of plants.Sugar plays a critical role in nutrition support,and it is also an signal molecule plant growth and development by regulating genes expression.Therefore,in this study,the effect of sugar,glucose and fructose on adventitious root formation was analysis from three aspects,and primary molecular mechanism regulated by sugar was summarized during adventitious root development.The following results was obtained:1、Different concentrations of sucrose,glucose,and fructose solutions were used to treat lotus seedlings,and we found that the number of adventitious roots were significantly increased with a low concentration of sucrose solution.Among which,the concentration of 20 g/L of sucrose obviously promoted the formation of adventitious roots,and while 40 g/L sucrose obviously inhibit the development of adventitious root.No significant difference was found among 10 g/L-30 g/L sugar.2、Paraffin section technology was applied to study the development of adventitious root under normal growth condition and treatment with 20 g/L and 50 g/L sucrose solution.The results showed that the adventitious root could not break through the epidermis of hypocotyl with the treatment of 50 g/L sucrose solution,although the primordium of adventitious root was developed.The developed process of adventitious root treated by 20 g/L sucrose solution was faster than that of two treatment(CK and 50 g/L).So we concluded that 20 g/L sucrose solution was benefit for the formation of adventitious root of lotus.3、The seedlings of lotus was treated by 10 g/L,20 g/L,30 g/L,40 g/L,50 g/L sucrose solutions(normal growth was considered as control)was used to analysis the change of POD and SOD.We found that the POD activity was firstly decreased,and then increased,and decreased at last within 8 d for all treatments.The adverse tendency was found for SOD change with the same treatment.We found that the SOD activity was firstly improved,and then reduced,and improved again among investigated time(8 d).4、Lotus seedlings were treated with exogenous 20 g/L and 50 g/L sucrose solution(normal growth was considered as control)to analysis the change of endogenous IAA content.We observed that the change of IAA content with various concentrations of sucrose showed upward tendency at first,and then a downward trend appeared with treated time was processed.Among which,IAA content under 20 g/L sucrose condition was more than that of other treatments.5、Different concentration(CK,10 μM and 150 μM)of IAA was used to treat seedlings of lotus to study the endogenous sucrose change.It was showed that the endogenous sucrose content was firstly increased,and then decreased within 0-8 d.the content of sucrose under 10 μM IAA condition was significant higher than that of control and 150μM treatment.At the same time,the fructose content in the early stage was more than other treatments under 10 μM IAA condition,and glucose content treated by 10 μM IAA was lower than 150μM IAA at later stage.6、RNA-seq technology was used to sequence hypocotyls of seedlings treated by different concentrations of sucrose solution.By analyzing gene expression changes in 3 libraries,the effects of sucrose on the metabolism of adventitious roots of lotus root seedlings were studied.In CK vs GL20 libraries,the expression of 1089 genes changed,of which the expression of 426 genes was increased and 663 genes was decreased;In CK vs GL50 libraries,1 544 differentially expressed genes were found with 430 up-regulated genes and 1114 down-regulated genes;In GL20 vs GL50 libraries,a total of 401 genes changed their expression,of which 85 genes increased expression and 316 genes decreased expression.The enrichment of the above-mentioned differentially expressed genes was related with carbohydrate metabolism pathway indicated that carbohydrates played an important role in the formation of adventitious roots in seedlings.qRT-PCR technique was used to study the expression of six differential genes to further verify the accuracy of sequencing data.The results showed that qRT-PCR and expression profile data from RNA-seq were basically the same.