The Response Of Seedling Root Of Main Planting Tree Species In The Loess Plateau To Drought

For systemic researching the interreaction mechanism between root and water,guiding the choosing of sivilculture species and sivilculture practice scientifically,the study choosed 2 year-old seedlings of Pinus tabulaeformis,Robinia pseudoacacia,Platycladus orientalis and Hippophae rhamnoides which are the main tree species on Loess Plateau as material. An artificial controlling soilmoisture(70%, 50% and 35%WHC three levels, time of each treatment level is 7 d, 14 d and 21 d)test was made to observe responses of root biomass, aboveground biomass,fine roo(tΦ<2 mm)indexes(surface area,length and tips quantity),and the mass allocation pattern of each part to varying stress degree and dealing time of drought condition;Besides,a analysis was made to study the changes of contents and components for soluble protein in their roots tips. The result showed that:(1)With the increasing stress degree and dealing time,the root biomass and fine root indexes of Pinus tabulaeformis augment markedly;The root biomass of Robinia pseudocacia increases totally,but fine root indexes maintain stable;The root biomass of Platycladus orientalis increases on moderate drought but decreases on severe drought,and the two levels have the decreasing trend with the increasing dealing time,and fine root indexes reduce significantly only on severe drought(21 d);The root biomass and fine root indexes of Hippophae rhamnoides increase obviously on moderate drought condition but the increasing amount decreases for longer dealing time,and it can not survive on severe drought condition.(2)The mass allocation pattern of root,stem and leaf changes on drought,and there are significant difference among tree species. With the increasing stress degree and dealing time,every part biomass of Pinus tabulaeformis increases by a stable proportion;Robinia pseudocacia's organic synthesis presents negative growth on moderate(21 d)and severe drought,and material centralizes to root and stem from leaf;Platycladus orientalis'organic synthesis is blocked on severe drought,and material centralizes to stem from root;Hippophae rhamnoides'photosynthetic product is mainly distributed to leaf.(3)Content of soluble protein in root tips of Robinia pseudoacacia decreases on moderate drought for 7d,and increases in longer time (14d,21d) moderate drought and shorter time(7d)severe drought,and decreases on longer(21d)severe drought;Platycladus orientalis increased in shorter time(7d)moderate and severe drought,and decreases on longer time moderat(e21d)and sever(e14d,21d)drought;With the increasing of stress degree and treatment time,the content of soluble protein in Pinus tabulaeformis generally increased while Hippophae rhamnoides decreases.The soluble protein components in root tips of four trees do not change on drought,and the variation of content in most kinds of protein have the similar trends to the total.The soluble protein content in seedings root tips changing are big difference among degrees,treatment time of drought and tree species,and its responses to drought are realized by coincident change of the most of proteins components.(4)In the course of using the regular SDS-PAGE method to separate the soluble protein of Robinia Pseudoacacia root tips,the result was found not very good. The experiment increased the content of SDS,β-mercaptoethanol and glycerine in treating solution for sample by 50% and the separating effect in improved method is much better. After analysis,in treating solution for sample,the deficiency of SDS andβ-mercaptoethanol content which resulted in the insufficient dissolution of soluble protein of Robinia Pseudoacacia root and the deficiency of glycerine content which resulted in inferior sinking and congregating when supplied samples are the reasons of bad separating effect. The experiment supplys a better reference method of SDS-PAGE for separating soluble protein of plant tissue.