| The trend of climate warming and drying is becoming more and more obvious in Horqin sandy land.With the decrease of precipitation,drought has become one of the important factors restricting plant growth and development,seriously affecting the sustainable development of ecological environment in this area.In recent years,some Ulmus pumila have died and the natural regeneration process has been seriously hindered,which has been a serious problems for sustainable development of Ulmus pumila forests in Horqin sandy land.Therefore,it is urgent to study the regulation mechanism of Ulmus pumila to adapt to drought environment.To study the effect of drought stress on growth,non-structural carbohydrates(NSC)and carbon(C),nitrogen(N),phosphorus(P)ecological stoichiomethy of Ulmus pumila seedlings,we planted two-year-old Ulmus pumila seedlings in four different water treatments,including suitable water,light,moderate and serious drought stress,i.e.,80%,65%,50% and 35% of the field capacity.We compared the variations of biomass,soluble sugar,starch and NSC contents and C,N and P contents and their ratios in different organs under different drought stress times(15,30,45 and60 d).The main results are as follows:(1)Drought stress decreased height,basal diameter and biomasses of Ulmus pumila seedlings.With the increase of drought stress,Ulmus pumila seedlings increased allocation proportion of root biomass.(2)With the increases of drought stress,the starch transformed to soluble sugar in leaves to increase osmotic adjustment substance concentration.The starch and NSC content in stems,while the soluble sugar in coarse roots and fine roots increased for water resource utilization.(3)The absorption and upward translocation of N and P of Ulmus pumila seedlings were influenced by drought stress.Nitrogen limitation for the growth of Ulmus pumila seedlings was found.With the increases of drought stress,C increased,photosynthetic rate decreased,and growth rate slowed down. |
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