The Study Of Nutrient Utilization Strategy In Seed Germination And Seedling Growth Period On Several Xerophytic Shrubs

Xerophytic shrub plays an important role in the maintenance of ecological service function,biological diversity and stability in desert ecosystem.The study of Xerophytic shrub growth strategy had an important significance for understanding its mechanism adapt to the drought environment and formulate the desert ecological construction scheme.The research mainly studied the nutrient utilization strategy of several xerophytic shrubs seed germination and seedling growth period.The analysis of eight xerophytic shrubs(Artemisia sphaerocephala,Reaumuria soongorica,Haloxylon ammodendron,Hedysarum mongdicum,Zygophyllum xanthoxylum,Nitraria tangutorum Bobr.,Ammopiptanthus mongolicus,Caragana korshinskii)seed germination characteristics and nutrient content In the process of drought and re-watering and the change of two xerophytic shrubs(Zygophyllum xanthoxylum,Artemisia sphaerocephala)morphologic expression,nutrient content in drought and rehydration had draw the following conclusions:1.Through the comparison of the seeds of 8 kinds of xerophytic shrubs small seeds with high germination rate,leguminous lowest water content of seed germination is higher.The chemical composition of the seeds have a large difference among species.2.The seed fat content,protein content,nitrogen(N)content had a significantly positive correlation to the lowest water content of seed germination,while the single chemical composition and C:N,C:P,N:P of seed had no significant influence on germination rate.3.Eight kinds of xerophytic shrubs seed germination strategy is divided into two categories:one needs a higher moisture and germinated rapidly and intensively;the other one needs a lower moisture and germinated continuously and dispersedly.4.Zygophyllum xanthoxylum is superior to Artemisia sphaerocephala on the drought resistance of morphology performance,Zygophyllum xanthoxylum specific leaf area(4.03 m2/kg)is less then Artemisia sphaerocephala(5.36 m2/kg),but specific root length(129.44 cm/g)and root-shoot ratio(0.45)were greater than Artemisia sphaerocephala(74.64 cm/g,0.19).5.In the process of drought the relative growth rate of Artemisia sphaerocephala is higher then Zygophyllum xanthoxylum nearly 20 times,but in the process of rehydration the relative growth rate of Zygophyllum xanthoxylum is about 2 times then Artemisia sphaerocephala.In addition,kindred plant compared with the relative growth rate of drought and rehydration Zygophyllum xanthoxylum rose by nearly 20 times,and Artemisia sphaerocephala was reduced by 34%,shows that after drought exercise Zygophyllum xanthoxylum growth recovery ability is stronger than Artemisia sphaerocephala,Zygophyllum xanthoxylum is more easily to use effective rainfall of desert.6.In the process of drought and rehydration compared with Zygophyllum xanthoxylum and Artemisia sphaerocephala,the C and N content in root?stem and leaf changes lesser,but the variation of P is larger.Especially in drought stage Zygophyllum xanthoxylum's P content in root and stem increased by 203.74%and 84.98%respectively,but in leaf was reduced by 32.6%.For Artemisia sphaerocephala,mainly the P content was reduced by 46.5%;C:N:P of two plants is mainly affected by P element,leads to after drought stage Zygophyllum xanthoxylum C:P and N:P in root and stem are decreased obviously.The results show that the P content in desert plant is intensely regulated by the moisture content,and determines its C:P and N:P features,Zygophyllum xanthoxylum is affected more strongly than Artemisia sphaerocephala.7.In the process of drought and rehydration,the ability of transport P element in Zygophyllum xanthoxylum root and stem was higher than Artemisia sphaerocephala,P element can faster accumulation in root and stem in the period of drought,also it can quickly release to the leaf in the period of rehydration.Show that in response to drought,Zygophyllum xanthoxylum root and stem played an repository role in use of P element;the absorption efficiency of P in Artemisia sphaerocephala(46.5%)is higher than Zygophyllum xanthoxylum(32.6%)in the process of drought,but due to the Artemisia sphaerocephala growth rate is higher than Zygophyllum xanthoxylum in the process of drought,strong diluting lead to the root and stem of Artemisia sphaerocephala don't have obvious Storage function.8.Relative growth rate changes mainly affected by P element,Artemisia sphaerocephala leaf with high P content in the dry process(low C:P and N:P)can promote plant growth;in the process of rehydration,Zygophyllum xanthoxylum's root and stem of high P distribution also promote the growth of plants,and the results accord with the growth rate in ecological stoichiometry theory.