A Study On Nitrogen,Water,and The Compound Effect Of Response And Adaptation Mechanism Of Machilus Pauhoi Seedlings

To investigate multiplicate effects of water and nitrogen on Machilus pauhoi seedlings’ leaf phenotypic traits,photosynthetic characteristics,biomass allocation,carbon(C),nitrogen(N),phosphorus(P)content and root orders fine root morphological indexes and so on,as the provenance of Jiangxi Suichuan annual cutting seedlings of Machilus pauhoi potted in greenhouse were set according to different gradients of water and nitrogen.Analysis the influence of the addition of N,drought stress and their interaction on mechanism of the Machilus pauhoi seedlings.The results is as follows:(1)After three months of the experiment found that drought stress significantly reduced the Machilus pauhoi seedling’s high relative growth rate and base diameter relative growth rate.Effect of the addition of N and the interaction of the drought stress and the addition of N on Machilus pauhoi seedling’s high relative growth rate and base diameter relative growth rate were not significant.(2)Drought stress had no significant effect on the leaf dry matter content(LDMC),but reduced leaf area,leaf thickness and the number and increase the specific leaf area(SLA)of the Machilus pauhoi seedlings.The addition of N only had a great effect on Machilus pauhoi seedlings of specific leaf area.Interactions of the drought stress and the addition of N were no significant effects on the above indicators.(3)Drought stress significantly reduced the seedlings of net photosynthetic rate(Pn),stomatal conductance(Gs)and transpiration rate(E),total biomass and leaf weight ratio,increased the stem weight ratio,but influence on Intercellular CO2 concentration,root weight ratio and root shoot ratio was not significant.The addition of N and interactions the drought stress and the addition of N had no significant influence on photosynthetic characteristics and biomass allocation of the seedling.(4)Drought stress significantly reduced the morning and midday leaf water potential of Machilus pauhoi seedlings,while no significant impact on the LRWC.The addition of N only significant effect of the LRWC.Interactions of the drought stress and the addition of N were no significant effects on the above indicators.(5)In addition to the C content in stem and the P content in root,drought stress reduced C,N and P content in each organs,and increased the parts of each organ C:N and C:P,but decreased N:P in each organs and C:P in the root.The addition of N only had a great effect on the leaf C content,the leaf N:P are more than 16.Interactions of the drought stress and the addition of N effects are not significant C,N and P stoichiometric ratio of the Machilus pauhoi seedlings.(6)Drought stress increased root order from first to the third’s average diameter,surface area,volume,bifurcation,while reduced specific root length and tissue density.the addition of N mainly impacted on the third root of Machilus pauhoi seedlings.Interactions of the drought stress and the addition of N only has significant effects of individual index has no obvious rule.At the same time,the most root morphology index was significant different in order root.