Quatitive Relationship Between Xylem Conduits Structure And Hydraulics

Water is a key factor maintaining the normal psychological activity in plants and it limits plant growth and development process.The hydraulic traits depend on its conduits structure and closely related to the mechanism of woody plants.Gymnosperms and angiosperms have different conduits structure,so that they have different water transport regimes.Our research developed vulnerability curves of two gymnosperms,Metasequoia glyptostroboides and Cryptomeria fortunei with advanced Chinatron centrifuge method,compared the cavitation resistance and mechanical traits.In the meantime,we measured the vessel diameter and vessel length of four angiosperms.It has been explained the relationship between hydraulic architecture and water efficiency,cavitation resistance,mechanical traits.Also we compared the vessel diameter and vessel length within same species in four angiosperms,Acer truncatum,Populus alba×Populus glandulosa,Vitis vinifera cv Cabernet Sauvignon,Quercus variabilis,with rubber injection method and found out that there were some links among them and the rules of vessel distribution.The conclusions are as follows,1.M.glyptostroboides had higher theoretical specific hydraulic conductivity?K_s-T?,measured specific hydraulic conductivity?K_s-M?and weaker cavitation resistance(P₁₂?P₅₀and P₈₈)than C.fortunei;M.glyptostroboides had wider(D_mean)and longer(L_mean)tracheid with higher hydraulic diameter?H_w?but lower density than C.fortunei;we also found that flushing with short time had little influence on the pits.However,the hydraulic conductivity decreased significantly if flushing with long time under pressure.The torus-margo of M.glyptostroboides was more flexible than that of C.fortunei.Ca²⁺weakened the flexibility of torus-margo while K⁺had a little influence on the flexibility of pits.Due to the narrow,short and less dense tracheids with less flexible torus-margo,C.fortuneiwas less cavitation resistant and more tolerant to drought stress,compared with M.glyptostroboides.2.The order of mean vessel diameter(D_mean)of four species was:A.truncatum<P.alba×P.glandulosa<Q.variabilis<V.vinifera;the order of mean vessel length(L_mean)of four species was:A.truncatum<P.alba×P.glandulosa<V.vinifera<Q.variabilis.It had been demonstrated that wider vessels had longer length within a species.