Study On Salt Tolerance Of Betula Halophila Seedling And Sapling

In this study,the seeds of Betula halophila was treated with different concentrations of NaCl,the germination rate,vigour of germination,germination index,relative germination rate, relative salt damage rate,length of shoot and root were determined.The results showed that lower salt content effect lower,but it restrain the germination and growth of high salt contentration; Phenological phenomena of germination,foliation,flowering maturity and growth of new treetop of Betula halophila are mainly observed.The results showed that the flower bud generally bourgeons from the first ten days of April,which indicate the advent of the process of growing. The species begin to bud at the middle ten days of April and the spring shoot occurred in early April and the second occurred in May.Betula halophila started to flower at the April 14. Full-bloom stage at the middle ten days of April,fruit mature at September.This study could provide fundamentals for the protection and propagation of Betula halophila.Using different concentrations of salt tolerance Betula halophila seedling and sapling.The net photosynthetic rate and other physiological indexes of leaves were measured at different growth stages.The results showed that the content of chlorophyll decreased with the NaCl concentration and treated time.However,it increased under 1.00%NaCl.The content of chlorophylla dropped more rapidly than that of chlorophyllb.The net photosynthetic rate(Pn), stomatal conductance(Cond)and transpiration rate(Tr)changed similarly with increasing salt tolerance,and all decreased.Stomatal conductance and intercellular concentrations of CO₂(Ci)changed similarly under 1.80-2.20%NaCl stress.The changes of stomatal conductance were contrary to intercellular concentrations of CO₂ under 1.00-1.60%NaCl.It was stomatal limitation that leading the photosynthesis declined in the treatments with higher concentrations.On the contrary,non-stomatal limitation was the dominative causation in the treatments with lower concentrations;under different NaCl stress pressure.The results showed that with the increase of salt concentration and the prolonging time of salt tolerance,the contents of proline,soluble sugar,relative membrane permeability and MDA increased gradually.