Study On Tissue Culture And Salt Tolerance Ability Of Betula Microphylla

Using dormant axillary bud as initial explants,the plant micropropagation process,including induction of adventitious bud and root,transferring of in vitro plantlets was studied in Betula microphylla.Furthermore,various combinations of phytohormones for callus inducting and the appropriate medium composition for dedifferentiation of calli were tested using shoot-tip explants;and an efficient and stable micropropagation system was established.To understand the growth and photosynthetic responses of Betula microphylla seedlings to various levels of NaCI stress and evaluate its salt tolerance abilities,a series of studies with pot experiments were conducted.The main results of these studies are as follows:1.The optical basal medium of the regeneration system of Betula microphylla was MS;the appropriate medium for induction of adventitious bud was MS+6-BA 1.0mg/L+sucrose 20g/L+ agar 6g/L,on which the inducing rate was 99%and the bud proliferation rate was 12.5;2.Compared to NAA,IB A was more efficient phytohormone for inducting of roots;the most optical medium for rootings was 1/2MS+IBA 0.2mg/L+sucrose 20g/L+agar 6g/L,on which the rooting rate was 100%;the average number of roots was 7-8 per plantlets;average length of roots was 4.11cm.The optimum potting soil for plantlets produced by tissue culture was peat soil:vermiculite:perlite=6:2:2,the survival rate was more than 99%.3.For callus induction,the most suitable medium was MS+6-BA3.0mg/L+KT0.5mg/L+2,4-D0.5mg/L+sucrose20g/L+agar6g and weak light environment,whereas MS+6-BA1.0mg/L+NAA0.02mg/L+sucrose20g/L+agar6g/L was most efficient for callus dedifferentiation.4.The photosynthetic responses of young plants to treatment with a range of NaCl concentrations were investigated in a glasshouse experiment.The net photosynthetic rate(Pn),stomatal conductance(Cond)and transpiration rate(Tr)declined during the time course of the experiment,across the whole range of external salt.By higher than 1.5%of NaCl,chlorophyll fluorescence parameter with increasing time of treatment.5.The Betula microphylla growth at after treatment with different several concentrations of NaCl were observed,under NaCl treatment,the seedlings growth are subject suffered atto different degrees of inhibition,and as with increases of the salt concentration increases,the degree of suppression more obvious.When theBy less thanl.5%of NaCl concentration less than1.5%,the leaf color of seedlings showing were normalas usual leaf color,and plant growth by lesssalt injury.And when the NaCl concentrationby more higher than 1.5%of NaCl,the leaves turned were yellow,scorch and fall off,the plant grewowth weakened.6.Under salt stress condition,chlorophyllcontent changed little with the increase of concentration and time chlorophyllcontent changed little,under 300mM NaCl treatment,of Betula microphylla seedling leaves the activity of superoxide dismutase(SOD),peroxidase(POD),demonstratshowed increased first and then decreased,under 400mM NaCl concentration,SOD and POD activity increased significantly with prolonged stress time,malondialdehyde(MDA),showed agradualincreasing trend.