Study On The Growth And Physiological Effects Of Saline-Alkali Stress On Keteleeria Davidiana

At present,China’s saline-alkali land is large and wide,with various types,and a large area of soil is potentially salinized due to climate,human and other reasons.Breeding saline-alkali-tolerant plants to adapt to saline-alkali land is the direction of governance and utilization of saline-alkali land.To study the physiological response mechanism and salt-tolerance mechanism of Keteleeria davidiana(Bertr.)Beissn.Under different kinds of salts and different concentrations,and to analyze its adaptation range under different kinds of salts,can provide a theoretical basis for the introduction,cultivation and application of K.davidiana.It is also of positive significance to screen salt-tolerant plants and manage and develop saline-alkali land.In this study,three treatments of neutral salt NaCl,alkaline salt NaHCO3 and mixed saline-alkali(NaCl:NaHCO3=1:1)were used for K.davidiana.The morphological changes were observed and the growth indexes(plant height and ground diameter growth),physiological indexes(RWC,MDA,SOD,Pro,SP)and photosynthetic indexes(chlorophyll content,photosynthetic gas-exchange parameters and characteristic values of light response curve)were measured.The results were:(1)Under the neutral salt NaCl treatment,in plant form,the plants in the 0.8%treatment group showed symptoms of salt damage on the 30th day of the experiment,while the 0.5%treatment group plants appeared on the 10th day after the end of the experiment.The growth of plant height decreased with the increase of salt concentration,and the growth of ground diameter increased first and then decreased.RWC decreased with the increase of concentration.The contents of MDA and Pro increased gradually with the increase of time and concentration:And the 0.8%treatment group increased the most.SOD activity approximately increased first and then decreased with the extension of time.And that in 0.8%treatment group decreased sharply from 30 days to 40 days,which was significantly lower than other groups.The content of SP first increased and then decreased with the increase of time and concentration.Chlorophyll content,photosynthetic gas-exchange parameters(except that Pn increased first and then decreased)and characteristic values of light response curve decreased with the increase of salt concentration.Principal component analysis showed that K.davidiana can adapt to the stress of 0-0.5%NaCl solution.(2)Under the treatment of alkaline salt NaHCO3,in terms of plant morphology,the plants in the 2.0%treatment group showed symptoms of salt damage on the 30th day of the experiment,while the 1.5%treatment group plants appeared on the 30th day after the end of the experiment.With the increase of salt concentration,the growth of plant height first increased and then decreased,and the growth of ground diameter gradually decreased.The RWC decreased with the increase of the concentration.The contents of MDA and Pro increased gradually with the increase of time and concentration,and the 2.0%treatment group increased the most.The SOD activity generally increased at first and then decreased with the prolongation of time.The SP content first increased and then decreased with the increase of time and concentration.Chlorophyll content increased gradually with time in the treatment group with a concentration of less than 1.0%,and increased first and then decreased in the treatment group with a concentration of more than 1.5%.The chlorophyll content of the high concentration(≥1.5%)treatment group in the early stress period was higher than that of CK,but gradually less than CK with the extension of time.Among the photosynthetic gas-exchange parameters,except for Pn,which first increased and then decreased with the increase of concentration,other parameters(Gs,Ci,Tr)all decreased gradually.With the increase of salt concentration,the eigenvalue of a Value and Pnmax first increased and then decreased;LSP and LCP decrease first and then increase,and Rd decreases first,then increases and then decreases.Principal component analysis showed that K.davidiana can adapt to the stress of 0-1.5%NaHCO3 solution.(3)Under mixed saline alkali treatment,in terms of plant morphology,the plants in the 1.8%treatment group showed symptoms of salt damage on the 35th day of the experiment,while the 1.5%treatment group plants appeared on the 15 days after the end of the experiment.With the increase of salt concentration,the growth of plant height first increased and then decreased,and the growth of ground diameter gradually decreased.RWC decreased with the increase of the concentration.The contents of MDA and Pro increased gradually with the increase of time and concentration.The activity of SOD basically increased first and then decreased with the prolongation of time.With the increase of time and concentration,the SP content first increased and then decreased.Chlorophyll content increased gradually with time in the treatment group with a concentration of less than 1.0%,and increased first and then decreased in the treatment group with a concentration of more than 1.5%.The content of chlorophyll in the high concentration(≥ 1.5%)treatment group in the early stage of stress was higher than CK,but it was gradually lower than CK with the extension of time.Pn,Gs and Tr gradually increased with the increase of salt concentration,while Ci first decreased and then increased.With the increase of salt concentration,the eigenvalues of a Values and Pnmax decreased gradually;LSP first decreases,then increases and then decreases;LCP and Rd decreased first and then increased.Principal component analysis showed that K.davidiana can adapt to the stress of 0-1.0%mixed saline alkali solution.(4)The comprehensive evaluation values under different concentration treatments were obtained through membership function analysis,and the upper salt tolerance value obtained by principal component analysis was used to compare different salt treatments.It was concluded that the salinity tolerance of K.davidiana under different salt stress was:NaHCO3>mixed saline-alkali>NaCl.To sum up,K.davidiana has different tolerance to different salt stress,and the tolerance to alkaline salt is the strongest,followed by mixed saline alkali,and finally neutral salt.It can be adapted by adjusting the salt tolerance mechanism in the concentration range of different salt adaptation,but exceeding the adaptation range will cause damage to the growth of it.