Physiological Responses Of Puccinellia Tenuiflora To Beneficial Soil Bacteria And Various K~+ And Na~+ Conditions

Soil salinity is an increasingly serious problem worldwide that reduces agricultural output potential.And it is a particularly acute issue in both irrigated and non-irrigated areas of the world.Most crop and forage plants that feed the global population are sensitive to high salt concentration in soils.Soil salinity promotes osmotic stress,water deficit,and stomatal closure and reduce leaf expansion;moreover,soil salinity causes deficiency of essential nutrients such as K+.Elevated Na+inside plants can decrease plant photosynthetic rates and biomass accumulation.Therefore,there is a dire need to find new ways to cope with the threat of global soil salinization to agriculture.Selected beneficial soil bacteria can promote plant growth and augment tolerance to biotic and abiotic stresses.Bacillus subtilis strain GB03 has been shown to confer growth promotion and abiotic stress tolerance in the model plant Arabidopsis thaliana and sevreral crops.Puccinellia tenuiflora growing in the northeast and northwest of China is the member of the grass family which can resist salt stress extremely.We found that the key mechanism for Puccinellia tenuiflora salt resistance is refusing Na+.However,the habitat for various ion flow dynamic change mechanism has not yet been reported.In this study,the regulation of Bacillus subtilis strain GB03 to seed germination,seedling growth,and salt tolerance was investigated in P.tenuiflora,the dynamic changing mechanism of ion fluxes of P.tenuiflora responding to various K+ and Na+ conditions was analyzed.The results are shown as following:1.GB03 significantly improved tseed germination rate and germination potential.5 mins treatment has the most significant effect on the seed germination.Compared with the control(LB),GB03 significant improve the germination potential by 22.8%,31.9%and 52.4%,and germination rate by 28.7%、44.6%、56.9%,under 0,100 and 200 mM NaCl,respectively.(P<0.05).2.Bacillus subtilis GB03,significantly decreased Na+ content,the reduction rate is 67.5%,35.3%and 35.7%respectively;significantly(P<0.05)increased the root K+/Na+ ratio by 302.5%,118.7%and 138.9%,under 0,100 and 200 mM NaCl,respectively(P<0.05).3.With the increase of salt concentration,P.tenuiflora maintained the K+ and ST value relative stability,indicating that exclusion of Na+ and selective absorption is one of the key strategies for P.tenuifkora adapting to saline condition.4.Maitaining active K+ absorption and K+ retention by increasing H+ efflux contribute to higher SA and ST values of P.tenuiflora.5.Increasing Na+ efflux and K+ influx is an important stategy for P.tenuiflora to adapt to high salinity(300 mM NaCI)and Na+ starvation;under high salinity rapid Ca2+ influx may induce SOS systems that play a key role in SOS signal transduction process and activated SOS1 may mediate Na+ efflux.