The Function Of Sodium On Stress Adaptation In Salt Excluding Plant Puccinellia Tenuiflora And Salt Accumulating Plant Zygophyllum Xanthoxylum

Puccinellia tenuiflora is widely found in saline marshes in north of China,and used for forage as well as soil improvement.Lots of studies were carried on its salt tolerance mechanism.However,the precise mechanisms for the salt tolerance of P.tenuiflora remain elusive.In our new study of P.tenuiflora,we measured unidirectional ²²Na⁺ influx and efflux, to assess the contributions of unidirectional Na⁺ fluxes on net accumulation in comparison with wheat(Triticum aestivum,another member of the Pooideae.At the same time, investigated the relationship between growth stage and unidirectional Na⁺ influx,and contrasted "plant analyzing method" and "efflux solution analyzing method"on unidirectional Na⁺ efflux.The main results are as following,1.Unidirectional ²²Na⁺ influx increased with growth stage both in P.tenuiflora and wheat. Under 100mmol/L NaCl,there is no different of ²²Na⁺ influx between P.tenuiflora and wheat at 3 leaves stage,but significantly lower in P.tenuiflora at 4 leaves stage,indicating stronger ability to restrict the unidirectional ²²Na⁺ influx in P.tenuiflora.Therefore,the optimized test stage was at 4 leaves.2.Unidirectional ²²Na⁺ influx was not different under 25 mmol/L NaCl lower in P. tenuiflora,by 37%and 31%respectively under 100 and 150 mmol/L NaCl,compared with wheat,indicating stronger ability to restrict the unidirectional ²²Na⁺ influx in P.tenuiflora.3.Plant analyzing method and efflux solution analyzing method were used and compared for testing the Na⁺ efflux rate of wheat root.The results showed that Na⁺ efflux rates were not significantly different between the two methods,though the rates were little higher from efflux solution analyzing method.The efflux solution analyzing method was recommended due to its facility and low system error.4.Unidirectional Na⁺ efflux was calculated from the difference of unidirectional ²²Na⁺ influx and net Na⁺ uptake rate,Results showed that Na⁺ efflux was not significantly different between P.tenuiflora and wheat under 25mmol/L NaCl,but significantly lower in P. tenuiflora under higher NaCl(100 and 150 mmol/L)concentrations.Also,unidirectional ²²Na⁺ effluxes were measured by efflux solution analyzing method between P.tenuiflora and wheat at 4 leaves stage under 25 and 100 mmol/L NaCl,obtaining similar results as that by calculated.However,the proportion of unidirectional Na⁺ efflux accounting for unidirectional Na⁺ influx was not significantly difference between the two species:about 80%Na⁺ was pumped out through plasma membrane under 25 mmol/L NaCl,and this proportion was achieved 92%-95%in both species under 100 and 150 mmol/L NaCl.These results indicated that unidirectional Na⁺ efflux contributed a little to lower net Na⁺ uptake in P.tenuiflora compared with wheat.Results as above indicate that P.tenuiflora and wheat have the similar capacity on Na⁺ efflux.Restricting unidirectional Na⁺ influx is the essential salt exclusion mechanism for P. tenuiflora. Appropriate content of Na⁺ could improve the growth and drought tolerance of succulent xenophile Zygophyllum xanthoxylum.According to the drought tolerance characteristic of succulent xenophile Zygophyllum xanthoxylum developed a kind of sodium compound fertilizer,for test effection of this sodium compound fertilizer on the root of Z.xanthoxylum, we designed this experiment.The main results are as following,1.After growth for 60d,sodium compound fertilizer could significantly improved the plant height,root fresh weight,root volume,root total length,total absorption area and Na⁺ concentration in leaves of Z.xanthoxylum than CK and NP fertilizer.The proportion that sodium compound fertilizer higher than CK and NP were,by 81%,40%of height,by 105%,29%of root fresh weight,by 106%,46%of root volume,by 36%and 32%of total absorption area respectively.The root total lengths were 2.5 and 1.8 times of sodium compound fertilizer treatment than that of CK and NP,and 1.8 and 2.3 times of Na⁺ concentration.Those indicate that sodium compound fertilizer significantly improved the lateral roots growth,but little improvenment on taproot than NP fertilizer.2.After 15d drought,the plant heights in the three treatments were not improved significantly.The plant height,root total volume,root total length,root total absorption areas and Na⁺ concentration in leaves of Z.xanthoxylum also significantly improved by sodium compound fertilizer contrasted with CK and NP fertilizer.On the other hand,Sodium compound fertilizer significantly enhanced root Na⁺ concentration and roots activity absorption area than CK and NP fertilizer,which were not improved before drought.Besides, sodium compound fertilizer inhibited the reduction of the root activity and Na⁺ concentration in root,while enhanced the root activity absorption area(by 23%),taproot length and diameter.This indicates sodium compound fertilizer has an effective drought resistance mechanism on drought tolerance of Z.xanthoxylum by maintaining higher Na⁺ concentration in root than NP fertilizer.3.The results showed that the survival ratio reach to 100%after transplanted for 20d, which showed that sodium compound fertilizer treatment has more effective improvement on plant biomass and growth ratio after transplant for Z.xanthoxylum.