Effect Of Salt Stress On The Seeds Germination And Seedlings Physiological And Biochemical Properties In Two Wheat In Northwest Of China

Ion toxicity and oxidative stress generated by the high salt treatmentseriously affect plant growth and development, resulting in a drop ingrain production, it was one of the most serious environmental problems.For avoiding themselves from injury, plant evolved a series ofmechanisms to adapt to saline environment, including the changes onstructure and external morphology, and the regulation aboutphysiological processes. The research about plant salt tolerancemechanism was important to provide a theoretical basis for thedevelopment and utilization of halophytes．In our study, cv "Ningchun4"and "Xihan3" were selected as experimental materials, which waspromoted as the spring wheat varieties in wider area in northwest China.We analysised the changes on seeds germination, seedling growth andphysiological and biochemical characteristics of two wheat, exposed todifferent NaCl concentrations. We were trying to investigate the responsemechanism of salt negative effected on two wheat, and compare thedifference on salt tolerance between two varieties of wheat and the causes.The main results were as follows:1. Compared with the control, germination was notable affected inNingchun when exposed to salt stress, while different NaClconcentrations did not affect the seed germination of Xihan. Inuntreated seedlings, the growth of shoots and roots in Ningchun werebetter than Xihan,50and150mmol·L^-1NaCl treatments significantlyresulted in decreased roots growth in two wheat seedlings. Ningchunshoots were siginificantly inhibited by50mmol·L^-1NaCl treatment, butdid not affect Xihan.2. There were no significant changes in leaf·OH and H₂O₂contents in twowheat seedlings when exposed to50mmol·L^-1NaCl concentration, while150mmol·L^-1NaCl treatment significantly resulted in increasedleaf O₂!、·OH and H₂O₂contents. Compared with the control, rootO₂! and H₂O₂contents were enhanced in two wheat seedlings under saltstress, while the highest elevation of·OH was found in150mmol·L^-1NaCl-treated roots. With fluorescent probes for detectingH₂O₂show that: the fluorescence intensity of root H₂O₂increased intwowheat with salt treatment enhanced, and the brightest of fluorescenceintensity was found in150mmol·L^-1NaCl-treated roots.3. Leaf SOD activity were increased significantly in two wheat with saltconcentration enhanced, the similar tendency was found in CAT andPOD activities in Xihan leaves. In contrast, root SOD activity wasdecreased in Ningchun when exposed different NaCl concentrations,while Xihan root SOD activity and CAT activitiy in the roots in twowheat were increased when exposed to salt stress. Compared with thecontrol, root APX activity was significantly decreased in Ningchunwhen exposed to50mmol·L^-1NaCl, but it was obviously elevated inresponse to150mmol·L^-1NaCl treatment. Significant decreased in GRactivity was observed in the shoots in two wheat seedlings undersalinity treatment, while Ningchun root GR activity was increased inresponse to only150mmol·L^-1NaCl treatment.4. In untreated seedlings, the content of leaf MDA in Ningchun roots washigher than that in Xihan ones.50mmol· L^-1NaCl resulted insignificantly increased in MDA content in the leaves of Ningchun, whilesalt stressed did not cause significantly change in MDA level in Xihanleaves.150mmol· L^-1NaCl treatment caused membrane lipidperoxidation reaction in Ningchun and Xihan roots, MDA content wereincreased by approximately87%and50%of control, respectively.5. Compared with the control,the amount of soluble protein in Ningchunshoots and roots as well as soluble sugar content in the roots increasedremarkably exposed to50mmol·L^-1NaCl stress,while soluble sugar,soluble protein and proline contents enhanced in the shoots and roots of two wheat with150mmol·L^-1NaCl-treatment．In addition,GK activity is significantly higher than that of OAT activityin Ningchun shoots and roots treated with150mmol·L^-1NaCl,while didnot affect in Xihan leaf GK activity. The leaf OAT activity was increasedsiginificantly in Xihan exposed to NaCl treatment, but a decresed in rootOAT activity. GK activity in the roots of Xihan was enhanced with150mmol·L^-1NaCl treatment．PDH activity significantly decreases in theshoots and roots of two wheat with50mmol·L^-1NaCl-treatment,whilethis enzyme activity in the shoots and roots of Xihan were inhibitedunder150mmol·L^-1NaCl-treatment．The results showed that salt stress significantly inhibited Ningchunseeds germination and the growth of two wheat seedlings, while the seedgermination of Xihan showed tolerance to different NaCl treatments；soluble sugar and proline accumulation in the leaves of two wheatseedlings were higher than that in roots, the higher leaf SOD activityresulted in a lower leaf O₂! cont ent com pared wit h root, which m ay besalt-tolerance mechanism that priority to the protection ofphotosynthetic organ under salt stress；Anyhow,salt stress induced bytwo wheats on accumulation of osmotics contents,which contributes tothe enhancement of plant salt tolerance；The accumulation of proline inNingchun shoots and roots may be assolociated with the GK activityincreased under high salt concentration of stress,the accumulation ofproline in XiHan3shoots is associated with the rise of OAT activity andPDH activity decreased,while the activity of GK increased and PDHdecreased may induce to the proline accumulation in roots of XiHan3．...