| Elaeagnus angustifolia L. is an important pioneer tree species for wasteland andsaline-akali land, which has been applied widely in saline-akali land improvement andmanagement. In order to select optimal E. angustifolia and reveal the salt-tolerance mechanism,E. angustifolia seedlings from six provenances (Alaer, Changji, Jinchang, Yinchuan, Yanchi,Dengkou) were used as experimental materials in this research. By pot experiment ingreenhouse, the salt tolerance of six E. angustifolia provenances were studied and comparedsystematically. The physiological changes and metabolic characteristics of mineral ions wereinvestigated with seedlings of salt-tolerance provenance and salt-sensitive provenance underdifferent NaCl concentrations and different stress time. Meanwhile, the electrophysiologicaland pharmacological properties were analyzed by using Non-invasive Mico-test Technique(NMT) with hydroponic seedlings of the two provenances. which systemic studied thephysiological mechanism from different aspects.The main results of this research were summarized as follow:1. The relative height growth, ground diameter, leaf area per plant, number of leaf,biomass accumulation and relative biomass were significantly reduced with the NaClconcentration increased, except the Alaer provenance under the150mmol·L-1NaCl stress. Theroot/shoot ratio, specific leaf area and leaf area ratio was not obvious difference under the150mmol·L-1NaCl, but under the300mmol·L-1NaCl concentration, the root/shoot ratio wassignificantly increased and decreased for specific leaf area and leaf area ratio. The growthindexes of Yinchuan provenance had a maximum inhibition under salt stress. Seedlingtolerance ability of six different provenances was assessed by membership function combinedwith weight, and the sequence from strong to weak was Alaer> Jinchang> Dengkou> Yanchi>Changji>Yinchuan. 2. Under the NaCl stress, the biomass accumulation of E. angustifolia seedlings wasinhibited more obviously with increasing salt concentration and stress time, and the Alaer E.angustifolia provenance had a lower inhibitory effect than Yinchuan provenance. When theseedlings of Alaer provenance were treated with150mmol·L-1NaCl, the biomass accumulationhad a little decline with the stress time prolonging, compared with the control, and theroot/shoot ratio was insignificantly change. The content of chlorophyll a, chlorophyll b, totalchlorophyll and chlorophyll a/b ratio were all remarkable reduced by salt stress, and thedecrement was gradually increased with the salt stress time extending. The salt stress hadgreater inhibited effect on chlorophyll content of Yinchuan provenance than that of Alaerprovenance. With increase of the NaCl concentration and stress time, malonaldehyde (MDA)content of E. angustifolia leaves was gradually increased, and the increased rate of MDAcontent in leaves of Yinchuan provenance was greater than that of Alaer provenance. Theproline content was significantly increased with increase of the NaCl stress, but the increasedrate of proline content decreased with prolong of the stress time. After salt treatment for7days,the soluble sugar content of E. angustifolia leaves decreased with the NaCl concentrationincreased, and the Alaer provenance had more decrement than Yinchuan provenance. Thesoluble sugar content rose after the first drop with increase of the salt concentration after saltstress30days. The soluble sugar content showed a gradual upward trend at NaCl stress60days later, and the rate of increment was greater in Alaer provenance than Yinchuanprovenance.3. After NaCl stress, the Na+content in organizations of E. angustifolia seedlingsincreased dramatically with increase of NaCl concentration, and the Na+contents in roots andleaves were more obvious increase with prolonged of stress time. The increment of roots ofAlaer provenance was greater than Yinchuan provenance, but in leaves which was opposite.With the increased of NaCl concentration and prolonged stress, K+and Ca2+content levelsshowed a gradual downward trend, but the contents of root and leaf were fall lower in Alaerprovenance than Yinchuan provenance. Variation of Mg2+content followed NaCl concentration which was changed with prolonged stress time. After salt stress for7days, the Mg2+content ofroots increased with increase of salt concentration, while the leaves were gradually reduced.There was no significant difference compared with the control group after30days, but theMg2+content showed a gradual downward trend in each tissue. K+/Na+ratio in each tissue of E.angustifolia seedlings and whole plant K+/Na+ratio were all decrease with increased of NaClconcentration and stress time, and K+/Na+ratio of the leaves dropped sharpest, followed by theroots and stem smallest. The decrement rate of roots and leaves K+/Na+ratio in Alaerprovenance was less than that of Yinchuan provenance. The K+selective absorption coefficientand transport coefficients of E. angustifolia increased or remained stable as the NaClconcentration increased in30days of salt stress, but the two coefficients were decreasedgradually with increasing salt concentration as the stress time reached60days. Meanwhile, theK+selective absorption coefficient and transport coefficients of Alaer provenance was slightlyhigher than Yinchuan provenance.4. The steady-state Na+and K+of E. angustifolia were efflux and significantly increasedafter NaCl treatment24hour. The Na+efflux of Alaer provenance was greater than Yinchuanprovenance, but the K+efflux was lower than Yinchan provenance. When the transientstimulation of NaCl was given, the K+efflux in E. angustifolia seedlings exhibited aremarkable increase, and net K+flux of Yinchuan provenance was higher than Alaerprovenance. In pharmacology experiment, Na+efflux and K+efflux which induced by NaClwere inhibited by three kinds of inhibitors (TEA, Amiloride, Vanadate). After amiloridetreatment, the Na+efflux of Alaer provenance was still significantly larger than Na+efflux ofYinchuan provenance. The Na+and K+efflux which were treated by vanadate had a littledifference or no difference compared with that of corresponding inhibitor treatment, whichindicated the Na+and K+efflux closely associated with the plasma membrane proton pumpactivity. When the E. angustifolia seedlings were under the NaCl stress, Na+of the roots wasexpelled by the Na+/H+antiporter. In the meantime, salt stress strengthened the celldepolarization and increased K+efflux. Because the Na+efflux required H+electrochemical potential gradient at the sides of the membrane which reduced the cell depolarization and K+efflux, this caused the competitive efflux of Na+and K+.Based on these results, the sequence of the salt-tolerance from strong to weak of the six E.angustifolia provenances is Alaer>Jinchang>Dengkou>Yanchi>Changji>Yinchuan. NaClstress can not only inhibit the accumulation of organic matter of E. angustifolia, but also canaffect the distribution of organic matter, and which has greater impact for salt-sensitiveprovenance. As the NaCl concentration increased and stress time prolonged, the salt-toleranceprovenance of E. angustifolia has a lesser decrement rate of chlorophyll content, and betterability to maintain the stability of the membrane system, thus all kinds of metabolisms areensured to successfully carry on. In the osmotic adjustment, the proline can regulate the vivomicroenvironment for early stress of E. angustifolia. The soluble sugar is mainly as an energysource in the short-term salt stress and primarily as an osmotic adjustment in the long-termstress, and the salt-tolerance E. angustifolia provenance has stronger regulation ability thansalt-sensitive porenance. Meanwhile, the salt-tolerance E. angustifolia provenance can be moreeffective to obstruct Na+in the roots, reducing leaf Na+content, and has a stronger ability toretain K+for the plants. In addition, the salt-tolerance E. angustifolia provenance has strongerNa+/H+antiporter activity, which increased Na+efflux and decreased K+efflux, thereby theplants can be better to maintain the cytoplasm K+/Na+balance. |
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