Star Grassroots The Salinization Composite Stress Resistance Physiological Series Integration Mechanism

Being a species of Puccinellia, Puccinellia tenuiflora is gramineous, perennial, and herbaceous. It can live in circumstance of pH10 owing to its salt-resistant ability. This experiment adopted four kinds of stress and ten methods of treatment (with 0.4%, 1.0% Na₂CO₃ culture solution being standards respectively: (1)different concentration of NaCl, Na₂CO₃ and PEG of the same osmotic pressure; (2)different concentration of NaCl, Na₂CO₃ and NaHCO₃ of the same Na+ level). The purpose was to study the physiological and ecological adaptation mechanism of P. tenuiflora seedlings roots against complex stress under iso-osmotic stress and iso-natrium ionic stress. Alkali salt as a kind of complex stress was decomposed into several singular factors to determine the mechanism of physiological and ecological changes under different saline stresses. These researches will be of value in supplementing the theory on salt-resistant ability of Puccinellia tenuiflora and meanwhile it will supply new viewpoints in the filedss of plant sress physiology, ecology of plant physiology, and cell biology.The results were as follows: By energy spectrum analysis of elements of P. tenuiflora, the relative values of Na,K on the roots surface tend to be similar with that inside the root tissures, displaying approximately the same ratio of the concentration of Na+,K+ (Na/K ratio being similar), so a transitional ion absorption gradient can be established to relieve the direct damage on the root cells by the external environment. P. Tenuiflora has the ability to maitain its K+ level under adverse circumstances to alleviate the stress from sole salt. Alkaline pH within some extent can promote P. tenuiflora to accumulate Na+ in the seedling roots. Under saline-alkaline stress, P. tenuiflora can reduce the ion transport to the aerial parts of the plants through maintained K+ concentration and accumulated Na+ in the roots. Under lower stress, pH stress does no damage to P. tenuiflora seedling roots, ion and osmotic stresses constitue the major stress; under higher stress, however, pH stress exerts a stronger effect while osmotic and ion stress act as a supporting collaboration role in roots osmotic pressure.Under a low level of stress, the osmotic regulation pressure of P. tenuiflora seedling roots mainly comes from the osmotic stress, and the ion-osmotic sress is the major factor in damaging the membrane permeability; while under a high level of stress, pH and ion-osmotic stress together play a role to comprise the osmotic regulation pressure of P. tenuiflora seedling roots, and all the three factors of the compound stress inflict injury to the membrane, hence the barrier function of the cell membrane of roots are destroyed. After different stress, SOD activity decreased but the isozyme band changes are not sonsistent. SOD isozyme in P. tenuiflora seedlings roots displayed the most significant changes, showing that the structure of SOD is the most sensitive to external environment, and its synthesis pathway changes most quickly in answer to external stress. POD showed relatively consisten activity and isozyme bands, proving that its structure and espression in P. tenuiflora seedling roots are stable. CAT activity increased remarkbly but the isozyme bands underwent no change, which suggested that CAT synthesis pathway is stable and only the synthesis magnitude will be enhanced by sressing environments. In sum, under different treatments, the activities of SOD, POD and CAT of P. tenuiflora seedlings roots displayed significantly different changes, jointly and effeciently scavenging active oxygen.