Integrated Study Of A Single Stress Resistance In The Composite Stress Tolerance Of P. Tenuiflora

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 exploer the adaptation and modification of the osmotic regulating mechanism and the Na+, K+ ion balance system, the light energy utilizing and heat dissipation of PSⅡ, the membrane-lipid peroxidation and active oxygen scavenging system of P. tenuiflora seedlings 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 inverstigate the mechanism of physiological and ecological integration.The results showed that ion stress and pH might play a major role to the osmotic regulation ability of P. tenuiflora seedlings under iso-osmotic stress. As a kind of salt-resistant plant, P. tenuiflora might prefer to live in alkali salinity enviroment. The content of elements on the leaves was analyzed using EDS, and it was suggested that P. tenuiflora seedlings maintained K/Na balance to resist ion stress by discharging Na and reducing K ejection under lower iso-osmotic stress; that pH had the main effect on Na+/K+ balance by the enhanced fluctuation of Na+, K+ under ion-pH stress. pH could accelerate accumulation of Na in P. tenuiflora seedlings. P. tenuiflora maintains its relatively high K/Na ratio under salt alkali stress by extruding Na or the compartmentation of Na. Under a low level of iso-osmotic stress, P. tenuiflora shows a higher leaf K/Na ratio when treated with NaCl than with Na₂CO₃, while under a high level of iso-osmotic stress, the result is just the opposite, suggesting that P. tenuiflora has different regulating mechanisms under varied stress intensities.It was concluded that there may be refined osmotic regulation mechanism in a salt stress, which regulated the stomatal conductance, improved PSⅡand resulted in a higher photosynthesis efficiency. The results showed that P. tenuiflora had higher salt-resistant ability than alkali-resistant ability, pH stress had larger effect on the photosynthesis of P. tenuiflora seedlings than ion toxicity. It was also indicated that the safeguard mechanism of P. tenuiflora was different under varied stresses of salt alkali stress and could be an important reason for P. tenuiflora to be able to complete its life history in salt alkali salinity soil, and it also suggested that there were different ways in adjusting the balance between light energy absorbing and utilizing under different stress intensities.The results demonstrated that pH stress than ion toxicity had a main effect on the membrane permeability of P. tenuiflora seedlings rather. The MDA concentration of P. tenuiflora seedlings changed with treatments under high ion tensity stress, and that treated with Na₂CO₃ was higher than that with NaHCO₃, and the concentration of seedlings treated with NaCl was the lowest, but the effect on memberane-lipid peroxidation might be from the complex stresses caused by osmotic and pH factors. The study showed different increases in the activeties of SOD, POD and CAT of P. tenuiflora followling different treatments, jointly scavenging active oxygen.