| A series of experiments were performed to determine the influence of chillingand low irradiation under different level of salinity on its S. salsa growth. At present,photosynthetic characteristics and the concentration of unsaturated fatty acids inmembrane lipids in S. salsa were investigated to explore the mechanism of chillingand salt resistance and establish foundation for the development and utilization ofsaline soil. The results are as follows:1. Effect of chilling and low irradiation (4°C,100μmol m-2s-1) on S. salsa atstages of seed germination and young seedings under salinityYoung seedings (seedlings were cultivated4days in petri dishes) of S. salsaunder salt treatment (200and500mM NaCl) showed a resistance to chilling and lowirradiation stress. It was more obvious in the200mM NaCl treatment group. Underchilling stress with low irradiation and salt treatment, the seed germination of S. salsaat three different salt treatment groups (0,200,500mM NaCl) all delayed. But thegermination rate of salt treatment groups increased continually, while the controlgroup increased first and then stable. The fresh and dry weight of young seedings atsalt treatment increased, while the control decreased. Moreover, concentration of Na+in control group significantly increased compared with that of salt treatment groups,and a significant reduction of K+was observed in the control. With the treatment ofchilling and low irradiation, the concentration of chlorophyll, activities of APX andCAT in control were significantly decreased compared with salt treatment groups.After chilling stress under low irradiation for12h, the unsaturated fatty acid, DBIand DGDG/MGDG of PG are increased in S. salsa under200mM NaCl treatment.The results indicated that S. salsa lived very well under200mM NaCl treatment, withthe concentration of chlorophyll, activities of APX and CAT increased. Although500mM NaCl exerted damage to the plant, there were some protective substancesproduced in the process of adaptation to salt environment, so the salt treatment canalleviate the harm of chilling and low irradiation.2. Effect of chilling and low irradiation on S. salsa seedling under salinityUnder chilling stress with low irradiation, chlorophyll concentration of S. salsa seedling (six weeks) in non-NaCl treatment group was significantly decreasedcompared with salt treatment group. The membrane permeability was increased with agreat deal of Na+got into cells, but the absorption of K+was blocked. Activities ofAPX and CAT in salt and non-salt treatment groups increased first and then decreased.However, after12h, the decrease was slight in salt treatment groups compared withthe control. Salinity had no significant effect on the photosynthesis of S. salsaseedling. But under chilling and low irradiation, maximal efficiency of PSIIphotochemistry (Fv/Fm), actual PSII efficiency (ΦPSII) and activity of PSI (△I/Io)decreased and the oxygen-evolving complex OEC was seriously hurt, which wassignificant in the control. Treatment of chilling and low irradiation can significantlyincrease the level of membrane unsaturation. Under200mM NaCl treatment, PGconcentration and the DGDG/MGDG in200mM NaCl treatment group increased46.9%and53.7%, respectively, but decreased22.5%and4.2%in control group.Under salt treatment, the concentration of unsaturated fatty acid and the antioxidantenzyme activity increased, which can maintain the membrane fluidity, protect thephotosynthetic apparatus and increase chilling tolerance. These results indicated that S.salsa produced osmotic adjustment substances under salt treatment to decreaseosmotic potential of cells, maintained highter antioxidant enzyme activity and higherunsaturated fatty acid to protect photosystem. |
