Effect Of NaCl Stress On Physiology,Leaf Anatomical Structure And Growth Character In Ulmus Pumila Clones

In order to cultivating, modifying and utilizing salinized soil of coastal saline area, 3 elm clones (EC46, EC65225 and EC51) were chosen as test materials, watering with 5 salt concentrations of Og/L, 3g/L, 5g/L, 7g/L and 9g/L by pot-cultivated experiments in the greenhouse. The change of growth, physiology and leaf anatomical structure of Elm Clones and the correlation of the indexes were analyzed. In addition, salt resistance of the 3 clones was comprehensively evaluated by the method of subordination function and principal component analysis. The results of this paper may also provide a certain theoretical significance for cultivating elm clones in the future. The results showed that:(1) NaCl stress has inhibited growth of elm clone, the reduce of root system could lessens the NaCl damage to elm clone and inhibition phenomenon on the ground is more obvious. Under low salt concentration stress of 3g/L-5g/L, EC65225 and EC51 to resist salt injury actively by increasing the longitudinal elongation of root system, and the facilitation of EC51 is more obvious. Under low salt concentration stress of 3g/L, the root biomass increase of EC46 and EC65225 could improve the mineral nutrition and water uptake amounts to reduce the poisonous effect of salt. Biomass change of EC51 is more stable, with stronger adaptability. Under the condition of salt stress, salt damage symptoms of elm clone such as etiolated and withered leaves will aggravate with increase of concentration and under high salt concentration stress of 9g/L, EC46 plant died while EC51 and EC65225 didn’t. Under the same NaCl concentration, salt damage symptom of EC65225 is more serious than that of EC51.(2) Elm clone could reduce the injury of active oxygen species by improving the he activities of dismutase (SOD) and peroxidase (POD). The activities of catalase (CAT) in antioxidant system have no important function. EC51 sustained high antioxidant enzyme activity under different salt concentrations, meaning it had the strongest antioxidant capacity.While as the antioxidant capacity of EC46 was the worst, because its antioxidant enzyme activity decreased in greatest. The activities of MDA increased with the salt stress increasing,the greatest increase was from EC46, while the smallest from EC51 and the salt injury to EC51 was the least.(3)The three elm clones could reduce solute potential by absorbing the inorganic salt ions(Na+ and Cl-) to defense the hyperosmotic stress. Through the regulation of ion distribution mode of could reduced accumulation of salt damage ions in photosynthetic organ.The increasing amplitude of Na+ content in each organ of EC51 is smaller than that of EC65225 and EC46. Under the stress of salt concentration more than 5g/L, Cl- accumulation in root is more than that in leaf for EC51. Cl- content in stem is the minimum, it can be deduced that stem organ may be just a transmission channel. K+ content in each organ decreases significantly compared with the contrast and the decreased magnitude of EC51 is least. Under the salt concentration more than 5g/L, K+ content in each organ of EC51 is higher than that of EC65225 and EC46. . Under the salt concentration more than 5g/L, the rate K+/ Na+ in the leaf is higher than that of steam and root, that is to say the selective absorption of Na+could reduce the harm of the young tissues. The rate K+/ Na+ in each organ of EC51 is higher than that of the other two clones under the same concentration, which indicates that EC51 has better adaptability in hypertonic environment with salt stress.(4) Elm clones reduced water loss through thick leaves and cuticular layer under salt stress. The thickness of leaves and cuticular layer increase of EC51 is higher than that of EC65225 and EC46. Under the higher salt concentration, the thickness of palisade tissue and ratio of palisade tissue to spongy tissue of EC51 was significantly bigger than in other two clones, is more favourable to the photosynthesis of the plant. EC51 shows up greater adaptability under salt stress.(5) Through principal component analysis to establish convenient evaluation system of salinity tolerance for elm clones. This evaluation system has ten indicators include MDA、Na+ content and Cl- content in each organ、corneous layer’s thickness、upper and lower epidermis’s thickness. Salt tolerance of the 3 elm clones was comprehensively evaluated with principal component analysis and subordinative function. The sequence of salt tolerance of the 3 elm clones from strong to weak was: EC51 >EC65225 >EC46, we recommend that EC51 is the preferred clone in afforestation in the coastal areas.