Relieving Effects Of Exogenous Salicylic Acid On The Growth Of Cotton Seedling Under NaCl Stress

In order to study the NaCl effects of exogenous Salicylic Acid(SA) on the relief mechanism of cotton, Zhongmiansuo41(salt tolerant) and Zhongmiansuo49(moderate salt tolerant variety) were taken as materials researched under the stress of 0.60% NaCl, the effects of SA soaking + spraying compound treatment on cotton growth, photosynthesis the characteristics, chlorophyll fluorescence characteristics and antioxidant enzyme activity and osmotic adjustment substances content effects on physiological and biochemical indicators reveal the mechanism of exogenous SA on alleviating salt stress in cotton, and provide theoretical and technical basis for relieving salt of cotton, new ideas to solve the cotton cultivation and resistance breeding practice comprehensive stress damage. The main results as follow:(1)SA seed soaking + foliar application of composite treatment is superior to the SA seed soaking, in which 0.05 mmol·L-1 seed soaking +0.2 mmol·L-1 foliar spray effect is excellent, made the cotton plant height increased 8.10% ~ 15.86%, leaf area increased 17.21% ~ 22.68%, and the roots and stems to promote greater than the leaves with SA, stem and root dry matter distribution ratio significantly increased, and leaf dry matter distribution ratio was reduced,cotton seedling root growth is one of the ways to SA improve the salinity tolerance of cotton, SA for Zhongmiansuo49 was greater than the Zhongmiansuo 41.(2)The Chla, Chlb, Chla+Chlb, Car and Chla/Chlb of two varieties were decreased under NaCl. While Pn decreased, Ci also decreased, Ls liters but highed. With SA, Ci rise, Gs would increased. The SA to handle the increased effect on the cotton Chla greater than Chlb, 0.05 mmol·L-1 seed soaking +0.2 mmol·L-1 foliar spray treatment could Zhongmiansuo41 Pn increased 18.76%, increased 25.19 % of Pn with Zhongmiansuo49.(3)SA can increase cotton seedling leaves of Mo, Vj, N, ABS/RC, DIo/RC, TRo/RC, ETo/RC and PI abs salt stress, chlorophyll fluorescence parameters, reduced ?Po, ?o, ?Eo and N parameters, SA can change cotton seedling leaf photosynthetic organs of light energy absorption, transformation and heat dissipation, coordination of light energy distribution, improve the energy in the absorption, dissipation and captures the distribution. However on the acceptor side electron transfer did not increase, but on the reaction center electron transfer had significant promoting effect and influence on the photochemical efficiency.(4)Salt stress can change the permeability of cell membrane, reduce the ability of antioxidant enzymes in roots and leaves, while the content of malondialdehyde in the leaves of cotton seedlings, soluble sugar and soluble protein after SA treatment increased, leaves and roots of super oxide dismutase, the activity of peroxidase, and catalase increased significantly, which to 0.05 mmol·L-1 soaking + 0.2 mmol·L-1 foliar spraying treatment was the best. It was showed that SA could improve the salt tolerance of cotton seedlings and reduced the membrane damage by regulating the osmotic and antioxidant capacity of cotton seedlings.