棉 花 学 报 Cotton Science 2006，18(4)：248-54
Advance in Studies of the Mechanism of Salt Tolerance and Controlling of Salt Damage in Upland Cotton Abstract：The mechanism of salt tolerance，methods of salt tolerance identification，and the techniques for salt damage controlling were reviewed in this paper. The cotton （Gossypium hirsutum L.）was placed in the moderately salt-tolerant group of plant species with a salinity threshold level 0.3% at which initial yield of cotton declines and with a 50% reduction in yield at 0.5%. However，the growth of cotton plant is severely affected at different stages of the plant life cycle in saline medium，especially at germination and emergence stages. Salt stress adversely affects the biomass production，i.e.，an inhibition in both length and number of secondary roots，a decrease in leaf area，stem thickness，shoot and root weight，the number of bolls and an increase in the percentage of bolls shedding，which ultimately brings about decrease in seed cotton yield. There are various reports regarding the salinity stress on fiber characteristics，which may be due to the differential responses of different genetically based cultivars to salt stress with respective to fiber characteristics. High salinity level adverse affects photosynthesis and reduces N and P uptake in cotton. Research studies indicate decrease in nitrogen of leaf cotton with increasing salinity levels. Salinity increases Na+ and Cl- and decreases K+，Ca2+ and Mg2+ in leaves of cotton. Slight increases in K+ and modest accumulation of Na+ with increase in salinity have also been found in literature. Maintenance of high tissue K/Na and Ca/K ratio is suggested to be an important selection criterion for salt tolerance in cotton. There are some difference in the mechanism of the salt tolerance between cotton and other crops，and many scientists have worked on that field to find out the mechanism of the salt tolerance in the distribution of the differentions in the plant，the structure and stability of the cell membrane during the salty stress，as well as the regulating effect of the osmotic pressure. Generally salt tolerance in cotton has been associated with partial Na+ exclusion and the salt-tolerant cotton cultivars have higher concentrations of K+，Ca2+ and K/Na ratios in leaves than those of the salt-sensitive lines. In view of some latest studies concerning the role of some antioxidants in salt tolerance of cotton it was suggested that high levels of antioxidants and an active ascorbate-glutathion cycle are associated with salt tolerance in cotton. Additionally the accumulation of osmotic substance，such as glycine betain，proline，soluble carbohydrate etc. and late embryogenesis abundant protein are all closely correlated with salt tolerance in cotton. For the cotton breeding，the traditional breeding method combined with the model biotechnology was applied，such as selection，introduction，hybridization，gene engineering and mutation. The progress of salt tolerant cultivars breeding has been achieved to some extent. In addition，the complex techniques for the cotton production in the salinized land such as the cotton cultivar，cultivation techniques，seed treatment with chemical solution or microelement and hormone，soil improvement with rational fertilization and so on were suggested in this paper.
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