In the southwestern and western Cotton Belt of the U.S. soil salinity can reduce cotton productivity and quality. This study was conducted to determine the physiological responses of six genotypes including five Upland cotton (Gossypium hirsutum L.) cultivars and one Pima cotton line (G. barbadense L.) to NaCl under greenhouse conditions. Seeds were germinated and grown for 14 days prior to salt treatment (daily 100？ml of 200？mM NaCl) for 21 days. Compared with the control (daily 100？ml tap water), the NaCl treatment significantly reduced plant height, leaf area, fresh weight, and dry weight. The NaCl stress also significantly increased leaf chlorophyll content, but did not affect leaf fluorescence. Of the six genotypes, Pima 57-4 and SG 747 had the most growth reduction, and were most sensitive to NaCl; DP 33B, JinR 422 and Acala Phy 72 had the least growth reduction and were most NaCl tolerant. Although all the six genotypes under the salt treatment had significantly higher Na and Cl accumulation in leaves, SG 747 and Pima 57-4 accumulated more Na and Cl than DP 33B. Increases in leaf N, Zn, and Mn concentrations were also observed in the NaCl-treated plants. While leaf P, Ca, and S concentrations remained unchanged overall in the genotypes tested, leaf K, Mg, Fe, and Cu concentrations significantly decreased during salt stress. Reduction in plant height is a simple, easy, sensitive, non-destructive measurement to evaluate salt tolerance in cotton. 1. Introduction In the southwestern and western Cotton Belt of the U.S., soil salinity can ultimately lead to reduced crop productivity. In many areas secondary salinization, as a result of irrigation practices, drainage, or water quality, are primary factors contributing to the loss of productive agricultural land [1]. Three viable options are plausible to solve the problem of saline growing environments: (1) cease the agronomic usage of salinized soils, (2) desalinize soil, or (3) use salt-tolerant cultivars. Options (1) and (2) may not be agronomically or financially viable. Salt tolerance is measured by the relative decrease in yield of cultivars grown under saline conditions relative to nonsaline conditions [2]. Even though many studies have demonstrated salt tolerance in crops including cotton, high yielding and high fiber-quality cultivars with known salt tolerance are not commercially available [3]. Identification of salt-tolerant genotypes from the cotton germplasm pool is needed. High salinity reduces plant growth by affecting the plant’s osmotic or ionic homeostasis [4]. Many studies have
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