中文摘要：

选用目前生产上主推的抗虫棉品种99B和鲁棉研28,用400μgmL^-1甜菜碱浸种,及用含或不含0.4%NaCl的Hoagland营养液盆栽培养,以研究其对棉花幼苗生理特性的影响。结果表明,无论在盐胁迫还是非盐胁迫条件下,甜菜碱浸种对棉花幼苗生理特性均有显著影响,可促进棉花苗期叶片叶绿素合成,降低叶绿素的a/b值,增加叶绿素荧光动力学参数Fv/Fm、Fv/Fo、光合电子传递速率（ETR）和光系统Ⅱ的实际量子效率（ΦPSⅡ）值,从而提高棉花苗期叶片的光合能力;并提高棉花苗期叶片和茎秆可溶性糖含量及叶片脯氨酸含量,降低棉花苗期子叶相对电导率,提高棉花苗期渗透调节能力,缓解盐胁迫伤害;同时还增强棉苗子叶硝酸还原酶活性,促进棉苗氮素代谢。两种品种对甜菜碱的反应趋势一致,但99B比鲁棉研28更敏感一些。

英文摘要：

Cotton is a main agricultural product in the world and salty soils have a tremendous impact on farmers livelihood. Finding ways to increase salt tolerance of cotton is crucial in agricultural. Glycinebetaine （GB） is an amino-acid derivative accumulated in certain plants under water stress, which has been studied as an osmoprotectant in the adaptation to water, salt and cold stress. The adaptation varies with and depends on numerous factors including types of crop, timing and rate of fertilizer application, and environmental conditions. Exogenous GB may help to reduce the negative effects of salt stress in cotton production. The objective of this study is to determine the effects of seed soaking with GB on the salt tolerance of cotton seedlings whether under salt stress or not. Two transgenic insect resistant cotton cultivars 99B and LMY28 abroad generalized in production were used in these examinations. Some of the seeds of the two cotton cultivars were soaked with 400 μg mL^-1 GB for 15 h and others with water for 15 h, and then cultured with Hoagland solution or Hoagland solution containing 0.4% NaCl in pots under field conditions. The results indicated that seed soaking with GB promoted the synthesis of chlorophyll, but decreased the value of Chl a/b; increased the chlorophyll fluorescence dynamic parameters Fv/Fm, Fv/Fo, photosynthetic electron transport rate （ETR） and actual quantum efficiency （ΦPSⅡ）, which improved the photosynthetic capacity of cotton seedlings, leaves consequently. In addition, seed soaking with GB also increased the soluble sugar content in leafs and stems of cotton seedlings, increased the proline content in leafs of cotton seedlings, but decreased the relative electrical conductivity of cotyledon, indicating that seed soaking with GB can promote osmotic adjustment ability and alleviate the harm caused by salt stress. Seed soaking with GB also promoted N metabolism through increasing the activity of NR of cotyledon. Two cotton cultivars had the same reaction trend to GB