Abstract:

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 F_v/F_m, F_v/F_o, 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 treatment.

Key words:

Cotton, Glycinebetaine, Soaking seed, Salt stress, Physiological characteristics