Exogenous Hormones Alleviated Salinity and Temperature Stresses on Germination and Early Seedling Growth of Sweet Sorghum

Abstract

Germination and vigorous growth are critical for seedling establishment, especially under salinity and high temperature. A laboratory experiment was done to determine the effects of salinity (0, 100, 200, and 300 mM NaCl) and temperature (25, 35, and 39°C) on germination and early seedling growth of two genotypes (Yajin 13 and Yajin 71) of sweet sorghum [ Sorghum bicolor (L.) Moench]. Seeds were soaked in solutions with one of three hormones [288.7 μM gibberellic acid (GA 3 ), 232.3μM kinetin, or their combination] and germinated under controlled conditions. Water imbibition, germination, radicle and shoot length, and the electrical conductivity of leachate were measured. Seed water imbibition increased with increasing temperature and decreased with increasing salinity level. Yajin 13 had 17.9% higher germination percentage with 16.3% higher germination velocity index than Yajin 71. Salinity and temperature stresses clearly affected germination and decreased subsequent shoot and root growth. The application of GA 3 , kinetin, or their combination alleviated the negative effects of salinity and temperature stresses on all the measurements. Among the tested hormones, GA 3 was better in alleviating salinity and temperature stress in both genotypes in germination and other parameters except water uptake. It was concluded that seeds treated with suitable exogenous hormones may serve as a possible way to improve water imbibition and to alleviate the negative effects produced by salinity and high temperature on germination and early seedling growth of sweet sorghum.