Effects of Drought Stress on Germination and Radicle Growth of Sweet Sorghum (Sorghum bicolor (L.) Moench)

Sweet sorghum is a C4 species that is well adapted to temperate and tropical semiarid environments (Cosentino, 1996). In these areas water deficit is one or the main limiting factors of plant production, and it may adversely affect germination and seedling establishment (Murillo-Amador et al., 2002). Indeed, high evaporation rates may occur during the opti mal sowing time of sorghum resulting, even when irrigation is applied at sowing, in rapid drying of the medium surrounding the seed and in a marked decrease in water potenti al. Drought resistant varieties are under breeding and selection for these environments. In this paper, the effects of increasing levels of water stress on seed germination in two lines of sweet sorghum selected for drought-tolerance, as compared to a commerciai cultivar, were studied, in order to also determine their differences in water potential threshold at which germination and radicle growth are inhibited.