Rapid and uniform crop stand is a prerequisite for better quality produce. If seeds germinate erratically over a long time, seedling growth will not be uniform and plants will mature over a wider period. Seed invigoration treatments are therefore developed to improve seed performance during germination and emergence.
Dry-heat treatment of seeds is used to control external and internal seed borne pathogens such as fungi, bacteria, viruses, and nematodes (Nakagawa and Yamaguchi 1989), and to break seed dormancy (Zhang 1990). In general, the high temperature in this treatment reduces seed viability and seedling vigor, but the optimum temperature for breaking dormancy promotes seed germination and seedling emergence in cereal crops (Lee et al 2002) and cotton (Basra et al 2003). The degree of promotion of seed germination by dry-heat treatment showed wide intraspecific variation (Herranz et al 1998). Nonlethal heat shock treatment before radicle emergence effectively promoted the germination of bar- ley, wheat, and cotton seeds (Dell' Aquilla and Di Turi 1996, Dell' Aquilla et al 1998, Basra et al 2003).