Hydrothermal Variations and Physio-Osmotic Conditioning E.ects on Five African Millet Varieties during Short Term Substrate Desiccation

Abstract

Environmental factors di.erentially a.ect the germination of millet (Pennisetum americanum L.) and impact both the rate and extent of .eld emergence. The extent and uniformity of emergence depends on hydrothermal variations in both soil moisture and temperature levels. To determine the impact of these two factors and counteracting physiological and osmotic conditioning seed treatments, two growth chamber trials were conducted on African millet. Five genotypes responded to di.erences in temperature or osmotic seed conditioning. Seed conditioning with GA₃, Kinetin, NaCl and KNO₃ was tested. Increasing incubation temperature decreased the final proportion of seeds germinating and slowed germination for each of the five genotypes tested when exceeding a 29°C threshold. GA₃ improved the performance of seed lots, while physio-osmotic conditioning and temperature interacted to affect the proportion of germinating millet seeds. These germination tests partially explain interspecific differences in the impact of timing of heat fluctuations in the field. Patterns of millet germination in response to temperature and rainfall fluctuations could be explained by its response to seed conditioning, temperature or moisture levels.