The present study aims to investigate the effects of osmotic water potential simulated by reduced osmotic water potential, s, temperature (T) and zinc (Zn) addition to the seed incubation medium and to evaluate the effects of their interactions on the germination processes of seeds in three plant species of different ecological affiliation, namely: Senna alexandrina, Senna italica (native to hot deserts) and Senna occidentalis (a wild mesophytic plant). The Results indicate that:1. The germination percentage as well as elongation of both radicle and hypocotyl of the three plants under investigation decreased by water stress and this effect was dependent on the temperature and zinc concentration in the incubation medium.2. Generally, zinc treatment induced significant improvement in the germination characteristics of the experimental plants (xerophytes) under certain conditions (high) of water stress and temperature.3. addition of zinc improved the adjustment of radicles to water deficiency conditions through increasing the allocation of water soluble metabolites into the radicles and hence increasing the osmotic potentials of radicles.4.