The present study aims to investigate the effects of osmotic water potential simulated by reduced osmotic water potential, $\Psi_s$, temperature (T) and zinc (Zn) addition to the seed incubation medium and to evaluate the effects of their interactions on soluble proteins in germinating seeds of three plant species of different ecological affiliation. The experimented species were namely: Senna alexandrina, Senna italic (native to hot deserts) and Senna occidentalis (a wild mesophytic plant). It was observed tha t, the presence of high Zn concentration yielded a high content of soluble proteins under low osmotic water potential and high temperature. Also, addition of zinc improved the adjustment of radicles to water deficiency conditions through increasing the allocation of water soluble proteins into the radicles. The germinating seeds in S. occidentalis (wild mesophyte) was characterized by the presence of high molecular weight protein bands, whereas radicles of xerophytes contain low molecular weight protein ba nds. The statistical analysis indicated that the trifactorial interaction ($\Psi_s \times T \times Zn$) had the major effect on the soluble proteins in different organs of the three-plant species. Exceptionally, the effect of osmotic water potential was the dominant in storage tissue proteins of S. occidentalis.