Efficiency of selenium compounds in breaking dormancy of Townsville stylo seeds

Selenium compounds break dormancy of seeds of Townsville stylo (Stylosanthes humilis) through the induction of ethylene production. This was supported by the fact that antiethylenic substances inhibited germination of Se-treated dormant seeds. Under these conditions germination was restored by ethylene-producing compounds. Efficacy of the compounds was monitored through an Efficiency Index (I_ef ) which takes into account not only the maximal germination but also the optimal concentration responsible for eliciting the process. The most efficient compounds were SeCl₄, SeO₂ and Na₂SeO₃ and the least efficient were selenourea, H₂SeO₄ and selenomethionine. Although ethylene was required for dormancy breakage the compounds triggering the highest ethylene productions were not necessarily the same ones leading to the largest I_ef (s). Hence it was concluded that the index is an overall integrating parameter, encompassing uptake of the compound, arrival to target cells and also post-ethylene biosynthesis effects.