F.J.A. Pinheiro

Bio: F.J.A. Pinheiro is an academic researcher. The author has contributed to research in topics: Germination & Dormancy. The author has an hindex of 1, co-authored 1 publications receiving 4 citations.

Efficiency of selenium compounds in breaking dormancy of Townsville stylo seeds

Abstract: 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 (Ief) 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 Ief(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.

Dormancy breakage of Stylosanthes humilis seeds by aluminium

Abstract: Physiological dormancy of scarified seeds of Townsville stylo (Stylosanthes humilis HBK) was released by acidic aluminium (Al3+) solution. Antiethylenic substances inhibited germination of low-pH-stimulated dormant seeds, with a correspondingly low ethylene production and low activity of 1-aminocyclopropane-1-carboxylate (ACC) oxidase in seeds. On the other hand, antiethylenic substances did not decrease the germination of Al3+-stimulated seeds, but ACC oxidase activity and ethylene production by the seeds was decreased to a large extent. These data provide evidence that dormancy breakage by Al3+ differs from that caused by low pH and is not associated with ethylene production. Similarly to Al3+ action, methyl viologen (MV), a reactive oxygen species-generating compound, broke dormancy of Townsville stylo seeds. Sodium selenate and N-acetyl cysteine, antioxidant compounds, largely decreased germination of MV- and Al3+-stimulated dormant seeds. Altogether these data point to oxidative radicals constituting key molecules in the chain of events triggered by Al3+ leading to dormancy breakage.

Action of ferric and aluminium ions on the dormancy breakage of Stylosanthes humilis seeds

Abstract: Dormancy of scarified seeds of Stylosanthes humilis was broken by acidic Al3+ and Fe3+ solutions. Fe+3-stimulated seeds exhibited a high activity of 1-aminocyclopropane-1-carboxylate (ACC) oxidase and produced great amounts of ethylene, which showed correlated with the germination process. In addition, specific inhibitors of ethylene biosynthesis and action largely depressed the Fe3+-stimulated germination, leading to the conclusion that the ion broke dormancy by triggering ethylene production by the seeds. By contrast, inhibitors of ethylene biosynthesis and action did not impair germination of Al3+-stimulated dormant seeds. Moreover, ethylene production and activity of ACC oxidase of Al3+-treated seeds was substantially decreased by inhibitors of ethylene biosynthesis, but germination kept large. Together these data suggest that ethylene biosynthesis was not required in the chain of events triggered by Al3+ leading to dormancy breakage. Methyl viologen (MV), a reactive oxygen species-generating compound, broke dormancy of seeds to the same extent as Al3+ did. Germination of both Al3+- and MV-stimulated dormant seeds was inhibited by sodium selenate, an antioxidant compound; selenate, however had no effect on germination of Fe3+-stimulated seeds. Together these data indicate that the mechanisms underlying the germination of Al3+- and Fe3+-treated seeds are not the same.