The influence of seed structures on dormancy in seeds of <i>Urochloa</i> hybrid cultivar ‘Mulato Ⅱ’

Abstract

This study determined the effects of seed structures on seed dormancy and tested methods to break dormancy in seeds of Urochloa hybrid cultivar ‘Mulato II’. Seeds stored for 10 months in indoor ambient conditions were studied to determine effects of seed structures on seed germination and their water permeability. Results showed that seed structures presented a barrier to water permeability. Removal of lemmas, puncturing the seed coat, seed structure removal and sulfuric acid immersion all reduced seed dormancy. Water and alcohol extracts from different parts of seeds inhibited seed germination of Brassica pekinensis seeds. There were 3 mechanisms responsible for seed dormancy; first, the mechanical barrier of seed structures, which excluded water and reduced gas exchange as well as restricting growth of the embryo; second, an endogenous germination inhibitor mainly found in lemmas; and third, water permeability of the seed coat (including pericarp and testa). The mechanical removal of lemmas and immersion in concentrated sulfuric acid reduced seed dormancy, although mechanical removal of the lemma alone was effective, convenient and safer.

Studies on the Germination and Emergence of Castor Seedlings

“…The hydration of Uruchloa sp. seeds occurred faster and reached a higher level when the seed was punctured [26]. Impermeability to water was observed in seeds of Tilia miqueliana as a mechanism of physical seed dormancy [30].…”

“…In the opposite direction, the seed coat imposes a mechanical force to restrict embryo growth and block the radicle protrusion. As the embryo and endosperm increase the turgor, specific enzymes are produced in order to digest and weaken some specific seed coat cells to make it easier to crack [23][24][25][26][27][28][29][30].…”

“…This article reports a series of studies evaluating factors that were previously observed to influence the seed germination of castor and other plant species. The objective was to test the following hypotheses: (1) that castor seed germination is delayed because the castor seed coat is impermeable to water [17][18][19], (2) that the time for germination is influenced by temperature [20][21][22], (3) that the mechanical resistance of the seed coat is a mechanism to delay germination [23][24][25][26][27][28][29][30], (4) that the germination ability is influenced by the seed weight, volume, density, and seed coat thickness [7,15,16], (5) that castor seed germination is influenced by the hormone gibberellin [4,29], (6) that selection for fast germination changes the morphological characteristics of the seed in its descendants [7,31,32], and (7) that the time for germination can be reduced with a pre-germination treatment [3,17].…”