Micropilar and embryonic events during hydration of Melanoxylon brauna Schott seeds

Eventos micropilar e embrionário na hidratação de sementes de Melanoxylon brauna Schott

Abstract:

Germination is a complex process that involves molecules properties that make up the cell walls, hydrolytic enzymes that break the bonds between the polymers and action of reactive oxygen substance. Melanoxylon brauna is a forest species of high economic value. In order to evaluate the physiological and biochemical changes that occur in the embryonic axis during germination, fresh matter, length, activities of the enzymes pectin methylesterase, polygalacturonase, superoxide dismutase, catalase, peroxidase and hydrogen peroxide levels were quantified in the embryonic axis. Furthermore, in the micropyle area the composition of carbohydrates and micropyle physical resistance were evaluated with and without drying. During soaking, if there are increases in fresh matter and length of the embryonic axis, there is the same trend of polygalacturonase and pectin methylesterase enzymes. The hydrogen peroxide content was reduced during the soaking, as well as the puncture force of the micropylar area. It is concluded that the seed coat and the cotyledons are responsible for 90% of the water soaked by the seeds. The events in the micropyle and embryonic axis occur independently in the first 16 hours. The weakening of the micropyle features an elastic step and a plastic one. Enzymes pectin methylesterase and polygalacturonase act in cellular expansion of the embryonic axis.

Index terms:
puncture force; hydrogen peroxide; cell wall; germination