Micropilar and embryonic events during hydration of Melanoxylon brauna Schott seeds

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 braunais 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.

摘要：种子萌发是一个复杂的过程，涉及构成细胞壁的分子特性、可断裂聚合物间化学键的水解酶以及活性氧物质的作用。Melanoxylon brauna是一种具有高经济价值的林木物种。为评估萌发过程中胚轴（embryonic axis）发生的生理生化变化，本研究对胚轴的鲜重、长度，果胶甲酯酶（pectin methylesterase）、多聚半乳糖醛酸酶（polygalacturonase）、超氧化物歧化酶、过氧化氢酶、过氧化物酶的活性与过氧化氢含量进行了定量检测。此外，本研究还在干燥与未干燥条件下，对珠孔（micropyle）区域的碳水化合物组成及珠孔物理抗性进行了测定。浸种过程中，随着胚轴鲜重与长度的增加，多聚半乳糖醛酸酶与果胶甲酯酶的活性也呈现相同的变化趋势。浸种阶段内，过氧化氢含量以及珠孔区域的穿刺力均有所降低。研究表明，种子吸水量的90%由种皮与子叶所负责。萌发初始的16小时内，珠孔与胚轴的生理事件独立发生。珠孔的弱化过程包含弹性阶段与塑性阶段。果胶甲酯酶与多聚半乳糖醛酸酶参与胚轴的细胞扩张过程。