| Popis: |
During embryogenesis and maturation of an embryo the tissues covering it produce phenolic compounds the localization of which changes during maturation of the embryo. In the ovary containing a globular embryo, phenolics are located in the epidermis of the integumentum externum and the innermost layer of the integumentum internum. In the ovule at the stage at which heart- and torpedo-shaped embryos are present, phenolic compounds are visible in the stellar cells, the innermost cells of the integumentum internum and the endosperm. In hard, green seeds, after the integumentum internum and layers over the stellar cells gradually disappear, the remaining tissue contains cell walls impregnated with phenolics. Mature, black seeds contain only one distinct layer of cells—stellar cells, which, like the other compressed cell walls, are impregnated with phenolics. In this way they constitute a barrier between the embryo and its environment. |
