Embryo and endosperm development in coriander (Coriandrum sativum)

Abstract

Coriander ( Coriandrum sativum L.) seeds are rich in lipids and are potentially important sources of oils for industrial use. The objective of this study was to determine the details of embryo and endosperm development and the sites of storage reserves using microscopy and histochemistry. In coriander, the zygote divides unequally, giving rise to a large basal cell and a smaller terminal cell. Subsequent divisions in the basal cell result in the formation of a suspensor, and divisions in the terminal cell give rise to cells of the embryo proper. A defined cell lineage is absent in the formation of the proembryo. Contrary to other flowering plants, the suspensor persists as the embryo matures and storage products are present within the cytoplasm of the suspensor cells. After fertilization, the primary endosperm nucleus divides rapidly, resulting in a large syncytium of nuclei and cytoplasm. The rapid nuclear divisions occur prior to the first division of the zygote. Cellularization of the endosperm occurs soon after. Within the developing seed, the endosperm can be separated into two main regions, i.e., the “embryo surround region” (ESR) of endosperm and the persistent endosperm. The endosperm cells in these two regions have different cell fates and storage products. In the ESR, the endosperm cells undergo distinct structural changes and are destined to degenerate. These endosperm cells produce a significant amount of polysaccharides and these materials appear to aid in cell separation prior to cell degeneration. At the boundary of the ESR, the endosperm cells are partially degenerated with a large accumulation of lipids. The bulk of the endosperm cells next to the seed coat persist and they are responsible for the production and accumulation of storage lipids and proteins.