ABSTRACT
The cell and molecular biology of the embryogenic development of somatic cell of angiosperms and gymnosperms, known as somatic embryogenesis, has been dealt with extensively in the literature (1-5). In contrast to the rigorously programmed development of the embryo from the zygote (zygotic embryogenesis), is somatic embryogenesis, virtually any somatic cell of the plant body can, under certain experimental conditions, behave like a zygote and faithfully replay a developmental program, producing embryolike structures while remaining innocent of sex. Thus, all plant cells except those that have undergone irreversible differentiation are totipotent and retain the developmental potential to proliferate into an adult plant. Compared to the limited number of embryos arising from gametic fusion, and the difficulty of extracting them from the confines of the ovule, the enormous number of somatic cells potentially capable of developing into embryolike structures by simple experimental manipulation provides an attractive alternative to seed propagation. Although zygotic embryos are identical in appearance and morphogenetic potential to somatic embryos, to emphasize the divergent pathways of their evolution, the latter are generally referred by the term embryoid (1).
