This collection of micrographs follows the development of the embryo from fertilisation until the grain is harvest ripe. For convenience it is divided into three sections.
From Fertilisation to Day 7
After fertilisation the newly formed zygote does not rest but cell divisions are slow. One transverse division produces a basal cell, which does not divide again, and an apical cell which divides twice to form a five celled globular shaped embryo. Cell division continues but differentiation is slow so that, by seven days after fertilisation, there is a simple dermatogen surrounding a central core of cells.
From Day 11 to Day 16
The embryo increases in size and continues to divide and by eleven days after fertilisation a cleft is seen on the dorsal side. This heralds the rapid differentiation of the two components of the embryo; the embryonic axis (comprising the mesocotyl and the shoot and root poles) and the scutellum. The scutellum is the specialised organ that transfers nutrients from the endosperm reserves to the embryo.
From Day 20 to Harvest Ripe
The structure of the embryo is completed during the grain filling period but it will not finish receiving storage reserves of lipid droplets and protein bodies until later.
Within the space of forty days the single cell of the fertilised ovum has become a perfectly formed miniature plant with a fully differentiated embryonic shoot and embryonic root.