Development of the embryo

Embryo growth completed


26 days after flowering. The embryo in longitudinal section has a well developed root radicle and primordial leaves at the shoot apex. The vascular tissues of the scutellum link to the mesocotyl of the embryonic axis. The embryo stores reserves in the form of lipid droplets and protein bodies but starch is not stored.
The above section in polarized light reveals that the bulk of the endosperm is packed with starch, but not so the embryo. The 'crushed cell layer' however has developed slightly differently where the starch reserves have been made available to the embryo.
The shoot pole of the embryo at high magnification. Primordial leaves enclose the shoot apex. A tiller bud can be seen in the axil of the first leaf.
The root pole of the embryo at high magnification. The cap, quiescent centre, cortex, stele and epidermis of the primary root are already differentiated. Additionally there are two pairs of secondary rootlets produced laterally but these cannot be seen in this LS, which is median through the ventral groove.
20 days after flowering and the embryo is developing very rapidly. The shoot pole now has a coleoptile enclosing primordial leaves and the root pole has a differentiated root cap. Inside the root we can see the cell files of the stele and the cortex. The small flap of tissue in the middle of the dorsal side is the epiblast, which has little morphological significance (allegedly).
Montage of the shoot and root poles of the embryo at 26 days after flowering. A complete miniature plant is already present in the immature seed.