Cell Determination During Embryogenesis in Citrus Jambhiri. Ii. Epidermal Differentiation as a One‐time Event

Shallow peridermal tissue slices taken from leaves, stems, and roots of various ages and positions resulted in wound periderm formation at the cut surface. The outcome was similar in embryos treated and grown in a nurse ovule culture system. Torpedo and older embryos developed wound periderm, while globular and heart‐shaped embryos formed a disorganized, extensible callus. Epidermis did not regenerate at any time. These responses are consistent with the conclusion that epidermis is normally initiated only one time in the life of the shoot system. They also support our proposal that internal derivatives of the zygote diverge from epidermal differentiation and cannot retreat back to an epidermal pathway.