Root apical organization in gymnosperms : Root apex of Ephedra foliata, with a suggestion on the possible evolutionary trend of root apical structures in gymnosperms.

The roots of Ephedra foliata have a long cap. The root apical meristem can be distinguished into (1) a discrete layer of stelar initials, (2) the columella and its initials, and (3) a common initiating region for the cortex and the peripheral region of the cap. The study of the cell lineages brings out that the first zone and its derivatives show a "Körper" complex of cells, the second and its derivatives divide in a transverse plane, and the third zone exhibits the "Kappe" complex.This organization resembles the "gymnospermous" type mentioned in the older literature in the discreteness of the "plerome".A possible line of evolution of the root apical structures of gymnosperms is suggested.