Coleus apex detail LS

This longitudinal section of the apex shows several regions, which contain compact (darkly-stained) meristematic areas. The shoot apex proper, lies between two developing leaf primordia at the top, and the bumps and projections which occur down the flanks, represent zones where leaf primordia have been formed previously.

Two axillary meristems can be seen in this micrograph. These will produce lateral branches once the meristematic tissue is far enough away from the influence of the shoot apical meristem. Hormone gradients, particularly an auxin gradient produced by the apex, will suppress their growth.

Click here to see the apex

Click here to see the procambium