Question

A flow chart to explain the processes involved in the initiation of flower primordia.

Answer 1

Plants are made up of the shoot axis, the root axis and the organs produced by each including leaves, petals, some tendrils, some thorns and lateral roots. These organs are produced throughout the lifespan of the plant, their production involves changes in cell fate, delineating boundaries, patterning the new organ and controlling its outgrowth. Shoot organs are formed in a regular pattern on the flanks of the shoot apical meristem. They lose the indeterminacy of meristem cells. Signals from the meristem pattern the organ, establishing an upper (adaxial) and a lower (abaxial) side. Organs of the root are produced from nonmeristematic cells the peri‐cycle cells which surround the vasculature. If these cells receive the correct signal they start to divide and produce a new indeterminate meristem. This meristem activates as it breaks through the primary root tissues.


Key Concepts:

Plant organs form throughout the lifespan of the plant.

Shoot organs include leaves, floral organs and some tendrils or thorns.

Shoot organs form on the flanks of the shoot apical meristem.

Root organs include lateral roots and nodules.

Root organs form by the dedifferentiation of pericycle cells and activation of new meristems.

Auxin plays a key role in the origin of new organs.

Patterning of organs occurs early in their development.

Keywords: meristem; lateral root primordia; leaf primordia; phyllotaxy; auxin; cell division