Agriculture Reference
In-Depth Information
Fig. 2.5.
Diagrammatic longitudinal section through an onion or garlic stem
(baseplate) showing the main tissues, leaf bases, root origination and regions of cell
division (left side); and how the vessels of the stem, root and leaves interconnect
(right side) (based on Mann, 1952 and de Mason, 1979).
roots get pushed progressively further away from the shoot apex while whorls
of new roots continue to initiate and emerge near to the apex.
Branching, which can give rise to multiple growing points as seen in
tillering shoots and doubled or multiple-centred bulbs, is fundamentally no
different to axillary branching on a more typical elongated stem.
A new lateral growing point can develop in the leaf axil between the
original shoot apex and the youngest leaf. The lateral develops on the same side
of the parent growing point as the adjacent leaf blade. Lateral growing points
proceed to initiate and develop leaves in the same way as the parent apex. On
such side shoots the plane in which opposite leaves are initiated is at right
angles to this plane on the parent shoot. The leaves from such shoots are
initially enclosed by the sheath of the leaf in whose axil they originate. When
this decays they may appear as separate side shoots.
