Question

Write a note on phyllotaxy.

Answer 1

Hint: Ultimately, local degradation of the plant hormone auxin in some parts of the meristem regulates the sequence of leaves on a plant.

Complete Answer:
Opposite and alternate (also recognized as spiral) are the essential arrangements of leaves on a stem. Leaves can also be whorled from the same stage on a stem if many leaves emerge, or tend to emerge. For an adjacent leaf arrangement, at the same position (at the same node), on separate ends of the stem, two leaves emerge from the stem.
- The pattern of distribution of leaves on the branch or stem of a plant is phyllotaxy. Three forms are primarily present:
- Alternate: Where a single leaf emerges in an alternate manner from each node. For example: sunflower, etc.
- Opposite: At each node, pairs of leaves emerge and reside opposite each other in this form. E.g.: guava, calotropis, etc.,
- Whorled: At every node, over than two leaves emerge and are organized in the shape of a whorl. For example: Devil Tree, Nerium etc.

Note: Distichous phyllotaxy is a particular incident of either opposite or alternating leaf arrangement in which the leaves on a stem are distributed on opposite sides of the stem in two vertical columns, often termed "two-ranked leaf arrangement." Multiple bulbous plants, like Boophone, are examples.