Morphology of Flowering Plants

A pinnately compound leaf has many leaflets on a common axis called the rachis. The rachis represents the midrib of the leaf, as in neem.

A palmately compound leaf has the leaflets attached at a common point, i.e. at the tip of the petiole, as in silk cotton.

Phyllotaxy is the pattern of arrangement of leaves on the stem or branch.

The main types are:

1. Alternate — a single leaf arises at each node in an alternate manner. Examples: china rose, mustard, sunflower.
2. Opposite — a pair of leaves arise at each node and lie opposite to each other. Examples: Calotropis, guava.
3. Whorled — more than two leaves arise at a node and form a whorl. Example: Alstonia.

Aestivation is the mode of arrangement of sepals or petals in the floral bud with respect to the other members of the same whorl.

Placentation is the arrangement of ovules within the ovary.

An actinomorphic flower shows radial symmetry and can be divided into two equal radial halves in any radial plane passing through the centre.

A zygomorphic flower shows bilateral symmetry and can be divided into two similar halves only in one particular vertical plane.

In a superior ovary, the gynoecium occupies the highest position on the thalamus and the other floral parts are situated below it. Such a flower is called hypogynous.

A perigynous flower has the gynoecium in the centre and the other parts of the flower on the rim of the thalamus almost at the same level. The ovary is said to be half inferior.

An epipetalous stamen is a stamen attached to the petals.