What is Leaf?
Based on the nature of the incision, there are two types of leaves – simple and compound. In simple leaves, the lamina is either entire or the incision does not touch the midrib.
However, in compound leaves, the incisions of the lamina are deep, thus touching the midrib, and breaking it into a number of leaflets. Furthermore, the compound leaves may be of two types – Pinnately compound leaf and palmately compound leaf.
When the number of leaflets is present on a common axis called the rachis, then the leaf is said to be pinnately compound (E.g. Neem leaves). However, in palmately compound leaves, the leaflets are attached to a common point, which is the tip of the petiole (E.g leaves of silk cotton).
A. Pinnately compound B. Palmately compound
Phyllotaxy: The pattern of arrangement of leaves on the stem or branch is defined as phyllotaxy. Three main types of phyllotaxy are observed namely, alternate, opposite, and whorled.
Alternate phyllotaxy: In this type, a single leaf arises from each node in an alternate pattern. E.g. China rose, sunflower plants
Opposite phyllotaxy: In this type, a pair of leaves arise at each node, thus lying opposite to each other. E.g. guava plants
Whorled phyllotaxy: In this type, two or more leaves arise at a node to form a whorl. E.g. Alstonia
A. Alternate B. Opposite C. Whorled
What is Modification of Leaves?
Leaves are often modified to tendrils in some plants so as to support the function of climbing to adjacent support. Otherwise, leaves are modified into spines for providing protection to the plant, as in the case of cactus plants. In onion and garlic plants, the fleshy leaves store food. In some plants, the leaves are short-lived and the petioles expand to perform photosynthesis (E.g. Australian acacia). In insectivorous plants, the leaves are modified into a pitcher for trapping insects.
What is Inflorescence?
The Inflorescence: The arrangement of flowers on the floral axis is defined as an inflorescence. Based on whether the apex is converted into a flower or continued growth of the apex, the inflorescence is divided into two types, namely racemose and cymose.
Racemose: In this type, the main axis continues to grow with the flowers arranged on lateral sides in an acropetal succession
Cymose: In this type, the main axis terminates in a flower and the flowers are arranged in basipetal order due to the limited growth of the plant.
