Question

Parallel venation occurs in dicot
(a) Corymbium
(b) Ageratum
(c) Carthamus
(d) Centipeda

Answer 1

Hint: Parallel venation is exhibited by mostly all monocots and some dicots. The dicot among the following in which parallel venation occurs belongs to the sunflower family. It is famous for its compound inflorescence or arrangement of flowers.

Complete answer:
Venation is the pattern of arrangement of veins and veinlets on the leaf lamina. Two types of venation can be observed in plants- parallel venation and reticulate venation. All monocots and some dicots like Corymbium exhibit parallel venation. In parallel venation, veinlets are inconspicuous with a midrib and lateral veins of more or less equal sizes.
- The vascular tissue branches off into the main vein and its lateral veinlets. Apart from being conductive in function, they also provide structural support to the leaf blade.
- Based on the orientation of lateral veins, parallel venation can be convergent and divergent. In convergent venation of Bamboo or grass, the principal vein converges towards the apex of a leaf unlike in a divergent venation of Fan palm, where they converge towards the margins.
- Reticulate venation is a characteristic property of all dicots except plants like Corymbium and Calophyllum. Here, the veinlets are prominent enough to form a network or reticulum. A single midrib branches into two or more principal or lateral veins which further branches off to a number of smaller veinlets.
So, the correct answer is ‘(a) Corymbium.’

Note:
- A typical leaf consists of three main parts namely a leaf base, petiole, and lamina. A leaf base attaches a leaf to the node of the stem or its branches.
- The petiole is a tiny, thin stalk connecting the lamina to its leaf base. Its flexibility helps a leaf to twist so that its lamina can be properly exposed to sunlight. The leaf blade or lamina is the main photosynthetic organ due to the presence of chloroplasts bearing chlorophyll.