What is the reason for the similar size of the vascular bundle in monocot leaves?

Correct — B. A monocot leaf is isobilateral, and its veins run parallel to one another from base to tip.

Parallel veins do not branch away into a net of ever-finer veinlets, so the vascular bundles they carry stay of similar size right across the blade, the ones in the main vein being the larger exception.

Reticulate venation in a dicot leaf branches repeatedly and therefore produces bundles of many sizes. Parallel venation is the reason monocot bundles match → option (b).

Why the others are wrong

• (a)
  Radial venation — Radial describes xylem and phloem sitting on alternate radii inside a root, not a pattern of leaf veins. It is an anatomy term borrowed from the wrong organ.
• (c)
  Cubical venation — There is no cubical venation. Leaf veins are described as reticulate or parallel, and cubical is not a term in that classification.
• (d)
  Rectangular venation — Rectangular venation is not a botanical category. Parallel veins are often joined by small cross-veins, giving a ladder-like look, but the pattern is still named parallel.

Venation is the arrangement of veins on a leaf blade, and a vein is a vascular bundle wrapped in supporting tissue.

Reticulate venation, where veins form a network, goes with dicots. Parallel venation, where veins run side by side without a net, goes with monocots.

Because the monocot pattern never branches into progressively finer veinlets, a cross-section of an isobilateral leaf shows vascular bundles of nearly uniform size, with the larger ones sitting in the midrib.

Key facts

• Monocot leaves show parallel venation, dicot leaves reticulate venation.
• In an isobilateral monocot leaf the vascular bundles are similar in size except in the main veins.
• Maize, wheat, grasses and banana are monocots with parallel-veined leaves.
• A leaf vein is a vascular bundle carrying xylem and phloem.

Common traps

• Treating radial as a venation type when it describes vascular tissue in roots.
• Forgetting that the midrib bundle of a monocot leaf is larger than the rest, so uniform means nearly uniform.

No directly related past PYQ was found.