Question

One of the following is wrong for comparison between dicot and monocot stem. In dicot stem

• A. Vascular bundles are arranged in ring and in monocots they are scattered
• B. Vascular bundles are oval and in monocots wedge shaped
• C. True pith is present and absent in monocot stem
• D. There is no protoxylem lacuna

Answer 1

Answer: (B)

Vascular bundles are oval and in monocots wedge shaped

Presence of scattered, oval vascular bundles is characteristic feature of a monocot stem. Dicot stem has wedged shaped vascular bundles arranged in ring.

Dicot stem has pith with thin walled parenchymatous cells but monocot stem lack it.

Both monocot and dicot stem has endarch xylem in which xylem formed first is present near the centre and is termed as protoxylem, while metaxylem is present towards the periphery.

Xylem in monocot is arranged as 'Y'shape with two metaxylem vessels are situated at the upper two arms and one / two protoxylem vessels at the bottom.

Disintegration of the lowest protoxylem creates a cavity, the protoxylem lacuna, which is absent in dicots.