Question

Select the correctly matching set.

• A. Monocot stem - Kidney shaped guard cells;
  Dicot stem - Dumb bell-shaped guard cells
• B. Monocot stem - Sclerenchymatous hypodermis;
  Dicot stem - Collenchymatous hypodermis
• C. Monocot stem - Medullary rays present;
  Dicot stem - Medullary rays absent
• D. Monocot stem - Vascular bundles of similar size;
  Dicot stem - Vascular bundles of different sizes

Answer 1

The correct option is B Monocot stem - Sclerenchymatous hypodermis;

Dicot stem - Collenchymatous hypodermis
Minute pores called stomata are present on the epidermis of leaves and stem. They are surrounded by guard cells that help regulate gaseous exchange and transpiration. Monocot stems have characteristic dumb bell-shaped guard cells while dicots have kidney-shaped guard cells.

The hypodermis in the monocot stem is multi-layered and is composed of sclerenchyma fibres. These fibres provide mechanical strength to the stem. The hypodermis in the case of dicot stem is collenchymatous in nature. In addition to providing mechanical support, the collenchyma cells can help in storage as well as the manufacture of food.

Medullary rays are the extensions of the pith region as rays into the pericycle as well as between the vascular bundles. The rays serve as radial conduction of materials like food and water. Medullary rays are absent in monocot stems.

The vascular bundles in dicots are angular and are of similar size. In monocots, the vascular bundles are scattered, oval and polymorphic. The larger vascular bundles are located towards the centre of the stem while smaller bundles are arranged towards the periphery.