Question

Hard bast (bundle cap) occurs in
A. Sunflower stem
B. Wheat stem
C. Sunflower root
D. None of the above

Answer 1

A patch of sclerenchyma present on the outside of the vascular bundle that forms a bundle cap over each of them is hard bast. Hard bast fibres are tough and resistant in nature and they help in providing mechanical strength to the plant.

Complete answer:
-Hard bast bundle cap is present in the sunflower stem. Internal structure of the young stem shows the presence of three tissue systems- dermal or epidermal tissue system, fundamental or ground tissue system and vascular or fascicular tissue system. The transverse section of sunflower stem shows the following layers:
-Epidermis- It is the outermost layer, made up of large and compactly arranged thin walled parenchymatous cells. On the outer side, it has a layer of cuticle.
-Hypodermis- It is made up of a few layers of collenchymatous cells. These are angular cells that bear cellulose and pectin thickenings. Its main function is photosynthesis, providing mechanical strength to the plant and storage of food.
-Cortex- It is made up of parenchymatous cells and it lies between hypodermis and endodermis.
-Endodermis- It is the innermost layer that separates vascular tissue from the cortex.
-Vascular tissue- It is made up of a number of vascular bundles that are arranged in a ring. These are conjoint, collateral and open type. The vascular bundles have few layers of compactly arranged sclerenchyma cells or hard base layers.
-Primary medullary rays- It is the ground tissue present between vascular bundles.
-Pith- This is the ground tissue which is present in the centre.

So, the correct answer is “Option A”.

Note:
-The vascular bundles of monocot stems have a layer thick walled bundles sheath surrounding them.
-Roots have radial vascular bundles i.e. xylem and phloem are present on different radii.