Practicing Success

Target Exam

CUET

Subject

Biology

Chapter

Anatomy of Flowering Plants

Question:

Which statement is incorrect about dicot stem?

Options:

Collenchymatous hypodermis, sclerenchymatous pericycle, parenchymatous pith

Ring arrangement of vascular bundles, parenchymatous medullary rays and endodermal starch sheath

Multiple layered cortex; semi-lunar pericycle; conjoint, open and endarch protoxylem

None of the above

Correct Answer:

None of the above

Explanation:

The correct answer is Option (4) -None of the above

The transverse section of a typical young dicotyledonous stem shows that the epidermis is the outermost protective layer of the stem . Covered with a thin layer of cuticle, it may bear trichomes and a few stomata. The cells arranged in multiple layers between epidermis and pericycle constitute the cortex.

It consists of three sub-zones. The outer hypodermis, consists of a few layers of collenchymatous cells just below the epidermis, which provide mechanical strength to the young stem. Cortical layers below hypodermis consist of rounded thin walled parenchymatous cells with conspicuous intercellular spaces.

The innermost layer of the cortex is called the endodermis. The cells of the endodermis are rich in starch grains and the layer is also referred to as the starch sheath. Pericycle is present on the inner side of the endodermis and above the phloem in the form of semi-lunar patches of sclerenchyma.

In between the vascular bundles there are a few layers of radially placed parenchymatous cells, which constitute medullary rays. A large number of vascular bundles are arranged in a ring ; the ‘ring’ arrangement of vascular bundles is a characteristic of dicot stem. Each vascular bundle is conjoint, open, and with endarch protoxylem. A large number of rounded, parenchymatous cells with large intercellular spaces which occupy the central portion of the stem constitute the pith.