Question

Closed vascular bundles lack
A. Ground tissue
B. Conjunctive tissue
C. Cambium
D. Pith

Answer 1

Hint: Many dicotyledonous plants exhibit an expansion in girth. This rise is considered as secondary growth.Monocots do not form secondary tissues, and are referred to as closed .

Complete answer:
The plant tissues are divided into two main types- meristematic and permanent tissues based on whether the cells being formed are capable of dividing or not. The meristematic tissues are those that are the site of active division. Permanent tissues in plants are those that are no longer undergoing division.

There are three types of tissue systems in plants depending on their structure and location. They are the epidermal tissue system, the ground tissue system, and the vascular tissue system. Ground tissues include all tissues excluding the epidermis and the vascular bundles. It consists of simple tissues such as parenchyma, collenchyma and sclerenchyma.

Xylem and phloem are a type of complex permanent tissue. They form vascular bundles or conduct tissues in plants. In the conjoint form of vascular bundles, xylem and phloem are located in the same radius of vascular bundles. These vascular bundles are generally seen in the leaves and stems. The phloem in the conjoint vascular bundles is present just outside of the xylem.

Dicotyledons have cambium between phloem and xylem. These vascular bundles are capable of forming secondary xylem and phloem tissues and are also referred to as open vascular bundles. In monocotyledons, cambium is absent in the vascular bundles. As a result, they do not form secondary tissues and are referred to as closed vascular bundles.

Thus, the correct answer is C, i.e., Cambium.

Note: Secondary growth in plants occurs due to two lateral meristems called vascular cambium and cork cambium. Secondary growth occurs in most dicotyledonous roots and stems and expands the girth of the tissues by the action of the vascular cambium and the cork cambium.