Dicot and Monocot Stems Practice Questions

Correct answer: Collenchyma

The hypodermis in dicot stems consists of a few layers of collenchymatous cells just below the epidermis. These cells provide mechanical strength to the young stem while it is still growing.

Correct answer: Scattered in the ground tissue

Monocot stems feature numerous vascular bundles scattered throughout the ground tissue. Unlike dicots, they do not have a ring arrangement and typically lack a distinct pith and cortex.

Correct answer: Endodermis

The innermost layer of the cortex in a dicot stem is the endodermis. It is referred to as the starch sheath because its cells are particularly rich in starch grains.

Correct answer: Sclerenchymatous bundle sheath

Each scattered vascular bundle in a monocot stem is enclosed by a sclerenchymatous bundle sheath. This sheath provides structural support to the vascular tissues.

Correct answer: Cambium

Vascular bundles are considered 'open' when a layer of cambium is present between the xylem and phloem. This cambium allows the plant to undergo secondary growth in thickness.

Correct answer: Monocot stem

A unique feature of monocot vascular bundles is the presence of water-containing cavities. These are formed by the dissolution of some protoxylem vessels during development.

Correct answer: Sclerenchyma

The pericycle in a dicot stem is found as semilunar patches of sclerenchyma. These patches are situated specifically above the phloem of each vascular bundle.

Correct answer: Phloem parenchyma

Phloem parenchyma is absent in the phloem of monocotyledons. This is a key anatomical distinction used to differentiate monocot stems from dicot stems under a microscope.

Correct answer: Pith region

The pith is the central-most region of the dicot stem. It consists of parenchymatous cells that function primarily in storage.

Correct answer: Parenchyma

Medullary rays are radially arranged parenchymatous cells located between the vascular bundles. They serve to connect the pith with the pericycle and cortex for radial conduction.

Correct answer: Sclerenchyma

While dicot stems have a collenchymatous hypodermis, monocot stems possess a sclerenchymatous hypodermis. This provides the necessary rigidity to the stem.

Correct answer: Xylem and phloem are on the same radius

Conjoint vascular bundles are those in which the xylem and phloem are joined together on the same radius. This is the standard arrangement in stems and leaves.

Correct answer: Smaller

In a cross-section of a monocot stem, the vascular bundles located near the periphery are generally smaller and more numerous than those located toward the center.

Correct answer: All stems

In stems (both monocot and dicot), the protoxylem is directed toward the center (pith) and the metaxylem toward the periphery. This arrangement is called endarch.

Correct answer: Interfascicular parenchyma

The primary medullary rays are formed by the parenchymatous cells situated between the vascular bundles. They link the central pith with the outer cortical layers.

Correct answer: Lack cambium

Monocot vascular bundles are 'closed' because they do not possess cambium. Consequently, they do not undergo normal secondary growth or increase in girth like woody dicots.

Correct answer: Trichomes

Trichomes are multicellular epidermal hairs found on the stem. They help in reducing water loss by transpiration and may also have a defensive function.

Correct answer: Cortical layers

The cortex of a dicot stem consists of three sub-zones: the outer hypodermis, the middle cortical layers (parenchymatous), and the inner endodermis.

Correct answer: Mechanical support

Collenchyma is a living mechanical tissue. Its presence in the hypodermis provides flexibility and mechanical strength to the growing regions of the dicot stem.

Correct answer: Well-developed pith is present

In monocot stems, the ground tissue is a continuous mass of parenchyma that is not clearly divided into cortex, endodermis, pericycle, or pith. Therefore, a well-developed central pith is absent.