Question

Read the following statements. (1) Multicellutar epidermal hair (ii) Collenchymatous hypodermis (ii) Pith present (iv) Vascular bundles present in a ring ie. eustele Above given features describe which of the following plant perts? (a) Monocot stem (b) Monocot root ic) Dicot stem (d) Dicot root

Short answer

The features given describe a (c) Dicot stem.

Step-by-step solution

Examine Given Features

Review the characteristics provided in the question to understand which plant structure they represent.

Match Features to Plant Parts

Relate each feature to the typical anatomical characteristics of monocot and dicot stems and roots.

Identify the Plant Part

(1) Multicellular epidermal hair is a feature of dicots. (ii) Collenchymatous hypodermis is also typical of dicot stems, providing support. (iii) Pith is present in dicot stems, generally absent in monocot stems. (iv) Vascular bundles arranged in a ring, or eustele, is characteristic of a dicot stem. Therefore, the features describe a dicot stem.

Key concepts

Multicellular Epidermal Hair

Plants have diverse strategies to survive, and one such adaptation is the presence of multicellular epidermal hairs, commonly found on the surface of dicot stems.

These tiny, hair-like structures are made up of multiple cells, which distinguish them from the unicellular hairs that might be found in other plant types. They serve various functions, such as protecting the plant from herbivores, reducing water loss by trapping a layer of moisture around the plant surface, and shielding the stem from intense sunlight. Also known as trichomes, these epidermal hairs can be glandular or non-glandular, and their presence is a key indicator of a dicotyledonous plant when assessing stem anatomy.

Moreover, these multicellular hairs can sometimes secrete substances that deter pests or serve as a physical barrier, enhancing the plant's ability to thrive in its environment.

Collenchymatous Hypodermis

The hypodermis layer sits just below the epidermis and in dicot stems, it is often composed of collenchyma cells, resulting in a collenchymatous hypodermis.

This layer provides extra support to the stem while still allowing for flexibility, which is vital as the plant sways in the wind. Collenchyma cells are known for their thickened cell walls, which contain cellulose and pectin, and their ability to extend and grow as the plant grows. They also help in resisting bending or breaking by offering mechanical strength and support.

Functionally, this layer acts like a reinforced rubber hose, cushioning and protecting the delicate inner tissues of the plant stem while maintaining the stem's structural integrity. The collenchymatous nature of the hypodermis is a hallmark of the dicot stem, contributing to its ability to stand upright and sustain the pressures of the environment.

Vascular Bundles Arrangement

The vascular system in plants is akin to the circulatory system in animals, comprising of xylem and phloem that distribute water, nutrients, and sugars throughout the plant. In the case of a dicot stem, the vascular bundles are arranged in a ring—a configuration known as eustele.

The xylem typically occupies the center of each bundle, transporting water and minerals from the roots to the aerial parts of the plant. Surrounding the xylem, the phloem moves sugars and other metabolic products downward from the leaves.

This circular arrangement not only enables efficient transport but also allows for the potential secondary growth of the stem through the activity of the vascular cambium. It's a defining feature of dicot stems and helps in differentiating them from monocots, where the vascular bundles are scattered throughout the stem.

Pith in Plant Stems

The pith is an integral part of the plant's stem, located centrally within it. In dicot stems, the pith is quite prominent and is composed of soft, spongy parenchyma cells that store nutrients and help in the transport of water within the plant.

The presence of a pith is another distinguishing aspect of dicots compared to monocots, which typically have a hollow stem or, if a pith is present, it tends to be quite small. The pith occupies the central region of the stem in dicots and is surrounded by the ring of vascular bundles, and its cells can also contribute to the healing of the stem if it's injured.

It's important to note that the pith's function is not simply as a filler; it plays a role in both storage and structural support of the plant. Understanding the role of the pith is crucial when studying the anatomy of a dicot stem and for identifying the type of plant from a cross-sectional perspective.