Test: Plant Tissue - UPSC MCQ

The water conducting elements of gymnosperms and primitive angiosperms are tracheids. Tracheids are elongated, tube-like cells that have tapered ends and are interconnected through pits. They are responsible for transporting water and minerals throughout the plant. Tracheids are found in the xylem tissue of these plants and are one of the key adaptations for conducting water in these groups.

Most metabolism in plants is carried out in parenchyma tissue. Parenchyma cells are the most common and versatile type of plant cells. They are found throughout the plant body and are involved in various metabolic activities such as photosynthesis, storage of nutrients, and secretion.

Phloem is a vascular tissue responsible for the transportation of sugars and other organic compounds throughout the plant. It plays a role in the distribution of nutrients produced in the leaves to other parts of the plant.

Meristem refers to the undifferentiated cells in plants that are responsible for growth and development. They are found in the tips of roots and shoots and contribute to the formation of new tissues.

Collenchyma is a type of ground tissue in plants that provides mechanical support to growing parts. It is characterized by its thickened cell walls and often found in young stems and petioles.

So, the correct answer is C: parenchyma.

The process by which plant tissue becomes woody is called lignification. Lignification is the deposition of lignin, a complex polymer, in the cell walls of certain plant cells. Lignin provides strength and rigidity to the plant, allowing it to grow upright and support its own weight. During lignification, specialized cells called cambium produce lignin, which is then deposited in the cell walls of xylem vessels and fibers. This process results in the hardening and thickening of the plant tissue, making it woody. Suberisation refers to the formation of cork in plant tissues, pectification involves the formation of pectin in cell walls, and calcification refers to the accumulation of calcium carbonate in plant tissues.

In a collateral vascular bundle, the xylem and phloem are arranged in such a way that the phloem is positioned towards the outer side of the xylem. This means that when you look at a cross-section of the bundle, you will see the xylem located towards the center, and surrounding it on the outer side will be the phloem. This arrangement is characteristic of most dicotyledonous plants, where the vascular bundles are arranged in a ring or cylinder within the stem or root. The xylem is responsible for transporting water and minerals upwards from the roots, while the phloem transports sugars and other organic compounds both upwards and downwards within the plant.

The bark of a tree is composed of multiple layers of tissues that are located outside the vascular cambium. The vascular cambium is a layer of meristematic tissue that produces new xylem and phloem cells, contributing to the growth in girth of the tree. The bark includes several layers, starting from the outside and moving inwards, such as the cork, cork cambium (also known as the phellogen), phelloderm, and the secondary phloem. These layers together make up the bark of the tree. The cork is the outermost protective layer, formed by the cork cambium, while the secondary phloem is responsible for transporting sugars and other organic materials throughout the tree.

Velamen cells are specialized cells that are found in the roots of epiphytic plants. Epiphytes are plants that grow on the surface of other plants, such as trees, without taking nutrients from the soil. Velamen cells are located just outside the exodermis, which is the outermost layer of the root. These cells are part of the epidermis and have a spongy or velvety appearance, giving them their name.

Velamen cells have several functions that help epiphytic plants adapt to their environment. They provide protection against desiccation by absorbing and retaining moisture from the air and rainwater. They also assist in the absorption of nutrients from the atmosphere, including moisture, dust particles, and dissolved gases.

Therefore, the correct answer is D: Velamen cells are found just outside the exodermis in epiphytes.

Abnormal secondary growth, also known as anomalous secondary growth, is found in Dracaena plants. Dracaena is a genus of tropical and subtropical plants that exhibit unique growth patterns. Unlike most plants that undergo normal secondary growth by producing secondary vascular tissues in a cylindrical arrangement, Dracaena exhibits an anomalous pattern of secondary growth.

In Dracaena plants, the secondary growth occurs in a scattered or irregular manner, leading to the formation of patches or bands of secondary vascular tissues. This results in a distinctive appearance where the secondary xylem and phloem are not arranged in a concentric manner like in normal secondary growth. The abnormal secondary growth in Dracaena is a characteristic feature of this genus.

Triticum (wheat), Helianthus (sunflower), and Cucurbita (squash) do not exhibit abnormal secondary growth.

The correct answer is C: elongated cells with thickening at the corners.

Collenchyma cells are characterized by their elongated shape and thickening at the corners. These cells have primary cell walls composed of cellulose and pectin, similar to other plant cells. However, collenchyma cells have additional localized thickenings in the cell corners, which provide mechanical support to the plant.

The thickened corners in collenchyma cells can vary in shape and appearance. They may appear as discrete spots, continuous bands, or even form a complete ring around the cell. The thickened areas contain extra cellulose and may also contain hemicellulose and lignin, which contribute to the cell's rigidity and strength.

The thickened corners of collenchyma cells allow them to provide flexible support to growing plant organs, such as stems and petioles. They help the plant withstand bending and mechanical stress while still allowing for some degree of flexibility.

The correct answer is C: Sclerenchyma. Sclerenchyma tissue is characterized by having lignified cell walls. Lignin is a complex compound that provides rigidity and strength to the cell walls, making them rigid and impermeable to water. The lignified cell walls of sclerenchyma cells make them highly durable and able to provide structural support to the plant. Sclerenchyma cells are often found in areas of the plant that require strength and support, such as the stems, roots, and vascular tissues.

The correct answer is A: organ. Many different types of tissues organize and work together to form an organ. An organ is a distinct structure composed of two or more tissue types that work collectively to perform specific functions in the body. Examples of organs include the heart, liver, lungs, and brain. Each organ is specialized for a particular function and consists of different types of tissues that contribute to its overall structure and function. Organs are an essential component of higher-level organization in living organisms.

The correct answer is B: Sclerenchyma. Sclerenchyma tissue is composed of cells that are dead at maturity. These cells have thick, lignified cell walls that provide strength and support to the plant. The thickening of the cell walls with substances like lignin makes them rigid and durable. Due to their hardened cell walls, sclerenchyma cells are unable to undergo significant changes in size or shape. They are often found in regions of the plant that require mechanical support, such as the stems, roots, and vascular tissues.

The correct answer is C: Cuticle. The cuticle is a waxy, protective noncellular layer found on the outside of plant organs, such as leaves, stems, and fruits. It is primarily composed of a waterproof substance called cutin, which helps reduce water loss through evaporation and provides protection against environmental stresses such as drought, excessive sunlight, and pathogens. The cuticle also helps prevent mechanical damage and acts as a barrier against the entry of harmful substances.

The correct answer is B: Alternate radii. In radial vascular bundles, the xylem and phloem occur in alternating radii within the stem or root. The xylem and phloem tissues are arranged in a circular pattern, with the xylem located towards the center and the phloem located towards the periphery. This arrangement allows for efficient transport of water, minerals, and nutrients throughout the plant. The alternating arrangement of xylem and phloem in radial vascular bundles helps in maintaining a balance and facilitates the exchange of substances between the two tissues.

The tissue that provides maximum mechanical strength to the plant is the xylem. Xylem is a complex tissue responsible for transporting water and minerals from the roots to the rest of the plant. It consists of specialized cells called tracheids and vessel elements that have thick cell walls containing lignin, a rigid substance that provides strength and support. The presence of lignin in the cell walls of xylem cells makes them strong and capable of withstanding tension and pressure, allowing the plant to maintain its structural integrity.

Intercalary meristem is a type of meristematic tissue found in certain regions of plants, typically between mature tissues. It is responsible for primary growth, which refers to the increase in length of plant structures such as stems and roots.

Unlike apical meristems, which are located at the tips of shoots and roots and are responsible for primary growth as well, intercalary meristems occur in specific regions along the length of the plant. These regions include the base of nodes in grasses, where intercalary meristems contribute to the elongation of the stem, and the base of leaf blades, where they promote leaf growth.

Secondary growth, on the other hand, involves an increase in the girth or thickness of plant structures such as stems and roots. This type of growth is not influenced by intercalary meristems.

Therefore, intercalary meristem primarily contributes to primary growth (option C).

The external protective tissue of plants consists of two main components: the epidermis and the cork.

The epidermis is the outermost layer of cells that covers the entire surface of the plant, including the leaves, stems, and roots. It serves as a protective barrier against physical damage, water loss, and pathogens. The epidermis may also contain specialized structures such as stomata, which are small openings that regulate gas exchange and transpiration.

The cork, also known as the periderm, is a secondary protective tissue that forms in the outer bark of woody plants. It is composed of dead cells that are waterproof and provide additional protection against injury and water loss. Cork cells are produced by the cork cambium, a meristematic tissue that replaces the epidermis in older stems and roots.

Therefore, the external protective tissue of plants consists of the epidermis and cork (option C).

Vascular bundles in a dicot stem are characterized as open, collateral, and endarch. Let's break down each term:

• Open: Dicot stems have vascular bundles that are open, meaning there is a distinct cambium layer present between the xylem and phloem. This cambium layer is responsible for the secondary growth and thickening of the stem.
• Collateral: The vascular bundles in dicot stems are collateral, which means that the xylem and phloem are arranged side by side within each bundle. The xylem is located towards the inner side, while the phloem is positioned towards the outer side of the bundle.
• Endarch: The xylem in dicot stems is endarch, meaning that the development of the xylem progresses from the center towards the periphery of the stem. The youngest xylem cells are found towards the center of the stem, while the older, more mature cells are positioned towards the outer part.

Therefore, the correct answer is D: Vascular bundles in a dicot stem are open, collateral, and endarch.

The correct answer is C: Intercalary meristem.

Intercalary meristem is the meristem present at the base of leaves or internodes on twigs. It is a specialized type of meristem found in certain plants, particularly monocots. Intercalary meristem is responsible for the growth and elongation of internodes in the stem or the base of leaves.

Unlike apical meristem, which is located at the tips of shoots and roots and contributes to primary growth, and cambium, which is a lateral meristem involved in secondary growth, intercalary meristem is specific to certain regions of the plant. It allows for elongation and growth of the stem or leaf base, contributing to overall plant development.

Epidermis, on the other hand, is the outermost layer of cells in plants that covers the surfaces of leaves, stems, and roots. It functions as a protective barrier and helps regulate gas exchange and water loss. Epidermis is not directly associated with meristematic activity or growth at the base of leaves or internodes.

Xylem is not a simple tissue; it is a complex tissue. Complex tissues are composed of two or more types of cells with different functions and structures. Xylem is a complex tissue that is responsible for transporting water, minerals, and nutrients throughout the plant. It is composed of various types of cells, including tracheids, vessel elements, fibers, and parenchyma cells.

On the other hand, parenchyma, collenchyma, and sclerenchyma are examples of simple tissues. Simple tissues consist of a single type of cell and perform a specific function in the plant. Parenchyma cells are involved in various functions such as storage, photosynthesis, and secretion. Collenchyma cells provide support and flexibility to growing plant parts. Sclerenchyma cells provide strength and support to mature plant tissues.

Therefore, the correct answer is A: Xylem is not a simple tissue.

The study of tissues is called histology. Histology involves the examination and analysis of tissues at a microscopic level to understand their structure, organization, and function. It encompasses the study of various types of tissues found in plants, animals, and humans.

Histologists use specialized techniques to prepare tissue samples for microscopic examination. This often includes fixation, sectioning, staining, and mounting of tissue specimens on slides. Microscopes are then used to observe and analyze the cellular and architectural characteristics of different tissues.

Cytology, on the other hand, is the study of cells, their structure, and functions. Embryology focuses on the development and formation of embryos and their organs. Pathology is the study of diseases, their causes, mechanisms, and effects on tissues and organs.