Free Growth and Development MCQs with Answers

121. Cut or excised leaves remain green for long if induced to root or dipped in :

• A. Gibberellins
• B. Cytokinins
• C. Auxins
• D. Ethylene

Explanation: b) : Cytokinin are plant growth hormones which are basic in nature. Cytokinins induce formation of new leaves chloroplasts in leaves, which inturn keeps the leaves green for a longer duration of time. Cytokinins applied to marketed vegetables can keep them fresh for several days. Shelf life of cut shoots and flowers is prolonged by employing the hormones.

122. Gibberellins promote:

• A. Seed Germination
• B. Seed Dormancy
• C. Leaf Fall
• D. Root Elongation.

Explanation: (a) : Gibberellins promote seed germination. Gibberellins are weakly acidic growth hormones having ring structure and which cause cell elongation of intact plants in general and increased internodal length of genetically dwarfed plants. Giberellins are synthesized in the apical shoot buds, root tips and developing seeds. During seed germination, especially of cereals gibberrellin stimulates the production of some messenger RNAs and then hydrolytic enzymes like amylases, lipases, proteases. The enzymes solubilize the reserve food of the seed

123. Phytochrome is involved in:

• A. Phototropism
• B. Photorespiration
• C. Photoperiodism
• D. Geotropism

Explanation: c) : Phytochrome is a photoreceptor molecule which mediates several developmental and morphogenetic responses of plants to light. This is called photoperiodism. Borthwick, Hendicks and Parker in 1952, discovered phytochrome, which is a pigment that received light and existed in two inter convertible forms: active form and inactive form.

124. Movement of leaves of sensitive plant, Mimosa pudica are due to

• A. Thermonasty
• B. Seismonasty
• C. Hydrotropism
• D. Chemonasty

Explanation: a) : Nastic movements occur in response to a stimulus. It is independent of its direction. They are shown by bifacial organs (leaves, sepals, petals) and are in response to diffused external stimulus. Seismonastic movements are due to shock or touch stimulus. Such movements are shown by Mimosa pudica. The leaf ofMimosa is compound having four pinna and each pinna is having many pinnules. If a terminal pinnule is touched, the whole leaf droops down. This is due to fact that at the bases of pinnules, pinna and whole leaf, swollen structure called pulvinus is present and drooping is due to loss of turgidity of lower portion of pulvinus.

125. The study of a process of progressive changes through which a fertilized egg passes before it assumes an adult form is :

• A. Histology
• B. Embryology
• C. Entomology
• D. Ecology
• E. Ecdysis

Explanation: The study of a process of progressive changes through which a fertilized egg passes before it assumes an adult form is embryology. Embryology is the branch of biology that focuses on the study of the development and formation of embryos and fetuses, especially during the early stages of development. It is a subfield of developmental biology and encompasses a wide range of research and study areas related to how organisms grow and develop from a single cell into a complex multicellular organism. Many studies in embryology use model organisms, such as fruit flies (Drosophila), frogs (Xenopus), and mice (Mus musculus), to understand developmental processes and genetics.

126. Process in which plants develop, results in the formation of a seed which become a new plant is:

• A. Plasmolysis
• B. Deplasmolysis
• C. Fertlization
• D. Germination
• E. Cytoplasmic Localization

Explanation: Germination is the process by which a seed develops into a young plant or seedling. It is a critical stage in the life cycle of many plants, as it marks the transition from a dormant seed to an actively growing plant.Germination begins when a seed, which is typically in a state of dormancy, becomes active. Various factors, including moisture, temperature, and sometimes light, can trigger this process.Germination is a remarkable process that enables seeds to give rise to new plants, ensuring the survival and reproduction of many plant species. The successful germination of seeds is influenced by a complex interplay of environmental factors and genetic traits specific to each plant species.

127. The increase in thickness of stems and roots due to activity of lateral meristems is called:

• A. Primary Growth
• B. Secondary Growth
• C. Tertiary Growth
• D. Both A and B
• E. All are incorrect

Explanation: The increase in thickness of stems and roots due to activity of lateral meristems is called secondary growth secondary growth is one of the two main types of growth that occurs in plants, with the other being primary growth. Secondary growth is responsible for the increase in the width or girth of plant stems and roots. It occurs in certain plants, primarily woody plants, and is facilitated by the activities of lateral meristems. Secondary growth is driven by the activity of lateral meristems, which are regions of undifferentiated cells located in the cambium and cork cambium. These meristems produce new cells in a horizontal direction, allowing the plant to grow wider or thicker.The vascular cambium is the primary lateral meristem responsible for secondary growth in plants. It is a layer of actively dividing cells located between the xylem and phloem tissues in the stem. The cork cambium is responsible for the production of the outermost protective layer of the stem or root, called cork.In plants with secondary growth, the vascular bundles (xylem and phloem) are arranged in a circular pattern. This differs from herbaceous plants with primary growth, where the vascular bundles are scattered throughout the stem.Understanding secondary growth is essential for the study of woody plants and is of practical importance in forestry, agriculture, and horticulture. It is also responsible for the production of wood, which is a valuable resource for construction and various industrial applications.

128. Secondary growth is the increase in diameter of stems and roots due to activity of secondary meristem, called:

• A. Xylem
• B. Phloem
• C. Cambium
• D. Cortex
• E. Epidermis

Explanation: Secondary growth is the increase in diameter of stems and roots due to activity of secondary meristem, called cambium.Cambium is a layer of meristematic tissue found in the stems and roots of vascular plants. It's responsible for secondary growth or lateral growth in plants, which results in the thickening of the plant body. Cambium cells are undifferentiated and actively dividing, which allows for the continued production of new cells. These new cells can mature into different types of tissues, contributing to both the plant's girth and the development of its protective outer layer.The growth produced by cambium is crucial for plants, particularly for woody perennials, as it enables them to become larger and stronger, providing support and allowing for the transport of water, nutrients, and organic compounds over long distances. This secondary growth allows trees to become taller and wider with each passing year.

129. The phase restricted to the tips of roots and shoots, where the cells constantly divided & increase, in number is:

• A. Formative Phase
• B. Elongation Phase
• C. Maturation Phase
• D. Differentiation Phase
• E. Permanent Phase

Explanation: The phase restricted to the tips of roots and shoots, where the cells constantly divided & increase, in number is formative phase. The "formative phase" generally refers to a period or stage in a process where important formative or shaping activities occur. The term "formative" itself relates to the shaping or development of something. The exact meaning of "formative phase" can vary depending on the context in which it is used. It is often used in education, psychology, and various other fields.

130. Most common correlation found in plant is:

• A. Seed Dominance
• B. Shoot Dormancy
• C. Apical Dormancy
• D. Peduncle Dormancy
• E. None of these

Explanation: Most common correlation found in plant is Apical Dormancy "Apical dormancy" is a term used to describe the dormancy or inactivity of the apical meristem of a plant. The apical meristem is the growing tip of a plant's stem or shoot and is responsible for the production of new cells, which lead to the extension of the stem and the formation of new leaves and branches. Dormancy of the apical meristem means that growth at the tip of the stem is temporarily halted. Apical dormancy can be induced by environmental stressors such as extreme temperatures, water scarcity, or low light conditions. When conditions become unfavorable, the apical meristem goes dormant to conserve energy and protect itself from damage.