1. Question: Discuss the role of roots in the morphology of flowering plants.
Answer: Roots play a crucial role in the morphology of flowering plants. They anchor the plant in the soil, provide support, and absorb water and nutrients from the soil. The root system consists of the main root, called the taproot, and its lateral branches, known as fibrous roots. The taproot grows vertically into the soil, while fibrous roots spread horizontally. The root hairs present on the surface of the roots increase the surface area for absorption. The absorption of water and minerals occurs through the process of osmosis and active transport. Additionally, roots also store food reserves, such as starch, which are essential for the plant’s growth and development.
References: Principles of Plant Physiology by Wilhelm Ruhland, Plant Anatomy by Katherine Esau
2. Question: Explain the various modifications of stems in flowering plants.
Answer: Stems in flowering plants exhibit various modifications to perform different functions. Some common modifications include:
a) Underground stems: Rhizomes, tubers, and bulbs are examples of underground stems. Rhizomes are horizontal stems that grow below the soil surface and give rise to new shoots. Tubers, like those found in potatoes, are swollen underground stems that store food reserves. Bulbs, such as those in onions, consist of modified leaves called scales, which store food reserves.
b) Aerial stems: Climbing stems, runners, and tendrils are examples of aerial stems. Climbing stems have specialized structures, such as thorns or hooks, which help the plant to climb and support itself. Runners are long, slender stems that grow horizontally above the ground and produce new plants at nodes. Tendrils are slender, coiling structures that help the plant in climbing or twining around support.
c) Modified stems for food storage: Some stems, like cacti, have modified to store water and food reserves. These stems are succulent and can store a large amount of water to survive in arid environments.
References: Plant Physiology by Lincoln Taiz and Eduardo Zeiger, Plant Anatomy by Katherine Esau
3. Question: Describe the structure and functions of leaves in flowering plants.
Answer: Leaves are the main organs of photosynthesis in flowering plants. They are typically flat, thin, and green in color. The structure of leaves consists of various parts:
a) Leaf blade: It is the broad, flat part of the leaf that is responsible for capturing sunlight. The upper surface of the leaf is called the adaxial surface, while the lower surface is called the abaxial surface.
b) Petiole: It is the stalk that connects the leaf blade to the stem. It provides support and allows the leaf to orient itself for maximum exposure to sunlight.
c) Leaf veins: Veins are vascular bundles that transport water, minerals, and sugars throughout the leaf. They also provide structural support to the leaf.
d) Leaf margin: It refers to the edge of the leaf, which can be smooth, serrated, lobed, or toothed, depending on the plant species.
The functions of leaves include photosynthesis, transpiration, and gas exchange. The chlorophyll present in the leaf cells captures sunlight energy and converts it into chemical energy through photosynthesis. Transpiration helps in the movement of water and minerals from the roots to the leaves. Leaves also exchange gases with the atmosphere, facilitating the uptake of carbon dioxide and release of oxygen.
References: Plant Physiology by Lincoln Taiz and Eduardo Zeiger, Plant Anatomy by Katherine Esau
4. Question: Discuss the structure and functions of flowers in flowering plants.
Answer: Flowers are reproductive structures in flowering plants. They have a complex structure consisting of various parts:
a) Sepals: Sepals are the outermost whorl of the flower. They are usually green and protect the developing flower bud.
b) Petals: Petals are the colorful, modified leaves that attract pollinators, such as insects or birds. They are usually brightly colored to enhance their visibility.
c) Stamens: Stamens are the male reproductive organs of the flower. Each stamen consists of a filament and an anther. The anther produces pollen grains, which contain the male gametes (sperm cells).
d) Carpels: Carpels are the female reproductive organs of the flower. Each carpel consists of an ovary, style, and stigma. The ovary contains ovules, which develop into seeds after fertilization. The style connects the ovary to the stigma, where pollen grains are received for fertilization.
The functions of flowers include pollination and fertilization. Pollination is the transfer of pollen from the anther to the stigma, either by wind, water, or pollinators. Fertilization occurs when the pollen grain germinates on the stigma and grows a pollen tube, which delivers the sperm cells to the ovules. After fertilization, the ovules develop into seeds, and the ovary transforms into a fruit.
References: Plant Physiology by Lincoln Taiz and Eduardo Zeiger, Plant Anatomy by Katherine Esau
5. Question: Explain the different types of fruits found in flowering plants.
Answer: Fruits are mature ovaries of flowering plants that develop after fertilization. They can be classified into various types based on their structure and origin:
a) Simple fruits: Simple fruits develop from a single ovary of a single flower. Examples include berries (e.g., tomatoes), drupes (e.g., peaches), and pomes (e.g., apples).
b) Aggregate fruits: Aggregate fruits develop from a single flower with multiple separate carpels. Each carpel forms a small fruit, and all these fruits fuse together to form a larger fruit. Examples include raspberries and blackberries.
c) Multiple fruits: Multiple fruits develop from a cluster of flowers, where each flower contributes to the formation of the fruit. Examples include pineapples and figs.
d) Accessory fruits: Accessory fruits develop from structures other than the ovary, such as the receptacle or floral tube. Examples include strawberries, where the fleshy part is derived from the receptacle.
Fruits serve various functions, such as protecting the developing seeds, aiding in seed dispersal, and attracting animals for seed dispersal. They can be fleshy or dry, depending on the plant species.
References: Plant Physiology by Lincoln Taiz and Eduardo Zeiger, Plant Anatomy by Katherine Esau
6. Question: Discuss the structure and functions of seeds in flowering plants.
Answer: Seeds are the mature ovules of flowering plants. They have a complex structure and perform various functions:
a) Seed coat: The seed coat is the protective outer covering of the seed. It prevents desiccation, mechanical injury, and microbial attack.
b) Embryo: The embryo is the young, developing plant inside the seed. It consists of a plumule (develops into the shoot system), a radicle (develops into the root system), and one or two cotyledons (seed leaves). The cotyledons store food reserves that nourish the growing embryo during germination.
c) Endosperm: Some seeds have endosperm, a tissue that stores food reserves. It provides nourishment to the developing embryo during germination.
d) Dormancy: Seeds can enter a state of dormancy, where they remain inactive until conditions are favorable for germination. Dormancy helps seeds survive unfavorable environmental conditions.
The functions of seeds include dispersal, protection, and propagation. Seeds can be dispersed by wind, water, animals, or self-dispersal mechanisms. The seed coat protects the embryo and its food reserves from desiccation, pathogens, and predators. Seeds also serve as a means of reproduction, allowing plants to propagate and colonize new areas.
References: Plant Physiology by Lincoln Taiz and Eduardo Zeiger, Plant Anatomy by Katherine Esau
7. Question: Explain the process of germination in flowering plants.
Answer: Germination is the process by which a seed develops into a young plant. It involves the following steps:
a) Imbibition: Imbibition is the absorption of water by the seed. Water activates enzymes and triggers metabolic processes necessary for germination.
b) Activation of enzymes: Enzymes become active and break down stored food reserves, such as starch, into simpler forms, such as sugars. These sugars provide energy for the growing embryo.
c) Growth of the radicle: The radicle, or embryonic root, emerges from the seed and grows downwards into the soil. It anchors the plant and absorbs water and minerals from the soil.
d) Growth of the plumule: The plumule, or embryonic shoot, emerges from the seed and grows upwards towards the light. It develops into the stem and leaves of the plant.
e) Development of true leaves: As the plumule grows, it produces true leaves, which are distinct from the cotyledons. These leaves start performing photosynthesis and provide energy for further growth.
Germination is influenced by various factors, including temperature, water availability, oxygen supply, and light conditions. Different plant species have specific requirements for germination.
References: Plant Physiology by Lincoln Taiz and Eduardo Zeiger, Plant Anatomy by Katherine Esau
8. Question: Discuss the importance of plant anatomy in understanding the morphology of flowering plants.
Answer: Plant anatomy is the study of the internal structure of plants. It plays a crucial role in understanding the morphology of flowering plants by providing insights into the organization and functioning of different plant parts. Here are some key points:
a) Tissues and cells: Plant anatomy helps in identifying and classifying different types of tissues, such as meristematic, ground, and vascular tissues. It also provides information about the different types of cells present in these tissues, their arrangement, and their functions.
b) Vascular system: Plant anatomy reveals the complex network of xylem and phloem tissues responsible for transporting water, minerals, and organic compounds throughout the plant. It helps in understanding the mechanisms of water uptake, translocation, and nutrient distribution.
c) Structural adaptations: Plant anatomy helps in identifying and studying the structural adaptations of different plant parts, such as roots, stems, leaves, flowers, fruits, and seeds. These adaptations enable plants to survive and thrive in diverse environmental conditions.
d) Reproductive structures: Plant anatomy provides insights into the structure and development of flowers, fruits, and seeds. It helps in understanding the processes of pollination, fertilization, and seed dispersal.
By studying plant anatomy, researchers can gain a deeper understanding of plant morphology, evolution, and ecological interactions. It also aids in plant breeding, agriculture, and conservation efforts.
References: Plant Anatomy by Katherine Esau, Plant Physiology by Lincoln Taiz and Eduardo Zeiger
9. Question: Explain the process of transpiration in plants and its significance.
Answer: Transpiration is the process by which plants lose water vapor through their leaves. It occurs through small openings called stomata present on the leaf surface. The process of transpiration is driven by several factors:
a) Transpiration pull: Transpiration creates a negative pressure or tension in the xylem vessels, which pulls water from the roots to the leaves. This transpiration pull helps in the upward movement of water and minerals against gravity.
b) Cohesion-tension theory: According to the cohesion-tension theory, water molecules are cohesive, meaning they stick together due to hydrogen bonding. As water evaporates from the leaf surface, it creates tension, which pulls the water column upwards.
c) Stomatal regulation: Stomata control the rate of transpiration by opening and closing their pores. They open to allow the exchange of gases for photosynthesis but can also lose excessive water if the environmental conditions are unfavorable. Factors like light intensity, temperature, humidity, and CO2 concentration influence stomatal opening and closure.
The significance of transpiration includes:
a) Water transport: Transpiration provides a driving force for the upward movement of water and minerals from the roots to the leaves. It helps in maintaining the water balance and nutrient uptake by the plant.
b) Cooling effect: Transpiration helps in regulating the temperature of the plant and its surroundings. As water evaporates from the leaf surface, it cools the plant and the surrounding environment.
c) Photosynthesis: Transpiration facilitates the exchange of gases, such as carbon dioxide and oxygen, between the plant and the atmosphere. This exchange is essential for photosynthesis, where carbon dioxide is taken up and oxygen is released.
References: Plant Physiology by Lincoln Taiz and Eduardo Zeiger, Plant Anatomy by Katherine Esau
10. Question: Discuss the role of hormones in the growth and development of flowering plants.
Answer: Hormones play a crucial role in the growth and development of flowering plants. They are chemical messengers produced in one part of the plant and transported to other parts, where they regulate various physiological processes. Here are some key hormones and their functions:
a) Auxins: Auxins promote cell elongation, apical dominance, and phototropism. They are responsible for the growth of stems and roots towards light and gravity, respectively. Auxins also play a role in tropic responses, such as bending of plants towards a light source.
b) Gibberellins: Gibberellins stimulate stem elongation, seed germination, and flowering. They promote the growth of internodes, resulting in taller plants. Gibberellins also regulate various developmental processes, such as fruit development and seed dormancy.
c) Cytokinins: Cytokinins promote cell division, delay senescence, and stimulate shoot and root growth. They are involved in regulating the balance between shoot and root development. Cytokinins also play a role in the formation of lateral buds and the prevention of leaf senescence.
d) Abscisic acid (ABA): ABA inhibits growth, promotes seed dormancy, and regulates stomatal closure during water stress. It acts as a stress hormone, helping plants cope with adverse environmental conditions.
e) Ethylene: Ethylene is involved in various physiological processes, such as fruit ripening, senescence, and abscission (shedding of leaves and fruits). It also regulates responses to biotic and abiotic stresses, such as pathogen attack and drought.
These hormones interact with each other and respond to environmental cues to regulate plant growth, development, and responses to stimuli. The balance and coordination of hormone levels are crucial for proper plant growth and adaptation.
References: Plant Physiology by Lincoln Taiz and Eduardo Zeiger, Plant Anatomy by Katherine Esau