Long Questions: Getting to Know Plants | NCERT Summary: UPSC PDF Download

Q1: Explain the function of the leaf.
Ans: Leaf is a thin, broad green structure arising from nodes of the stem. 

• Photosynthesis is the primary function of the leaf. Plants use sunlight to create compounds that are used as food in a process known as photosynthesis. Only particular green pigments known as chlorophyll can trap sunlight. Chlorophyll absorbs sunlight and converts carbon dioxide and water into glucose, which serves as nourishment. Presence of chlorophyll also makes the leaves green in colour.
• Another structure called stomata is present on the leaf surface which helps in exchange of gases i.e. respiration.
• In addition, the leaves serve as a means of transpiration. The loss of water as water vapour from aerial portions of plants, such as leaves, is known as transpiration. Transpiration aids in the cooling of the plant. It's also crucial for the root's water absorption.
• In some plants like Bryophyllum, leaves also help in reproduction through vegetative propagation.
• Leaves also store food in some plants. E.g. Aloe.

Q2: Compare herbs, shrubs and trees.
Ans: Difference between herbs, shrubs and trees are following:

Q3: Explain the process of photosynthesis in plants. What are the essential components and conditions required for photosynthesis to occur? Provide a real-life example.
Ans: Photosynthesis is the process by which plants make their own food using sunlight, carbon dioxide, and water. It takes place in the leaves of plants. Here's how it works:
Process: Plants have tiny pores called stomata on their leaves. Carbon dioxide from the air enters the leaves through these stomata. Water is absorbed by the roots and transported to the leaves. Sunlight is absorbed by a green pigment called chlorophyll present in the leaves. In the presence of sunlight, carbon dioxide, and water, chlorophyll helps convert these substances into glucose (sugar) and oxygen.
Components and Conditions:

• Sunlight: It provides energy for the process.
• Carbon dioxide: It is taken from the air through stomata.
• Water: It is absorbed by roots and transported to leaves through the stem.
• Chlorophyll: It's the green pigment that captures sunlight.
• Chloroplasts: Cellular structures where photosynthesis occurs.
• Example: A common example is a potted plant. As sunlight reaches the plant's leaves, photosynthesis occurs, producing energy-rich glucose and releasing oxygen.

Q4: Describe the process of pollination in plants. How does it contribute to the formation of fruits and seeds? Provide an illustration.
Ans: Pollination is the transfer of pollen from the male part (anther) to the female part (stigma) of a flower. It is a crucial step in the reproduction of flowering plants.
Here's how it works:

• Process: Pollen grains are produced in the anther of a flower. These grains need to reach the stigma of another flower of the same kind to pollinate it. This can happen through various agents like wind, water, insects, or birds. When pollen lands on a stigma, it travels down the style to the ovary. In the ovary, fertilization occurs, leading to the formation of seeds and fruits.
• Contribution to Formation of Fruits and Seeds: Pollination is necessary for the transfer of male gametes (pollen) to female gametes (ovules) in the ovary. This fertilization results in the development of seeds. The ovary also enlarges and forms a fruit to protect and disperse the seeds.
• Illustration: Consider a mango tree. When bees carry pollen from one mango flower to another, the fertilized flower develops into a fruit containing seeds.

Q5: Explain the difference between self-pollination and cross-pollination. Provide advantages of cross-pollination in plants.
Ans:

• Self-Pollination: In self-pollination, pollen from the anther of a flower reaches the stigma of the same flower or another flower on the same plant. It doesn't require external agents like wind or insects. It occurs within the same plant.
• Cross-Pollination: In cross-pollination, pollen from the anther of one flower is transferred to the stigma of a flower on a different plant of the same kind. External agents like wind, insects, or birds often aid in this process.

Advantages of Cross-Pollination:

• Variation: Cross-pollination leads to greater genetic diversity in plants, as it involves the mixing of genetic material from different individuals.
• Adaptation: Variations produced through cross-pollination help plants adapt to changing environments, making them more resistant to diseases and pests.
• Improved Seeds: Cross-pollination produces better-quality seeds, enhancing the chances of survival and growth of the plant species.
• Evolution: Over time, cross-pollination contributes to the evolution of new plant varieties with beneficial traits.

Q6: Explain the importance of seed dispersal in plants. Describe at least three methods of seed dispersal and give examples of plants that use each method.
Ans: Importance of Seed Dispersal: Seed dispersal is crucial for the survival and growth of plant species. It helps prevent overcrowding and competition among plants of the same kind. Dispersed seeds have a better chance of finding suitable conditions for germination and growth.
Methods of Seed Dispersal:

• Wind Dispersal (Anemochory): Seeds with structures like wings or hairs are carried by the wind. Examples: Dandelion, Maple tree.
• Animal Dispersal (Zoochory): Seeds are carried by animals that eat the fruits. They may be digested and released in a new location. Examples: Berries eaten by birds, burrs sticking to fur.
• Water Dispersal (Hydrochory): Seeds float on water, carried away to new areas. Examples: Coconut, Water lily.

These methods ensure that plants can colonize new areas, reduce competition, and survive in diverse environments.

Q7: Describe the life cycle of a flowering plant, including the stages of germination, growth, reproduction, and death. Provide a detailed explanation and highlight the significance of each stage.
Ans: The life cycle of a flowering plant involves several stages:

• Germination: A seed absorbs water and swells. The embryo inside the seed starts to grow. The radicle (embryonic root) emerges first, followed by the plumule (embryonic shoot). The seed coat eventually breaks, and the young plant emerges.
• Growth and Vegetative Stage: The plant grows leaves, stems, and roots during this stage. Photosynthesis occurs, providing energy for growth. The plant also develops a strong root system to anchor itself and absorb water and nutrients from the soil.
• Reproductive Stage: The plant produces flowers, which are its reproductive structures. Pollination occurs, leading to the transfer of pollen from the anther to the stigma. Fertilization takes place, resulting in the formation of seeds within the ovary. The flower then matures into a fruit, protecting the seeds.
• Seed Dispersal and Germination (Next Generation): The fruit, containing seeds, is dispersed by various methods (wind, animals, water). When a seed lands in a suitable environment, germination begins, restarting the life cycle.
• Senescence and Death: After a plant has completed its reproductive cycle, it undergoes senescence (aging). The plant's energy is diverted towards producing seeds and fruit. Eventually, the plant may die, completing its life cycle. The dead plant matter decomposes, enriching the soil for future plant growth.

Each stage of the life cycle is significant as it ensures the survival, growth, and reproduction of the plant species, contributing to the ecosystem's balance.

Q8: Explain the role of roots in a plant's life. Describe the different types of roots and their functions with suitable examples.
Ans: Role of Roots: Roots play a vital role in a plant's life. They anchor the plant in the soil, absorb water and minerals, and store food.
Types of Roots and Their Functions:

• Taproot: A single, thick root that grows deep into the soil. It provides stability to the plant and stores food. Example: Carrot.
• Fibrous Roots: Numerous thin roots that spread horizontally near the soil surface. They absorb water and nutrients efficiently. Example: Grass.
• Adventitious Roots: Roots that arise from stems or leaves instead of the main root. They help in vegetative propagation (reproduction without seeds). Example: Sweet potato.
• Aerial Roots: Roots that grow above the ground, often from stems. They help support and anchor climbing plants. Example: Money plant.

Different types of roots adapt to various soil and environmental conditions, aiding in the plant's survival and growth.

Q9: Discuss the significance of leaves in a plant's life. Explain their main functions and the adaptations that help leaves perform these functions effectively. Provide suitable examples.
Ans: Significance of Leaves: Leaves are crucial to a plant's life as they are the primary sites for photosynthesis, where the plant makes its food.
Functions of Leaves:

• Photosynthesis: Leaves contain chlorophyll, a pigment that captures sunlight for photosynthesis.
• Transpiration: Leaves release excess water vapor through tiny pores called stomata, maintaining water balance.
• Gas Exchange: Leaves allow the exchange of gases like oxygen and carbon dioxide with the atmosphere.

Leaf Adaptations:

• Shape and Arrangement: Different leaf shapes and arrangements optimize light absorption and reduce water loss. Example: Needle-like leaves of cacti.
• Stomatal Arrangement: Stomata are often on the lower leaf surface to minimize water loss. Example: Lotus leaves.
• Modified Leaves: Some leaves are modified for other functions, like spines for protection (cacti), tendrils for support (pea plants), or traps for capturing insects (Venus flytrap).

These adaptations enable leaves to efficiently carry out their functions and contribute to a plant's survival and growth.

Q10: Describe the various methods of vegetative propagation in plants. Provide examples of plants that reproduce through each method. Explain how vegetative propagation benefits plants and humans.
Ans: Methods of Vegetative Propagation:

• Cuttings: A part of the plant, like a stem or leaf, is cut and planted in soil. New roots and shoots develop. Example: Rose.
• Layering: A low branch is bent and covered with soil, and roots and shoots form before it is separated from the parent plant. Example: Jasmine.
• Grafting: A part of one plant (scion) is attached to another plant (rootstock). They grow together as one plant. Example: Apple trees.
• Budding: A bud from one plant is attached to another plant. The bud develops into a new shoot. Example: Citrus trees.

Benefits of Vegetative Propagation:

• Rapid Reproduction: Plants reproduce faster than from seeds.
• Preservation of Desirable Traits: Desired characteristics of parent plants are passed on.
• Propagation of Rare Varieties: Rare or special varieties can be maintained.
• Agricultural Advantages: Consistent quality and yield in crops.

These methods are used by humans for crop production, gardening, and maintaining specific plant traits.