Seeds contain a living part that can grow into a new plant. Only seeds that have life will germinate. A seed needs water, air, and suitable temperature to germinate, but soil and sunlight are not essential for germination. During germination, the seed absorbs water, swells, and the radicle (future root) grows downward, and the plumule (future shoot) grows upward. The cotyledon supplies food for the young plant until leaves begin photosynthesis.
Seeds have different structures:
- Dicot seeds (like pea) have two cotyledons.
- Monocot seeds (like corn) have one cotyledon and an endosperm providing food.
Plants can grow from other parts too—such as roots, stems, and leaves (e.g., hibiscus, miracle leaf).
Seeds need to be dispersed to avoid overcrowding. Dispersal happens through wind, water, animals, and bursting fruits, and seeds adapt to their mode of dispersal. Leaves show patterns of reticulate or parallel venation, which relate to root types—taproot for reticulate venation and fibrous root for parallel venation. Plants are also classified as dicot and monocot based on cotyledons and venation.
Some plants are becoming rare due to habitat destruction; protecting habitats helps prevent extinction.
Questions with Short Answers
- What is necessary for a seed to germinate?
Water, air, and suitable temperature. - Is soil necessary for germination? Why?
No. Seeds can germinate without soil as long as they get water and air. - Is sunlight necessary for germination?
No. Seeds can germinate even in darkness. - What is the first part to emerge from a germinating seed?
The radicle (future root). - What is the function of the radicle?
It develops into the root of the plant. - What is the plumule?
It is the part of the seed that grows upward to form the shoot. - What is the role of the cotyledon?
It provides stored food to the young plant during early growth. - What is the difference between a dicot seed and a monocot seed?
Dicots have two cotyledons; monocots have one cotyledon. - What is the endosperm?
A food-storing tissue in monocot seeds. - Give an example of a dicot plant.
Pea or tamarind. - Give an example of a monocot plant.
Corn or rice. - What is hydroponics?
A method of growing plants without soil using nutrient solution. - Why do plants store food in seeds?
To support the young plant until it can make its own food. - Name two plants that grow without seeds.
Hibiscus, miracle leaf plant. - What is seed dispersal?
The process by which seeds are spread away from the parent plant. - Why is seed dispersal necessary?
To prevent overcrowding and ensure adequate resources for growth. - How do coconuts disperse?
Through water—they float. - Name a seed adapted for wind dispersal.
Milkweed (appooppan thadi). - How do animals help in seed dispersal?
By eating fruits and dropping seeds elsewhere. - What type of venation is seen in jackfruit leaves?
Reticulate venation. - What type of root system is seen in grass?
Fibrous root system. - What root system is associated with reticulate venation?
Taproot system. - What root system is associated with parallel venation?
Fibrous root system. - What causes a seed to swell before germination?
Absorption of water. - What is extinction?
The reduction and disappearance of an organism from Earth due to habitat destruction.
Questions with Long Answers
- Explain an experiment to check whether soil is necessary for seed germination. What conclusion do you get?
Place some pea or green gram seeds on a wet cotton ball without using soil. Give them water, air, and sunlight. Observe them daily. The seeds swell, the seed coat breaks, and the radicle and plumule appear, proving that seeds can germinate even without soil. Conclusion: Soil is not essential for germination. - Describe the experiment used to find out whether water is essential for seed germination. What did you observe?
Take two glasses—one with dry soil and one with moist soil. Place identical seeds in both. Only the seeds in moist soil germinate. Seeds in dry soil remain unchanged. Observation: Water is essential for germination. - How can we check whether sunlight is needed for seed germination? Describe the steps and findings.
Place identical seeds in two glasses with air, water, and soil. Keep one glass in sunlight and the other in a dark steel container. In both glasses, seeds germinate. Finding: Sunlight is not essential for germination but is needed later for healthy growth. - Explain the changes that occur in a seed from day one to day five during germination.
Day 1: Seed absorbs water and swells. Day 2: Seed coat loosens; radicle begins to emerge. Day 3: Radicle grows downward; plumule begins to appear. Day 4: Plumule grows upward toward the light; cotyledons shrink. Day 5: Root and shoot are visible; the seedling starts independent growth. - Describe the roles of radicle, plumule, and cotyledon in the early growth of a plant.
Radicle: First to emerge; forms the main root. Plumule: Grows upward; develops into shoot and leaves. Cotyledon: Stores food; supplies energy until leaves begin photosynthesis. - What are the differences between dicot and monocot seeds? Use examples from the textbook.
Dicots: Two cotyledons, reticulate venation, taproot system. Example: pea. Monocots: One cotyledon, endosperm present, parallel venation, fibrous roots. Example: corn. - Explain the concept of hydroponics and how it relates to germination studies.
Hydroponics is a soil-less method of cultivation in which plants grow in a nutrient-rich water solution. It proves that soil is not required for plant growth; only nutrients, water, and support are needed. It supports the observation that seeds can germinate without soil. - Why do cotyledons shrink during germination? What happens to them later?
Cotyledons shrink because the stored food is consumed by the growing seedling. As the plumule develops leaves for photosynthesis, cotyledons dry up and eventually fall off. - Explain how seeds of coconut are adapted for water dispersal.
Coconut has a fibrous, air-filled husk that makes it buoyant. Its seed does not rot in water. These features help the coconut float across water bodies and disperse to new locations. - Describe the adaptations in milkweed (appooppan thadi) seeds for wind dispersal.
Milkweed seeds have silky, hair-like structures (pappus) that catch the wind easily. They are extremely light, allowing them to float long distances. - How do animals and birds help in seed dispersal? Give examples.
Animals eat fleshy fruits such as guava and deposit seeds far away through droppings. Birds carry seeds while eating fruits. Some seeds have hooks that stick to animal fur for transport. - Why is seed dispersal important for plant survival? Explain with reasons given in the textbook.
If all seeds fall beneath the parent plant, they compete for water, minerals, sunlight, and space. Dispersal spreads seeds to new areas, ensures better growth, and increases the chance of plant survival. - Explain with examples how some fruits burst to release seeds.
Plants like balsam and rubber have fruits that dry and develop tension. When they ripen, the tension releases suddenly, causing the fruits to burst and scatter seeds. - Explain the relationship between venation and root system in plants.
Reticulate venation → Taproot system (e.g., jackfruit). Parallel venation → Fibrous roots (e.g., grass).
This relationship helps identify monocot and dicot plants. - Describe the procedure for examining venation by using leaves that have lost their green parts.
When green tissues decay, veins remain. Inspect these skeleton leaves to identify venation patterns. Reticulate venation shows a network of veins; parallel venation shows straight lines from base to tip. - What are prop roots, stilt roots, clinging roots, and pneumatophores? Explain with functions.
Prop roots: Support trees like banyan. Stilt roots: Provide balance (e.g., sugarcane). Clinging roots: Help plants climb walls (e.g., money plant). Pneumatophores: Breathing roots in mangroves; exchange gases. - How can plants grow without seeds? Give examples from the chapter.
Plants like hibiscus (stem), miracle leaf (leaf), and pagoda flower (root pieces) grow from vegetative parts. These parts have growing points that form new plants. - Explain the process of germination using the illustration of green gram seed given in the textbook.
The seed absorbs water, swells, and the seed coat breaks. The radicle grows downward forming roots. Later the plumule grows upward. Cotyledons supply food until leaves appear. This entire process is visible clearly in green gram seeds. - Why do different seeds germinate at different rates?
Seeds differ in size, thickness of seed coat, water absorption speed, and temperature requirements. Therefore, their germination time varies. For example, green gram germinates faster than tamarind. - How do humans assist in seed dispersal? Provide examples.
Humans transport seeds during farming, gardening, trading fruits, and carrying plants from one place to another. They also create new habitats where dispersed seeds grow. - Describe the adaptations seen in seeds that attach themselves to animals or clothing.
Seeds like love grass have hook-like or sticky surfaces. These cling to animal fur, bird feathers, or human clothes. This helps them travel long distances without direct dispersal structures. - Explain how the structure of the corn seed supports the growth of a monocot plant.
Corn has one cotyledon and a large endosperm that stores food. During germination, the embryo uses this endosperm for nutrition. Its fibrous roots spread quickly, helping the young seedling absorb water and minerals. - What is meant by the life inside a seed? How did Ping’s story highlight this?
A living embryo lies inside every seed. It can grow only if the seed is alive. In Ping’s story, he brought a pot with no plants because the king had given dead seeds. This proved that only seeds with life can germinate. - How would you conduct an experiment to compare the germination of seeds in soil vs. hydroponics?
Set up two groups: Soil Group: Seeds placed in moist soil with sunlight. Hydroponic Group: Seeds placed in nutrient solution. Observe root and shoot growth daily. Result: Both germinate, but hydroponic roots remain exposed and take nutrients from solution rather than soil. - What causes certain plants to become rare or face extinction? How can this be prevented?
Habitat destruction, pollution, excessive harvesting, and climate changes cause reduction in plant populations. Prevention: Protect natural habitats, reduce deforestation, cultivate rare plants, and create awareness among people.