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Seeds and Germination - Methods of Seed Dispersal

Grade 5CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Seed Dispersal is the process by which seeds are scattered away from the parent plant to ensure they have enough space, sunlight, H2OH_2O, and nutrients to grow.

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Dispersal by Wind: Seeds are usually small and light. Some have wings (like Maple) or hair-like structures (like Dandelion) to help them float in the air.

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Dispersal by Water: Seeds or fruits develop fibrous or spongy outer coats to float on H2OH_2O. Example: Coconut and Lotus.

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Dispersal by Animals: Some seeds have hooks or spines (like Xanthium) that stick to the fur of animals. Other fruits are eaten by animals/humans, and the seeds are excreted in different locations.

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Dispersal by Explosion: Some plants have pods that dry up and burst open with a sudden force, scattering the seeds in all directions. Example: Pea, Balsam, and Bean plants.

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Germination: The process by which a seed grows into a new plant (seedling) given the right amount of H2OH_2O, air (O2O_2), and warmth.

📐Formulae

Seed+H2O+Air(O2)+Warmth→Germination\text{Seed} + H_2O + \text{Air} (O_2) + \text{Warmth} \rightarrow \text{Germination}

Rate of Dispersal=Distance traveled by seedTime taken\text{Rate of Dispersal} = \frac{\text{Distance traveled by seed}}{\text{Time taken}}

💡Examples

Problem 1:

A scientist observes a seed that has a thick, fibrous outer shell and is found floating near a riverbank. Identify the agent of dispersal and explain why.

Solution:

The agent of dispersal is Water.

Explanation:

Seeds like the coconut have a fibrousfibrous outer covering that traps air, allowing the seed to become buoyant and float on H2OH_2O to reach distant shores.

Problem 2:

Why do seeds like XanthiumXanthium have hooks or stiff hair on their surface?

Solution:

To facilitate dispersal by Animals.

Explanation:

The hookshooks allow the seeds to get attached to the fur of animals or the clothes of humans. As the animal moves, the seed is carried away and dropped at a new location where it can grow without competing with the parent plant for H2OH_2O and sunlight.

Problem 3:

A farmer notices that a pea pod suddenly 'pops' and seeds fly out. What is this method called?

Solution:

Dispersal by Explosion (or Autochory).

Explanation:

When the fruit (pod) dries, it creates internal tension. This results in a sudden bursting of the pod, which acts like a forceforce to fling the seeds away from the mother plant.