What is Reproduction in Plants Class 7: Complete NCERT Guide

Definition and Importance of Reproduction in Plants

Reproduction in plants is the process through which plants create new plants, maintaining their species over time. It is essential because:

• It ensures the survival and continuation of plant species.
• It helps plants adapt to changing environments.
• It increases the number of plants, supporting ecosystems and human needs.

In Class 7 NCERT Science, reproduction is introduced to help students understand how plants grow and multiply, which is crucial for biology studies and exams.

Types of Reproduction in Plants

Plants reproduce mainly in two ways:

1. Sexual Reproduction

• Involves the fusion of male and female gametes.
• Takes place in flowers.
• Results in seeds that grow into new plants.

2. Asexual Reproduction

• Does not involve gametes.
• New plants grow from parts like stems, roots, or leaves.
• Examples include budding, vegetative propagation, and spore formation.

Both types help plants multiply but differ in their processes and outcomes.

Sexual Reproduction in Plants: How It Happens

Sexual reproduction in plants involves several steps:

• Flower Structure: Flowers have male parts (stamens) producing pollen and female parts (carpels) containing ovules.
• Pollination: Transfer of pollen from stamen to stigma, often by wind, insects, or animals.
• Fertilization: Pollen fertilizes the ovule to form a zygote.
• Seed Formation: The fertilized ovule develops into a seed.
• Germination: Seeds grow into new plants under suitable conditions.

This process ensures genetic variation, which is important for plant diversity.

Asexual Reproduction in Plants: Methods and Examples

Asexual reproduction creates new plants without seeds or spores. Common methods include:

• Vegetative Propagation: New plants grow from parts like stems (e.g., sugarcane), roots (e.g., sweet potato), or leaves (e.g., Bryophyllum).
• Budding: A new plant grows from a bud on the parent plant (e.g., yeast, though not a plant, but similar concept).
• Spore Formation: Some plants like ferns produce spores that grow into new plants.

Advantages of asexual reproduction:

• Faster reproduction.
• Offspring are genetically identical to the parent.

Pollination and Fertilization: Key Processes in Plant Reproduction

Pollination and fertilization are crucial for sexual reproduction:

• Pollination: The process of transferring pollen grains from the anther to the stigma of a flower.
• Types: Self-pollination (same flower) and cross-pollination (different flowers).
• Agents: Wind, water, insects, birds.

• Fertilization: After pollination, pollen travels down the style to fertilize the ovule.

Example worked formula:

If a flower produces $n$ ovules and $m$ pollen grains successfully fertilize, then the number of seeds formed = $m$ (assuming all fertilize).

Understanding these processes helps explain how plants reproduce sexually and form seeds.

How Seeds Germinate and Grow into New Plants

Seed germination is the process where a seed develops into a new plant. It requires:

• Water: Activates enzymes inside the seed.
• Oxygen: Needed for respiration.
• Suitable Temperature: Helps enzyme activity.

Steps of germination: 1. Seed absorbs water and swells. 2. Seed coat breaks. 3. Radicle (root) emerges. 4. Shoot grows upward.

Example: If a seed takes 7 days to germinate under ideal conditions, changing temperature or water availability can speed up or slow down this process.

Germination marks the beginning of a new plant’s life cycle.