**Reproduction** is a fundamental characteristic of all living organisms, enabling them to produce new individuals of their own kind. In this chapter, we explore the various ways plants reproduce.

Modes Of Reproduction

Most plants consist of **vegetative parts** like roots, stems, and leaves, which are essential for growth and survival. However, after a certain period, most plants produce **flowers**. Flowers are the structures responsible for **reproduction** in plants; they are the **reproductive parts**.

Plants reproduce through different methods, broadly classified into two types:

1. **Asexual Reproduction:** In this mode, new plants are produced **without the involvement of seeds**. A single parent plant gives rise to new individuals that are genetically identical to the parent.

2. **Sexual Reproduction:** In this mode, new plants are obtained from **seeds**. Sexual reproduction usually involves the fusion of specialised reproductive cells from two parents.

Asexual Reproduction

Asexual reproduction in plants occurs through several methods, all of which produce new plants without seeds.

Vegetative Propagation

**Vegetative propagation** is a type of asexual reproduction where new plants grow from the **vegetative parts** of the parent plant, such as roots, stems, leaves, or buds. Since reproduction occurs via vegetative parts, it's named vegetative propagation.

Advantages of vegetative propagation include:

• New plants take **less time to grow** and mature compared to those grown from seeds.
• Plants produced often **bear flowers and fruits earlier**.
• The new plants are **exact copies** (clones) of the single parent plant, retaining all its characteristics.

Activity 12.1

Growing new plants from a **stem cutting**. A piece of stem (cutting) from a plant like rose or champa is taken, ensuring it includes a **node** (the point on the stem where a leaf or bud arises). This cutting is buried in soil and watered regularly. Observing its growth over time shows the development of roots from the node and the emergence of new leaves, indicating the formation of a new plant from the stem cutting. The same activity can be done with money plant cuttings placed in water.

**Vegetative buds** are buds located in the axil (angle between a leaf and the stem) of leaves or at the tip of the stem. These buds contain undeveloped shoots and can develop into new plants.

Activity 12.2

Growing new plants from a potato. A potato tuber has small indentations called "eyes". These eyes are actually **vegetative buds**. Cutting the potato into pieces, ensuring each piece has at least one eye, and burying these pieces in moist soil allows new shoots and roots to grow from the eyes, forming a new potato plant. Other underground stems like ginger and turmeric also reproduce vegetatively through their buds.

Some plants reproduce from their leaves. **Bryophyllum** (sprout leaf plant) has buds along the margins of its leaves. If a Bryophyllum leaf falls on moist soil, the buds along the edge can develop into new plantlets.

Some plants also reproduce vegetatively from their roots, such as sweet potato and dahlia.

In plants like cacti, new plants can grow from parts of the main plant body that detach and fall onto the ground.

Budding

**Budding** is a method of asexual reproduction seen in simple organisms like yeast, which are single-celled. Yeast cells reproduce rapidly under favourable conditions.

Activity 12.3

Observing yeast under a microscope shows that a small, bulb-like projection grows from the parent yeast cell. This projection is called a **bud**. The bud grows and eventually detaches from the parent cell, forming a new, independent yeast cell. This new cell grows, matures, and can also produce more buds. Sometimes, buds remain attached, forming a chain of buds, leading to rapid multiplication of yeast cells.

Fragmentation

**Fragmentation** is a method of asexual reproduction occurring in organisms like algae (e.g., Spirogyra) found in ponds or stagnant water. When conditions are suitable (water and nutrients available), algae grow and multiply rapidly. The alga breaks up into two or more pieces or **fragments**. Each fragment then grows into a new, complete individual organism. This allows algae to spread and cover large areas quickly.

Spore Formation

Many non-flowering plants and fungi reproduce through **spores**. Spores are microscopic, asexual reproductive units.

Organisms like fungi (e.g., bread mould) and non-flowering plants (like moss and ferns) reproduce using spores. In fungi, structures called sporangia contain spores. When mature, these sporangia release spores into the air.

Spores are very light and can be easily carried by wind over long distances. Each spore is protected by a hard outer coat that helps it survive in unfavourable conditions (like high temperature, low humidity). Under favourable conditions, a spore germinates and grows into a new individual plant.

Sexual Reproduction

**Sexual reproduction** in plants involves the fusion of male and female reproductive cells (gametes) to form a new individual. Flowers are the sites of sexual reproduction in flowering plants.

The reproductive parts of a flower are:

• **Stamens:** The **male** reproductive parts. A stamen consists of an **anther** (which produces pollen grains) and a **filament** (stalk supporting the anther).
• **Pistil (or Carpel):** The **female** reproductive part, usually located in the center of the flower. A pistil consists of the **stigma** (receptive tip), **style** (stalk), and **ovary** (swollen base). The ovary contains one or more **ovules**, which contain the female gamete or egg cell.

Activity 12.4

Examining the reproductive parts of a flower (like mustard, china rose, or petunia) involves carefully separating the stamens and pistil to identify their individual components (anther, filament, stigma, style, ovary, ovules).

Based on the presence of reproductive parts, flowers can be:

• **Unisexual flowers:** Contain either only stamens (male flower) or only pistil (female flower). Examples: Corn, papaya, cucumber.
• **Bisexual flowers:** Contain both stamens and pistil in the same flower. Examples: Mustard, rose, petunia.

Male gametes are produced within the pollen grains, which are found in the anther. The female gamete (egg cell) is formed inside the ovule, which is within the ovary.

In sexual reproduction, a **male gamete fuses with a female gamete** to form a single cell called a **zygote**.

Pollination

**Pollination** is the process by which **pollen grains are transferred from the anther** (male part) to the **stigma** (female part) of a flower. Pollen grains have tough coats to prevent drying.

Pollination can occur in different ways:

• **Self-pollination:** Transfer of pollen from the anther to the stigma of the **same flower** or to the stigma of another flower on the **same plant**.
• **Cross-pollination:** Transfer of pollen from the anther of a flower on one plant to the stigma of a flower on a **different plant of the same kind**.

Pollination is often facilitated by external agents like **wind, water, or animals** (especially insects, which are attracted by colourful, fragrant flowers and carry pollen on their bodies).

Fertilisation

After pollination, the pollen grain germinates on the stigma and grows a tube (pollen tube) down through the style to reach the ovary and the ovule. The male gamete travels down the pollen tube and enters the ovule to fuse with the female gamete (egg cell).

The process of **fusion of the male and female gametes** is called **Fertilisation**. This fusion results in the formation of a single cell called a **zygote**.

The zygote is the first cell of the new individual plant. The zygote then develops into an **embryo** within the ovule.

Fruits And Seed Formation

Following fertilisation, significant changes occur in the flower:

• The **ovary** develops and ripens to form the **fruit**. The fruit is essentially the mature ovary of the flower.
• The **ovules** within the ovary develop into **seeds**. Each seed contains the embryo (developing plant) enclosed within a protective **seed coat**.

Other parts of the flower, such as the petals, sepals, stamens, and style, usually wither and fall off after fertilisation.

Fruits vary greatly in appearance. Some are fleshy and juicy (mango, orange), while others are hard and dry (almonds, walnuts).

Seeds are the result of sexual reproduction and are capable of germinating to grow into new plants under suitable conditions.

Seed Dispersal

**Seed dispersal** is the process by which seeds are carried away from the parent plant to new locations. This process is crucial for the survival and spread of plant species.

If all seeds from a plant were to fall and grow in the same spot, the young seedlings would face intense **competition** for essential resources like sunlight, water, minerals, and space from the parent plant and each other. This would likely result in unhealthy or stunted growth.

Seed dispersal benefits plants by:

• **Preventing overcrowding** and reducing competition for resources.
• Enabling plants to **colonise new habitats**, increasing their geographical distribution and survival chances against local environmental changes or diseases.

Seeds and fruits have various adaptations that aid in their dispersal by different agents:

• **Dispersal by Wind:** Seeds or fruits that are light, small, or have structures like **wings** (drumstick, maple), **hairs** (aak/madar seeds, sunflower fruits), or are very light like grass seeds, can be easily carried by wind to distant places.
• **Dispersal by Water:** Seeds or fruits adapted for water dispersal often have structures that help them float, such as spongy or fibrous outer coats (coconut). They are carried by water currents.
• **Dispersal by Animals:** Many seeds or fruits are dispersed by animals. Some have **spines or hooks** that attach to the fur or clothes of animals/humans (Xanthium, Urena) and are carried away. Other fruits are eaten by animals, and the seeds pass through the digestive tract and are deposited in a new location with the animal's waste.
• **Dispersal by Bursting of Fruits:** Some fruits burst open suddenly when mature, scattering the seeds with force away from the parent plant (e.g., castor, balsam).

Seed dispersal ensures that new plants can establish themselves in different areas, contributing to the plant species' survival and wide distribution.

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