Sexual Reproduction in Plants
Sexual Reproduction in Plants
Definition
- Sexual reproduction in plants involves the fusion of male and female gametes.
- This process leads to genetically diverse offspring, enhancing survival chances in changing environments.
Flower Structure
- The flower is the reproductive organ of plants.
- The stamen is the male part of a flower which produces pollen grains (male gametes).
- The carpel or pistil is the female part of a flower. It comprises the stigma, style and ovary.
- The ovary houses ovules which develop into seeds (female gametes) once fertilised.
- Petals and sepals contribute to attracting pollinators.
Pollination
- Pollination is the transfer of pollen from an anther (part of stamen) to a stigma (part of carpel).
- Self-pollination occurs within the same flower or a different flower on the same plant, while cross-pollination occurs between flowers of different plants.
- Methods of pollination include wind, water and various pollinators such as bees, birds, bats and butterflies.
Fertilisation
- Fertilisation in plants occurs when a pollen grain lands on a stigma, grows a tube down to the ovary, and a sperm cell travels down the tube to fuse with an ovule.
- This creates a zygote, which divides by mitosis to form a seed.
Seed and Fruit Formation
- The seed develops from a fertilised ovule, and contains an embryo plant and a food store for it to use until it can carry out photosynthesis independently.
- The fruit forms from the ovary and protects the seed as well as aiding in its dispersal.
- Fruit can be dispersed by animals, wind, water and ballistic methods.
Vegetative Propagation
- Though not a form of sexual reproduction, plants can also reproduce vegetatively.
- This process involves parts of a plant growing into new individuals and can occur through roots, stems or leaves.
- Examples include bulbs, runners, and tubers.
Advantages of Sexual Reproduction in Plants
- It leads to genetically diverse offspring, which can better adapt to changing environments.
- The production of fruits and seeds enables wide dispersal, helping the species to colonise new habitats.
Disadvantages of Sexual Reproduction in Plants
- It is a slower process compared to asexual reproduction.
- It is energy intensive as plants need to produce flowers and fruit.
- Pollination and fertilisation are reliant on environmental conditions and other organisms, making it less reliable.
Importance of Sexual Reproduction in Plants
- Apart from ensuring survival, sexual reproduction is important for agriculture and biodiversity.
- Cross-breeding allows the selection of desirable characteristics like disease resistance or increased yield, improving crop varieties.