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.