Sexual Reproduction in Plants

Overview of Sexual Reproduction in Plants

  • Plants reproduce sexually through the process of pollination, fertilization, and seed development.
  • Sexual reproduction results in genetic variation within a plant population, enhancing its resilience to environmental changes.
  • Involves the transfer of pollen from the male anther to the female stigma, which then develops into a seed after fertilisation.

Flower Structure

  • The male reproductive organ of a flower is the stamen – made up of the anther (which produces pollen) and the filament.
  • The female reproductive organ is the carpel – consisting of the stigma (where pollen is received), the style, and the ovary containing ovules.
  • Some flower species are hermaphrodites, having both male and female reproductive organs, while others have separate male and female flowers.

Pollination

  • Self-Pollination is the transfer of pollen from the anther to the stigma of the same plant or another plant with identical genetic composition.
  • Cross-Pollination involves the transfer of pollen between genetically different plants and is facilitated by wind, insects, birds, or other animals. This process increases genetic diversity.

Fertilisation

  • Fertilisation in sexual reproduction refers to the fusion of a sperm cell (contained in pollen) with an egg cell (contained in the ovule of a flower).
  • Following successful fertilisation, the zygote undergoes mitotic cell divisions to develop into an embryo.
  • The surrounding ovule develops into a seed, which contains the plant embryo and nutritive tissue, protected by a seed coat.

Seed Development and Dispersal

  • After fertilisation, the ovary of the plant grows into a fruit, which houses seeds.
  • Seed dispersal can occur by various means including wind, water, animals or self-dispersal mechanisms.
  • The place where a seed lands (soil type, availability of water, light, etc.) greatly influences plant growth and survival.
  • After dispersal, under suitable environmental conditions, the seed germinates, giving rise to a new plant.

Genetic Variation

  • Sexual reproduction in plants promotes genetic variation through meiosis, crossing-over, and fertilisation.
  • It is critical for the adaptation and evolution of plant species.
  • Genetic variation in sexually reproducing plant populations increases their ability to respond to changes in the environment.