Plant Reproduction

• Lesson 3 is about plant reproduction
• Plants reproduce in a variety of ways: either vegetatively, or sexually via seeds.
• The key question for this lesson is simply - how do plants reproduce?

Objectives

• Define vegetative propagation
• List the advantages and disadvantages of vegetative propagation
• Use diagrams to identify the different parts of flowers and their functions
• Describe the pollination mechanisms of plants including: wind or animal
• Compare and contrast the development of the seed and the fruit in flowering plants (angiosperms) only from where both originated
• List three examples of seed dispersal
• Summarize, in steps, the germination process of seeds

Vegetative Reproduction

• This is a form of asexual reproduction where a new plant grows from parts of an old one.
• Vegetative reproduction results in a clone of the original plant.
• Some noted advantages are faster growth which produces uniform offspring and the ability to produce fruit without seeds.
• It is a relatively quick way to produce new plants.
• Good characteristics of a parent can be passed to the offspring.
• No external factors or other plants are needed for reproduction to occur.
• Overcrowding can occur which causes competition for resources.
• Disease of parent plant can easily be transmitted to the offspring.
• Does not allow for new features in offspring which adapt to changes in environmental conditions.
• Undesirable characteristics are passed on to the offspring.

Flower Structure

• Flowers have organs for protection, support, and reproduction
• Flowers generally have four organs: sepals, petals, pistils, and stamen
• Sepals protect the flower bud, they can resemble small leaves.
• Petals are colorful structures which attract pollinators and provide a landing platform for them.
• Stamen is the male reproductive structure.
• Pistil is the female reproductive structure.
• Animal pollination is facilitated by flowers that are brightly colored or strongly scented to attract pollinators.
• Wind pollination occurs with flowers that lack showy or fragrant flowers and produce large amounts of lightweight pollen.

Seed and Fruit Development

• Zygotes undergo many cell divisions to become an embryo.
• Endosperm tissue provides nutrients to the growing embryo.
• Endosperm is mostly absorbed into the cotyledons of eudicots.
• Endosperm accounts for a large seed volume in monocots.
• As the endosperm matures, the outside layers of the ovule hardens and forms the seed coat.
• The ovary of a plant can contain one or many layers.
• As the ovule develops into a seed, changes occur in the ovary which causes it to develop into a fruit.

Seed Dispersal

• Fruits help disperse the seeds away from the parent, reducing competition, which increases their chance of survival
• Some seeds pass unharmed through the digestive tracts of animals before being deposited.
• Other seeds have structural modifications that allow them to be transported by water, animals, or wind.

Seed Germination

• When the embryo in the seed begins to grow, the process is called germination.
• Germination begins when a seed absorbs water.
• The first part of the embryo to appear outside of the seed is the radicle.
• The hypocotyl is the first part of the seed to appear above ground.
• Seeds produced near the end of a growing season enter dormancy, where there is little to no growth to increase survival in harsh conditions.
• The length of dormancy varies from species to species.

Learn about plant reproduction through vegetative and sexual methods. Understand the mechanics such as the different parts of flowers, pollination, seed development and germination. Also learn about vegetative propagation.