g-11

• Plant reproduction


  Production of new offspring in plants, which can be accomplished by sexual or asexual reproduction

  
• Types of plant reproduction

  • Sexual
  • Asexual
• Asexual reproduction


  • Only requires DNA from one parent
  • Creates offspring that are genetically identical to the parent (clones)
  • Clones lack genetic diversity, making them less able to fight disease and less adaptable to changes in the environment
• Methods of asexual reproduction

  • Vegetative propagation
  • Fragmentation

  
• Vegetative propagation

  1. Offspring grow from a part of the parent plant

  2. Examples: Garlic, onions and tulip plants using true bulbs (short underground stems surrounded by modified leaves forming a papery covering)

  3. Tubers (modified underground stems)

  4. Corms and rhizomes (other examples of specialized stems)

  
• Fragmentation

  1. New plants growing from small parts of a parent plant that fall to the ground

  2. Used by plants like liverworts and mosses

  3. Horticulturists use this to propagate new plants from cuttings

  
• Sexual reproduction

  • Requires genetic material (DNA) from two parents
  • Parent plants have male and female sex cells (gametes)
  • Genetic material from male and female gametes combines to produce offspring (fertilization)
  • Offspring are not genetically identical to either parent (genetic diversity)

  
• Pollination


  1. Flowering plants reproduce sexually through this process

  2. Flowers contain male sex organs (stamens) and female sex organs (pistils)

  3. Pollen (containing male gametes) must be moved to the stigma (part of the pistil) for reproduction to take place

  4. Sepals protect the flower before it opens, petals are usually colourful, stamens contain pollen-producing cells, carpel contains the ovary with the eggs/ovules

  
• Types of pollination

  • Self-pollination (plant's own pollen fertilizes its own ovules)
  • Cross-pollination (wind or animals move pollen from one plant to another)

  
• Pollinators

  Animals that carry pollen between plants, including insects like bees, butterflies, moths and beetles, as well as some birds and mammals

  
• Fertilization

  1. Male gametes from pollen join with female gametes in the egg/ovule

  2. Creates fruit containing seeds

  
• Types of plants

  • Flowering plants (angiosperms)
  • Non-flowering plants (mosses, ferns, conifers)
• Seed


  Reproductive structure containing a plant embryo and food source, surrounded by a seed coat

  
• Seed dispersal

  Plants use various mechanisms to disperse their seeds over distances to increase survival probability
• Germination

  1. When a seed breaks through the seed coat and grows under suitable conditions of water, oxygen and warmth

  2. Seed embryo consists of root, stem and cotyledon (first leaves)

  3. Embryo draws on food source (endosperm) during early growth, then cotyledons produce food by photosynthesis