Bi 103 Notes: Chapter 25: Plant Reproduction and Development

  1. Plant Reproduction: Alternation of Generations

      A. Plants can use either Sexual or Asexual reproduction

      B. Alternation of generations

                  1. Diploid sporophyte

                  2. Haploid gametophyte (in angiosperms, this stage does not live independently)

  1. Flower Structure

      A. Purpose is to attract pollinators (flowers are modified leaves)

                  1. Nectar: Attractant, Petals, etc:=Flashy advertisement

      B. Parts of a complete flower

                  1. Sepals         2. Petals          3. Stamens     4. Carpels

      C. Pollen  (Male Gametophyte) development (all inside the flower in angiosperms!)

                  1. Pollen sac with microspore mother cells (2n)

                  2. Produce microspores (1n)à Pollen grains

      D. Embryo sac (female gametophyte) development

                  1. Ovules in ovary

                  2. Includes integuments and Megaspore mother cell

                  3. Meiosis produces megaspores

                  4. Megaspore divides (mitosis) to form embryosac: egg cell, central cell                

  1. Pollination and fertilization

      A. Steps

                  1. Pollen lands on stigma (pollination)

                  2. Tube cell from pollen grows to ovule

                  3. 2 Sperm travel in tube cell (Double Ferilization)

                              a. one fertilizes egg, other fertilizes central cellà 3n Endosperm

  1. Seed/Fruit Development

      A. Steps

                  1. Fruit develops

                              a. integuments form seed coat

                              b. Zygote develops

                                          1. Dicocots absorb all endosperm

                                          2. Monocots partially absorb endosperm

                              c. Fruit body = ovary wall

  1. Germination

      A. Seeds stay dormant until germination is signaled by

                  1. Drying          2. Cold             3. Seed coat disruption

      B. Germination events

                  1. Roots emerge

                  2. Shoots push to surface (monocots – coleoptile, dicots- hypocotyls)

                  3. Cotyledons nourish sprouting seed

  1. Adaptations for pollination: Coevolution between Flowers and pollinators

      A. Benefits flowers offer pollinators

                  1. Food source in nectar/pollen

                  2. Resemblance to insect appearance/odor: orchids

                  3. Nurseries: Yucca moth and Yucca

  1. Seed dispersal: make sure offspring and parents don’t compete

      A. Approaches

                  1. Shotgun dispersal: explosive

                  2. Wind dispersal: lightweight

                  3. Water dispersal: hollow

                  4. Animal dispersal: colorful/sweet