Chapter 10 Plants Reproduction and Growth

• Asexual reproduction


  The production of new individuals / offspring whose genes all come from one parent, without fusion of egg and sperm, relying entirely on mitotic cell division
• All progeny are genetically identical to parent and to each other
• Types of asexual reproduction in plants

  • Apomixis
  • Natural vegetative propagation
  • Artificial vegetative propagation
  • Sporulation
  • Binary fission
• Apomixis


  A form of asexual reproduction in plant in which seeds are produced without pollination or fertilization
• Apomixis


  1. A diploid cell in the ovule gives rise to an embryo

  2. The ovules mature into seeds, which are dispersed
• Advantage of apomixis


  • The seeds and fruits produced by apomixis can be dispersed by methods associated with sexual reproduction
• Plants that exhibit apomixis


  • Some citruses
  • Certain grasses (such as Kentucky bluegrass)
  • Dandelions

  
• Vegetative propagation


  A form of asexual reproduction in plant in which new plants are produced from vegetative parts of parent plants, without producing an embryo
• Vegetative propagation


  1. Fragmentation & regeneration of a plant part (e.g. stem, leaves) to grow into a whole new plant

  2. Growth of specialised vegetative (non-sexual) plant parts (e.g.: bulbs, runners, and tubers)
• Vegetative propagation can occur naturally or artificially
• Natural fragmentation


  • Small parts of a plant (e.g. liverwort stems or leaves) fall off and grow into clones of the parent plant
• Artificial fragmentation


  • A gardener taking a cutting (stem or leaves) from a plant
• Vegetative structures involved in propagation

  • Bulbs
  • Rhizome
  • Runner / stolon
  • Stem tubers & Root tubers
  • Tap root
  • Corm
  • Suckers
  • Leaves
  • Stem
• Bulbs


  Thick and short underground stems for food storage
• Rhizome


  Horizontal underground stems for food storage
• Runners/stolon


  Horizontal stems that grow along the surface of the ground
• Tap roots


  Swollen food-storing tap roots
• Tubers


  Enlarged/ swollen ends of horizontal underground stems (stem tubers) or adventitious roots (root tubers)
• Corm


  Vertical underground stem
• Leaves


  Have buds at the edge of leaves
• Suckers


  Young shoots that arise from underground stem / root
• Methods of artificial vegetative propagation

  • Cuttings
  • Layering
  • Grafting
  • Micro-propagation / Test tube cloning (by tissue culture method)
• Cutting


  A vegetative part (e.g. stem, root or leaf) of a plant is cut and planted in the soil, along with some nutrients, to develop into a new plant
• Types of cuttings


  • Stem cuttings (e.g. sugar cane, Duranta, Colues, rose, china-rose)
  • Root cuttings (e.g. tamarind, lemon)
  • Leaf cuttings (e.g. Peperomia, Begonia, African violets)
• Micro-propagation / Test tube cloning

  1. A small piece of tissue is excised from a plant and is grown in a nutrient medium under aseptic conditions to proliferate into an undifferentiated callus

  2. Portions of the callus tissue are transferred to another medium with specific hormones to induce differentiation of plantlets

  3. The plantlets are transplanted in pots or soil and raised to maturity
• Plants propagated by micro-propagation


  • Orchids
• Advantages of vegetative propagation

  • For propagation of plant that produce little or no viable seeds
  • To provide consistent quality without variation
  • Helps plant spread
  • Enables survival following damage to parent tree (disease, burning, felling)
• Disadvantages of vegetative propagation

  • More susceptible to diseases as the entire plant may get affected as there is no genetic variation
  • No new varieties can be produced
• Sexual reproduction


  Production of new individuals/offspring by the fusion of egg and sperm (involve fertilization between male and female gametes) to form a zygote
• Sexual reproduction results in offspring genetically different from the parents
• Main groups of seed-producing plants

  • Angiosperms
  • Gymnosperms
• Angiosperms


  Also called flowering plants, have seeds that are enclosed within an ovary (usually a fruit), rely on animals for pollination, the vast majority of plants in the world
• Gymnosperms


  Have no flowers or fruits, but they have unenclosed or "naked" seeds on the surface of scales or leaves, rely on wind for pollination, evergreens (pines, cedars, and spruces)
• Pollination


  Enables gametes to come together within a flower
• Angiosperm reproduction


  The dominant sporophyte (embryo) produces spores that develop within flowers into male gametophytes (pollen grains) and female gametophytes (embryo sacs)
• Flower


  The reproductive shoots of the angiosperm sporophyte, composed of four floral organs: sepals, petals, stamens, and carpels
• Floral symmetry variations


  • Bilateral symmetry (e.g. orchid)
  • Radial symmetry (e.g. daffodil)
• Ovary location variations


  • Superior ovary
  • Semi-inferior ovary
  • Inferior ovary
• Floral distribution variations


  • Lupine inflorescence
  • Sunflower inflorescence
  • Maize (monoecious)
  • Sagittaria latifolia (dioecious)
• Flower terminology


  • Complete
  • Incomplete
  • Perfect
  • Imperfect
  • Monoecious
  • Dioecious
  • Synoecious
  • Polygamous