asexual reproduction - results in genetically identical offspring

• self-pollination still generates genetic variability
• found in unchanging environments >> plant less likely to survive if environment suddenly changes
  • most asexual plants found in harsh environments
• vegetative reproduction - new plants cloned from parts of adults
  • runners - long stems growing along the soil surface, new shoot grows from each 2nd node
  • rhizomes - underground horizontal stems, new shoot can grow from each node
  • suckers - sprouts from roots that can become new plants
  • adventitious plantlets - reproductive leaves
• apomixes - seeds produced asexually from parent
  • requires seed dispersal

plant tissue culture - cloning plants from tissues w/ growth hormones

• cell wall removed >> protoplast (plant cell enclosed only by plasma membrane)
• protoplasts can fuse >> create hybrids (form of genetic engineering)
• cell wall can regenerate

plant life span - age dependent on species

• annual plants - grow, flower, form fruits/seeds within a growing season
  • includes most crop plants
  • almost entirely herbaceous (non-woody)
  • starves itself to death after flowering (senescence)
• biennial plants - 2 year life cycles, only flowers once
  • stores photosynthate underground during 1st year
  • flowering stems produced in 2nd year using energy from underground storages
  • mostly harvested for roots (carrots, beets, cabbage)
• perennial plants - herbaceous/woody, continues to grow yearly
  • majority of vascular plants
  • trees either deciduous (leaves fall once a year) or evergreen (plants never bare)
• abscission - process by which leaves/petals are shed
  • gets rid of unproductive parts
  • takes place in abscission zone at base of petiole
  • protective layer filled w/ suberin (fat) on stem side of petiole
  • separation layer develops on leaf side of petiole >> weakened connections between stem/leaf