AP Notes, Outlines, Study Guides, Vocabulary, Practice Exams and more!


root types - 2 types

  • taproot - enlarged radical root in most dicots
    • smaller lateral roots branch off
    • stores food, reaches for water deep underground
  • fibrous roots - mass of small roots, in most monocots
    • extensive, clings to soil
    • prevents erosion

root structure - split into 4 regions

  • root cap - made of inner columella cells, outer root cap cells
    • columella cells - function in perception of gravity
    • protects tissues behind it as it grows
    • golgi bodies secrete slimy substance to outside >> eases root through soil
    • constantly replaced by new cells
  • zone of cell division - where cells divide ever 12-36 hours
    • daughter cells of apical meristem
    • quiescent center - group of cells at the center of apical meristem, divides slowly
    • inner cell layer >> endodermis, intercellular flow of water
  • zone of elongation - cells from primary meristems elongate >> roots lengthen
    • small vacuoles merge/grow >> occupies 90% of cells’ volume
    • no more size increase beyond zone of elongation
  • zone of maturation - where cells become differentiated
    • root hairs form on each epidermal cell, only stays functional for a few days
    • cortex - made of parenchyma cells, functions as food storage
    • Casparian strips - bands of suberin (fatty substance) that blocks intercellular transport
    • pericycle - cylinder of parenchyma cells interior to the endodermis, becomes lateral roots or vascular cambium
    • primary xylem differentiated as solid core in center of roots
    • primary phloem differentiated as groups of cells
    • secondary tissues added >> primary tissues are replaced

modified roots - usually either taproot (single large root) or fibrous (many smaller roots) 

  • adventitious root - produced from anyplace other than the plant root
  • prop roots - grows from the lower stem to brace plants against the wind
  • aerial roots - extends into the air to prevent water loss
  • pneumatophores - spongy outgrowths formed by plants in swamps
  • contractile roots - roots spiral to pull plant deeper into the soil
  • parasitic roots - found in plants w/o chloroplasts
  • food storage roots - contains extra parenchyma cells
  • water storage roots - found in members of pumpkin family
  • buttress roots - in figs, tropical trees; provides stability at base of trunk
Subject X2: 

Need Help?

We hope your visit has been a productive one. If you're having any problems, or would like to give some feedback, we'd love to hear from you.

For general help, questions, and suggestions, try our dedicated support forums.

If you need to contact the Course-Notes.Org web experience team, please use our contact form.

Need Notes?

While we strive to provide the most comprehensive notes for as many high school textbooks as possible, there are certainly going to be some that we miss. Drop us a note and let us know which textbooks you need. Be sure to include which edition of the textbook you are using! If we see enough demand, we'll do whatever we can to get those notes up on the site for you!