Table of Contents

1.1 What are Roots?
1.2 Function of Roots
1.3 Types of Roots
1.4 Structure of Roots
1.5 Root Specializations
1.6 Human Uses
1.7 Interesting Facts
1.8 Gloissary
1.9 Mini Quiz

1.1 What are Roots?
Roots are the lower part of the plant that are usually underground that provide a solid anchor for the plant and transfer water and nutrients from the soil to the plant.

1.2 Function of Roots
The first main job that roots have are to "anchor" the plant and keep it upright. The second main job is to absorb water, nutrients except carbohydrates. Carbohydrates are produced during photosynthesis. Some roots store water and carbohydrates for the rest of the plant.

1.3 Types of Roots
There are two basic types of roots:
Figure 1 & Figure 2
Figure 1 & Figure 2

  • A taproot has a large, main root, which grows straight downwards (Figure 1).This root can also have lateral root that branch off of it. Both taproots and lateral roots are covered with "hairs" that are called root hairs. A root hair is a tiny hair-like outgrowth from an epidermal cell. Taproots are able to push deep down into the soil. Gymnosperms and angiosperms both have taproots.

  • A fibrous root has many small roots (Figure 2). Each of the roots have lateral roots branching off of them also. Just like taproots, fibrous roots have root hairs too. Fibrous roots tend to not go as deep into the soil as apposed to taproots which go very deep. Fibrous roots occur in angiosperms.

1.4 Structure of Roots

All roots have the same general structure. (Figure 3)
  • The root capis a thick layer of cells that produce a slippery substance that helps the too to penetrate the soil, minimizing the damage to the root.
  • The meristem produces new cells to increas the length of the root.
  • The root hairsdramatically increas the surface area of the epidermis allowing the root to absorb more water and dissolved nutrients.
  • The root cortexis the part of the parenchyma cells underneath the epidermis layer of the root.
  • The root cortex cells store carbohydrates and help transport water from the epidermis to the xylem.
  • The root cortex stretches out all the way to the endodermis.
  • The walls of the endodermis are covered in a wax-like substance called the Casparian Strip. (Figure 4)
  • Vascular tissue of the roots is contained in the vascular cylinder
Figure 3
Figure 3

  • Figure 4
    Figure 4










1.5 Root Specializations
Figure 5
Figure 5

  • May help roots to more efficiently absorb water and nutrients, anchor the plant, or store carbohydrates.
  • Different specializations protect the plant root from being eaten.
  • Lateral roots modified for storage are called tuberous roots. Ex. Yams, cassava and sweet potatoes are tuberous roots that are important for our food supply (Figure 5)
  • Roots that store carbs have a higher risk of being eaten by other organisms, so some roots produce chemicals to reduce that risk.
  • Some roots produces chemicals to harm other roots. Ex. Black walnut and the common Reed
    Figure 6
    Figure 6
  • An adventitious root is any root that doesn't grow from the root apical meristem that emerges from the seed after it starts to grow. (Figure 6)

1.6 Human Uses
  • Many of the vegetables we eat are roots including, parsnips, turnips, beets, taro, and sweet potatoes.
  • Roots can alsp be used in drinks. Ex. root beer was originally made from sassafras root
  • The roots of some plants also have medicinal uses. Ex.Ipecac (substance that will rapidly induce vomiting)
  • Kava kava root has been shown to reduce anxiety.
  • The valerian root is a common garden plant the produces a mild sedative that can be used to relieve insomnia
    Root Beer
    Root Beer
1.7 Interesting Facts
  1. Roots are delicious when boiled or pickled. The roots of the South African wild fig treecan grow 120 m down into the ground.
  2. Root beer was originally made from the root of the Sassafras plant.

1.8 Glossary

Adventitious Root: A root that develops from somewhere other than the root apical meristem that emerges from the seed.
Angiosperms: A plant that produces flowers; angiosperms form the argest group of living plants.
Casparian Strip: A wax-like strip that runs through the cell wall of an endodermal cell.
Endodermis: The innermost layer of cells in the cotex of a root.
Fibrous Root: A root made up of many small, brnaching roots.
Gymnosperms: A vascular plant that produces seeds in special structures called cones.
Lateral Root: A smaller root that branches off from a larger root.
Root Cap: The mass of cells that for a protective covering for the meristem
Root Cortex: A region of the parenchyma cells under the epidermis of a root.
Root Hair: A microscopic extension of the epidermal cells of the root.
Taproot: A root composed of a large, thick root; can have smaller lateral roots.
Tuberous Root: A lateral root specialized to store carbohydrates.
Vascular Cylinder: A central portion of a root that contains the xylem and the phloem.

1.9 Mini Quiz

  1. What are the functions of a root?
  2. What are the two types of roots?
  3. What is one human use of plant roots?
  4. Which of these is a root specialization?

Answers
  1. sʇuǝıɹʇnu puɐ ɹǝʇɐʍ qɹosqɐ 'ʇuɐld ǝɥʇ ɹoɥɔuɐ
  2. snoɹqıɟ puɐ ʇooɹdɐʇ
  3. ǝuıɔıpǝɯ ǝʇɐǝɹɔ

References

Dulson J, Fraser D, LeDrew B, Vavitsas A. Biology 11. University Preparation. Toronto: Nelson; 558-561p