Roots are the hidden half of most plants, but they are essential for survival. They anchor the plant in soil, absorb water and dissolved minerals, and often store food. A young root has specialized regions that divide, lengthen, and mature as it pushes through soil.
Understanding root structure helps explain how plants grow, survive drought, and support ecosystems.
Key Facts
- Water enters root hair cells mostly by osmosis, moving from higher water potential in soil to lower water potential inside the root.
- Mineral ions often enter root cells by active transport, which requires energy from ATP.
- The root cap protects the root tip as it grows through soil and helps the root sense gravity.
- The zone of cell division contains the apical meristem, where new root cells are made by mitosis.
- The zone of elongation lengthens the root as cells expand, pushing the root tip deeper into soil.
- The xylem carries water and minerals upward, while the phloem carries sugars to growing and storage tissues.
Vocabulary
- Root cap
- A protective layer of cells at the root tip that shields the growing meristem as the root pushes through soil.
- Apical meristem
- A region of actively dividing cells near the root tip that produces new root tissues.
- Root hair
- A thin extension of an epidermal cell that increases surface area for absorbing water and minerals.
- Xylem
- Vascular tissue that transports water and dissolved minerals from roots to the rest of the plant.
- Phloem
- Vascular tissue that transports sugars made by photosynthesis to roots and other plant parts.
Common Mistakes to Avoid
- Thinking roots absorb food from soil. This is wrong because plants make sugars by photosynthesis, while roots mainly absorb water and mineral ions.
- Labeling the root cap as the main absorption zone. This is wrong because most absorption occurs in the zone of maturation where root hairs are present.
- Confusing xylem and phloem functions. Xylem moves water and minerals upward, while phloem moves sugars between sources and sinks.
- Assuming root hairs are tiny roots. Root hairs are extensions of single epidermal cells, not separate organs with their own tissues.
Practice Questions
- 1 A root hair cell has a surface area of 0.020 mm2. If 5000 similar root hairs are active, what total absorbing surface area do they provide?
- 2 A young root grows 18 mm in 6 days. What is its average growth rate in mm per day?
- 3 Explain why a plant with damaged root hairs may wilt even if the soil is moist.