Organ for Water and Mineral Salts Uptake

3.2 Organ for Water and Mineral Salts Uptake
  1. Organ of mineral and water uptake in root.
  2. There are two main functions of roots:
    • Provide support and strength to anchor the plant in the soil
    • Absorb water and mineral salts from the soil and transport them to the stem and leaves

The structure of roots and their functions:

Structures Functions
Root hairs
  • Adapted from epidermal cells of the roots
  • Increases the total surface area of the roots to increase the uptake of water and mineral salts
Root cap
  • Located at the tip of the root
  • Protects the root from damage when going through the soi
Root adaptations of water and mineral salts uptake
Structures   Functions
  • Epidermal cells are closely arranged
  • Thin cell walls and water-permeable cell membranes facilitate water movement in the roots
  • There are epidermal cells which form root hairs by elongating towards lateral sides from the outer walls
  • Root hair cells are not layered with cuticle to allow water absorption
  • The root hair cells also have big vacuoles to store water and mineral salts to increase water absorption
  • Cortex is located under the epidermal layer
  • Has thin cell walls, facilitating water movement in the roots
  • The cells are loosely arranged to facilitate gaseous exchange
  • Most of the cortex consists of parenchyma cells
  • Separating layer between cortex and vascular cylinder
  • Endodermal cells are closely arranged and one cell thick
  • Most of the endodermal cells have suberin or lignin thickening at the walls which form Casparian strips
  • Endodermis allows water and mineral salts absorbed from the soil to enter the vascular cylinder, but not air bubbles
Vascular cylinder  
  • Vascular cylinder is the root core that consists of xylem and phloem tissues surrounded by one cell thick pericycle cell tissues
  • Pericycle is involved in secondary growth and the formation of lateral roots.
  • Usually, xylem and phloem tissues are arranged in a star-shaped pattern
  • Xylem tissue transports water and mineral salts, whereas phloem tissue transports organic substances such as sucrose and plant hormone.