Structure of Roots, Stems, and Leaves

Rucete ✏ Biology In a Nutshell

1. Structure of Roots

a) Cortex

• Makes up the bulk of the root
• Main function: storage of starch

b) Epidermis

• Produces root hairs
• Increases absorptive surface area

c) Endodermis

• Wrapped with the Casparian strip
• Controls selective movement of water and minerals

d) Vascular Cylinder (Stele)

• Contains xylem and phloem for transport

2. Structure of Stems

a) Basic Structure

• Epidermis (with cuticle)
• Cortex (ground tissue)
• Vascular cylinder: xylem, phloem, pith

b) Vascular Cambium

• Produces secondary xylem and phloem
• Runs the length of the plant

c) Cork Cambium

• Produces protective covering that replaces epidermis during secondary growth

d) Vascular Bundles

• Dicots: bundles arranged in a ring
• Monocots: bundles are scattered

3. Structure of Leaves

a) Epidermis

• Covered with a cuticle for protection
• Contains upper and lower epidermis

b) Palisade Mesophyll

• Composed of parenchyma cells with many chloroplasts
• Main site of photosynthesis

c) Spongy Mesophyll

• Loosely arranged cells that allow gas exchange (CO₂, O₂)

d) Vascular Bundles (Veins)

• Xylem: delivers water for photosynthesis
• Phloem: transports sugars produced in photosynthesis

e) Bundle Sheath Cells (in C₄ Plants)

• Surround the veins
• Site of CO₂ fixation in hot, dry environments

f) Stomata

• Pores controlled by guard cells
• Allow CO₂ in, and O₂ and H₂O out