Lecture Notes: Structure and Function of Leaf Interiors

Overview

• Discusses the structure and function of leaves, particularly in relation to photosynthesis.
• Two major types of leaves: simple and compound.
• Leaves gather light for photosynthesis to produce sugars and carbon-rich compounds.

Leaf Structure

Waxy Cuticle

• Thin hydrophobic layer on the leaf surface.
• Reduces water loss via transpiration.
• Causes water to bead on the surface rather than soak in.

Upper Epidermis

• Tightly packed cells to prevent water loss.
• Translucent, allowing light to pass through.

Palisade Mesophyll (Palisade Parenchyma)

• Main site of photosynthesis.
• Tightly packed, column-shaped cells full of chloroplasts.
• Photons penetrate to strike chloroplasts.

Spongy Mesophyll (Spongy Parenchyma)

• Irregularly shaped cells with some chloroplasts.
• Allows gas exchange through intercellular spaces.

Vascular Bundle

• Contains xylem and phloem.
• Xylem: Transports water from roots (upwards).
• Phloem: Transports photosynthesis products (up and down).
• Bundle Sheath Cells: Aid in specialized photosynthesis in arid conditions.

Lower Epidermis

• Prevents water loss.
• Contains stomata for gas exchange.
• Stoma: Openings for CO2 in and O2 out, with guard cells to open/close.

Trichomes

• Hair-like structures on leaf surface.
• Deter herbivores and restrict insects.
• Some store terpenes, giving distinct smell and non-soluble in water.

Photosynthesis and Carbon Fixation

• Plants convert CO2 and water into glucose and oxygen using sunlight.
• Carbon fixation: Extract carbon from atmospheric CO2.
• C4 and CAM plants adapt to dry environments with modified photosynthesis.

Conclusion

• Understand the leaf structure through diagrams and cross-sections.
• Connect structures to photosynthesis reagents and products.
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