Integrative Physiology and Ecology Lecture 1 Summary
Plant Evolution and Anatomy
- Land plants evolved from aquatic ancestors.
- Major challenges: Acquiring CO₂ and preventing water loss.
- Structures: Waxy cuticle and stomata regulate gas exchange.
- Xylem transports water; Phloem transports carbohydrates.
Photosynthesis and Water Loss
- Leaves are primary site for photosynthesis; thin structure aids access to light and CO₂
- CO₂ uptake leads to water loss (transpiration).
- Plants require water for growth despite minimal use in photosynthesis.
Leaf Structure and Function
- Key tissues in leaves:
- Epidermis: Protective outer layer.
- Mesophyll: Photosynthetic cells.
- Veins: Vascular system linking leaf to plant.
- Stomata provide gas exchange but also cause water loss.
Guard Cells and Stomata Control
- Guard cells regulate stomata opening/closing based on:
- Light conditions
- Internal CO₂ levels
- Water availability
- Osmosis influences guard cell volume.
- CAM plants store CO₂ at night to reduce water loss during the day.
- Adaptation found in desert plants; enhances water-use efficiency.
C4 Photosynthesis
- C4 plants concentrate CO₂ in bundle-sheath cells to minimize photorespiration.
- Photosynthesis occurs in different cells compared to C3 plants.
- Results in reduced O₂ competition for Rubisco, improving efficiency in hot environments.
Vascular Tissue
- Xylem: Water and nutrient transport; structure includes lignified, hollow vessels.
- Phloem: Transport carbohydrates and signaling substances; operates via turgor pressure.
Roots and Nutrient Uptake
- Roots enhance nutrient absorption through root hairs and extensive surface area.
- Endodermis regulates nutrient movement to xylem via a Casparian strip.
Plant Nutrients and Symbioses
- Mineral nutrients essential for plant growth; include nitrogen, phosphorus, potassium, etc.
- Mycorrhizae: Fungal associations enhance nutrient uptake.
- Symbiotic bacteria fix atmospheric nitrogen, making it bioavailable for plants.