Plant Vascular Tissue and Transpiration Notes

Vascular Tissues in Plants

• Vascular plants have tissues for transporting water and minerals.
• Non-vascular plants (e.g., moss) do not have these tissues.

Plant Organization

• Dermal tissue: Lines the outside of plants.
• Vascular tissue: Transports water and nutrients.
• Ground tissue: All other plant tissues.
• Root system: Roots.
• Shoot system: Leaves, stems, flowers, fruit.

Vascular Tissue Types

• Xylem: Transports water and minerals from roots to leaves (one-way).
  • Consists of dead tubes strengthened by lignin.
• Phloem: Transports sugars and nutrients in both directions.
  • Living tissue; transports products of photosynthesis.

Xylem vs Phloem

• Xylem: Transports water and minerals, one-way flow, no end walls, outer cells are not living.
• Phloem: Transports organic molecules, two-way flow, end walls (sieve plates), cells are living but need support

Transpiration

• Evaporation of water from leaves and movement up the xylem.
• Water vapor loss through stomata creates a suction force (transpiration pull).

Forces Allowing Water Movement

• Osmosis: Water moves into root cells from low to high solute concentration.
• Adhesion: Water attracted to xylem vessel walls.
• Cohesion: Water molecules attracted to each other.
• Transpiration stream: Continuous flow of water upwards due to evaporation.

Translocation

• Nutrient movement in the phloem from source (synthesis) to sink (storage).
• Occurs both up and down the plant.

Water Loss in Plants

• Most water loss occurs through stomata.
  • Stomata open: gas exchange, water loss.
  • Stomata closed: reduced gas exchange, reduced transpiration.

Factors Affecting Transpiration Rate

• Temperature: Higher temperature, more evaporation (↑).
• Light: High light, stomata open, increased CO2, increased transpiration (↑).
• Humidity: High humidity, less evaporation (↓).
• Wind: Removes humid layer, encourages evaporation (↑).
• Water availability: High availability, increased transpiration (↑).