Transpiration + translocation

• How do root hair cells absorb water from the soil?

  Osmosis. There is a higher concentration of water in the soil than in the root hair cell, so water will diffuse in by osmosis.
• How do root hair cells absorb mineral ions from the soil?

  Active transport There is a lower concentration of mineral ions in the soil than in the root hair cells, so active transport is required to absorb them against they concentration gradient.
• What is the role of the xylem tissue?

  Xylem tissue transports water and mineral ions from the roots to the stem and leaves.
• What is the xylem tissue made of?

  It is composed of hollow tubes of deal cells, strengthened by lignin.
• What do we call the flow of water molecules that pass through the xylem?

  The transpiration stream.
• In which direction(s) can water move through the xylem?

  Water can only move up the plant through the xylem.
• What is the role of the phloem tissue?

  Phloem tissue transports dissolved sugars and amino acids (cell sap) from the leaves to the rest of the plant for immediate use or storage.
• What is the phloem tissue made of?

  Elongated cells which for long tubes.
• What do we call the flow of cell sap through a plant?

  Translocation.
• In which direction(s) can cell sap move through the phloem?

  Cell sap cam move either up or down the phloem.
• Transpiration: The evaporation of water from the leaves of plants.
• Which 4 factors affect transpiration?

  1. Temperature.
  2. Light intensity.
  3. Humidity.
  4. Wind speed (air flow).
• Explain how temperature affects the rate of transpiration.

  Transpiration increases with temperature.

  Higher temperature --> higher energy particles --> more likely to evaporate and diffuse out of the stomata.
• Explain how light intensity affects the rate of transpiration.

  Transpiration increases with light intensity.

  Higher light intensity --> more photosynthesis --> stomata open more (to let carbon dioxide in) --> more water can diffuse out.
• Explain how wind speed affects the rate of transpiration.

  Transpiration increases with wind speed.

  1. The windier it is, the more quickly evaporated water will blow away from the area around the stomata.
  2. This means there will be a stronger concentration gradient form water vapour to diffuse out of the leaf.
  3. So water vapour will diffuse out more quickly.
• Explain how humidity affects the rate or transpiration.

  Transpiration decreases as humidity increases.

  1. The higher the humidity, the more water vapour there is in the air surrounding the leaf.
  2. This decreases the concentration gradient of water vapour between the inside and outside of the leaf.
  3. The lower the concentration gradient means water vapour will diffuse out more slowly.