transpiration & translocation

• explain how 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 their 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
• explain how 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
• what is the xylem tissue made of

  it is composed of hollow tubes of dead 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

  it is made up of elongated cells which form long tubes
• what do we call the flow of cell sap through the phloem

  translocation
• in which direction(s) can cell sap move through the phloem

  cell sap can move either up or down the phloem
• what does transpiration mean

  transpiration refers to the evaporation of water from the leaves of plants
• which 4 factors affect the rate of transpiration

  • temperature
  • light intensity
  • humidity
  • 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 opens more (to let in carbon dioxide) -> more water can diffuse out
• explain how wind speed affects the rate of transpiration

  • transpiration increases with wind speed
  • the windier it is, the more quickly evaporated water will blow away from the area around the stomata
  • this means there will be a stronger concentration gradient for water vapour to diffuse out of the leaf
  • so water vapour will diffuse out moe quickly
• explain how humidity affects the rate of transpiration

  • transpiration decreases as humidity increases
  • the higher the humidity, the more water vapour there is in the air surrounding the leaf
  • this decreases the concentration gradient of water vapour between the inside and outside of the leaf
  • the lower concentration gradient means water vapour will diffuse out more slowly