Plant transport gas exhange

• Describe the role of phloem in transporting sucrose and amino acids between the leaves and other parts of the plant?

  Phloem transports sucrose and amino acids up and down the plant

  - cells are living but need support

  - there is 2 way movement

  - they have end walls (sieve plates)

  - they have organic molecules
• Describe the role of xylem in transporting water and mineral ions from the roots to other parts of the plant?

  The xylem vessels are the dead cells that are stacked end to end. They form a tube-like structure and are responsible for the transportation of water and dissolved minerals.

  - no end between cells

  - one way only

  - outer cells are dead
• How is water absorbed by a root hair cell?

  Plants absorb water from the soil by osmosis

  - osmosis= the net movement of water particles from an area of higher concentration to lower across a partial permeable membrane

  - Root hair cells are adapted for taking up water and mineral ions by having a large surface area to increase the rate of absorption.
• What is transpiration?


  The evaporation of water from plant leaves

  
  

  Transpiration also cools plants, changes osmotic pressure of cells, and enables mass flow of mineral nutrients
• What affects the rate of transpiration?

  - humidity= humid air near the leaf lowers the concentration gradient of the water vapour

  - light intensity= more stomata are open in the light so more water vapour is lost

  - temperature= higher temperatures cause more evaporation so more water vapour is lost

  - wind= higher wind speed blows humid air away from the leaf, increasing the concentration gradient of the water vapour
• What causes the change in the appearance of the plant after 24 hours?


  Water loss is greater than water uptake.
• Which process is an example of translocation?


  Movement of sucrose from the leaves through phloem to other parts of the plant.
• By which process is water lost from a leaf?

  Diffusion
• Which process transports sucrose from the leaves to the flowers of a plant?

  Translocation
• What is transported in the phloem?


  Sucrose
• In which direction is sucrose transported in the phloem?


  Up and down
• In which order does water pass through the cells of a plant from the roots to a leaf?

  Root hair → root cortex → xylem → mesophyll cells
• What environmental change could cause a change in the appearance of a plant shoot after six hours?


  A decrease in available water
• What is found at Q in the cross-section of a plant root that is stained red?

  Xylem
• What produces a continuous space for the flow of water in xylem vessels?


  Continuous columns of water due to cohesion and adhesion
• What is present in the liquid collected from the xylem in the stem of a plant?


  Inorganic ions
• What is a primary function of phloem?


  Translocation
• What effect does removing the bark from a tree have on the branches?

  It disrupts the transport of nutrients to the lower branch.
• Which plant will have the highest rate of transpiration under the same environmental conditions?


  The plant with the largest leaf surface area.
• A decrease in which factor normally causes the transpiration rate to increase?


  Humidity
• What is the path of water through a plant?

  Roots → root hair → xylem → mesophyll cells → stomata
• In which order does water pass through these tissues in a plant?

  Root cortex → xylem → mesophyll