Transport in plants - Combined Science

• There are two types of vascular tissues:

  Xylem vessels & Phloem
• Phloem is a sieve tube cells (long tube of cells with lack of nuclei,cytoplasm and many mitochondria)which functioned to transport manufactured food (sucrose and amino acids from the leaves to other parts of the plant)
• Xylem is a hollow tube with these functions:

  Conducts water and dissolved mineral

  salts from the roots to the stem and leaves

  Provides mechanical support for the plant
• Vascular bundle is a combination of phloem and xylem with cambium in between.

  Cambium is young tissue to grow phloem and xylem.

  Pith and Cortex are for a place to storage the nutrients before it is distributed.

  Epidermis is for protection to te other structures of stem.
• The sap(water and minerals) in the root hair cell is

  more concentrated due to the presence of sugars and

  mineral salt; it has a lower water potential than the soil

  solution. Hence, water enters the root hair by osmosis

  (movement from high concentration of water).
• Transpiration is the loss of water vapour from plant

  leaves by evaporation of water at the surfaces of the

  mesophyll cells. Mesophyll cells are cells just under

  epidermis.

  
  

  Function:

  1. It gives a pull on the xylem to take water from the roots.
  2. Maintain the amount of water on plants.

  Transpiration is followed by diffusion of water

  vapour through the stomata so plants will not be

  dehydrated.
• Mineral salts are absorbed into root hair cells

  by:

  • Diffusion

  When the concentration of ions is higher in

  the soil solution than in the root hair cell, ions

  diffuse into the root hair cell.

  • Active transport

  When the concentration of ions is higher in

  the root hair cell than the soil solution, ions

  are taken into the cell with the use of energy.
• Calculating the rate of transpiration

  Rate of transpiration = Loss in mass (g)

  (g/h)/Time taken (h)

  Rate of transpiration = Loss in volume (cm3)

  (cm3/h)/Time taken (h)
• • Unicellular organisms and multicellular organism do not need a transport system for exchange or distribution of materials.
  • No part of the cell is far from environment outside.
  • Exchange of materials occurs easily by diffusion.