Water/Mineral Uptake

• Xylem:

  Transports? Water and dissolved minerals

  Typically larger or smaller than the phloem? Larger

  Xylem vessel is made up of dead or alive cells? Dead

  What break down the end wall? Ezymes

  Forming what? Continuous pipes

  This means the cells lose what? Nuclei and organelles
• Phloem:

  Transports? Sugars made by photosynthesis

  Transports from? Leaves

  Phloem is made up or dead or alive cells? Alive

  What are the tubes in the phloem called? Sieve tubes

  What cells are found alongside these tubes? Companion cells

  What do these cells do? Load and unload the tubes
• Water uptake:

  Where does water enter? Root hairs extensions

  Of the what? Epidermis

  They are extremely fine and increase the surface area of the root that is in contact with soil and water
• Root cell membranes are?

  Semi-permeable

  Water is drawn into root hairs via? Osmosis (water moving from a high concentration to a low concentration)
• What is central region of a plant root (the inner circle containing endodermis, xylem, phloem and pericycle) called?

  Vascular stele
• How does water get to the central pipes in the root?

  Travels through or between the epidermis and the cortex

  What are the 2 ways it can do this?

  Extracellularly or intracellularly
• What regulates water uptake?

  The Casparian strip

  Where is this located?

  Between endodermal cells
• Intercellular route:

  Water travels via?

  Cell interiors

  The water passes through special passages in the cell wall and membrane called?

  Plasmodesmata
• Extracellular route:

  Water travels via?

  Cell walls

  What is the water stopped by?

  The Casparian strip
• Water movement:

  Water molecules exhibit both cohesion and adhesion

  Adhesion to the cell wall causes it to rise up

  Cohesion causes the whole liquid surface to be drawn up with it
• Transpiration:

  The loss of water via the stomatal pores on the surface of a leaf. This is known as diffusion.

  However, the plant must keep stomata open for carbon dioxide
• Influencing the opening/closing of stomata:

  What are responsible for the opening and closing of stomata?

  Guard cells

  Does the uptake of potassium cations stimulate them to open or close the stomata?

  Open

  Examples of factors influencing opening/closing stomata:

  sunlight=open

  Low carbon dioxide level= open

  Biological clock= open in day, close at night

  Loss of too much water= close
• How is water transported up tall trees?

  A force is generated by transpiration, creating tension in the xylem water column, therefore the water is drawn up the tree

  (like drinking through a straw)
• Plants absorb nutrients in inorganic form.

  For example potassium as K+, nitrogen as NO3- and calcium as Ca2+