Plants 9.1 Transportation in the xylem of plants Flashcards Preview

Biology 9. Plants > Plants 9.1 Transportation in the xylem of plants > Flashcards

Flashcards in Plants 9.1 Transportation in the xylem of plants Deck (51)
Loading flashcards...

What is Transpiration

Transpiration is the loss of water vapour from the leaf/stomata as an inevitable consquence of gas exchange in the leaf


What is a primary organ of photosynthesis?

Plant leafs


What must be involved to sustain photosynthesis?

Exchange of two gases (CO2 and Oxygen as waste) as carbon dioxide is essential


What the problem with plants and their stomota?

if stomota allow carbon dioxide to be absorbed, they will also allow water vapour to escape


What is stomata?

These are pores in the epidermis


Why are stomata so important?

Because the waxy cuticles of plant leaves are not permeable (do not allow much water to pass through) pores are needed known as stomata


How do plants minimize water loss through the stoma?

Guard cells (on either side of a stoma)


What is the role of a guard cell?

Found in pairs, can controle the aperture of stoma and adjust from wide open to closed (to minimize water loss of leaf)


What is an exception of plants where stomata are not found?



Why can gases not be exchanged on the surface of leafs without stomata?

the epidermis and waxy cuticle are impermeable to carbon dioxide and water


What causes a stoma to close?

  • water shortage, where the hormone absistic acid is produced, forcing closure to prevent dehydration
  • darkness


What happens to leaves in hot weather?

guard cells in the lower epidermis become flaccid which closes the stomata to prevent excessive water loss


What happens when leaves are well hydrated?

  • Guard cells remain turgid 
  • Opens Stomata 
  • water vapour diffuse out of leaf (transpiration)
  • carbon dioxide diffuses into the leaf (photosynthesis


What are xylem vessels?

Long/thin and hollow continues tubes in plants.

Their walls are contain cellulose and a polymer called lignin that makes them rigid, and able to withstand low pressures without collapsing.


How are xylem vessels formed?

files of cells where cell wall material is largely removed (most do not have plasma membrane)

Mature cells are nonliving so water movement is passive


Is pressure inside xylem vessels lower or higher than atmospheric?

Much lower pressure but does not collapse because of rigid structure


How can water be pulled up from the xylem in a continuous stream?


  • hydrogen bonds in water (polar intermolecular attraction) keep water molecules sticking together 


  • water is attracted to hydrophilic parts of xylem 

The connection between molecules pulls water up in continous stream


What does adhesion cause when water evaporates from surface of leaf?

Adhesion causes water to be drawn through cell wall from nearest available supply which is the xylem vessel (to replace water lost from evaporation)


What reduces pressure in the xylem?

When water is sucked out of the xylem even though pressure may already be low, but force of adhesion between water and cell walls are still strong enough


What is transpiration-pull?

A pulling force is generated by the low pressure that is transmitted through the water in the xylem vessels down the stem.

This is strong enough to move water upwards  


What is cavitation?

When the liquid is unable to resist the low pressures in the xylem vessels and the column of liquid would break(it can even happen to water)


How is water absorbed into root cells?


  • solute concentration is higher inside root cell than in soil


What are most solutes in root cells/soils?

Mineral ions


How/Why does osmosis occur between root cells and soils?

  • concentration gradients of mineral ions between root cells and soils created by active transport
  • using protein pumps in plasma membranes of root cells
  • separate pumps for type of ion that plant requires (ions can only be absorbed with speicifc protein)


Why do some ions move through soils slowly?

ions bind to surface of soil particles


How do overcome their slow movement through soil?

certain plants developed relationship with fungus

  • fungus grows on surface of roots (sometimes into cells)
  • the hyphae of gungus grow out into soil and absorb mineral ions from surface of soil
  • ions are then supplied to roots

allows plants to grow in mineral deficient soils


What is an example of plant that recieves its mineral ions through fungus?

Heather family and orchids


If fungus provides mineral ions to the plants, and plants provide sugars to the fungus, what is this relationship called?

mutalistic relationship


Describe 3 ways in which terrestial plants support themselves

  • cellulose in cell wall around all plant cells (give strength, support and shape)
  • osmosis ensures all plants to be hydrated, creating turgor pressure
  • rings of lignin inside the xylm vessels provide strength 


What 3 factors can affect transpiration in terrestial plant?

  • light intensity
  • humidity
  • temperature
  • wind

all affect