Chapter 9- Plant Bio Flashcards
Transpiration
The loss of water vapour from the leaves and stems of plants
Stomata formed from?
2 specialized guard cells.
When it’s light what happens to the stoma and why?
It opens because plant need carbon dioxide to photosynthesise.
At night what happens to the stoma and why?
It closes to prevent excessive water loss! Don’t photosynthesise at night (cuz there’s no light!)
The active process of drawing water into the stomata
Protein pumps (K+ ion pumps) in guard cell membrane = accelerates opening of the stomata by pumping in ions
* reduces the water potential
therefore water enters
Abiotic factors influencing Transpiration
- Lots of stomata allows more transpiration than less big ones
- Wind blows away evaporated water = reduces humidity around stomata
(Evaporation is more difficult in higher humidity, as air is more saturated with water) - Hotter temps = cause more evap = more transpiration
- More light = stimulates stomata opening and leaf warming
Characteristic of Xylem
- Hollow dead cells joined end-end
- continuous tubes (narrow) = strengthened with lignin (polymer)
- Rigid structure = prevents them from collapsing under low-pressure
- Pits in the wall = allows movement across
- No cell content, no nucleus, no cytoplasm, no end wall!
Xylem only function when they’re___?
dead
Cohesion of water, and what it allows to happen in plants?
When one water molecule is attracted by other ones by Hydrogen bonding.
Allows water to be pulled up from the xylem in a continuous stream.
Adhesion of water, and what it allows to happen in plants?
When water = attracted to hydrophilic parts of cell walls of xylem.
Causes water to be drawn through the cell wall from the nearest available supply to replace water loss from evap.
Adhesive property and evap, generates what?
Tension force in the leaf cell wall.
Transpiration pull is caused by?
The low pressure, generating a pulling force that goes up from the roots through the xylem.
*Strong enough to move water upwards, against the force of gravity.
Is transpiration passive or active?
PASSIVE. With all the energy needed coming from the thermal energy that causes transpiration.
What does the active process of minerals in roots cause?
Absorption of water by OSMOSIS.
Where is the vascular bundle in the roots, and why is it in that position?
In the middle = to support the root and prevent it from being pulled out.
Where is the vascular bundle in the stem, and why is it in that position?
Scattered = cuz the stem needs to be able to bend.
Is the concentration of mineral ions in soil or roots higher?
Roots (can be up to 100x higher!)
How do the minerals (positively charged so stick onto soil) that are stuck onto soil particles (negatively charged) taken into plants?
+ Root hairs pump out H+ ions to knock out (displaces) the minerals stuck onto the soil particles.
+ so that the plants can suck the minerals up through the roots through PUMP PROTEIN.
Symplastic pathway
When water moves from Cytoplasm - Cytoplasm
* Through the PLASMODESMATA (holes in the cellulose wall to make cytoplasm continuous!)
Apoplastic pathway
When water moves by capillary through CELLULOSE CELL WALL.
* Cohesion occurs between water molecules also adhere to cellulose fibres.
