Transpiration Flashcards
(19 cards)
Why is water required structuraly
Maintain structural turbidity
Enables cells to stand upright
Why is water required in plants
Photosynthesis
To transport minerals as a solvent
Regulates temperature
How are water and minerals obtained by plants
- absorbed from soil by osmosis + moves up stem from roots to leaves
- mineral ions absorbed by active transport from the soil (inc nitrates and phosphates) are dissolved in water
What do plants need nitrogen for
- production of new cells amd enzymes (amino acids —> proteins—> enzymes —> hormones)
- DNA
-chlorophyll production - helps with rapid growth
How do plants use Phosphorus
- atp
- phospholipids bilayer
- needed for photosynthesis
-encourages root growth and blooming
How do plants use potassium
- encourages uptake of water
- essential in the development of flowers and fruits
- increases plants resistance to disease
How do plants use magnesium
Chlorophyll
Features of xylem
Elongated tube formed of dead cells called vessel elements joined together in bundles
No end wall between cells
Thick walls made of lignin - strength and waterproof
Gaps in cell wall- allows water to be pushed out due to high hydrostatic pressure
How does water potential drive transpiration
- water movement up a plant increases as the transpiration rate increases
-waste evaporates from the spaces between cells in the leaf through the stomata, it moves down the water potential gradient so for water to leave through the stomata there was to be less water in the atmosphere then the leaf
How does light intensity effect rate of transpiration
Describe graph
Stomata open when it is light to let in CO2 for photosynthesis. When it is dark no photosynthesis is happening so the stomata close
Little transpiration happens at night
Steady increase then plateau due to limiting factors
How does temperature affect the rate of transpiration
Describe graph
In warmer conditions water particles have more kinetic energy so they are able to evaporate from the surface of the leaf faster, this increases the WP gradient inside and outside of the leaf so more transpiration occurs
Steady increase then plateau due to limiting factors
How does wind speed affect rate of transpiration
Describe graph
Lots of wind blows water molecules away from the stomata increasing the WP gradient and therefore increasing the transpiration rate
Starts further up then zero on y axis. Sharp increases for about 1cm them steady increase
How does humidity affect rate of transpiration
Describe the graph
If the air around the plants is dry the WP gradient is increased so transpiration occurs faster
In humid environments the WP gradient is reduced as there is a lot more water in the atmosphere so the rate of transpiration decreases
Small amount of plateau then steady decrease then plateau
Conditions for high transpiration rate
Wind movement
Low humidity
High temp
High light intensity
Conditions for low transpiration rate
Low wind movement
High humidity
Low temp
Low light intensity
Evidence to support cohesion tension theory
Day time
- transpiration is at its greatest
- adhesion of water molecules to walls of xylem results in tension.
- pulling in walls, diameter decreases
Night
-transpiration at its lowest
- less water, less tension so diameter of trunks increases
What occurs if a xylem is damaged
Water doesn’t leak out
Air enters and tree can no longer draw up water as continuous column has been broken
Considerations when using a photometer
Shoot must be cut underwater amd on an angle
End of capillary tube must stay submerged in water and apparatus must be air amd water right
Diameter of capillary tube should be known
Leaves must be dry amd plant allowed to acclimatise ( start transpiring) before experiment started
How to measure the rate of transpiration
Ensure air bubble is formed at the end of the capillary tube
Record start point (position can be pushed back by emptying water from the resivoir
Record time taken for bubble to move a certain distance
Rate = distance per unit time
