chap 8- Transport in plants Flashcards
What is the function of the xylem?
- Water carried from roots to leaves in the xylem
- Transports water and minerals up the plant
What is the function of the phloem?
- Carries sugar from the leaves up and down rest of plant
How is a root hair cell adapted?
- Large surface area
o Increases rate of water absorption by osmosis
o Increases ion uptake by active transport
Describe the pathway of water in a plant
- Root hair cell
- Root cortex
- Xylem
- Mesophyll cells
How could you investigate the path of water in a plant?
- Cut a piece of celery
- Put in water
- Add stain (methylene blue or eosin)
- Wait a few hours and cut surface - dye appears in xylem
process of transpiration?
- Loss of water vapour from leaves by evaporation at surface of mesophyll cells
- Water vapour then diffuses through stomata
- Water loss related to large surface area of leaf
- Water evaporates in to air spaces in plant
- Water diffuses out of stomata down concentration gradient
- Loss of water at leaves reduces water potential
- Causes transpiration pull
- Column of water drawn up xylem, held by cohesion
What is wilting?
- Water loss exceeds uptake, cells go flaccid
Investigate effect of temperature and humidity on transpiration rate
- Use bubble podometer
- Connect plant to podometer with rubber tubing
- Record speed of air bubble in capillary tube (dependent variable)
- Vary temp or humidity as independent variables
- Increased humidity slows transpiration —> Decreases water potential gradient
- Increased temperature increase transpiration —> Increases water holding capacity of air
Describe and explain how rates of transpiration may be increased
- Hot - water evaporates faster
- Dry - increases the concentration gradient between the leaf and the surrounding air
- Windy - water is blown off the leaf increasing concentration gradient
Describe and explain how rates of transpiration may be decreased
- Cold - water evaporates slower
- Humid - small concentration gradient between the leaf and the surrounding air
- Still air - water is not removed from the surface of the leaf
Transpiration-
loss of water vapor from plant leaves by evaporation of water at the surface of the mesophyll cells followed by diffusion of water vapor through the stomata
Translocation
it is the movement of sucrose and amino acids in phloem from the regions of production (source) to the region of storage or the region where they are used in respiration or growth (sink).
