9 TRANSPIRATION + TRANSLOCATION Flashcards
How is the xylem specialised for transporting water and mineral ions from the roots to the leaves
- Cell wall contrains lignin - waterproof
- End walls are broken to form a continuios sytem throughout the plant
- Made of thick walled dead cells that are completely hollow arranged end to end
How is the phloem specialised to transport sucrose and amino acids around the plant
- Tubes of living cells arranged end to end but have cellulose cell walls
- Energy is required
What is translocation
The movement of sucrose and amino acids around the plant using energy
Why is glucose made in respiration, converted to sucrose
Less soluble - easier to transport
How is the root hair cell specialised for water absorption
- Thin walled - short distance
- Hair like extentions - increase the surface area
- Mineral ions are actively transported into cells
- Water enters by osmosis
- Water continues up xylem maintaining a concentration gradient for more water molecules
Define transpiration
The evaporation of water from the surface of a plant
How does water leave the plant from the start of the leaf
- Leaves cells of mesophyll
- Evaporated into air spaces between spongy mesophyll
- Water vapour diffuses out of stomata
Functions of the transpiration stream
- Carry mineral ions to leaves for synthesis of amino acids and chlorophyll
- Keep turgor pressure high in leaf cells, holding them up
- Evaporation cools the leaf
- Supplies water for photosynthesis
How is the rate of transpiration affected by hot temperatures
- Increase
- Water will evaporate quicly from leaves as molecules have more kinetic energy
How is the rate of transpiration affected by an increase in humidity
- Decrease
- Humid air contains water vapour sot here is a smaller concentration gradient
- Diffusion of water happens slower
How is the rate of transpiration affected by an increase of wind speed
- Increase
- The water vapour outside the stomata will be blown away as it diffuses out
- Higher concentration gradient for diffusion
How is the rate of transpiration affected by a higher light intensity
- Increase
- Stomata of leaves stay open for CO2 to enter for photosynthesis
- Allows more water to diffuse out of leaves
How does the water avaliability affect the size of the stomata opening
With lots of water, the gaurd cells either side the stomata become turgid so an opening forms
How to measure the rate of transpiration
- Set up potomoter underwater, preveinting air bubbled entering xylem
- Cut stem of shoot and put into bung, greasing with petroleum jelly
- Put bung into potometer
- Close tap and take out of water
- Get air bubble in capillary tube, then remove ffrom water
- Measure rate, by bubble moving
How do Co2 and O2 enter/leave the plant leaf for photosynthesis and respiration
Through the stomata
