Plant Transportation And Coordination Flashcards
Describe the role of the phloem in transporting sucrose and amino acids between the leaves and other parts of the plant
Phloem transports sucrose and amino acids from the leaves (made there) to the growing points (tips of shoots) or storage areas (roots). This requires energy and is called translocation.
Describe the structure of the phloem
Tubes of living cells arranged end to end but have cell walls made of cellulose
Tube to the right, which is hollow and the one outside the circle
Describe the structure of the xylem
Thick walled vessels, which are dead cells and contain no cytoplasm - they are completely hollow and are arranged end to end. The end walls have disappeared so they form a continuous transport system throughout the plant
One to the left with lots of little ones and the one inside
Describe the role of xylem in transporting water and mineral ions from the roots to other parts of the plants
Transports water and mineral ions from the roots to the leaves, nitrate ions are need to make amino acids and proteins, magnesium ions are needed to make chlorophyll
How is water absorbed by root hair cells?
Water has some solutes dissolved in but their conc is lower than the conc of solutes in root hair cells. The soil water has a higher conc of water molecules and water will enter cell by osmosis.
What is a root hair cell and its function?
Absorb water and minerals form soil, each hair is a single specialised cell of the root epidermis
What happens to water after being absorbed by the root hair cell?
Continues down a water conc gradient from where there are more water molecules to where there are fewer. Gradient maintained as water continually taken up by xylem in middle of root. Carried by xylem vessels to all parts
Define transpiration
Evaporation of water from the surface of a plant
Describe how water vapour is lost
Osmosis through the leaves and the waxy cuticle (impenetrable to water).
Passes out of stomata (as water vapour) and also leaves the cells of the mesophyll and evaporates into air spaces between the spongy mesophyll and diffuses into stomatal pores.
Loss of water makes cells have lower conc of water molecules, this draws water by osmosis from surrounding mesophyll cells
What is the transpiration stream and its functions?
Transpiration causes avert to be pulled up xylem in the stems and root in a continuous flow.
- Carry mineral ions to leaves for synthesis of amino acid and chlorophyll
- Keep turgor pressure high in lead cells (hold leaves up)
- Evaporation cools leaves
- Transpiration is inevitable as stomata have to be partly open to allow O2 and CO2 to diffuse in and out
What effect does temperature, humidity and wind speed have on transpiration?
Temp, hot means H2O will evaporate quickly (transpiration high)
Humidity, humid air contains water vapour (can accept v little from plants, transpiration slows), dry air can so transpiration is quick
Wind speed, still air has saturated air (with water vapour) so none can escape, moving air will sweep away water vapour, speeds up
How does light intensity and water supply affect transpiration?
Light does not affect but in daylight stomata are open to supply CO2 for photosynthesis, allows more water in and out
If water is in short supply and the plant is losing water by transpiration than being taken up by roots it will wilt. Stomata will close to reduce transpiration and wilting
What is a potometer and how is it used?
Device to estimate transpiration rates
The distance moved by an air bubble can be recorded every minute to indicated rate of water taken up by plant
How to set up a potometer
Must be set up under water.
- Cut stem of shoot
- Put shoot stem into bung, grease joint w vasoline
- Put bung into potometer
- Make sure tap is closed and lift out of water
- Leave end of capillary tube out of water until an air bubble forms then put it into beaker of water
How do plants respond to stimuli?
They respond by slowly changing rate of growth, such as a stimuli like light and will grow towards the light.
The growth of a plant towards a direct stimulus is called a trophism.
