3 - Plant Nutrition and Transport Flashcards
What is photosynthesis?
The process that produces glucose as a food for plants by converting light energy into chemical energy. the chemical energy is released in respiration
- Happens in the leaves of all green plants
- Happens inside the chloroplasts
- The chlorophyll absorb the sunlight
What is the word and balanced symbol equation for photosynthesis?
Carbon Dioxide + Water —-> Glucose + Oxygen
6CO2 + 6H2O —> C6H12O6 + 6O2
What are the leaf adaptations for photosynthesis?
- Broad so large surface area exposed to sunlight
- Chloroplasts are in the palisade layer which is closest to sunlight
- the upper epidermis is transparent so light can pass through easily to the palisade layer
- Leaves have a network of vascular bundles (which are xylem and phloem) to deliver water and food to every part of the leaf (also supports leaf structure)
- Waxy cuticle reduces water lost by evaporation
- Stomata allow CO2 to diffuse directly into the leaf
What are the factors limiting photosynthesis?
- Light intensity
- Temperature
- CO2 levels
If one factor is really good the graph of photosynthesis rate will stop eventually as another factor will begin to limit it
Describe an experiment to test a leaf for starch
- Kill the leaf by dunking it in boiling water (holding with tweezers) to stop any chemical reactions taking place
- Put the leaf in a boiling tube with some ethanol and heat in a water bath to get rid of any chlorophyll left in the leaf
- The leaf will now be a pale white colour
- Rinse the leaf in cold water and add a few drops of iodine solution
- If starch is present the leaf will turn blue/black
Describe an experiment for showing chlorophyll is needed for photosynthesis
- Take a variegated leaf (green and white) that has been exposed to light for a bit (record what is green and what is not)
- Test the leaf for starch
- The green bits will turn blue/black and the white bits will turn brown/orange as no starch is present
- Blue/black bits have starch so photosynthesised and have chlorophyll
Describe an experiment showing CO2 is needed for photosynthesis
- Set up a plant in a sealed bell jar next to some soda lime. Have a light shining in over the plant
- The soda lime will absorb all the CO2 present
- Leave for a while and do the starch test
- No starch will be present as the leaf did not photosynthesise
- CO2 is needed
Describe an experiment showing light is needed for photosynthesis
- Put a plant in a cupboard with no light for 24 hours
- Cut a leaf from the plant and do the starch test
- Starch won’t be present
- Light is needed for photosynthesis
Describe an experiment showing the effect of light intensity for photosynthesis
- Use Canadian pondweed
- Put a source of white light at a specific distance from the pondweed
- Leave it to photosynthesise for a set amount of time
- The oxygen released will be collected in the capillary tube
- At the end of the experiment the syringe will show the volume of oxygen produced
- temperature and time should be controlled
- Repeat the experiment with the light at different distances
What are the minerals needed for plant growth?
Magnesium (only a little bit)
Nitrates
Phosphates
Potassium
Why are nitrates needed in plants?
Contain amino acids and proteins needed for cell growth
Lack of leads to stunted growth and yellow older leaves
Why are phosphates needed in plants?
Contain phosphorus for making DNA and cell membranes. Also needed for respiration and growth.
Lack of leads to poor root growth and purple older leaves
Why is potassium needed in plants?
Helps the enzymes needed for photosynthesis and respiration
Lack of leads to poor flower and fruit growth and discoloured leaves
Why is magnesium needed in plants?
Only a small amount needed
Makes chlorophyll needed for photosynthesis
Lack of leads to yellow leaves
What are the two transport systems in plants?
Xylem and Phloem vessels
Why are Xylem vessels needed?
Carries water and mineral salts from the roots up the shoot to the leaves in the transpiration stream
Why are Phloem vessels needed?
Transports sugars (e.g. sucrose) and amino acids from where they're made in the leaves to other parts of the plant This movement of food is known as translocation
What is translocation?
The movement of food around a plant through Phloem tubes
What is the role of a root hair cell?
- Long ‘hairs’ that stick out into the soil
- Gives the plant a big surface area for absorbing water and minerals from the soil
- Water is drawn into the root through osmosis
- Minerals are drawn into the root through active transport
Why are transport systems needed?
In multicellular organisms molecules cannot diffuse directly in and out as it is too slow because there is a big distance to travel
Transport systems move substances to and from individual cells quickly
What is transpiration?
The loss of water from a plant usually by evaporation and diffusion from the plant’s surface. Mostly happens at the leaves
What are the effects of transpiration?
It creates a slight shortage of water in the leaf so xylem vessels are needed to replace it.
This means more water is drawn up from the roots so there is a constant transpiration stream of water through the plant
Transpiration is a side effect of the way leaves are adapted for photosynthesis
What are factors effecting transpiration?
Light intensity - brighter = more transpiration. As it gets dark stomata close and water is trapped in
Temperature - warmer = more transpiration. Particles have more energy to evaporate and diffuse out of the leaf
Wind speed - more wing = more transpiration. If there is no wind so water vapour surrounds the leaf so diffusion is slow
Humidity - more humid = less transpiration. If the air is humid there is lots of water in it meaning less transpiration
Describe an experiment to measure the rate of transpiration in a plant
- Set up a potometer to measure the water uptake of the plant
- Cut a shoot underwater to prevent air from entering the xylem. Cut at a slant so there is a larger surface area
- Assemble the potometer in water and insert the shoot under water so no air can enter
- Remove the apparatus from the water but keep the end of the capillary tube submerged in a beaker of water
- Check the apparatus is air and water tight
- Dry the leaves and allow time for the shoot to acclimatise and then shut the tap
- Remove the end of the capillary tube from the beaker of water until one air bubble has formed then put the tube back into water
- Record the starting position of the air bubble
- Start a stopwatch and record the distance moved every hour
- Keep temperature and humidity constant
