3 - Plant Nutrition and Transport

Question 1

What is photosynthesis?

Answer 1

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

Question 2

What is the word and balanced symbol equation for photosynthesis?

Answer 2

Carbon Dioxide + Water —-> Glucose + Oxygen

6CO2 + 6H2O —> C6H12O6 + 6O2

Question 3

What are the leaf adaptations for photosynthesis?

Answer 3

• 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

Question 4

What are the factors limiting photosynthesis?

Answer 4

• 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

Question 5

Describe an experiment to test a leaf for starch

Answer 5

• 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

Question 6

Describe an experiment for showing chlorophyll is needed for photosynthesis

Answer 6

• 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

Question 7

Describe an experiment showing CO2 is needed for photosynthesis

Answer 7

• 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

Question 8

Describe an experiment showing light is needed for photosynthesis

Answer 8

• 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

Question 9

Describe an experiment showing the effect of light intensity for photosynthesis

Answer 9

• 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

Question 10

What are the minerals needed for plant growth?

Answer 10

Magnesium (only a little bit)
Nitrates
Phosphates
Potassium

Question 11

Why are nitrates needed in plants?

Answer 11

Contain amino acids and proteins needed for cell growth

Lack of leads to stunted growth and yellow older leaves

Question 12

Why are phosphates needed in plants?

Answer 12

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

Question 13

Why is potassium needed in plants?

Answer 13

Helps the enzymes needed for photosynthesis and respiration

Lack of leads to poor flower and fruit growth and discoloured leaves

Question 14

Why is magnesium needed in plants?

Answer 14

Only a small amount needed
Makes chlorophyll needed for photosynthesis
Lack of leads to yellow leaves

Question 15

What are the two transport systems in plants?

Answer 15

Xylem and Phloem vessels

Question 16

Why are Xylem vessels needed?

Answer 16

Carries water and mineral salts from the roots up the shoot to the leaves in the transpiration stream

Question 17

Why are Phloem vessels needed?

Answer 17

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

Question 18

What is translocation?

Answer 18

The movement of food around a plant through Phloem tubes

Question 19

What is the role of a root hair cell?

Answer 19

• 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

Question 20

Why are transport systems needed?

Answer 20

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

Question 21

What is transpiration?

Answer 21

The loss of water from a plant usually by evaporation and diffusion from the plant’s surface. Mostly happens at the leaves

Question 22

What are the effects of transpiration?

Answer 22

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

Question 23

What are factors effecting transpiration?

Answer 23

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

Question 24

Describe an experiment to measure the rate of transpiration in a plant

Answer 24

• 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

Question 25

Describe an experiment for measuring the effect of light intensity during transpiration

Answer 25

• Use a lamp to increase the intensity of light that hits the plant
• This will increase transpiration
• To decrease put the plant in a cupboard with no light

Question 26

Describe an experiment for measuring the effect of temperature during transpiration

Answer 26

• Increase or decrease the temperature by putting a potometer in a room that’s warmer or colder than where you did the control experiment

Question 27

Describe an experiment for measuring the effect of humidity during transpiration

Answer 27

• Increase the humidity by spraying a little water into a clear plastic bag before sealing it around the plant
• This will decrease the rate of transpiration

Question 28

Describe an experiment for measuring the effect of wind speed during transpiration

Answer 28

• Use a fan to increase wind speed around the plant

- This will increase the transpiration rate