Plant nutrition and Photosynthesis 18 May 2019 Plant nutrition and Photosynthesis Define photosynthesis as the process by which plants manufacture carbohydrates from raw materials using energy from light

Advanced preparation In a future lesson you will look at the process of translocation. Measure and record the mass of a potato tuber and then plant it. You will observe the growth of the tuber over the next few weeks. 18 May 2019

Learning objectives Define autotroph Define photosynthesis State a word and chemical equation for photosynthesis State the role of chlorophyll 18 May 2019

Autotrophs An autotroph is an organism that is able to make its own food through the process of photosynthesis 18 May 2019

Plants make starch Plants can make glucose and store it in their cells as starch! This incredible process is called photosynthesis. Inside the plant cells are chloroplasts which contain a pigment called chlorophyll to absorb the sunlight. What is the word equation for photosynthesis 18 May 2019

How does a plant make starch? Starch is made of long chains of glucose. Glucose is made by a process called photosynthesis. sunlight + + Carbon dioxide Water Glucose Oxygen chlorophyll sunlight + + CO2 H2O C6H12O6 O2 chlorophyll Can you balance this equation? 18 May 2019

How does a plant make starch? Starch is made of long chains of glucose. Glucose is made by a process called photosynthesis. sunlight + + Carbon dioxide Water Glucose Oxygen chlorophyll sunlight + + CO2 H2O C6H12O6 O2 chlorophyll Can you balance this equation? 18 May 2019

Balancing the equation Its easy to balance the photosynthesis equation. Just remember that everything has a 6 before it except the glucose. + + 6CO2 6H2O C6H12O6 6O2 18 May 2019

Test a leaf for starch You can test a leaf with iodine to show it contains starch. Test leaves for their starch content by firstly removing their chlorophyll 18 May 2019

Test a leaf for starch First remove a leaf from the plant. First remove the green pigment called chlorophyll from the leaf so you can see the results clearly. First remove a leaf from the plant. Place it in a beaker of boiling water for 30 seconds to soften it. 3. Then place it in a boiling tube of ethanol, inside the beaker of boiling water, and make sure the Bunsen flame is switched off. 4. Remove the leaf after a minute using forceps and rinse with cold water under the tap. 5. Spread it out on a white tile and drip iodine over it. 6. Iodine will turn blue black if starch is present. 18 May 2019

Test a leaf for starch This leaf contains starch as it has gone blue black This leaf contains no starch This is because the leaf has been destarched. It has been left in a dark cupboard for a few days, the plant has not been able to photosynthesise and has therefore used up its store of starch for energy instead. 18 May 2019

Is chlorophyll needed Plan and carry out an investigation to determine of chlorophyll is needed for photosynthesis 18 May 2019

Starch and light What happens when we block out the light on part of the leaf? Can you get a plant to write your name with starch? 18 May 2019

Learning objectives Identify the different layers of a leaf Explain how different parts of the leaf are linked to photosynthesis and gas exchange 18 May 2019

The structure of a leaf Cuticle Chloroplasts Upper epidermis Palisade Mesophyll Spongy Lower epidermis 18 May 2019 Guard cell Stoma Air space

The Leaf 10 18 May 2019

The Leaf Waxy Cuticle Chloroplast Upper Epidermis Palisade Mesophyll Spongy Lower Epidermis 18 May 2019 Guard Cell Air Space Stoma

The leaf- an alternative view B C 18 May 2019

Adaptations of the leaf The palisade layer is packed with chloroplasts for photosynthesis. The leaf has a transparent upper epidermis to let light through to the palisade layer. The leaf has a broad shape to catch more light. The leaf is thin to allow rapid diffusion for gaseous exchange. The leaf has air spaces in the spongy layer to allow for gaseous exchange. The leaf has lots of stomata to allow for gaseous exchange. The leaf has guard cells to control if the stomata or open or closed. 18 May 2019

Observing the air spaces and stomata Dip different leaves in to biolong water and look for any air bubbles on the underside of the leaf These air bubbles indicate the presence of air spaces and stomata 18 May 2019

Observing stomata Paint a 1cm2 of clear nail varnish on the under and upper side of a leaf Allow the nail varnish to dry- carefully remove it from the leaf Observe the stomata frequency Repeat the procedure for a second plant and compare the two samples 18 May 2019

A Chlorophyll chromatogram Extension task - Produce a chromatogram of the extracted pigment Break a leaf up in to small pieces and place in to a mortar Add a small amount of propanone Grind the mixture with a pestle to release the chlorophyll Draw a pencil mark 1 cm from the bottom of a piece of chromatography paper Using a capillary tube place one tiny drop of the mixture on the pencil line and allow it to dry Add a second drop and allow it to dry also Repeat until you have added 5 drops Place a small amount of propanone in to a beaker and then place the chromatography paper in to the beaker Observe what happens

Learning objectives Identify the uses and storage of the products of photosynthesis 18 May 2019

Do all leaves from the same plant photosynthesize at the same rate? Plan and investigation to find an answer to this question. You should first propose a hypothesis 18 May 2019

Do all leaves from the same plant photosynthesize at the same rate? Plan and investigation to find an answer to this question. You should first propose a hypothesis AIM- To find out if the leaves at the top of a plant photosynthesise more than leaves at the bottom of the plant 18 May 2019

Testing a leaf for glucose Remove a leaf from the upper part of the plant Break the leaf in to small pieces and place in a mortar Add water to the mortar and grind the leaf using the pestle After a few minutes, remove the water from the mortar and place into a test-tube Add Benedicts solution to the test-tube and heat at 80oc for a few minutes Repeat the procedure the a leaf from the bottom of a plant Record your observations How can you make the investigation a fair test? 18 May 2019

Learning objectives Compare the rate of respiration and photosynthesis taking place in a plant 18 May 2019

What happens to the glucose? Stored as starch Used in respiration to release energy Stored in fruit as sucrose Turned into cellulose to make cell walls Turned into proteins with the addition of nitrogen so the plant can grow 18 May 2019

Gaseous Exchange in plants Gaseous exchange in plants occurs through the stomata in the leaves. The gases move by diffusion Carbon Dioxide Respiration Photosynthesis Oxygen During photosynthesis, carbon dioxide enters the leaf and oxygen exits the leaf. During respiration, oxygen enters the leaf and carbon dioxide exits the leaf. 18 May 2019

The Leaf- explain the path taken by O2 and CO2 as they enter and leave the cell Waxy Cuticle Chloroplast Upper Epidermis Palisade Mesophyll Spongy Lower Epidermis 18 May 2019 Guard Cell Air Space Stoma

Gaseous Exchange in plants Respiration occurs in plants 24 hours a day. However photosynthesis only occurs when sunlight is available. Therefore the net exchange of gasses depends on how much light is available. 18 May 2019

How can you measure gas exchange in plants? There is an indicator which is used to measure the amount of carbon dioxide. It is called Hydrogencarbonate indicator. It is red in equilibrium with atmospheric air. It becomes more orange/yellow with increased carbon dioxide levels. It changes from red through magenta to deep purple as carbon dioxide is removed. 18 May 2019

How can you measure gas exchange in plants? This is an aquatic plant placed and hydrogencarbonate indicator The indictor has had carbon dioxide bubbled through it which has turned it yellow CO2 Level It is placed under a light and as it uses up the available carbon dioxide the indictaor turns to purple How will the results differ if we placed the pond weed into the dark? 18 May 2019

Possible method Take a sample of pondweed and place in to a boiling tube Cover the pond weed with hydrogen carbonate indicator Shine the light from a lamp on to the boiling tube and leave for 30 minutes Repeat the procedure but this time cover the tube with card and a further tube with tissue paper Record your observations Aim- to observe the effect of light on photosynthesis and respiration 18 May 2019

Discussion of results Which had the most and the least carbon dioxide? Why was this? What can you say about respiration and photosynthesis in relation to light intensity? 18 May 2019

Learning objectives Describe the effects of chlorophyll, carbon dioxide and light on photosynthesis Discuss limiting factors 18 May 2019

How fast can a plant grow? The rate of photosynthesis relies on three things. Temperature Amount of CO2 Light intensity 18 May 2019

Temperature As the temperature rises, the rate of photosynthesis increases – provided there is plenty of carbon dioxide and light. This is because the temperature affects the enzymes controlling photosynthesis. However, at a certain point the higher temperature causes the enzymes to denature and photosynthesis slows down and stops. Rate of photosynthesis Temperature 18 May 2019

Amount of CO2 The higher the carbon dioxide level, the faster the rate of photosynthesis – again, provided there is plenty of light and a suitable temperature. At a certain point it wont matter how much more CO2 you give the plant the rate is at its maximum or one of the factors is in short supply. That is why the graph plateaus. Rate of photosynthesis CO2 18 May 2019

Light intensity The higher the light intensity, the faster the rate of photosynthesis – provided that there is lots of carbon dioxide and the temperature is warm enough. At a certain point it wont matter how much more light you give the plant the rate is at its maximum or one of the factors is in short supply. That is why the graph plateaus. Rate of photosynthesis Light Intensity 18 May 2019

Limiting Factors The factor that is at the lowest level will be the factor which limits the rate of reaction. This factor is called the limiting factor. If the limiting factor is increased, the rate of photosynthesis will increase until one of the other factors becomes limiting. Light intensity Amount of CO2 Temperature What conditions are needed for maximum output in a greenhouse? 18 May 2019

Photosynthesis Experiments You can use an aquatic plant such as Elodea to measure the rate of photosynthesis under various conditions. 18 May 2019

Photosynthesis Experiments As the plant photosynthesises it produces oxygen gas as bubbles. You can measure the volume produced in a given time to calculate the rate. 18 May 2019

Photosynthesis Experiments One variable at a time can be changed to then investigate their effect on the rate. For example the lamp can be moved. Or sodium hydrogencarbonate can be added to increase the CO2 in the water, or the temperature of the water could be changed. 18 May 2019

Photosynthesis Experiments Remember only to change one variable (light intensity, temp or CO2), this will be your independent variable for the investigation. All the other variables in the investigation must stay controlled. The variable measured which will be the number of bubbles of oxygen is the dependent variable. 18 May 2019

Plan an investigation to see the effect of different CO2 concentrations on plant growth 18 May 2019

Learning objectives Discuss the effect of minerals on plant growth 18 May 2019

Plant minerals As we know the plant makes it’s food by the process of photosynthesis in the leaves. However it needs various mineral ions and water from the soil in order to stay healthy. Two of these are nitrates and magnesium. 18 May 2019

Magnesium Used to make chlorophyll for the plant. Deficiency turns the leaves yellow Used to make chlorophyll for the plant. 18 May 2019

Nitrates Used to make DNA, proteins and many other molecules for the plant. Deficiency causes stunted growth and yellow leaves 18 May 2019

Phosphorous Needed for good root and shoot growth Deficiency purple leaves Needed for good root and shoot growth 18 May 2019

Potassium Used to promote good general growth Deficiency dead spots on leaves Used to promote good general growth 18 May 2019

Plan an investigation in to the growth of plants with different fertilizers 18 May 2019