Handbook b2 photosynthesis

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Photosynthesis Handbook B2

“Reading is not walking on the words, it is grasping the soul of them.�

-Paulo Freire (1921-1997) From The Pedagogy of Freedom

1

Handbook – B2 Photosynthesis ABL

CONCEPT

60

PAGE NO. 4

3

60

17

Effect of light on photosynthesis

2

60

29

Transpiration

2

60

41

ABL1

Introduction to photosynthesis

ABL2

What happens during photosynthesis

ABL 3 ABL 4

NO. OF ACTIVITIES 3

TIME (min)

OVERVIEW OF HANDBOOK

ABLs WITH REFERENCE TO STANDARD S. No.

STANDARD

RELEVANT ABL

1 2 3 4

7,8,9 8,9 8,9,10 9,10

ABL 1 ABL 2 ABL 3 ABL 4

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LIST OF FIGURES, CHARTS AND WORKSHEETS

S. No Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Chart 1 Worksheet 1

Name Test for start in leaves – (a) Test for starch in leaves – (b) Hydrilla leaf under microscope Hydrilla experiment Hydrilla balloon setup Reference table – Cresol red experiment Transpiration experiment setup Internal structure of leaf Student observation sheet – Hydrilla experiment

Page No 8 8 12 18 22 24 37 12 39

Note to Instructor: All the figures in this handbook are for the Instructor’s reference only. The Charts need to be printed and shown to the learners during the course of the activity. Worksheets need to be printed out in advance for the learners. The number of worksheets required is mentioned in the Material List.

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ABL 1 - Introduction to photosynthesis Activity

1.1

Learning Objective

Where does our food come from?

Key Messages

Time (min)



We get much of our food/energy from plants.

Food from plants commonly contains starch.

20

Starch is also present in green leaves.

Green leaves are the sites for photosynthesis, the process by which glucose is produced. This glucose is stored as starch.

20

Cells in the mesophyll tissue of leaves are the chief sites for photosynthesis. Photosynthesis takes place in plant parts where chloroplasts (containing chlorophyll pigment) are present.

Green leaves are often referred to as the kitchens of plants.

20

 

1.2

Do green plants have starch in them?





1.3

Where in the leaves of plants does photosynthesis take place?



Total Time

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4 Time: 20 min

ABL 1.1 LEARNING OBJECTIVE - Where does our food come from?

Note to Instructor– These activities should help the learners understand that our food comes from plants and animals, and the food of those animals ultimately comes from plants. We get energy from the food that is made by plants and stored in them in the form of starch.

ADVANCE PREPARATION Material List S.

Material

Required Quantity

Piece of potato Piece of fruit apple/banana/any fruit Pinch of wheat flour Pinch of rice flour Piece of bread Dropper Iodine solution Petri dish Napkin/Tissue paper Spatula (or small spoon)

2 per class 2 per class 2 per class 2 per class 2 per class 2 per class 1 per class 1 per group 1 per group 1 per group

N o .

1 2 3 4 5 6 7 8 9 10

Things to Do This is a group activity. Arrange the above materials such that each group has the following: one food item, napkin/tissue paper, spatula and a Petri dish. Plan the activity such that you are able to give each group a different food item – potato, apple, banana, wheat flour, rice flour, etc. Place the droppers and iodine solution in a common area for all groups to use by turn - one by one.

Safety Precautions Not Applicable

SESSION SESSION 1.1a Link to known information/previous activity Not Applicable Agastya International Foundation. For Internal Circulation only.

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Procedure Ask 15-20 learners what they have eaten for breakfast/lunch (the last meal before class). Write their answers on the black-board in one column. Once you have 10 to 15 food different items (like dosa, idly, poori, chapathi, rice, eggs, milk, vegetables, fruits, bread, cakes, biscuits, oats, upma, lemon rice etc.), ask the class the following questions.

UNDERSTANDING THE ACTIVITY Leading Questions 1. What are the ingredients of each item? What is the chief raw material to make each one of these items?

2. What is the source of each raw material – does it come from plants, animals or something else? Write these answers in a second column. Only after getting all the answers for this question from the selected learners, go to the next question.

3. We get most of our energy comes from three kinds of compounds – carbohydrates, proteins and fats.

The question is - what does each of the raw materials contain? For example, if a learner has answered that bread contains wheat or wheat flour, what is it made up of - carbohydrates, proteins or fats, some or all of them? And what does it mostly contain – carbohydrate, protein or fat? Write these answers in the third column.

Discussion and Explanation 1. The chief raw materials are seeds, stems, fruits, vegetables, roots and leaves. They are often processed so we see them in some other form; for example, wheat is often in the form of wheat flour.

2. Most of the answers are likely to be ‘plants’.

3. Most answers should give the answer ‘carbohydrates’. You can first ask the learners in what form the carbohydrates in plants are stored; they are not stored as glucose/sugars/carbohydrates. If they struggle to answer, tell them that plants store glucose in the form of starch, which is nothing but many combined glucose units.

SESSION 1.1b: Procedure Once you have arrived at ‘starch’ as the main energy in food from plants that we eat, lead the learners to the following activity that confirms the presence of starch in different kinds of food items that have plant materials in them. Let the learners know that it is only the presence or absence of starch that you are going to be able to test for, not the amount of starch in the food item.

Divide the class into four groups and provide each group with food samples in the Petri dishes along with a tissue/napkin and a spatula. As far as possible, give each group a different kind of food item. For example, give group 1 a fruit, group 2 gets a vegetable, group 3 a bakery items like biscuit/bread, and so on. Tell Agastya International Foundation. For Internal Circulation only.

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them to gently crush the food sample with the help of a spatula. Add 1 or 2 drops of dilute iodine to the food sample and ask the learners to watch for changes. If starch is present, iodine will react with it and turn blue-black in colour.

UNDERSTANDING THE ACTIVITY Leading Questions 1. What happened to the food? Do you see any change in the food in the Petri dish?

2. What colour is the iodine in the bottle? Use a dropper and place a drop of iodine on the Petri dish where there is no food and note its colour.

3. Do all the food items turn blue–black in colour?

4. Do you agree that starch is present in all the food samples?

Discussion and Explanation 1. The food samples in the Petri dishes all turned to a deep blue/blue-black colour. The listed food items are some plant part or the other. For instance, idly - it is made with the rice, which is nothing but the grains of rice plant. Similarly, Sambar is prepared using vegetables, which are plant parts. Cakes are prepared from wheat flour, where wheat is also a grain.

Plants perform photosynthesis and prepare food for their growth and other activities. This food is nothing but the glucose that is produced by photosynthesis. It is this glucose that is converted to starch for storage in one or the other parts like the fruits, leaves, seeds, stems and roots of the plant.

2. In the bottle and on the Petri dish, iodine is brown in colour.

3. Yes, all the food samples tested turned blue black in colour.

4. Yes, starch should be present in all the food items that have come from plants.

KEY MESSAGES:  We get much of our food/energy from plants.  Food from plants commonly contains starch.

LEARNING CHECK What is food/energy stored in plants as?

What turns the color of brown iodine blue-black?

(Answer for Instructor’s reference: Starch)

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7 Time: 20 min

ABL 1.2 LEARNING OBJECTIVE - Do green plants have starch in them?

Note to Instructor–First the children should be told about how iodine reacts with starch and that you can confirm the presence of starch in something with this test. These activities show that not only do many of our food items contain starch, but also that green leaves contain starch. Since the food we eat comes from plants, the starch we eat comes from plants. The following activity is a demonstration.

ADVANCE PREPARATION Material List SL.NO.

Material

1 2 3 4 5 6 7

Methanol 500 ml glass beaker 50 ml glass beaker Tripod stand Wire gauge Spirit lamp Forceps (big, with a long handle) Match box Tissue paper/filter paper Dustbin with sand/water

8 9 10

Required Quantity 30 ml 1 per class 1 per class 1 per class 1 per class 1 per class 2 per class 1 per class 15 per class 1 per class

Things to do Not Applicable Safety Precautions Do not heat methanol directly over a flame. Always heat methanol in a water bath.

SESSION

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Link to known information/previous activity In ABL 1.1 we saw that most of our food comes from plants. We also saw that the food that we get from plants all have starch. Since we also said that this starch is formed in leaves, here we are going to see if the green leaves of plants really do contain starch.

Procedure Arrange the heating setup as shown in the figure below. Ask a few learners to bring some leaves from different plant species. Then, take two leaves and put a drop of iodine on each leaf. Ask the learners to observe the leaves and note down any changes in them.

i

Figure 1 – Test for starch in leaves (a)

Next, take some water in a beaker and heat it using a spirit lamp. Put the remaining leaves in the hot water and boil the leaves for 5 to 10 minutes. Then, take 30 ml of methanol in the smaller beaker/boiling test tube. With the help of forceps transfer the leaves boiled in water into the methanol. Place the small beaker/test tube containing methanol and boiled leaves in the hot water bath for 5 minutes and observe the leaves. [If the water is not too hot, heat it.]

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Figure 2 – Test for starch in leaves (b) Note to Instructor: Do not heat methanol directly over a flame. Always heat methanol in a water bath.

With the help of forceps carefully remove the leaves from the methanol and place them on the filter paper/tissue paper to remove the wetness. Once the leaves are dry, give them to the learners. Ask them to put 1 or 2 drops of iodine on the leaves and note down any changes.

Throw the burnt match sticks and other waste in the dustbin with sand/water.

UNDERSTANDING THE ACTIVITY Leading Questions 1. What happened when you put iodine on the un-boiled leaves, and then on the boiled leaves?

2. Why have we boiled the leaves? Why did we not do this with the food items?

3. Why have we soaked the leaves in methanol solution? Why did we not do this with the food items?

4. Why did the methanol become green?

5. Why did you not get a blue colour when you put iodine on the un-boiled leaf?

6. What is the colour of iodine?

7. What does the deep blue colour indicate?

Discussion and Explanation 1. No change was observed when we put iodine on the (unboiled) leaves. Blue-black patches were observed on the boiled leaves.

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2. We boiled the leaves to make them soft, to break them, so that things can enter and leave the leaves more easily. We didn’t have to do this for the food items as the processing before and during cooking did that work.

3. To extract/remove chlorophyll from the leaves. There was no chlorophyll in the food. (In fact, methanol breaks the cell wall) 4. Chlorophyll that was in the leaves is now in the methanol, and turns it green.

5. Colour change was difficult to see when chlorophyll was present in the leaf, and once boiled, iodine entered the leaf more easily to react with the starch. Iodine does not react with starch in the unboiled leaf, as it is not able to enter the leaf.

6. Brown colour 7. Blue-black colour indicates the presence of starch. Starch is formed by the combination of many units of glucose. Glucose is produced by photosynthesis, (photo = light; synthesis = putting together or to make) a process where plants absorb sunlight with the help of chlorophyll. They then use energy from light to convert atmospheric carbon dioxide and water to glucose. This is a common process, carried out by most autotrophs. Photosynthesis can be represented by following word equation:

During this process, (1) the sun’s light energy is used to split up water molecules and produce chemical energy, (2) the chemical energy then reduces carbon dioxide to glucose in a series of steps, and (3) oxygen is produced, most of which is released into the atmosphere.

Another way of writing the above equation is: 6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O OR 6CO2 + 6H2O → C6H12O6 + 6O2 This glucose is used to make different kinds of carbohydrates. Simple sugars such as sucrose and maltose are used up by the plant immediately. Complex carbohydrates like starches are stored in the plant.

KEY MESSAGES  

Starch is also present in green leaves.

Green leaves are the sites for photosynthesis, the process by which glucose is produced. This glucose is stored as starch.

LEARNING CHECK Plants produce glucose by which process?

(Answer for Instructor’s reference: Photosynthesis) How is this glucose stored in plants?

(Answer for Instructor’s reference: As starch) Agastya International Foundation. For Internal Circulation only.

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11 Time: 20 min

ABL 1.3 LEARNING OBJECTIVE - Where in the leaves of plants does photosynthesis take place?

Note to Instructor – This is an activity to show learners the cells/tissues in which photosynthesis takes place. They should also be able to see chloroplasts. This activity should also teach them to draw what they see under a microscope and then compare it to a textbook or chart figure.

ADVANCE PREPARATION: Material List SL.NO

Materials

Required Quantity

1

Microscope

1 per class

2

Cover slips

2 per class

3

Hydrilla leaves

A few

4

Slides

1 per class

5

Water

6

Display chart of internal structure of Leaf (chart 1)

Up to an inch in a small beaker 1 per class

Things to Do Not Applicable Safety Precautions Not Applicable

SESSION Link to known information/previous activity So, now we have seen that the green leaves contain starch. Starch is produced by photosynthesis that takes place in all plants. Photosynthesis takes place mostly in the green parts of plants – the green pigment is necessary for this process. Let us see where in the leaf this process takes place.

Procedure

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Take a clean slide and using a pair forceps, place a Hydrilla leaf on the slide. Put a drop of water on the leaf. With the help of needle, careful fix a cover slip on the leaf without any air gap. (If required, add a drop of stain to the leaf. Then mount the cover slip by placing it gently over the stained part of the leaf).

Switch the objective lens of microscope to 10x. Place the slide on the stage and focus the objective lens on the part of the leaf you want to look at by rotating the coarse knob. Once you have the leaf in your view, fine tune the image by rotating the fine adjustment knob. Make sure that you are looking at all the internal parts of leaf just as shown in the figure below. Compare your observations with the internal structure of leaf chart.

Ask the learners to come up to the microscope one after the other to observe the leaf. Ask learners to draw what they see.

Display the chart – Internal structure of leaf

Figure 3 – Hydrilla leaf under microscope

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Chart 1

UNDERSTANDING THE ACTIVITY: Leading Questions 1. Compare the chart to your drawing. Can you match the structures on your drawing from your slide under the microscope to those on the chart?

2. Try and name some of the structures you have seen under the microscope.

3. Where in the leaf/in which internal part/tissue that you can see on the chart/under the microscope do you think that photosynthesis will takes place?

4. Do you think all leaves have similar internal structures? Why/Why not?

Discussion and Explanation 1. Each learner should be able to see the Internal structure of Hydrilla leaf.

2. Cells/Tissues/epidermis (accept all the answers).

Now move around the classroom and show the learners the stomata, parenchyma cells, chloroplasts etc. on the chart and if/where possible match it to each of the diagrams they have drawn.

3. In one or other cells of leaf/Mesophyll tissue.

Move back to the chart/front of the classroom and explain the functions of these different cells/structures in photosynthesis.

4. Yes, all the leaves have a similar structure, probably because all of them have to perform photosynthesis.

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KEY MESSAGES  

Cells in the mesophyll tissue of leaves are the chief sites for photosynthesis. Photosynthesis takes place in plant parts where chloroplasts (containing chlorophyll pigment) are present.

Green leaves are often referred to as the kitchens of plants.

LEARNING CHECK Where in a plant/leaf does photosynthesis take place?

(Answer for Instructor’s reference: In the cells/Mesophyll tissue)

TRY IT YOURSELF An activity based on the fact that plants require light to make sugars.

Take a potted plant with big leaves. Keep it in the dark for day and then place it where there is plenty of light. Take a film negative – perhaps one of a photograph of yourself. Fix the negative onto a leaf with bell pins (see figure). The negative should be smaller than the leaf. Now, different parts of the leaf will receive different amounts of light, since some areas are more transparent than others. Since plants use light as a source of energy to make sugar (glucose) by photosynthesis, the negative leaves a pattern of photosynthesis "printed" on the leaf.

If the leaf makes more sugar than it is able to use (or export to the rest of the plant), it stores the excess in the form of starch. In areas that receive more light, the cells will accumulate starch, while dark areas will not store starch.

Pluck the leaf from the plant. Remove chlorophyll and other pigments by boiling in methanol using over a water bath. Use iodine to stain the starch in the leaf. You should have your photo printed on the leaf.

INTERESTING INFORMATION There are plants that have red and yellow leaves all through the year. Crotons, garden ornamental plants are an example of such plants. However, photosynthesis takes place in these leaves as well. The thing is, these leaves contain pigments other than chlorophyll, in large quantities. So, at a distance they look yellow or red, but if you look at them closely, you may be able to see the green!ii

WEB RESOURCES http://blogs.scientificamerican.com/oscillator/2012/05/12/living-photography/

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http://www.nuffieldfoundation.org/practical-biology/testing-leaves-starch-technique 1

http://www.elateafrica.org/elate/biology/nutrition/studentactivities.html

1

http://www.madsci.org/posts/archives/1999-02/918588729.Bt.r.html

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ABL 2Process of photosynthesis

Activity

Learning Objective

Key Messages 

2.1

2.2

2.3

How can we say that plants are performing photosynthesis?

How can we confirm that the bubbles released in the Hydrilla experiment above are of oxygen gas?





Photosynthesis is the only plant process which releases oxygen as a by product. So, if oxygen is being released by a plant, we can say that photosynthesis is probably taking place.

Photosynthesis depends on external factors like sunlight, the concentration of carbon dioxide in the atmosphere and available water.

If a burning splinter burns even more in this gas released by the Hydrilla, then we can say that this gas is oxygen.



Plants do not perform photosynthesis at night. Hence, no oxygen is released.



Like animals, plants also respire the whole day.

Do plants release oxygen at night?

Time (min)

Total Time

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30

10

30

70

17

Time: 30 min

ABL 2.1 LEARNING OBJECTIVE - How can we say that plants are performing photosynthesis?

Note to Instructor – This is a group activity. The learners should all be able to see the bubbles emerging from the plant. Also, encourage the learners from one group to visit another group one by one so they can all see the different set ups for themselves.

ADVANCE PREPARATION: Material List S. No.

Material

Required Quantity

1

Beaker 400 ml

1 per group

2

Glass funnel

1 per group

3

Test tube

1 per group

4

Hydrilla twigs

5 per group

5

Water

6

Scissors

7

Graph sheets

1 per learner

8

Stop clock/watches

1 per group

9

Pencil

1 per learner

10

Erasers

1 per learner

11

Whistle

1 per class

12

Sodium hydrogen carbonate

13

Student observation sheets – Hydrilla experiment – Worksheet 1 Graph sheets

14

1 small bucket full 1 pair per group

1 spatula per class 1 per group 1 per group

Things To Do  Choose a sunny day for this activity.  This activity requires Hydrilla plants. Collect Hydrilla from a nearby pond. Keep them in fresh water in large containers like buckets, trays or troughs. Make sure the Hydrilla have sufficient water and sunlight, so they have enough air and stay healthy. Do not stuff the Hydrilla in small beakers or bottles – they will die, rot and turn black, and cannot be used for the activity.

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One of the groups will need a dark room; if a dark room is not available, cover three sides of a table with cloth and ask the group to perform the experiment under the table.

Make sure you have printed out/photocopied observations and graph sheets for all the children in all the groups. Keep some extra graph sheets handy.

Safety Precautions Not Applicable

SESSION: Link to known information/previous activity Now, we have learnt that that photosynthesis has taken place in plants if we can detect the presence of starch in them. This is because plants do not take in starch from the soil or the air; they can only produce it by photosynthesis.

Towards the end of ABL 1 we discussed that photosynthesis takes place in the cells of green leaves. In this activity we will learn how photosynthesis actually takes place in green leaves.

Procedure Divide the class into 4 groups; distribute the materials for the experiment. Hand the groups similar quantities of Hydrilla (4-5 twigs per group) and water. Make sure that you give all of them beakers, funnels and test tubes of the same size. Each group will perform the experiment under different conditions as given below: Group

Additional Requirement

Group 1

-

Group 2 A spatula of baking soda (NaHCO3) to be added to the water in the beaker.

Group 3 Group 4

-

Place of Experimentation Bright sunlight.

Both groups should perform side by side.

Shade/inside the classroom.

Dark room or under a table covered with cloth on three sides.

Write the table above on the board and show each group the location where it will do its experiment.

Gather the learners once again and show/draw the picture below on the board.

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Figure 4 – Hydrilla experiment

Tell the learners that their setups should look like the picture above. Then using one of the apparatus of one of the groups, demonstrate how to set up the experiment. Fill the beaker halfway with water and invert the funnel with twigs into the beaker. In a bucket, do the following under water. Carefully invert a test tube filled completely with water over the narrow end of the funnel. Once you have done this, distribute the observation and graph sheets. Draw the table given in the observation sheet on the board and explain how they should count air bubbles.

Time after which data Number of is to be recorded Bubbles st 1 five minutes 2nd five minutes 3rd five minutes 4th five minutes 5th five minutes Worksheet 1 – Student observation Sheet One learner will be a timekeeper. This learner will blow a whistle soon as all the groups have set up their experiments. Explain to them that when the first whistle blows, each group has to do two things – start their stopwatch and start counting bubbles. A few minutes after they have set up the experiment, the learners will be able to observe air bubbles rising from the Hydrilla to the top of the test tube. As the bubbles rise to the top of the test tube, the learners will also see the level of water in the test tube decreasing.

At the end of five minutes, each group has to note down how many bubbles have risen to the top of the test tube till that time. They then have to start counting the bubbles again, and write down the new number at the end of the next five minutes. Ask them to note the number of bubbles in the table on their observation sheet. For example, if one group counts 25 bubbles in first five minutes they must write down ‘25’ in the first row in the table above. Then they have to start counting bubbles again, starting with 1, for the second five minutes. If you get 12 bubbles at the end of the second five minutes, write that in the second row above. And so on... (This will help in plotting the graph later on).

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The time keeper should blow the whistle at the end of 25 minutes to signal the end of the observation period.

The learners then have to draw a graph. It is possible that this is the first time some of them are drawing a graph. Explain how to plot the graph by doing an example on the board next to the table that you drew earlier. Take time duration on X axis and number of bubbles on Y axis. The scale on Y axis depends on the numbers of bubbles. Plot the graph as per your observations.

UNDERSTANDING THE ACTIVITY: Leading Questions 1. What do you think the bubbles indicate?

2. What are the bubbles made of?

3. Why have we used Hydrilla plants? Why not use a potted plant?

4. Why did we add baking soda to the beaker in one of the experimental setup (of Group 2)?

5. Why is the graph not the same for all the groups?

6. What are the conditions that are essential for photosynthesis to take place?

7. Do you think that photosynthesis took place in the plants kept in the dark? Take the set-up and move it into sunlight and see what happens.

Discussion and Explanation 1. Bubbles indicate the release of a gas.

2. The bubbles are those of oxygen gas.

3. We have used Hydrilla, an aquatic plant, so that the gas released by its leaves can be seen, counted and collected. With a potted plant it would have been difficult to demonstrate the release of a gas from the leaves and collect it.

4. When sodium bicarbonate is added to water, carbon dioxide is released. This dissolved carbon dioxide is then available to the leaves of the plant (which are in water) for photosynthesis, along with the dissolved carbon dioxide that is normally available to aquatic plants. In other words, on adding this salt to water, we increased the quantity of carbon dioxide in the water for Hydrilla to use.

5. The number of bubbles of gas/oxygen released by the plants is not the same in each set-up. This is because conditions like the quantity of light and carbon dioxide are not the same for all the groups.

6. Light is essential. More carbon dioxide means more photosynthesis and more oxygen gas bubbles.

7. No, we did not see any bubbles coming out in the experimental set-up kept in the dark. Soon after we moved the set-up into sunlight, bubbles started coming out.

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KEY MESSAGES:  

Photosynthesis is the only plant process which releases oxygen as a by product. So, if oxygen is being released by a plant, we can say that photosynthesis is probably taking place.

Photosynthesis depends on external factors like sunlight, the concentration of carbon dioxide in the atmosphere and available water.

LEARNING CHECK: Where does the carbon in glucose made during photosynthesis come from?

(Answer for Instructor’s reference: carbon dioxide gas) What happens to the oxygen produced during photosynthesis?

(Answer for Instructor’s reference: The gas is released into the surroundings by the leaves)

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22 Time: 10 min

ABL 2.2

LEARNING OBJECTIVE - How can we confirm that the bubbles released in the Hydrilla experiment above are of oxygen gas?

Note to Instructor – This is a demonstration. It is an optional activity.

ADVANCE PREPARATION: Material List SL.NO. 1 2 3 4 5 6

Material Conical flask 250 ml One hole rubber cork Small thistle funnel Balloon Thread Water

Required Quantity 1 per class 1 per class 1 per class 1 per class 1 spool Half a bucket full

Things to Do First take the cork of the conical flask and push the thistle funnel through the hole in it. Next insert a few Hydrilla twigs into the stem of thistle funnel.Fill the conical flask completely with water and push the rubber cork with thistle funnel and Hydrilla into its mouth (see figure below). Make sure that there is no gap between the cork and the mouth of the flask through which air can escape; the cork should be fitted tightly.

Now pour water from the top into the thistle funnel (filling its mouth up to the brim). You should not be able to see any bubbles trapped in the thistle funnel, there should be no trapped air in it. Carefully tie a balloon to the mouth/opening of the thistle funnel with a thread (see green balloon in the figure below). Keep this set-up in sunlight for at least 3 – 4 hours. Keep the set-up in sunlight for at least for 3 to 4 hours before you bring it in to the learners.

Safety Precautions Not Applicable

SESSION: Link to known information/previous activity In the previous activity we saw that when a plant is placed in conditions that it can perform photosynthesis (in light), it releases a gas. Now, it is quite likely that this gas is oxygen. We know that from what we have read in books. But in the experiment, we cannot say for sure it’s oxygen, unless we test for it. In this activity, that is what we will do. We will collect the gas that comes out of a plant that is likely to be performing photosynthesis, and test if this gas is oxygen.

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Procedure Explain the initial set up to the students with the Link to previous activity and then do the following.

Once the balloon in the set up is inflated/filled with gas, carefully remove the balloon. Make sure that no gas escapes from the balloon. Keeping the balloon mouth closed, carefully bring a burning splinter near the mouth of the balloon. Then untie the balloon and release the gas collected over the burning splinter.

Figure 5 – Hydrilla – balloon set up

UNDERSTANDING THE ACTIVITY: Leading Questions 1. What happens when we release the gas collected from the Hydrilla over the burning splinter?

2. How can we confirm photosynthesis by the release of oxygen?

Discussion and Explanation 1. The splinter burns more than before, more vigorously.

2. As you have seen earlier the equation for photosynthesis is: 6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O Agastya International Foundation. For Internal Circulation only.

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Photosynthesis is the only process in plants in which oxygen is liberated. So, if you can confirm that the bubbles that come out from the tips of Hydrilla and that you collect in the balloon are made up of oxygen, then you can say that photosynthesis has probably taken place.

KEY MESSAGES: 

If a burning splinter burns even more in this gas released by the Hydrilla, then we can say that this gas is oxygen.

LEARNING CHECK: True or false – oxygen supports burning.

(Answer for Instructor’s reference: true)

ABL 2.3

Time: 30 min

LEARNING OBJECTIVE – Do plants release oxygen at night?

Note to Instructor – This is a group activity.

ADVANCE PREPARATION: Material List Sl. No. 1 2 3 4 5 6 7

Material Test tubes with rubber corks Water Cresol red indicator Hydrilla plant twigs of same size Markers Test tube stands Straws

Required Quantity 5 per group 200 ml per group 15 ml per group 4-5 per group 1 per group 4 for the class 1 per group

Things to do  For this experiment you will need a dark cupboard and a sunny area where the experimental test tubes can be kept undisturbed for about 20 minutes. You will have to decide these locations in advance.  As for ABL 2.1 and 2.2, this activity too requires Hydrilla plants. Collect Hydrilla strands from a nearby pond. Keep them in fresh water in large containers like buckets, trays or troughs. Make sure the Hydrilla have sufficient water and sunlight, so they have enough air and stay healthy. Do not stuff the Agastya International Foundation. For Internal Circulation only.

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Hydrilla in small beakers or bottles – they will die, rot and turn black, and cannot be used for the activity. You will have to arrange for Hydrilla plants or any other plant that grows in water.

Safety Precautions Not Applicable

SESSION: Link to known information/previous activity In the previous activity, we saw that changing the amount of light and carbon dioxide for a plant will change the number of air bubbles released by it, an indicator of how much photosynthesis is taking place.

Now, most of us have commonly heard that plants photosynthesize during the day and respire at night.

Now we know that it is difficult for us to show that plants respire during the day. This is because most or all of the carbon dioxide released by plant cells during the day is used for photosynthesis (in addition, carbon dioxide from the atmosphere is absorbed by leaves for this process). At night, or in the absence of photosynthesis then, they should release carbon dioxide released by plant cells, due to respiration. Let us see if that is the case.

Procedure Take three clean, dry test tubes and mark them 1, 2 and 3. Fill the three test tubes ¾th -way with water.

Add 2 ml of cresol red indicator to each the three test tubes. Next, drop a few twigs of Hydrilla into the 1st and 2nd test tubes (make sure that two test tubes contains similar amounts of Hydrilla, also check that all the twigs are completely submerged). Add nothing more to the 3rd test tube – it should contain only water and indicator Fix rubber corks in all the test tubes. Check that they are airtight. Record the colour of the solutions in all 3 test tubes.

Now keep the1st and 3rd test tube in bright light and the 2nd test tube in the dark. Keep the set-up undisturbed for at least 20 minutes.

After 20 minutes, record any changes in colour in the three test tubes. Students can just make note of the colour change on a piece of paper based on a table that you draw on the board. (No observation sheet required) Colour of Solution Test Tube 1 Test Tube 2 At the beginning After 20 – 30 minutes Figure 6 – Reference table – Cresol Red experiment

Test Tube 3

While waiting, let us understand how cresol red works. Cresol red is an acid-base indicator. This means that it is of a different colour in an acid and a different one in a base. So, if you add it to an acidic solution, it will be one colour and if the pH of that solution changes and it becomes less acidic, or more basic, it again changes colour. In this way, you can know the pH of a solution without actually measuring it.

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Cresol red works as an indicator over a specific pH range of 7.2-8.8. If you start with a strongly acidic solution (in the pH range 1.8-2.0) and add a few drops of cresol red, it will turn yellow in colour. Let us say that you then make this solution less acidic (or more basic) by adding chemicals. When the pH of this solution is so basic that it is in the range of 7.2-8.8, the colour of the solution will turn purple/dark pink. If you continue to make the solution even more basic, at a pH of greater than 8.8, the solution will be red. So with cresol red you can tell when a solution is in the range of pH 7.2-8.8 and when its pH crosses beyond 8.8. All this, without measuring the solution’s pH. To further understand how cresol red works, take two test tubes and label them 1 and 2. Fill them both halfway with water and add 3 ml of cresol red to each. Keep test tube 1 aside and using a straw blow air into test tube 2. Note any colour changes in the two. (As you blow, the solution starts turning yellow) Leading Questions – (For the above) 1. Do you see any colour change in the two test tubes?

2. What have you changed in one of the test tubes by blowing air into it?

Discussion and Explanation 1. In test tube 1 there is no change in colour. Test tube 2 changes to yellow.

2. Exhaled air has made the contents of test tube 1 more acidic. As exhaled air contains more carbon dioxide, it is this, which has caused the colour of cresol red to change to yellow. (in fact, blowing air into test tube results in high carbon dioxide which makes the solution acidic turning cresol red to yellow)

Leading Questions – (First experiment with three test tubes) 1. What happens to the colour of the solutions in the 3 test tubes? Are there any other changes that you saw?

2. Test tube 1 and 2 only differ in that one was in the light and one in the dark? How did that make a difference to the colour?

3. Why did we need to keep one test tube with no plant in it?

4. How are plants and animals similar in respiration?

Discussion and Explanation 1. The solution in test tube 1 turned dark pink/purple, in test tube 2 turned yellow, and there is no change in test tube 3 where the solution remained pink.

2. In both light and dark, the plant takes in oxygen and gives out carbon dioxide. But in the light, the plants utilize carbon dioxide gives out mostly oxygen. Also plants absorb carbon dioxide from water.

(Absorbing carbon dioxide from the water, reduces the acidic levels and turns to basic, which makes the cresol red to turn to pink) In the dark they do not produce oxygen instead gives out carbon dioxide that changes the colour in test tube 2 to yellow.

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3. Since there is no plant, test tube 3 does not change colour when kept in the sun. This also shows that just water plus indicator will not change colour in sunlight.

4. We have seen from both the experiments that both plants and animals give out carbon dioxide during respiration.

KEY MESSAGES: 

Plants do not perform photosynthesis at night. Hence, no oxygen is released.



Like animals, plants also respire the whole day.

LEARNING CHECK: Why do plants not release both oxygen and carbon dioxide at all times?

(Answer for Instructor’s reference: Plants release carbon dioxide at all times. In the day, what they release is taken up for photosynthesis. Plants release oxygen only when they perform photosynthesis.)

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ABL 3 Effect of light on photosynthesis Activity 3.1

Learning Objective Does photosynthesis take place in lights of all colours?

Time (min)

Key Messages 

In red light photosynthesis will be more when compared with other colours. There will be no photosynthesis in green light.

Total Time

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60

60

29 Time: 60 min

ABL 3.1 LEARNING OBJECTIVE – Does photosynthesis take place in lights of all colours?

Note to Instructor – This activity is only for Standard 10. This is a group activity.

ADVANCE PREPARATION: Material List S. No. 1

Material

Required Quantity

Hydrilla

4-5 per group 1 sheet per group

3

Red, Blue, Green, Yellow colour transparent plastic papers (cellophane papers) Black chart paper

4

Boiling test tubes

6 per group

5

Cotton plugs/test tube corks

6 per group

6

Test tube stand

2 per group

7

Cresol red solution

20 ml per group

8

Beaker 400 ml, glass

2 per activity

9

Plastic cups

1 per group

10

Marker Pen (to write on the test tubes)

1 per group

2

1 sheet per group

Things to Do  Prepare the cresol red solution before the learners come in. Do this by taking 400 ml of water in a beaker and adding 15 ml of cresol red. Stir it well. When the learners come in, distribute the cresol red to them in plastic cups from this beaker.

Safety Precautions

Not Applicable

SESSION: Link to known information/previous activity Not Applicable Procedure Agastya International Foundation. For Internal Circulation only.

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Divide the class into 4 groups. Distribute the materials amongst them.

Each group has to then do the following. Take 6 clean boiling test tubes and label them as Green, Red, Blue, Yellow, Black and Control. Add 4-5 twigs of Hydrilla to each of the 6 test tubes. The amount of Hydrilla should be same in all the test tubes.

Pour the cresol red solution into each test tube, filling them ¾ of the way. The Hydrilla twigs should be submerged inside the cresol red solution. No twig should come out of the surface of liquid. Then put the cotton plug or rubber cork on all the test tubes. It should be airtight. Wrap each test tube in paper of a different colour. The test tube labelled as ‘Green’ should be wrapped with green paper, similarly test tube labelled as black should be wrapped with black chart paper, and so on. Make sure that the wrapping in uniform with all the colours. Wrap each test tube with 2 rounds of coloured paper. Do not wrap the control test tube.

Place all the 6 test tubes in the beaker or in tray and expose it to sunlight. Keep in such a way that, all the test tubes should get uniform sunlight. Observe after 30 minutes.

Note to Instructor - Once you have set up the experiment, you will have to wait for 30 minutes before recording any observations. In these 30 minutes, you can do some other activity from ABL 1 or ABL 2.

UNDERSTANDING THE ACTIVITY: Leading Questions 1. Why have we wrapped colour papers around the test tubes?

2. Why have we used black paper?

3. Do you think the coloured light affects photosynthesis?

4. How can we measure the rate of photosynthesis?

Discussion and Explanation 1. Light, sunlight is made of a number of colours. In books we have read that it is made up of a spectrum, which we know as violet, indigo, blue, green, yellow, orange and red. Now, something looks red if it reflects red and absorbs all other colours. And something looks green if it reflects green and absorbs all other 6 colours. So, when you wrap a coloured transparent paper around a test tube, then red colour is being reflected. Or, in other words, all other colours of light are filtered, except red, which is passes into the test tube and reaching the Hydrilla. So, by wrapping a test tube with transparent paper of a certain colour, we are preventing other colours from reaching the Hydrilla.

2. To block out all light from reaching the Hydrilla.

3. Yes. Cresol red changes colour as carbon dioxide is produced/absorbed by the Hydrilla. This is because release of carbon dioxide (respiration) makes the water more acidic and absorbing carbon dioxide Agastya International Foundation. For Internal Circulation only.

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(photosynthesis) from water makes water basic. Thus depending on the colour change we can compare the photosynthesis in different colours.

4. In red colour, the test tube shows dark pink colour (due to absorption of more carbon dioxide), thus indicating maximum photosynthesis took place when compared to other colours. Similarly, green colour test tube shows yellow colour (no absorption of carbon dioxide, instead release of carbon dioxide by respiration), which indicates that no photosynthesis has occurred.

KEY MESSAGES: 

In red light photosynthesis will be more when compared with other colours. There will be no photosynthesis in green light.

LEARNING CHECK: In what colour light do chlorophyll best perform photosynthesis?

(Answer for Instructor’s reference: Red) What colour light does chlorophyll not absorb?

(Answer for Instructor’s reference: Green)

REFERENCES http://www.nuffieldfoundation.org/practical-biology/testing-leaves-starch-technique 1

http://www.elateafrica.org/elate/biology/nutrition/studentactivities.html

1

http://www.madsci.org/posts/archives/1999-02/918588729.Bt.r.html

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ABL 4 Transpiration Activity

Learning Objective 

4.1 What is transpiration?

4.2

Time (min)

Key Messages



Transpiration is a process where water moves up through a plant and out into the air surrounding it through pores present in leaves In transpiration, water absorbed by the roots moves up through the plant and evaporates from the leaves.

Total Time

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30

20

50

33 Time: 30 min

ABL 4.1 LEARNING OBJECTIVE – What is transpiration? 

Note to Instructor – This is a group activity. This activity needs some 30 minutes of waiting. Once the learners set up the activity, start activity 4.2 and come back to this.

ADVANCE PREPARATION: Material List

S. No.

Material

Required Quantity

1

Plastic covers

4 per group

2

Thread

1 roll per group

3

Scissors

1 pair per group

4

Vaseline

1 small bottle per group

5

Syringe small

1 per group

6

Graph sheets

4 per group

7

Pencil

1-2 per group

8

Eraser

1 per group

9

Cutter or Blade

1 per group

Things to Do 

Make sure that at least 4 plants with a minimum of 20 leaves each are easily available near the classroom. The plants should have big leaves so that calculation of leaf surface area is not difficult for the learners.

Safety Precautions Not Applicable Agastya International Foundation. For Internal Circulation only.

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SESSION:

Link to known information/previous activity: In the previous ABLs we have learnt that in photosynthesis, in the presence of light, carbon dioxide and water react chemically to form a carbohydrate that is glucose. We know that the source of light is usually sunlight and carbon dioxide is from the surrounding atmosphere (or water, in the case of aquatic plants). In this ABL, we will see where the water comes from. Water is not just necessary for photosynthesis, it is also important to transport the glucose made in the leaves and other nutrients all over the plant and to maintain the shape of stomata that allow gases to enter and exit leaves.

Procedure Divide the class into 4 groups. Distribute the materials and graph sheets.

Take 4 clean plastic covers and check that there are no holes in them. Label the plastic covers as 1, 2, 3 and 4.Select a plant (it can be a potted plant or one in the garden) with more than 20 leaves. Select four healthy leaves in the plant and label them 1, 2, 3 and 4. You can do this by tying a small piece of paper with a thread around the petiole of each leaf. The four leaves should be identical in size and surface. Do not pluck or tear any leaf off the plant.

Measure the surface area of each leaf. You can do this by first placing a graph sheet under the leaf in such a way that leaf is at the centre of graph sheet. Draw the outer line of leaf by moving the pencil on the margins of the leaf. [Keep an exam board/pad under the graph sheet if necessary.] Write the leaf number on each graph sheet. Keep the graph sheets from all four leaves carefully.

Wrap the plastic cover 1 over the leaf 1 and tie the cover at the stalk with a thread. To the leaf 2 apply Vaseline on the upper surface and wrap cover 2 over it and tie it so that it’s airtight. To leaf 3, apply Vaseline on the lower surface and wrap the cover 3 and tie it as you did for leaf 2.To leaf 4, apply Vaseline on both the upper and the lower surfaces, wrap cover 4 over it and as for the previous two leaves, tie the cover tightly with thread. Return to your classroom and calculate the surface area of the leaves and note down these values. After 30 minutes untie all the 4 covers. Bring them carefully along with any water in the covers to the classroom.

Note to Instructor: While waiting for 30 minutes, calculate the leaf surface area for all the leaves and you can also go to ABL 4.2, if you have the time and come back for the discussion.

Calculation of leaf surface area On your graph sheet, the outline of the leaf will have both full squares and half or partial squares. Consider only the big squares formed by the dark lines of the graph sheet. Ignore the small squares. Write Ain all the full squares and B in all the partial squares. Count all full squares i.e. A’s.Count all half or partial squares i.e.

B’s.Substitute the values of As and Bs in the formula A + (B/2). This gives the surface area of the leaf in cm2.

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UNDERSTANDING THE ACTIVITY: Leading Questions 1. Why have we wrapped the leaves with plastic cover?

2. Why have we applied Vaseline over the leaves?

3. What do you think will happen at the end of the experiment?

4. What happens if you leave covers for a longer time?

5. Do all the four leaves release equal amounts of water?

6. Which leaf releases more water?

7. Do plants release a lot of water in a year? How important are they in the global water cycle?

Discussion and Explanations 1. To trap the water vapour leaving the plant 2. To block the pores/stomata on the leaves.

3. Leaves release water in the form of vapours, which condense and from water droplets inside the plastic cover.

4. More amounts of water will be collected 5. No, the four covers have different amounts of water in them. In the case of first leaf, all the stomata are open hence water loss is maximum so you got more amount of water. In the case of second leaf, you have blocked the stomata present in the upper surface, but the stomata at lower surface are open, hence transpiration took place and you got water. Further the number of stomata in the lower surface is much more than in upper surface, hence you got water roughly equal to that of first leaf. In the case of third leaf, the water is less, because you have blocked the stomata on the lower region, stomata in the upper region are open but less in number. No water or negligible amount of water is released in the fourth leaf as all the stomata are blocked.

6. The leaf without Vaseline releases the most water as none of its stomata are blocked with Vaseline.

7. Open-ended discussion.

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KEY MESSAGES: 

Transpiration is a process where water moves up through a plant and out into the air surrounding it through pores in its leaves.

LEARNING CHECK: Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the chart of key messages. If you have time during the class, make up a small game, quiz or match the following as a learning check. This may have to be done as part of advance preparation.

Time: 20 min

ABL 4.2 LEARNING OBJECTIVE – What is transpiration?

Note to Instructor – This is a group activity. You will have to demonstrate a part of the experimental set-up.

This activity should be performed as soon as the learners finish the calculation of surface area of leaves in ABL 4.1.

ADVANCE PREPARATION: Material List S. No.

Material

Required Quantity

1

Plastic cups

2 per group, 2 for the Instructor

2

Card board 2’ x 2’

1 per group, 1 for the Instructor

3

Water

1 bucket full

4

Methylene blue/Saffranine/methyl orange

3 ml per group

5

Scissors

1 pair per group, 1 pair for the Instructor

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6

Cello tape

1 roll per group, 1 for the Instructor

7

Blade

1 for the Instructor

8

Small brush

1 for the Instructor

9

Petri dish

1 for the Instructor

10

Glass slide, cover slip

2 each for the Instructor

11

Microscope (10x)

1 for the class

12

Small measuring beaker (in ml)

1 per group

Things to Do 

Make sure there are small plants available near where you do this activity for the learners to collect.

Safety Precautions Not Applicable

SESSION: Link To known information/previous activity Not Applicable Procedure Ask the learners to sit in the same groups. Distribute the materials. Draw the sketch of the experimental setup on the board so the learners are clear about what needs to be done and can refer to it if any group gets confused.

Ask one person from each group to bring a small plant with roots.The plant should be of a size that can fit in the cups (figure below).Fill one cup halfway with water.Add 3 ml of stain (ink/saffranine/methylene blue) to the water in the cup. Next cut the card board just to fit on the mouth of the plastic cup (as given in the figure).

Now, the Instructor should do the remaining with the groups so they know what to do. Make a hole in the centre of cardboard, and introduce the plant through the hole. Then place the plant with cardboard over the plastic cup containing coloured water.Seal the hole with cellotape or Vaseline. Also fix the cardboard to the glass with the cello tape. Invert another cup over the plant and seal the two mouths of the cups. This is the experimental set-up. Place the set-up in bright sunlight and observe carefully for 15 to 20 minutes.

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Figure 7 – Transpiration experiment setup

Select any one of the plants at the end of the 20 minute waiting period. With the help of a blade, take thin transverse sections of the stem and roots at different points. Transfer the thin sections to a Petridish containing water. With the help of brush select a fine thin section and place it on a clean slide. Add a drop of water to the thin section and place a coverslip over it without any air bubbles. Focus under microscope. Ask the learners to come and see in a line one after the other. Ask them to write down what they see.

Now go and remove the plastic covers from the leaves in ABL 4.1. Make sure you don’t allow any water in the covers to spill. Collect the water in a small measuring beaker and note down how many ml of water has been released by each leaf. Count the number of leaves on the plant and calculate the approximate amount of water released by all leaves in 30 minutes. Next calculate the value for whole day i.e. 12 hours, this gives for 1 day. Now calculate how much water is lost in 1 year, assuming the plant has the same number of leaves throughout the year.

UNDERSTANDING THE ACTIVITY: Leading Questions 1. What do you see on the sides/walls of the upper plastic cup?

2. What is the colour of the water drops in the upper cup?

3. You supplied coloured water to the plant but you got colourless drops of water, what could be the reason? Where does the colour go?

4. Why do plants draw water from the roots and release it from their leaves?

5. What is the significance of this process?

Discussion and Explanations

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1. Water drops.

2. They are colourless.

3. The plant has absorbed the colour. You can see this colour in the sections of the stem and roots. (here, absorbing of colour from coloured water can be taken as that of absorbing dissolved nutrients from water) 4. Plants absorb water from the soil and utilize this for their activities like growth, photosynthesis etc.

Plants absorb sufficient quantity of water but hardly use some 3 to 5 percent, and the remaining unused water is sent out through the areal parts in the form of vapours. The process of sending the excess water though the areal parts (mostly leaves) in the form of vapours is called transpiration. This takes part mainly through the stomata.

5. Transpiration is important as the evaporating water from the leaves helps in pulling up water from the roots to different parts of the plant. Transpiration occurs mainly during the day time and in the night the stomata remain closed. Transpiration helps in the movement of nutrients all over the plant. It increases the absorption of nutrients from soil. It also has a cooling effect on leaves and reduces the heating of leaves by solar radiation. Plants use only 3 to 5 percent of absorbed water for their metabolic activities. The remaining 95% of water is released into the atmosphere through stomata by transpiration.

KEY MESSAGES: 

In transpiration, water absorbed by the roots moves up through the plant and evaporates from the leaves.

LEARNING CHECK: As water evaporates from leaves, water from roots move up through the plant. True or False?

(Answer: True).

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OBSERVATION SHEET – HYDRILLA EXPERIMENT – ABL 2.1 GROUP DETAILS: ________________________________________ ___________________________________________________________ ____________________________________________________________ Time after which data is to be recorded

Number of Bubbles

1st five minutes

2nd five minutes

3rd five minutes

4th five minutes

5th five minutes

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