INSTITUT PERGURUAN RAJA MELEWAR

LABORATORY REPORT

PRACTICAL 6

To Investigate Conditions Essential for Photosynthesis

AHMAD NAJIBULLAH BIN CHE MOHD

890205-11-5547

SCIENCE 1

PUAN SITI HARTINI BINTI HAJI PUNGUT

SCIENCE DEPARTMENT, IPRM

Practical 6: To investigate conditions essential for photosynthesis

Objective: a) To test the presence of starch in green leaf.b) To show that sunlight is necessary for photosynthesis.c) To show that chlorophyll is essential for photosynthesis.d) To show that carbon dioxide is necessary for photosynthesis.e) To show that oxygen is produced during photosynthesis.

Introduction:

Green plants are producers. This means that they can survive without animals. Plants make sugar, storing the energy of the sun into chemical energy, by the process of photosynthesis. The process of photosynthesis involves the use of light energy to convert carbon dioxide and water into sugar, oxygen, and other organic compounds.

Problem : What are conditions essential for photosynthesis?

Hypothesis : Plants needs sunlight, carbon dioxide and chlorophyll to make

process photosynthesis to produce starch and oxygen.

Material and apparatus:

LeavesHydrilla or any water plantBeakerBell jarFilter funnelPolythene bagTest tubeWhite tileMethanolIodine solutionBoiling waterCalcium hydroxideKalium hydroxide

Procedure:

(a) To test the presence of starch in green leaf1. A leaf from a plant that has been exposed to sunlight for a few hours had been

pluck.2. A leaf was placed in a beaker of boiling water. This kills it and softens it.3. A small amount of methanol was get in a boiling tube and had add the leaf to

this.4. The tube in the beaker was placed of hot water. Do nor relight any Bunsen.

Methanol is highly flammable.5. After about five minutes, the leaf was pull out of the methanol and check that the

leaf is decolourised. The methanol dissolves chlorophyll but not starch.6. The leaf was dip into hot water for a few seconds to soften it again. 6. The leaf was lay flat on a white tile and put three or four drops of iodine solution.7. Observation was record. (b) To show that sunlight is necessary for photosynthesis

1. A potted plant was keep in the darkness for about 24 hours.2. A leaf was pluck. 3. The leaf was tested for starch. Step 2-6 in was repeated (a).4. Observation was record.

(c) To show that chlorophyll is essential for photosynthesis

1. A variegated leaf that has been exposed to sunlight for a few hours had been removed.

2. A diagram to show the distribution of the green colour in the leaf was draw .3. The leaf was tested for starch. Step 2-6 in was repeated (a).4. Observation was record.

(d) To show that carbon dioxide is necessary for photosynthesis

1. Two potted plants was leaved in darkness for about one day to remove any starch present.

2. Their pots were covered with polythene bags. 3. The plants were placed under two bell jars, A and B were labeled respectively.4. In bell jar A put a beaker of kalium hydroxide to absorb any carbon dioxide from

the air that enters the jar. The air in jar A was free from the carbon dioxide.5. Bell jar B has an open tube at its upper end which allows atmospheric air to enter

the jar.6. The two bell jars were placed in sunlight for a few hours.7. The leaf was tested for starch. Step 2-6 in was repeated (a).8. Observation was record.

(e) To show that oxygen is produced during photosynthesis

1. Some freshwater plants (Hydrilla) was placed under an inverted filter funnel in a beaker of water, preferably pond water. The funnel was raised above the bottom of the beaker to allow free circulation of water.

2. A test tube completely filled with water was inverted over the stem of the funnel. Make sure no air bubble was trapped in the test tube. It had been labeled it as Set A.

3. The apparatus was placed in sunlight for a few hours.4. Another experiment was set up in a similar way but place it in a dark cupboard.

This acts as a control. It had been label it as Set B.5. The gas with a glowing splint was tested in the test tube for Set A and Set B.

Result :

Experiment A : To test the presence of starch in green leaf

Observation Inference

This is because the leaf contain starch, starch will change color to dark blue after

had been test with iodine

Leaf color became dark blue after a few drops of iodine

Experiment B : To show that sunlight is necessary for photosynthesis

Observation Inference

There is still starch on the leaf even though had been in darkness for 24

hours.

Leaf color became dark blue after a few drops of iodine.

Experiment C : To show that chlorophyll is essential for photosynthesis

Observation Inference

Starch is manufactured in the green part of the leaf

Only parts that were previously green turn blue with iodine, the other one part turn

brown.

Experiment D : To show that carbon dioxide is necessary for photosynthesis

Observation Inference

Starch was made in the leaves which had carbon dioxide. Leaf in Set A do not has carbon dioxide but leaf in Set

B have carbon dioxide

Set A Set BThe leaf in Set A does not turn blue.

The leaf in Set B turn blue

Experiment E : To show that oxygen is produced during photosynthesis

Observation Inference

The plant did not enough of light source to undergo photosynthesis process.

No air bubbles trap in the test tube.

Discussion:

Our results show that photosynthesis can only take place in areas where a green substance called chlorophyll is present.

This chlorophyll, which is responsible for making leaves green, is contained within small round structures in plant cells called chloroplasts. Chlorophyll is a remarkable molecule because it harvests the energy of sunlight and uses it in the process of reacting together CO2 and H2O to make glucose – photosynthesis.

Photosynthesis means to "put together using light". Plants use sunlight to turn carbon dioxide from the air, and water into food. Plants need all of these to remain healthy. When the plant gets enough of these things, it produces a simple sugar, which it uses immediately or stores in a converted form of starch. We don't know exactly how this happens. But we do know that chlorophyll, the green substance in plants, helps it to occur.

During photosynthesis, glucose is synthesised by green plants. This process occurs only in parts of plants which contain chlorophyll and mainly in the leaves. Glucose is used by all plant parts during respiration. Some excess glucose is converted to storage products, mainly starch, in the leaves. Stored food may take the form of a number of different food substances like starch, sucrose, oils and certain proteins. Glucose may also be converted to cellulose, a component of the cell wall.

Oxygen is a product of the photolysis reaction not the fixation of carbon dioxide, during the light independent reactions. Consequently, the source of oxygen duringphotosynthesis is water, not carbon dioxide.

Conclusion:

Photosynthesis the process by which plants, some bacteria, and some protistans use the energy from sunlight to produce sugar, which cellular respiration converts intoATP, the "fuel" used by all living things. The conversion of unusable sunlight energy into usable chemical energy, is associated with the actions of the green pigmentchlorophyll. Most of the time, the photosynthetic process uses water and releases the oxygen that we absolutely must have to stay alive. Oh yes, we need the food as wel.We can write the overall reaction of this process as:

6H2O + 6CO2 ----------> C6H12O6+ 6O2

The entire hypothesis was correct.

Question and Answer :

Questions:

1. What do you observe concerning the distribution of the blue-black colour in the leaf?

2. Can you say that only the green portions of the leaf manufacture starch in sunlight? That is photosynthesis occurs only when chlorophyll is present?

Answer:

1. Iodine solution used to detect starch. Presence of starch will convert the

yellowish color of iodine to blue-black color. If there is no starch the color will

become brown stain.

2. Can you say that only the green portions of the leaf manufacture starch in

sunlight? That is photosynthesis occurs only when chlorophyll is present?

Yes, chlorophyll is the green pigment that present in the chloroplast of the leaf

cells. In a variegated leaf there are areas of mesophyll that are unable to

manufacture chlorophyll. There are yellow or cream colored contrasts to the

surrounding green leaf tissue. If there is no chloroplast means no chlorophyll on

the leaf. Photosynthesis only occurs when chlorophyll is present.

Reference :

Hong, B. T. (2005): Siri Teks Referens Biologi SPM. Selangor: Pearson Malaysia Sdn.

Bhd.

Lee Soon Ching, L. S. (2003): Success in Biology for STPM Volume 1. Selangor: Fajar

Bakti Sdn. Bhd.

Belle Lowe :Experimental Cookery From The Chemical And Physical Standpoint :John Wiley &

Sons Year1937 Copyright1937, Belle Lowe

Carter, J. S. (2009, Feb Thu 26). http://sambal.co.uk/photosynthesis.html. Retrieved

February 2009, from http://sambal.co.uk.

Marking Scheme

Manipulative SkillFull

MarkScore

1. Planning the set-up of apparatus 10

2. Correct technique of testing 10

3. The way observation is carried out 10

ProductFull

MarkScore

1.Title/Objective/Hypothesis 10

2.Introduction/Theoretical knowledge 10

3.Equipments/Apparatus/Procedure 10

4. Results –drawing and labeling 10

5.Discusson/Conclusion 10

6.Questions/Answer 10

7.References 10

TOTAL MARK 100