Lesson

Purpose of the work:

– by experiment to investigate the factors necessary for the process of photosynthesis

Run time: 

Expected results:

After completing the work, students can:

•  develop teamwork skills
•  be able to analyze and summarize the information received
•  draw logical conclusions

Teacher’s Guide:

• The task is performed in groups of  3-4 people
• Working with a knife requires special care
• Before starting laboratory work, please read the safety rules by following the link:

To download the worksheet, follow the link:

Theory

External factors that directly affect photosynthesis

	Plants use light energy for photosynthesis. A certain level of illumination is necessary to start this process. Light energy is absorbed by chlorophyll, a pigment found in plant chloroplasts. The intensity and quality of light can affect the rate of photosynthesis.
	Plants also need carbon dioxide for photosynthesis. The level of carbon dioxide in the atmosphere can vary, and its availability affects the rate of photosynthesis.
	Temperature also affects photosynthesis. The optimum temperature may vary from plant to plant, but in general, temperatures that are too low or too high can slow down or even stop the process of photosynthesis.
	Plants need water for photosynthesis. Water serves not only as a source of hydrogen and electrons, but also transports the substances necessary for photosynthesis from the roots to the leaves. Lack of water can reduce the rate of photosynthesis.
	Plants need certain nutrients such as nitrogen, phosphorus, and potassium to support healthy growth and chlorophyll function. Nutrient deficiencies can reduce the ability of plants to photosynthesize.

Sources:

1. 11 сынып Биология 1 бөлім 11 тақырып – Атамұра (atamuraweb.kz)
2. Фотосинтез туралы қазақша мәлімет (ikaz.kz)
3. <a href=”https://ru.freepik.com/free-vector/diagram-showing-process-of-photosynthesis-in-plant_20498775.htm#query=%D1%84%D0%BE%D1%82%D0%BE%D1%81%D0%B8%D0%BD%D1%82%D0%B5%D0%B7&position=2&from_view=search&track=sph”>Изображение от brgfx</a> на Freepik

Practical part

In this experiment, it is recommended to use aquatic plants belonging to the following families: Hydrilla, Elodea, Chara. In case there’s no way to get these plants, any other type of plant can be used.

Step 1 First fill the glass with water and add 1 tablespoon of baking soda.

Step 2: Place the plant into the funnel.

Step 3. Now we attach the funnel to the bottom of the water so that it fully covers the plant.

Step 4. Fill the test tube completely with water and, by covering it with your thumb, carefully insert it into the tubular side of the funnel so that the water remains in the test tube. We will observe oxygen bubbles through the water inside the test tube.

Step 5. Turn on the table lamp.

Research part

Next, to determine the effect of light on the intensity of photosynthesis, we count how many air bubbles are released in one minute, placing a table lamp at different distances from the plant. To do this, first we place the lamp at a distance of 5 cm, then increase the distance to 10, 15, 20, 25 cm. To accurately measure the distance, we put a ruler between the plant and the lamp. We also use a timer to calculate the time.

Repeat the experiment 3 times so that the obtained numerical data is statistically accurate.

Enter your results in the table below:

To sum up, write down the answers to the following questions on your worksheet:

• How does changing light intensity affect the process of photosynthesis?
• What is the role of chlorophyll pigments in photosynthesis and how do they interact with light?
• What other factors besides light can affect the process of photosynthesis?

Conclusion

In this experiment, students determined how sunlight affects the process of photosynthesis.