Question

Design an experiment to demonstrate that carbon dioxide is essential for photosynthesis. Write the observation and conclusion of the experiment.

June 19, 2025

Answer

Take two healthy potted plants, A and B of nearly the same size.

Keep them in darkness for three days. (Destarch the plant)
Place a watch glass containing potassium hydroxide by the side of potted plant A but not in potted plant B.
Cover both the plants with separate bell jars and seal the bottom of the jars with Vaseline.
Keep both the plants in sunlight for two hours.
Pluck one leaf each from both the plants and test for the presence of starch with iodine solution.
Observation: The leaf of the potted plant A with KOH did not turn blue-black, indicating that starch was not present. The leaf of the potted plant B turns blue.
Conclusion: KOH absorbs CO₂ so photosynthesis did not occur in potted plant A.

💡 Some Related Questions

(a) Write the function of the following in the human alimentary canal:

Saliva

HCI in the stomach

Bile juice

Villi

(b) Write one function for each of the following enzymes:

Pepsin

Lipase

What causes the movement of food inside the alimentary canal in human beings?

Name an enzyme present in pancreatic juice.

(A) Write the correct sequence of steps followed during journey of oxygen rich blood from lungs to various organs of human body. (B) What happens when the system of blood vessels develop a leak?

(a) Why is there a difference in the rate of breathing between aquatic organisms and terrestrial organisms? Explain. (b) Draw a diagram of the human respiratory system and label it – the pharynx, trachea, lungs, diaphragm and alveolar sac on it.

(a) Why is nutrition necessary for the human body? (CBSE 2020)
(b) What causes the movement of food inside the alimentary canal?
(c) Why is the small intestine in herbivores longer than in carnivores?
(d) What will happen if mucus is not secreted by the gastric glands?

(a) Name the organs that form the excretory system in human beings. (b) Describe in brief how urine is produced in the human body.

(a) Describe the structure and function of the basic filtering unit of the kidney. (b) List two factors on which the reabsorption of water from urine depends.

(a) “Blood circulation in fishes is different from the blood circulation in human beings”. Justify the statement.
(b) Describe “blood circulation” in human beings.

Give reasons:
(a) Ventricles have thicker muscular walls than atria.
(b) The transport system in plants is slow.
(c) Circulation of blood in aquatic vertebrates differs from that in terrestrial vertebrates.
(d) During the daytime, water and minerals travel faster through the xylem as compared to the night.
(e) Veins have valves, whereas arteries do not.