, Ch-13: Photosynthesis in Higher Plants
Photosynthesis: Green plants synthesize their own food. It is a physico-chemical
process.
(Food/Glucose + Oxygen)
○ Early Experiments
2. Variegated Leaf Experiment: 1Proves that photosynthesis (P.S.) occurs only in the
○ Exposed leaf
○ Covered leaf
➡️ ➡️
green parts of leaves in the presence of sunlight.
➡️ ➡️
P.S. occurs
No P.S.
Starch present.
No starch.
3. Moll’s Half-Leaf Experiment (KOH):
○ A part of a leaf is enclosed in a test tube containing KOH soaked cotton (which
absorbs CO_2).
○ The exposed part shows starch formation, while the enclosed part doesn't.
○ Conclusion: CO_2 is essential for photosynthesis.
4. Joseph Priestley (1770): Bell Jar experiment.,
○ Discovered O_2 in 1774.
○ Conclusion: Plants restore to the air whatever breathing animals and burning
candles remove. (Used a Mint plant).
5. Jan Ingenhousz: Showed that sunlight is essential to the plant process.
○ Observed small bubbles (Oxygen) formed around green parts of aquatic plants
only in sunlight.
6. Julius von Sachs (1854):
○ Provided evidence for production of glucose when plants grow.
○ Glucose is usually stored as Starch.
○ Chlorophyll is located in special bodies (Chloroplasts).
7. T.W. Engelmann: Used a prism to split light into spectral components to illuminate
green alga (Cladophora).
○ Used aerobic bacteria to detect sites of O_2 evolution.
○ Action Spectrum: Bacteria accumulated mainly in Blue and Red light regions.
8. Cornelius van Niel: Studied purple and green sulphur bacteria.
○ Demonstrated that photosynthesis is a light-dependent reaction.
○ Hydrogen from a suitable oxidizable compound reduces CO_2 to carbohydrates.
1
1
Photosynthesis: Green plants synthesize their own food. It is a physico-chemical
process.
(Food/Glucose + Oxygen)
○ Early Experiments
2. Variegated Leaf Experiment: 1Proves that photosynthesis (P.S.) occurs only in the
○ Exposed leaf
○ Covered leaf
➡️ ➡️
green parts of leaves in the presence of sunlight.
➡️ ➡️
P.S. occurs
No P.S.
Starch present.
No starch.
3. Moll’s Half-Leaf Experiment (KOH):
○ A part of a leaf is enclosed in a test tube containing KOH soaked cotton (which
absorbs CO_2).
○ The exposed part shows starch formation, while the enclosed part doesn't.
○ Conclusion: CO_2 is essential for photosynthesis.
4. Joseph Priestley (1770): Bell Jar experiment.,
○ Discovered O_2 in 1774.
○ Conclusion: Plants restore to the air whatever breathing animals and burning
candles remove. (Used a Mint plant).
5. Jan Ingenhousz: Showed that sunlight is essential to the plant process.
○ Observed small bubbles (Oxygen) formed around green parts of aquatic plants
only in sunlight.
6. Julius von Sachs (1854):
○ Provided evidence for production of glucose when plants grow.
○ Glucose is usually stored as Starch.
○ Chlorophyll is located in special bodies (Chloroplasts).
7. T.W. Engelmann: Used a prism to split light into spectral components to illuminate
green alga (Cladophora).
○ Used aerobic bacteria to detect sites of O_2 evolution.
○ Action Spectrum: Bacteria accumulated mainly in Blue and Red light regions.
8. Cornelius van Niel: Studied purple and green sulphur bacteria.
○ Demonstrated that photosynthesis is a light-dependent reaction.
○ Hydrogen from a suitable oxidizable compound reduces CO_2 to carbohydrates.
1
1
