Question

Which of the following experiments showed that $C{O}_2$ is essential for photosynthesis?

• A. Half - leaf experiment
• B. Variegated leaf experiment
• C. Priestley’s experiment
• D. J. von Sach's experiment

Answer 1

Answer: (A)

• $C{O}_2$ is essential for PHS is demonstrated by half leaf experiment (by Moll’s).
• In this experiment a part of a leaf is enclosed in a test tube containing some $KOH$ soaked cotton ($KOH$ absorbs $C{O}_2$) while the other half is exposed to air.
• The setup is then placed in light for some time. On testing for starch later in the two halves of the leaf, you must have found that the exposed part of the leaf tested positive for starch while the portion that was in the tube, tested negative. This showed that $C{O}_2$ was required for photosynthesis.