Q. In half leaf experiment, a part of a leaf is enclosed in a test tube containing KOH soaked cotton, while the other half is exposed to air and then setup is placed in light for sometime. It was latter found that part of leaf which was exposed to air tested positive for starch. This indicates that
A) Light is essential for photosynthesis
B) Oxygen is liberated in photosynthesis
C) Water is essential for photosynthesis because in KOH soaked leaf, starch synthesis do not occurs as water reacts with KOH and it become unavailable for photosynthesis
D) Carbon dioxide is essential for photosynthesis because in KOH soaked leaf, starch synthesis do not occurs as $CO_{2}$ is absorbed by, so $CO_{2}$ is not available for photosynthesis
Explanation
$CO_{2}$ is required for photosynthesis is demonstrated by half-leaf experiment in which a part of a leaf is enclosed in a test tube containing some KOH soaked cotton (which absorbs $CO_{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, the exposed part of the leaf tested positive for starch while the portion that was in the tube, tested negative. This showed that $CO_{2}$ is required for photosynthesis
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.