Question

Given below is the figure of an experimental set-up, showing a physiological act of the plants. Study and answer the following questions:

1. What is the objective of this experiment?
2. Name and define the process shown here.
3. Why do we destarch the leaves before performing the experiment?
4. How do we destarch the leaves?
5. What will be the observation when we pour iodine solution over the bleached experimental leaf?
6. Write a well-balanced equation for the above process.

Answer 1

1. To demonstrate the need for sunlight for photosynthesis.
2. With the aid of water and carbon dioxide, photosynthesis is the process by which plants create food glucose, facilitated by the presence of plants' chlorophyll pigment in sunlight. Products from photosynthesis are glucose and oxygen. Plants employ glucose to drive their cellular functions; other species need oxygen to respire.
   We destarch a plant such that photosynthesis takes place in the sunshine. If the leaves already contain starch, photosynthesis does not take place.
3. The leaves will destarch if we put them in a dark room for 24 to 48 hours. Darkness lets the plant consume any pre-existing starch kept in the leaves and stops photosynthesis.
4. The bleached experimental leaf will assume a blue-black hue when iodine solution is applied to it, indicating the presence of starch. The absence of a colour change (the leaf remains brown) would suggest that the leaf is starch-free.
5. \[\ce{6CO2 + 6H2O ->[Sunlight][Chlorophyll] C6H12O6 + 6O2}\]