Question

To determine that light is essential for photosynthesis, the following are the steps, but not in sequence:
i) Pluck the leaf and do the starch test.
ii) Keep the selected plant in sunlight.
iii) Distarch the plant for 48 - 72 hours.
iv) Cover the leaf with black paper strip. The correct sequence is

A) (iii), (i), (ii), (iv)
B) (iii), (ii), (iv), (i)
C) (iii), (iv), (ii), (i)
D) (i), (ii), (iv), (iii)

Answer 1

Hint: Photosynthesis is a process that plants and other organisms use to transform light energy into chemical energy that can then be released to fuel the organism's metabolic activities through cellular respiration.

Complete answer:
During the photosynthesis process, the following events occur:
(a) Light is absorbed by chlorophyll pigments found in leaves.
(b) Light energy is converted into chemical energy, which is then used to split water into hydrogen.
as well as oxygen molecules
(c) Carbon dioxide is broken down into carbohydrates.

Destarching: When a plant is kept in darkness for approximately 48 hours, all of the carbohydrates generated and processed by the plant are used to provide energy to the plant. This is known as destarching.

Boiling the leaf in alcohol: The leaf is boiled in alcohol to extract the pigment chlorophyll, which would otherwise interfere with the starch examination. Since alcohol evaporates easily without making any contact with the leaves, it is not heated directly over the flame.

Starch test: When iodine solution is added to starch, it forms a blue-black starch-iodine complex. When a partially covered leaf is treated with iodine solution, the covered portion does not turn blue-black when iodine solution is added, while the exposed portion that obtained light turns blue-black due to starch synthesis.

So, Option "C" is the correct answer.

Note: Water is absorbed by plants through their roots, and carbon dioxide is absorbed by plants through their leaves. They produce glucose as a source of food. Glucose is further broken down into starch. Photosynthesis produces oxygen as a by-product.