Question

Two green plants are kept separately in oxygen free containers, one in the dark and the other in continuous light. Which one will live longer?
a. The plant kept in dark
b. The plant kept in light
c. Both the plants will live for the same time
d. None of the above

Answer 1

Hint: As we all know that green plants make their food through a process called photosynthesis in the presence of chlorophyll, carbon dioxide, sunlight and water, and breakdown of carbon dioxide results in release of oxygen that plays a very important role in cellular respiration in plants.

Complete answer:
As we have discussed, a plant requires carbon dioxide, sunlight, chlorophyll and water molecules to convert the light energy into chemical energy, thereby making food by and this process is called photosynthesis.

Now let us talk about sunlight, all green plants rely on it for their nutrients requirement and it is necessary for the conversion of $CO_2$ and water molecules into oxygen and glucose. Without light, plants will not be able to make their food, green colour will be lost and eventually they will die. As we know that chlorophyll molecules are basically arranged around the photosystems, absorbs the sunlight and convert this light energy into chemical energy.

Now, Carbon dioxide and water molecules react to form a sugar compound and release oxygen as a by-product. This oxygen is responsible for cellular respiration in plants along with sugar it helps in synthesis of energy rich molecules called ATP i.e. Adenosine triphosphate and in this process carbon dioxide is released as a waste. So, when plants are deprived of oxygen then they will not be able to perform the aerobic respiration to break down their food and get energy from it and will eventually die.

Therefore from the above explanation, we can say that the plants require oxygen and light for their survival. Hence, the plant kept in light will live longer and the one in dark will die soon.
Hence, the correct answer is option (B).

Note: There are some plants which grow with very less light or without light and these plants are called shade loving plants but still they need moisture and oxygen for their survival. Succulent plants are the one that need very less amount of water but need oxygen and sunlight to survive. Hence, light and oxygen are the critical components required by plants.