A few normal seedlings of tomato were placed in a dark room. After a few days, they were found to have turned white-coloured like albinos. Which of these can be used to describe them?

The correct option is Etiolated.

Step-by-Step Explanation:

1. Understanding the Effect of Darkness on Plants:
When normal green plants, such as tomato seedlings, are grown or placed in complete darkness, they cannot perform photosynthesis because light is essential for this process. Furthermore, light is required for the synthesis of chlorophyll, the green pigment in plants. In the absence of light, chlorophyll synthesis stops, and existing chlorophyll degrades, causing the plants to lose their green color and appear pale yellow or white (albino-like).

2. Defining the Terminology:
Let us analyze the terms provided in the options to see which one describes this physiological state:
• Etiolated: This is the correct botanical term used to describe plants that have grown in partial or complete absence of light. Etiolated plants exhibit pale or white coloration (chlorosis due to lack of chlorophyll), long and weak stems, fewer or smaller leaves, and longer internodes.
• Defoliated: This refers to a plant that has lost its leaves, which is not the case here since the seedlings are still intact but have changed color.
• Embolised: This refers to the formation of air bubbles (embolism) in the xylem vessels of a plant, which blocks water transport. It does not describe albino-like color change due to darkness.
• Mutated: This refers to a permanent change in the DNA sequence. The color change observed here is a physiological response to the environment (lack of light) and is temporary, not a genetic mutation.

3. Conclusion:
Therefore, the seedling behavior of turning white-colored due to being placed in a dark room is described as being etiolated.