Etiolation is causes by the influence of

Step 1: Analyze the question The question asks what factor causes etiolation in plants.

Step 2: Explain the concept Etiolation is the abnormal growth pattern seen in plants grown in the absence (or severe shortage) of light. Light normally controls how a plant grows, a process called photomorphogenesis. When light is missing, the plant shows these features:

• Long, thin, weak stems, because the plant stretches rapidly in search of light
• Pale yellow or whitish colour, because chlorophyll cannot form without light
• Small, underdeveloped leaves
• Poor structural strength

Step 3: Work through the options

• A. Mineral salts: A shortage of minerals causes deficiency symptoms such as chlorosis (e.g. lack of magnesium or nitrogen). It is not etiolation, which is a response to light.
• B. Water: Lack of water causes wilting, not etiolation.
• C. Carbon dioxide: It is a raw material for photosynthesis, but its absence does not produce the elongated, pale growth of etiolation.
• D. Light: Correct. Etiolation results from the lack of light.

Step 4: Answer The correct option is D. Light.

Tip: Remember "Etiolation = Eliminate light". A seedling grown in a dark cupboard comes out tall, thin and yellow. This is a common JAMB experiment, so picture it whenever you see the word. Also, do not confuse it with chlorosis, which is yellowing caused by mineral deficiency.