Question

Outer layer of microspore is made up of:

• A. Cellulose
• B. Pectin
• C. Sporopollenin
• D. Lignin

Hint:

The exine of pollen grains is made of sporopollenin, one of the most resistant organic substances known in nature. This allows pollen grains to remain preserved for thousands of years as fossils.

Answer 1

The Correct Option is C

Concept: A microspore develops into a pollen grain during the process of microsporogenesis in flowering plants. The pollen grain wall has two distinct layers:
• Exine – the outer layer
• Intine – the inner layer The exine is extremely tough and resistant to physical, chemical, and biological degradation. This outer layer is composed of a highly resistant organic substance called sporopollenin. Sporopollenin is known to be one of the most chemically stable biological materials, which protects the pollen grains from harsh environmental conditions such as high temperature, strong acids, and enzymes.

Step 1: Identify the layers of a microspore wall. The microspore (pollen grain) wall consists of:
• Outer layer → Exine
• Inner layer → Intine

Step 2: Determine the composition of the outer layer. The exine (outer layer) is composed of the highly resistant substance: \[ \text{Exine} \rightarrow \text{Sporopollenin} \]

Step 3: Eliminate incorrect options.
• Cellulose → Mainly present in plant cell walls and intine.
• Pectin → Found in middle lamella of plant cell walls.
• Lignin → Present in secondary cell walls of vascular tissues. Thus, none of these form the outer layer of the microspore.

Step 4: Select the correct option. Therefore, the outer layer of a microspore is made up of: \[ Sporopollenin \]