Question

Pollen tube is covered by:
A. Pectocellulose   
B. Sporopollenin
C. Cellulose        
D. Lignocellulose

Answer 1

Hint: A pollen tube is a tubular structure that the male gametophyte of seed plants produces as it germinates. Pollen tube elongation is a crucial phase in the life cycle of plants. This tube serves as a pathway for the male gamete cells to move from the pollen grain to the ovules at the base of the pistil or, in some gymnosperms, directly through the ovule tissue.

Step by step solution:
The male gametophytes are represented by the pollen grains. These are typically spherical objects with a diameter of 25–50 micrometres.
Pollen grains have a cell wall known as sporoderm, which has two layers, exine and intine.

Exine: It is a sporopollenin-based hard exterior layer (one of the most resistant organic materials known). The exine is a protective layer since it can tolerate high temperatures as well as potent acids and alkalis. So yet, there is no known enzyme that can break down sporopollenin.
Additionally, this aids in fossilisation. Due to sporopollenin, pollen grains can be stored and used as fossils for research.

When pollinated by biotic/abiotic agents, it is challenging for the pollen grains to remain sealed off from dangerous conditions and exhibit a diverse assortment of patterns and shapes that are important for taxonomic understanding.
It lacks sporopollenin, although it does have conspicuous openings called germ-pores.

Intine: It is the thin, continuous inner wall, which is composed of cellulose and pectin.
The pollen grain's plasma membrane encloses the cytoplasm.

So, option A is correct.

Note: Many species of pollen grains, particularly those from anemophilous plants, can cause severe allergies and bronchial problems in some people, frequently progressing to long-term respiratory conditions including asthma and bronchitis. The grains of pollen are nutrient-rich. They improve athletes' performance.