Question

Which plant has the longest pollen grain?

Answer 1

Hint: Pollen grains are microscopic structures that carry the androecium – the male reproductive part of a flower. They are the male microgametophytes of seed plants that later produce the male gametes – sperm cells. They are found in the powdery substance called pollen.

Complete answer:
- Pollen is the male gametophyte of seed plants – gymnosperms and angiosperms.
- The average size of pollen grains ranges from 15μm to 200μm.
- Also, when dry, their shape is usually oval or spherical.
- Most pollen grains have a hard coating made of the chemical substance sporopollenin, which protects the grains against harsh conditions.
- When pollen grains land on a compatible pistil (female reproductive part of flower), it will germinate and produce a long pollen tube that delivers the sperm to the ovule in the female flower.
- The longest pollen grain has been found on the plant Zostera.
- The pollen grains on Zostera are up to 2500μm long.
- Being longer, the outer wall of these grains is tougher and made of cellulose and sporopollenin.
- Zostera is commonly called seagrass and is a type of marine flowering plant.

Note: In contrast, the smallest pollen grains are found in the plant Myosotis. The process of stratification involves many factors such as - temperature modulation, choosing stratification medium, use of fungicide and methods of sowing the seeds as well.