Ubisch bodies are present in

The correct option is D

Tapetum

The correct option is D.

Explanation of the correct option:

1. Ubisch bodies are the small acellular structure of the sporopollenin.
2. Ubisch bodies are present in the cells of tapetum and help in the development of pollen grains.
3. Tapetum is a nutritive cellular layer found within the anther.
4. Tapetum belongs to the male reproductive structure of the flower.
5. The function of the tapetum is to provide nutrients and other regulatory molecules to the developing pollen grains.
6. Ubisch bodies are involved in the external thickening of exine because of the presence of sporopollenin.

Explanation of the incorrect options:

Option A:

1. A pollen tube is a slender tubular outgrown from a pollen grain that penetrates the ovule and releases male gametes.
2. The tip-growing pollen tube provides a good model system to study polar and oscillatory growth.

Option B:

1. A pollen grain is an immature male gametophyte.
2. The function of pollen is to deliver male gametes sperm from the stem of a plant to an ovule for fertilization of an egg which then develops into a seed.

Option C:

1. Microspore present in plant spore that develops into a male gametophyte.
2. A male gametophyte gives rise to the sperm cells and which are used for the fertilization of an egg cell to produce a zygote.

Final answer: Ubisch bodies are present in Tapetum.