False Statement: Pollen kitt is absent on pollen grains of Capsella.

Explanation:

Reproductive structures of plants are essential for sexual reproduction. Pollination is an important process that involves the transfer of pollen grains from the anther to the stigma of the flower. The pollen grains contain male gametes that fertilize the female gametes in the ovule, leading to the formation of seeds.

Here are some facts related to the given statements:

- Pollens are received by stigma: The stigma is the receptive part of the female reproductive structure of the flower. It is responsible for receiving the pollen grains and providing a suitable environment for their germination.
- Pollen tube discovered by Amici: The pollen tube is a structure that grows from the pollen grain after it lands on the stigma. It penetrates the style and reaches the ovary where fertilization takes place. The pollen tube was discovered by an Italian scientist, Giovanni Battista Amici, in the 19th century.
- Tigellum is the main axis of embryo: The tigellum is the embryonic axis that develops from the zygote after fertilization. It gives rise to the root and shoot systems of the plant and forms the main axis of the embryo.

However, the statement that pollen kitt is absent on pollen grains of Capsella is false. Pollen kitt is a sticky, oily secretion that is present on the surface of some pollen grains. It helps in the adherence of pollen grains to insects and other pollinators that visit the flowers. Capsella is a member of the Brassicaceae family, and many species in this family have pollen kitt on their pollen grains. Therefore, the given statement is false.