Question

Describe pollen-pistil interaction in detail.

Answer 1

Hint: Pollination does not guarantee the transfer of the right type of pollen grain on the stigma. The pistil needs to identify the right type of pollen grain so that it accepts it and carries out the post-fertilization events that lead to fertilization.

Complete answer:
During pollination, it may happen that a wrong type of pollen, either from other species or from the same plant(self-incompatible) lands on the pistil. In this situation, the pistil needs to identify the correct type of pollen grain(compatible) from the incompatible ones. Once the pistil identifies the pollen, it initiates a sequence of events that begins from the time the pollen lands on the stigma of the pistil and till the entry of the pollen tube inside the ovule. These events are called pollen-pistil interaction. Pollen-pistil interaction is a dynamic process that involves pollen recognition followed by promotion or inhibition of pollen.
After the pistil accepts the pollen, the pollen germinates and there is a formation of a pollen tube in which the pollen releases its contents. The pollen tube grows through the tissues of stigma and style of the pistil and reaches the ovary. After the pollen tube reaches the ovary, it enters the ovule through the micropyle and enters one of the synergids through the filiform apparatus.

Additional information: During pollination, sometimes the pistil does not accept the pollen grain from the same plant. This is called self-incompatibility.
Self-incompatibility is a mechanism that prevents pollen from one flower from fertilizing other flowers of the same plant.
It is observed in plants belonging to Solanaceae and Rosaceae families.

Note: The pollen tube will only grow if the pollen landing on the stigma is compatible and accepted by the pistil. If the pollen is self-incompatible or incompatible, the growth of the pollen tube will not occur which is an important step for fertilization as the generative cell divides and forms the two male gametes during the growth of the pollen tube in the stigma.