Name the part of gynoecium that determines the compatible nature of pollen grain.

Pistil has the capacity to recognize suitable (Right type) or not suitable (Wrong type) type of pollen grain. The pollen grain is right type then pistil accepts the pollen and promotes postpollination events that leads to fertilisation. If the pollen is of the wrong type pistil rejects the pollen.

The ability of pistil to recognise the pollen followed by its acceptance or rejection is the result of a continuous dialogue between pollen grain and pistil. This dialogue is mediated by chemical components of the pollen grain interacting with those of the pistil.