Which part of gynoecium determines the compatible nature of pollen ?

Stigma

The correct answer is Option (2) → Stigma

The stigma is part of the gynoecium (female reproductive structure) that plays a crucial role in determining the compatible nature of pollen. The stigma is located at the top of the style and style connects the stigma to the ovary. When pollen grains land on the stigma, they need to be compatible with the reproductive structures of the pistil for successful pollination to occur. Pollination does not guarantee the transfer of the right type of pollen (compatible pollen of the same species as the stigma). Often, pollen of the wrong type, either from other species or from the same plant (if it is self-incompatible), also land on the stigma. The pistil has the ability to recognise the pollen, whether it is of the right type (compatible) or of the wrong type (incompatible). If it is of the right type, the pistil accepts the pollen and promotes post-pollination events that leads to fertilisation. If the pollen is of the wrong type, the pistil rejects the pollen by preventing pollen germination on the stigma or the pollen tube growth in the style. The ability of the pistil to recognise the pollen followed by its acceptance or rejection is the result of a continuous dialogue between pollen grain and the pistil. This dialogue is mediated by chemical components of the pollen interacting with those of the pistil. It is only in recent years that botanists have been able to identify some of the pollen and pistil components and the interactions leading to the recognition, followed by acceptance or rejection