What is the main role of the stigma in the pistil?

The stigma plays a crucial role in the reproductive process of flowering plants by serving as the receptive surface for pollen. When pollen grains land on the stigma, they germinate and the pollen tube begins to grow down through the style to reach the ovary. This process is essential for fertilization as it allows sperm cells to travel from the pollen to the ovule.

While the stigma contributes to the overall reproductive success of the flower, it does not provide support to the flower structure, attract pollinators directly, or produce ovules; those functions belong to other parts of the flower, such as the sepal, petals, and ovary respectively. Therefore, the main role of the stigma is indeed to receive pollen, facilitating the critical step of fertilization in the plant's life cycle.