pollenstigma

Pollenstigma, or the stigma, is the receptive surface at the distal end of the pistil in flowering plants. It serves as the initial contact site for pollen and plays a central role in pollination and fertilization. The stigma sits atop the style and is the first tissue to encounter pollen grains carried by wind, water, or animal vectors.

Stigma morphology varies across species. It can be a wet stigma, which secretes fluids that hydrate and nourish pollen grains, or a dry stigma, which relies more on ambient moisture. The surface is often patterned with specialized epidermal cells called papillae, creating textures that influence pollen capture, adhesion, and hydration. Some stigmas are highly sticky or sculptured with grooves or ridges that affect pollen specificity and reception.

During pollination, pollen lands on the stigma and must adhere, hydrate, and germinate. If compatible, a pollen tube forms and grows through the stigma and into the style to reach the ovules in the ovary. In many plants, self-incompatibility mechanisms prevent self-pollen from germinating or progressing, promoting cross-pollination and genetic diversity.

Stigma structure and function impact reproductive success, pollen competition, and the potential for cross-pollination. It develops from the pistil during flower formation and responds to pollination events with physiological and biochemical signals that facilitate fertilization when appropriate pollen reaches the ovules.