The Stigma in a Flower: Plant Reproduction

Structure of a Flower

• Flowers have either a female reproductive system, a male reproductive system, or both.
• The female and male parts can be on the same plant or on different plants.
• The stigma is part of the female reproductive system, located in the center of a flower.

Stigma

• A stigma is a sticky bulb on top of the style, a thin stalk or stem.
• Stigmas can be large or small, and vary in shape, size, and color.
• The stigma is covered with stigmatic papillae, cells that receive pollen.

Functions of Stigma

• The stigma catches pollen transferred by wind or insects, such as bees and butterflies.
• The pollen is pulled down through the style and into the pistil, where fertilization occurs.
• The stigma helps to move pollen through the process by rehydrating dry pollen.
• Fertilization occurs in the ovaries, leading to the formation of seeds.

Adaptations of Stigma

• Over time, the stigma has become stickier to increase pollen capture.
• The style has become stronger to hold the stigma in place.
• Some plants have longer styles to allow the stigma to move in the wind.
• Stigmas come in different shapes and sizes, depending on pollinators and environment.

Stickiness of Stigma

• The stigma is sticky to help hold onto pollen from wind or insects.
• The stickiness also helps to move pollen down through the style.
• The moisture on the stigma rehydrates dry pollen, facilitating fertilization.

Variations of Stigma

• Sessile stigmas are on flowers with extremely short styles or no style at all.
• Some stigmas have three lobes that transfer pollen to facilitate fertilization.
• Stigmas can be tall and feathery, with a large surface area for catching wind-blown pollen.