Stigma (anatomy)

Anatomical structure in flowers

Stigma (anatomy)

The stigma is a vital part of the female reproductive system in flowering plants. It is the topmost part of the pistil, which is the female reproductive organ of a flower. The stigma plays a crucial role in the process of pollination and fertilization.

Diagram of a flower showing the stigma as part of the pistil.

Structure

The stigma is typically located at the tip of the style, which is a slender stalk that connects the stigma to the ovary of the flower. The stigma is often sticky or feathery, which helps it to effectively capture and hold pollen grains. The surface of the stigma can vary greatly among different species of plants, adapting to the specific pollination mechanisms they employ.

Function

The primary function of the stigma is to receive pollen during the process of pollination. Once pollen grains land on the stigma, they germinate and form a pollen tube that grows down the style to reach the ovary. This allows the sperm cells within the pollen to travel to the ovule, where fertilization occurs, leading to the formation of seeds.

Pollination

Pollination can occur through various means, including wind pollination, insect pollination, and animal pollination. The structure and position of the stigma are often adapted to the specific method of pollination. For example, in wind-pollinated plants, the stigma may be large and feathery to catch airborne pollen, while in insect-pollinated plants, it may be sticky to adhere to pollen carried by visiting insects.

Variations

Stigmas can vary widely in shape, size, and texture. Some stigmas are simple and flat, while others may be lobed or branched. The diversity in stigma morphology is often related to the plant's reproductive strategy and the type of pollinators it attracts.

Related pages

• Pistil
• Pollination
• Ovule
• Flower
• Reproductive system of plants