Stigma

Definition

The stigma is the part of the female reproductive structure of flowering plants where pollen grains land and germinate. It plays a critical role in reproduction by receiving pollen during pollination, which is essential for fertilization and the development of seeds. The structure is often sticky or feathery, adapted to enhance the likelihood of successful pollination by attracting pollen from various sources.

5 Must Know Facts For Your Next Test

1. The stigma's shape and surface characteristics vary among plant species, influencing the type of pollinators that can effectively transfer pollen.
2. Stigmas can be either dry or moist; moist stigmas tend to be more effective in capturing and retaining pollen grains.
3. In many flowering plants, multiple stigmas can be present, increasing the chances of successful cross-pollination.
4. Some stigmas produce chemical signals that attract specific pollinators, ensuring efficient pollen transfer from compatible plants.
5. The success of fertilization depends significantly on the compatibility between the pollen grain and the stigma, as not all pollen can germinate on every stigma.

Review Questions

• How does the structure of the stigma contribute to its function in pollination and fertilization?
  • The structure of the stigma is crucial for its role in pollination and fertilization as it provides a receptive surface for pollen grains. The surface can be sticky or feathery, allowing it to capture pollen effectively from various sources. This structural adaptation ensures that when pollen lands on a stigma, it can germinate and grow down through the style to reach the ovary for fertilization.
• Discuss how different types of stigmas might affect plant reproductive strategies and success rates in various environments.
  • Different types of stigmas can significantly influence a plant's reproductive strategies and success rates. For example, a sticky stigma may attract more pollinators, leading to higher chances of successful cross-pollination, while a feathery stigma may be better suited for wind-pollinated species. Additionally, environmental factors like humidity and temperature can affect how well a stigma captures and retains pollen, impacting overall reproduction success in diverse habitats.
• Evaluate the ecological importance of stigmas in flowering plants and their role in maintaining biodiversity.
  • Stigmas play a pivotal role in the ecological dynamics of flowering plants by facilitating reproduction and ensuring genetic diversity. By allowing various pollen types to fertilize ovules, stigmas help promote cross-pollination, which enhances genetic variation within plant populations. This genetic diversity is vital for resilience against pests and diseases and supports broader ecosystem health by ensuring a stable supply of seeds for future generations. Thus, stigmas not only contribute to individual plant fitness but also help maintain overall biodiversity in ecosystems.

Related terms

Style: The tube-like structure that connects the stigma to the ovary, allowing pollen to travel from the stigma to the ovules for fertilization.

Pollen: The male gametophyte produced by seed plants that contains sperm cells, essential for fertilizing ovules after being transferred to the stigma.

Ovule: The structure within the ovary that develops into a seed after fertilization, containing the female gamete and other necessary tissues.