key term - Abscisic acid

Definition

Abscisic acid is a plant hormone that plays a critical role in regulating various plant processes, especially in response to environmental stresses. This hormone helps plants manage water loss by promoting stomatal closure and also influences seed dormancy and germination, ensuring that seeds only sprout under favorable conditions. It acts as a key signaling molecule, helping plants adapt to changing environments.

5 Must Know Facts For Your Next Test

1. Abscisic acid is often referred to as the 'stress hormone' because it helps plants respond to drought and other stressful conditions.
2. This hormone is synthesized in response to water scarcity, leading to stomatal closure to reduce water loss through transpiration.
3. Abscisic acid also plays a significant role in seed dormancy, preventing seeds from germinating until conditions are suitable for growth.
4. The presence of abscisic acid can inhibit growth processes, which is crucial during times when a plant needs to conserve resources.
5. Research has shown that abscisic acid signaling pathways involve complex interactions with other hormones, such as gibberellins and ethylene, allowing for coordinated responses to environmental changes.

Review Questions

• How does abscisic acid influence stomatal behavior in response to environmental stress?
  • Abscisic acid influences stomatal behavior by promoting their closure during periods of environmental stress, particularly drought. When a plant experiences water scarcity, abscisic acid levels increase, signaling guard cells surrounding the stomata to close. This action reduces water loss through transpiration, allowing the plant to conserve moisture and survive under challenging conditions.
• Discuss the relationship between abscisic acid and seed dormancy.
  • Abscisic acid plays a vital role in regulating seed dormancy by preventing premature germination. High levels of this hormone ensure that seeds remain inactive until environmental conditions are favorable for growth, such as adequate moisture and temperature. When conditions improve, the decrease in abscisic acid allows for the activation of growth hormones like gibberellins, triggering germination.
• Evaluate how abscisic acid interacts with other plant hormones to coordinate responses to stress.
  • Abscisic acid interacts with other plant hormones, like gibberellins and ethylene, to create a balanced response to environmental stresses. For instance, while abscisic acid promotes stomatal closure and conserves water during drought, gibberellins may promote growth when conditions improve. This intricate hormonal interplay allows plants to adapt efficiently to changing environments, ensuring survival and optimal growth through various stages of development.

Related terms

Stomata: Tiny openings on the surfaces of leaves that allow for gas exchange, including the release of oxygen and uptake of carbon dioxide.

Gibberellins: A group of plant hormones that promote stem elongation, seed germination, and flowering, often working in opposition to abscisic acid.

Ethylene: A gaseous plant hormone involved in the regulation of fruit ripening, flower wilting, and leaf fall, which can interact with abscisic acid during plant stress responses.