Abscisic acid

Definition

Abscisic acid is a plant hormone that plays a crucial role in regulating various physiological processes, particularly in response to stress conditions such as drought and salinity. This hormone helps plants conserve water by promoting stomatal closure, thus reducing transpiration and aiding in the transport of water and solutes during challenging environmental conditions.

5 Must Know Facts For Your Next Test

1. Abscisic acid is often referred to as the 'stress hormone' because it accumulates in response to environmental stresses like drought and high salinity.
2. One of its primary functions is to signal stomata to close, which helps minimize water loss during dry conditions.
3. Abscisic acid also influences seed dormancy, ensuring that seeds do not germinate until conditions are favorable.
4. This hormone can promote root growth by enhancing the plant's ability to uptake water and nutrients under stress.
5. In addition to drought responses, abscisic acid also plays a role in plant development, influencing processes like fruit ripening and leaf senescence.

Review Questions

• How does abscisic acid influence the regulation of stomata in response to water stress?
  • Abscisic acid plays a key role in signaling the closure of stomata during water stress conditions. When a plant experiences drought, abscisic acid accumulates and binds to receptors in guard cells surrounding the stomata. This binding triggers a series of events leading to the loss of potassium ions from guard cells, causing them to lose turgor pressure and close. This response effectively reduces transpiration and conserves water, helping the plant survive in adverse conditions.
• Discuss the impact of abscisic acid on seed dormancy and germination processes.
  • Abscisic acid is vital for maintaining seed dormancy, preventing seeds from germinating until environmental conditions are optimal. High levels of abscisic acid inhibit the synthesis of enzymes needed for germination, keeping seeds inactive during unfavorable conditions. Once conditions improve—such as sufficient moisture—abscisic acid levels drop, allowing for the activation of these enzymes and facilitating germination. This ensures that seeds only sprout when they have the best chance for survival.
• Evaluate how abscisic acid functions as a signaling molecule in plants and its broader implications for plant responses to environmental stressors.
  • Abscisic acid serves as a critical signaling molecule that coordinates a plant's physiological responses to various environmental stressors, including drought and salinity. It triggers complex signaling pathways that enable plants to adapt by regulating processes such as stomatal closure, root development, and seed dormancy. These adaptations not only enhance individual plant survival but also have broader implications for ecosystem stability and agricultural practices. Understanding how abscisic acid operates could inform strategies for improving crop resilience in the face of climate change.

Related terms

Stomata: Tiny openings on the surfaces of leaves that allow for gas exchange; their regulation is essential for controlling water loss and photosynthesis.

Transpiration: The process by which water vapor is released from the plant into the atmosphere through stomata, playing a key role in nutrient transport and temperature regulation.

Hormones: Chemical signals produced by plants that regulate growth, development, and responses to environmental stimuli.