Abscisic acid

Definition

Abscisic acid (ABA) is a plant hormone that plays a critical role in regulating various physiological processes, particularly in response to stress conditions such as drought and salinity. It helps plants conserve water, promotes seed dormancy, and facilitates the aging process, making it essential for survival and adaptation.

5 Must Know Facts For Your Next Test

1. Abscisic acid is produced in response to environmental stresses such as drought, leading to the closure of stomata to reduce water loss.
2. It plays a vital role in seed dormancy by inhibiting germination until conditions are favorable for growth.
3. Abscisic acid is involved in the process of leaf senescence, promoting the breakdown of chlorophyll and the eventual shedding of leaves.
4. The synthesis of abscisic acid occurs primarily in the roots and leaves, allowing it to act locally or systemically within the plant.
5. ABA also regulates other developmental processes like fruit development and maturation, working alongside other hormones to ensure proper growth.

Review Questions

• How does abscisic acid influence the water conservation mechanisms in plants during drought conditions?
  • Abscisic acid is crucial for water conservation in plants during drought by triggering the closure of stomata. When ABA levels rise due to water stress, it signals the guard cells surrounding stomata to close, reducing transpiration and preventing excessive water loss. This helps the plant maintain hydration levels and survive under challenging conditions.
• Discuss the role of abscisic acid in seed dormancy and how it interacts with other hormones during this process.
  • Abscisic acid promotes seed dormancy by inhibiting germination until environmental conditions are optimal. It works against gibberellins, which encourage germination, ensuring that seeds do not sprout prematurely. This balance between ABA and gibberellins is essential for plant survival, allowing seeds to remain dormant during unfavorable conditions and only germinate when conditions improve.
• Evaluate the broader implications of abscisic acid's role in leaf senescence and its impact on overall plant health.
  • Abscisic acid's role in leaf senescence involves promoting chlorophyll degradation and facilitating nutrient mobilization back to the plant's roots. This process is crucial for recycling resources and preparing the plant for future growth cycles. Understanding ABA's influence on senescence helps highlight its importance not just in individual plant life cycles but also in ecosystem health by managing biomass and nutrient flow within plant communities.

Related terms

Gibberellins: A group of plant hormones that promote stem elongation, seed germination, and flowering, often opposing the effects of abscisic acid.

Ethylene: A gaseous plant hormone involved in fruit ripening, leaf abscission, and response to stress, which interacts with abscisic acid in regulating plant growth.

Stomata: Small openings on the surface of leaves that regulate gas exchange and transpiration, where abscisic acid plays a key role in closing them during water stress.