ABA

Definition

ABA, or abscisic acid, is a plant hormone that plays a crucial role in regulating various physiological processes, especially in response to environmental stresses. It is primarily involved in promoting seed dormancy, stomatal closure during water scarcity, and influencing plant responses to stress factors like drought and salinity. This hormone acts as a key player in the plant sensory systems, helping plants adapt to their changing environment.

5 Must Know Facts For Your Next Test

1. ABA is synthesized in response to environmental stresses such as drought, salinity, and cold temperatures, helping plants conserve water.
2. One of the primary effects of ABA is the closure of stomata, which reduces water loss by transpiration when the plant is under stress.
3. ABA also plays a vital role in inducing seed dormancy, preventing seeds from germinating until conditions are favorable for growth.
4. In addition to stress responses, ABA can influence other processes such as fruit ripening and leaf senescence.
5. Research indicates that ABA signaling pathways involve complex interactions with other hormones like gibberellins and ethylene, highlighting its importance in overall plant physiology.

Review Questions

• How does ABA influence stomatal closure in plants, and why is this important for their survival?
  • ABA influences stomatal closure by signaling guard cells to reduce their turgor pressure, leading to the closing of these pores on leaf surfaces. This process is vital for plant survival during water scarcity because it minimizes water loss through transpiration. By regulating stomatal behavior, ABA helps plants maintain hydration levels and survive in stressful environmental conditions.
• Discuss the relationship between ABA and seed dormancy in plants. How does ABA contribute to this process?
  • ABA plays a critical role in promoting seed dormancy by inhibiting germination under unfavorable conditions. When seeds are exposed to ABA, it signals them to remain dormant until environmental conditions are optimal for growth, such as sufficient moisture and warmth. This mechanism ensures that seeds do not germinate prematurely, which could lead to poor survival rates if conditions change unexpectedly.
• Evaluate the role of ABA in coordinating plant responses to environmental stressors compared to other hormones like gibberellins and ethylene.
  • ABA serves as a key hormone in coordinating plant responses to environmental stressors like drought and salinity by promoting protective measures such as stomatal closure and seed dormancy. In contrast, gibberellins promote growth and germination, often working against the effects of ABA. Ethylene also interacts with ABA but primarily regulates processes like ripening and senescence. The balance between these hormones allows plants to adapt efficiently to their environments, highlighting the complexity of plant hormonal interactions.

Related terms

Stomata: Small openings on the surface of leaves that allow for gas exchange, which ABA helps regulate by causing them to close during water stress.

Gibberellins:

A group of plant hormones that promote growth and development, often working in opposition to ABA during processes like seed germination.

Ethylene:

A plant hormone involved in fruit ripening and response to stress, which interacts with ABA in various plant processes.