Salicylic acid

Definition

Salicylic acid is a plant hormone and a key signaling molecule involved in the regulation of plant defense mechanisms and growth responses. It plays a vital role in the activation of systemic acquired resistance, helping plants respond to biotic stressors like pathogens, while also being implicated in various growth and developmental processes.

5 Must Know Facts For Your Next Test

1. Salicylic acid is synthesized from phenylalanine and is crucial for mediating plant defense responses, particularly against bacterial and fungal infections.
2. It enhances the expression of pathogenesis-related genes, which contribute to the plant's immune response and strengthen cell walls.
3. Salicylic acid can trigger a cascade of signaling events, leading to the production of reactive oxygen species that help combat pathogen attack.
4. Plants utilize salicylic acid to regulate their growth, as it influences processes like leaf senescence and flowering time.
5. In addition to its role in defense, salicylic acid is also involved in other physiological processes, such as thermogenesis in some plants.

Review Questions

• How does salicylic acid contribute to systemic acquired resistance in plants?
  • Salicylic acid plays a central role in activating systemic acquired resistance (SAR) by acting as a signaling molecule that helps the plant recognize and respond to pathogen attacks. When a part of the plant is infected, salicylic acid is synthesized and transported throughout the plant, inducing a defense response that includes the upregulation of pathogenesis-related genes. This prepares uninfected tissues for potential attacks, thus enhancing overall plant immunity.
• Discuss the interplay between salicylic acid and other plant hormones during stress responses.
  • Salicylic acid interacts with other hormones like jasmonic acid and ethylene during stress responses, creating a complex network of signaling pathways. For instance, while salicylic acid is primarily associated with defense against biotrophic pathogens, jasmonic acid is more closely linked to responses against necrotrophic pathogens. This hormonal crosstalk allows plants to fine-tune their defensive strategies depending on the type of stressor they encounter.
• Evaluate the broader implications of salicylic acid's role in plant physiology and agriculture.
  • Salicylic acid's involvement in both defense mechanisms and growth regulation has significant implications for agriculture, especially in developing disease-resistant crops. By understanding how salicylic acid mediates plant responses to biotic stressors, researchers can manipulate its pathways to enhance crop resilience. Additionally, using salicylic acid or its analogs as biostimulants can improve plant health and yield, promoting sustainable agricultural practices.

Related terms

Systemic Acquired Resistance: A form of induced defense in plants where a localized infection leads to a long-lasting increase in resistance throughout the plant.

Pathogen-Associated Molecular Patterns (PAMPs): Molecules associated with groups of pathogens recognized by plants, triggering immune responses.

Ethylene: A plant hormone involved in various processes such as fruit ripening and response to stress, often interacting with salicylic acid in signaling pathways.