Systemic acquired resistance

Definition

Systemic acquired resistance (SAR) is a plant's innate ability to develop a heightened state of defense against pathogens following an initial infection. This phenomenon is characterized by the production and signaling of various plant hormones and defense compounds, allowing plants to respond more effectively to subsequent attacks from pathogens or pests. SAR not only enhances local defenses at the site of infection but also triggers systemic changes throughout the plant, impacting growth regulators, herbivore interactions, and induced defense mechanisms.

5 Must Know Facts For Your Next Test

1. SAR is initiated when a plant is exposed to a pathogen, which leads to the production of signaling molecules like salicylic acid and proteins that enhance resistance.
2. Once systemic acquired resistance is activated, it can provide long-lasting protection against a wide range of pathogens and pests, even those not previously encountered.
3. The effectiveness of SAR can be influenced by environmental factors, such as temperature and humidity, which can affect the plant's ability to produce necessary defense signals.
4. SAR can lead to trade-offs in plant growth, as resources are reallocated from growth processes to enhance defensive strategies.
5. Some novel plant growth regulators have been shown to enhance SAR by either promoting the signaling pathways involved or directly inducing defense gene expression.

Review Questions

• How does systemic acquired resistance impact a plant's overall growth and development following a pathogen attack?
  • Systemic acquired resistance impacts a plant's growth and development by reallocating resources away from growth towards the activation of defense mechanisms. While this enhanced state of readiness allows for better protection against future attacks, it can also result in reduced growth rates or compromised reproductive success due to energy being diverted from these processes. Ultimately, while SAR provides crucial protection against pathogens, it may impose physiological costs that affect long-term plant fitness.
• Discuss the role of salicylic acid in the activation of systemic acquired resistance and its interaction with other signaling pathways.
  • Salicylic acid is pivotal in activating systemic acquired resistance by serving as a key signaling molecule that triggers defense gene expression and promotes systemic responses throughout the plant. It interacts with other signaling pathways, including those mediated by jasmonic acid, which is more involved in responding to herbivores. This interplay between salicylic acid and jasmonic acid demonstrates how plants coordinate their defenses against different types of threats, optimizing their responses based on the nature of the attack.
• Evaluate the implications of systemic acquired resistance for agricultural practices and pest management strategies in crop production.
  • The implications of systemic acquired resistance for agricultural practices are significant, as understanding and harnessing SAR can lead to more sustainable pest management strategies. By enhancing natural plant defenses through the application of certain growth regulators or biological control agents that stimulate SAR, farmers can reduce reliance on chemical pesticides. This not only helps in managing pest populations more effectively but also supports ecosystem health by minimizing chemical inputs. Furthermore, crops bred for stronger SAR traits may lead to varieties that are more resilient to diseases, ultimately improving yields and sustainability in agriculture.

Related terms

jasmonic acid: A plant hormone involved in regulating defense responses against herbivores and pathogens by activating genes associated with plant defense.

salicylic acid: A signaling molecule that plays a crucial role in the activation of SAR and the enhancement of defenses against biotrophic pathogens.

induced resistance: The process by which plants activate their defense mechanisms in response to specific stimuli, such as pathogen attack or herbivore feeding.