Plant Defence Against Pathogens

Introduction

Plants encounter numerous challenges posed by pathogens, impacting their health and survival. Understanding how plants defend themselves is crucial for maintaining ecological balance and agricultural productivity. This is particularly important in regions like Australia, where plants such as Eucalyptus and Acacia are prevalent.

Key Definitions:

Phytophthora cinnamomi: A significant source of ecological disruption, notably affecting Eucalyptus.

Importance of Plant-Pathogen Studies

Comprehending plant-pathogen interactions is essential for multiple reasons:

• Economic Significance: Agriculture depends on healthy plants, and understanding pathogens is vital to reduce crop losses.
• Ecological Impact: Native flora is crucial for ecosystems; preserving plant health supports biodiversity.

Overview of Common Pathogens

Several pathogens affect Australian flora, primarily fungi and viruses:

• Fungi: Phytophthora cinnamomi causes notable harm via root rot.
• Viruses: Impact plants such as Eucalyptus and Acacia by disrupting vital functions.

Plant-Pathogen Interaction Dynamics

Entry Points

• Stomata and Wounds: These act as primary entry points for pathogens.

Infection and Colonisation

• Initial Contact & Entry: Pathogens gain access through openings.
• Colonisation: This disrupts plant harmony, causing systemic issues.

Types of Plant Defences

Physical Defences

• Thick Cuticles: Function as barriers to prevent pathogen entry.
• Bark: Offers a robust shield against pathogens, notably in Eucalyptus and Acacia.
• Small Stomata: Minimise entry points for pathogens.

Chemical Defences

• Secondary Metabolites: Compounds like phytoalexins target pathogens.
• Signalling Molecules: Salicylic acid and jasmonic acid initiate defence responses.

Plant Immune System Components

Pathogen-Associated Molecular Patterns (PAMPs)

• Elicit immune responses by being recognised by plant receptors.

Effector-Triggered Immunity (ETI)

• Utilises specific resistance genes to detect pathogen effectors, following the gene-for-gene hypothesis.

Environmental Influences on Plant Defences

Temperature and Precipitation

• Influence structural and biochemical defences, affecting pathogen proliferation.

Soil Characteristics

• Nutrient Availability: Correlates with the strength of defences.
• Soil Salinity: Impacts water uptake and weakens defences.

Biotic Interactions

• Symbiotic Relationships: Enhance resilience through beneficial associations.

Visual and Practical Investigations

• Sample Collection: Practice sterile techniques to avoid contamination.
• Inoculation: Introduce pathogens within a controlled laboratory setting.

Conclusion and Summary

Investigating plant-pathogen interactions deepens the understanding of plant defences and aids in developing effective conservation strategies. This is particularly crucial for sustaining agricultural practices amidst evolving environmental conditions.

Recommendation: Utilise secondary data for comprehensive insights into plant defences and broader conservation outcomes.

Review Questions

• Which of the following is NOT part of a plant's immune defence?
  1. Production of phytoalexins
  2. Activation of T-cells