Question

How do plants defend themselves against pathogens? a. Plants produce resistance molecules (usually proteins) that bind pathogen elicitors, thereby preventing disease. b. Plants display a hypersensitive response that limits the ability of pathogens to survive and spread. c. Plants display systemic acquired resistance, whereby an infection induces immunity to diverse pathogens in other parts of a plant. d. All of the above are correct. e. None of the above is correct.

Short answer

The correct answer is d. All of the above are correct.

Step-by-step solution

Analyzing choice a

Choice a posits that plants produce resistance molecules, usually proteins, that bind to pathogen elicitors to prevent disease. This is in fact a mechanism employed by plants. When a pathogen is detected, some plants are known to produce proteins that neutralize the threat.

Analyzing choice b

Choice b suggests a hypersensitive response from plants that limits the ability of pathogens to survive and spread. This is true as well. A hypersensitive response is a mechanism in which the plant induces rapid cell death around the point of pathogen entry, thus restricting its spread.

Analyzing choice c

Choice c mentions systemic acquired resistance, where an infection induces immunity to diverse pathogens in other parts of a plant. This is also a correct statement. Systemic acquired resistance is a form of 'immunity' that can be triggered by a localized infection, allowing the plant to better resist subsequent infections.

Making the final decision

After Analyzing choices a, b, and c and finding each to be a valid mechanism for plants to defend against pathogens, the correct answer would be option d: 'All of the above are correct.'

Key concepts

Resistance Molecules

Plants have a variety of weapons at their disposal to fend off invading pathogens, and one of the first lines of defense are resistance molecules. These special proteins play a crucial role in recognizing and binding to pathogen elicitors, which are substances emitted by pathogens as they attempt to infiltrate the plant. Once these molecules bind to the elicitors, they essentially "flag" the pathogen as an enemy, preventing the disease from taking hold.

• Resistance molecules are often proteins that can specifically detect harmful pathogens.
• They can neutralize the threat by restricting the pathogen's ability to multiply.
• This helps the plant maintain its health and continue growing.

Understanding the function of resistance molecules is vital because they initiate the plant's immune response, setting off a chain reaction that strengthens the plant's defenses.

Hypersensitive Response

The hypersensitive response is an intriguing strategy plants use to combat pathogens. When a plant recognizes a pathogen, it responds by quickly causing cell death around the infection site. While it might seem counterintuitive for the plant to kill its own cells, this tactic effectively walls off the invading pathogen, preventing it from spreading further into healthy tissue.

• The hypersensitive response is localized to the infection site.
• This rapid cell death creates a barrier that stops the pathogen.
• It is a programmed response, ensuring minimal damage to the plant.

By sacrificing only a small area of tissue, the plant can safeguard the rest of its body from widespread disease, showcasing nature’s remarkable efficiency.

Systemic Acquired Resistance

Once a plant has dealt with an initial infection, it often gains an enhanced ability to fend off subsequent attacks, a phenomenon known as systemic acquired resistance. Essentially, this strategy "teaches" the plant's immune system to recognize and respond more efficiently to new threats throughout the entire organism, not just where the original infection occurred.

• Systemic acquired resistance provides long-lasting protection.
• This resistance can affect the whole plant, not just the area initially affected.
• It is akin to a plant's memory of the pathogen, allowing quicker future responses.

Through systemic acquired resistance, plants effectively bolster their toolbox against diseases, making this defense mechanism crucial for survival in a pathogen-rich environment.

Pathogens

In the realm of plant defense, pathogens are the antagonists that threaten plant health. These could include bacteria, fungi, viruses, or other microorganisms that seek to invade plant tissues. They often release elicitors, which are detected by plant defense systems. Once detected, plants spring into action to neutralize the threat.

• Pathogens aim to exploit plant resources for their own survival.
• Their elicitors trigger the plant’s defense mechanisms, such as resistance molecules.
• Understanding pathogens helps in developing resistant crop varieties.

By comprehending how pathogens function and interact with host plants, scientists and agriculturists can devise better methods to protect crops and ensure food security.

Plant Immunity

Plant immunity encompasses all the defense mechanisms that plants use to protect themselves against pathogens. Unlike animals, plants do not have a circulatory immune system, so they rely on local and systemic responses to fend off invaders.

• Plants employ both innate and acquired immune strategies.
• They can "remember" previous infections for faster future reactions.
• Healthy plant immunity is critical for growth and reproduction.

Through natural selection, plants have evolved complex immune systems that are both specific and broad-ranging to effectively manage threats from diverse pathogenic organisms and environmental stresses.