Correct option is A
Option 1 is correct : A, B and C
Breakdown of Statements:
Statement A: "H₂O₂ may be directly toxic to pathogens."
Correct: Hydrogen peroxide (H₂O₂) is one of the reactive oxygen species produced during plant defense responses. It can directly damage pathogens by oxidizing lipids, proteins, and DNA, leading to their destruction. This makes Statement A true.
Statement B: "In presence of iron, H₂O₂ gives rise to an extremely reactive hydroxyl radical."
Correct: When H₂O₂ interacts with iron, particularly through the Fenton reaction, it generates hydroxyl radicals (OH•), which are highly reactive and can cause severe damage to cellular components. This is a well-known process in oxidative stress and plant defense. So, Statement B is correct.
Statement C: "H₂O₂ leads to induced biosynthesis of salicylic acid (SA)."
Correct: H₂O₂ is involved in signaling pathways that lead to the synthesis of salicylic acid (SA), a key plant hormone that plays a critical role in plant defense, particularly in systemic acquired resistance (SAR). This statement is correct.
Statement D: "H₂O₂ production is always delayed during incompatible interactions."
Incorrect: H₂O₂ production in plants during defense responses is generally rapid and occurs early during pathogen attack or incompatible interactions (such as the hypersensitive response). The idea that H₂O₂ production is always delayed is not accurate. In fact, H₂O₂ production is usually one of the first responses to pathogen detection, so Statement D is incorrect.
Information Booster:
H₂O₂ and Pathogen Defense: H₂O₂ is a reactive oxygen species that plays an important role in plant defense mechanisms. It can directly damage pathogen cells, induce defense-related genes, and interact with other signaling molecules to activate plant immune responses.
Fenton Reaction and Hydroxyl Radical: The Fenton reaction involves the interaction between H₂O₂ and iron (Fe²⁺), producing hydroxyl radicals (OH•), which are highly toxic and contribute to oxidative damage in both plants and pathogens. This is a well-known reaction in oxidative stress and immune response.
Salicylic Acid (SA) and Plant Immunity: Salicylic acid is a key plant hormone involved in regulating plant immune responses. Its synthesis is induced by various stress signals, including the presence of H₂O₂. SA is crucial in mediating systemic acquired resistance (SAR) and other defense mechanisms in plants.
