Ethylene functions as which plant hormone?

• A. A plant hormone that inhibits fruit ripening
• B. A plant hormone that stimulates fruit ripening
• C. A nutrient absorbed by roots
• D. A pigment involved in photosynthesis

Answer: (B)

Ethylene acts as a plant hormone that stimulates fruit ripening. It’s a gaseous signaling molecule produced by many tissues, especially ripe fruit, and increases in concentration trigger a cascade of gene expression that activates enzymes responsible for softening the fruit, converting starches to sugars, and developing characteristic aromas and flavors. This ripening effect is the hallmark function highlighted in this question. It isn’t a nutrient absorbed by roots, nor a pigment involved in photosynthesis. Those roles belong to minerals and pigments like chlorophyll, respectively.