What type of directional plant growth curvature is exhibited when a growing pollen tube elongates down the style toward ovule chemical secretions?
Answer and explanation
Correct answer: A. positive chemotropism
- Step 1: Chemotropism is growth orientation in response to a chemical concentration gradient. Step 2. The pollen tube grows down the style toward calcium/sugary chemical attractants secreted by the embryo sac/micropyle (positive chemotropism). Answer: positive chemotropism. Why not the others: Thigmotropism is touch response; phototropism is light response; photonasty is non-directional light response.
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