GMAT Critical Reasoning (CR) | because plants have more nutrients

Because plants have more nutrients when they are exposed to sunlight and water at their roots, the growth of young plants generally increases when there is a decent amount of sunshine. By contrast, however, following a prolonged period of sunny days, the growth of hosta plant leaves is minimal and the outside edges of its leaves begin turning brown, even when rainfall is plentiful.

Which of the following, if true, does most to explain the contrast described above?
(A)
During periods of extreme
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