National League for Nursing (NLN PAX) Practice Exam

The correct term that describes how the stem of a plant grows toward the light is phototropism. This phenomenon occurs when plants detect light and respond by directing their growth toward it, which is essential for maximizing their exposure to sunlight and optimizing photosynthesis.

Phototropism is a positive growth response to light, meaning the plant grows towards the light source. This response is primarily regulated by plant hormones called auxins, which facilitate stem elongation on the side of the plant that is away from the light, causing the stem to bend toward the light source.

The other options involve geotropism, which pertains to a plant's growth response to gravity rather than light. Specifically, roots typically exhibit positive geotropism by growing downward, while stems demonstrate negative geotropism, growing upward. The addition of a "+" sign in front of phototropism or geotropism is unnecessary and does not alter the fundamental meaning of the terms. Therefore, phototropism is the most accurate and relevant term for describing plant growth towards light.