Question

the flower petals of a hydrangea plant change color as the acidity of the soil changes. the color changes are directly related to which factor?
photosynthesis
geographic location
gravitropism
environmental conditions

Explanation:

• Photosynthesis: It is the process by which plants convert light energy into chemical energy. It has no direct relation to flower petal color changes based on soil acidity.
• Geographic location: While it can influence various aspects like climate, the direct factor here is soil acidity (a part of environmental conditions), not just the broad geographic location.
• Gravitropism: This is the growth of plants in response to gravity. It is not related to color - change due to soil acidity.
• Environmental conditions: Soil acidity is an environmental factor. Hydrangea petal color changes as a response to this environmental (soil - related) condition.

Answer:

environmental conditions