Seed germination is sometimes dependent on which environmental factor, in addition to air, moisture, and temperature?

• A. Light
• B. Humidity
• C. Gravity
• D. Wind

Answer: (A)

Light acts as an environmental cue that can determine whether a seed will begin to germinate. Many seeds are photoblastic, meaning they respond to light via photoreceptors called phytochromes. When exposed to light, these receptors can shift to a form that promotes germination in some species; other seeds require darkness and will only germinate when buried or shielded. This light sensitivity is why light is the factor that matters in addition to air, moisture, and temperature for certain seeds. Gravity doesn’t trigger germination, it mainly influences the direction of growth after germination, and wind affects dispersal. Humidity relates to moisture already covered in the question.