In seed germination, some species require light to germinate, while others require darkness. Which statement is true?

• A. True; Some seeds require light to germinate, while others require darkness.
• B. False; All seeds require darkness
• C. False; Light has no effect on germination
• D. False; Light always inhibits germination

Answer: (A)

Germination responds to light in different ways across plant species. Some seeds are positively photoblastic, meaning they require light to trigger germination, while others are negatively photoblastic and germinate best in darkness. The light signal is detected by phytochrome receptors that shift between forms when exposed to red or far-red light, promoting germination in some seeds and inhibiting it in others. This mixture of responses explains why the true statement is that some species need light to germinate while others require darkness. For example, lettuce seeds germinate more readily when they see light, illustrating a light-requiring (positive photoblastic) response. Others germinate better in darkness, showing a darkness requirement. The other claims—that all seeds require darkness, that light has no effect, or that light always inhibits germination—don’t hold because germination responses to light vary by species.