Which factor is sometimes required for germination but not universally needed?

• A. Light
• B. Water
• C. Oxygen
• D. Temperature

Answer: (A)

Light acts as a germination cue for some seeds but isn’t required by all. Germination starts with water uptake and then relies on suitable temperature and oxygen to power the metabolic processes. Water, temperature, and oxygen are needed for most seeds to sprout, because without moisture you can’t resume metabolism, without the right warmth enzymes won’t function properly, and without oxygen respiration won’t occur. Light, however, varies by species: some seeds require light to begin germinating (positive photoblastism), some prefer darkness (negative photoblastism), and many are indifferent to light. That variability is why light is described as sometimes required but not universally needed. For example, lettuce seeds germinate best when exposed to light, whereas other seeds can sprout without regard to light conditions.