What conditions are necessary for seed germination?

Seed germination requires suitable temperature, adequate moisture, oxygen, and in some cases, light.

For a seed to germinate, it must be in an environment with a suitable temperature. This varies between species, but most seeds require a temperature between 20-30°C. The temperature affects the metabolic processes within the seed, which are necessary for germination. If the temperature is too low, these processes slow down, delaying germination. If it's too high, it can damage the seed's cells, preventing germination.

Adequate moisture is also crucial for seed germination. The seed absorbs water, which triggers the metabolic processes necessary for germination. The water also softens the seed coat, making it easier for the emerging root and shoot to break through. However, too much water can be harmful. It can lead to waterlogging, which deprives the seed of oxygen, another essential factor for germination.

Oxygen is necessary for the seed's respiration process, which provides the energy needed for growth. When a seed is sown, it begins to respire aerobically, using oxygen to break down the stored food reserves and release energy. This energy is used to drive the growth of the new plant. If the seed is deprived of oxygen, it will switch to anaerobic respiration, which is less efficient and can lead to the death of the seed.

Lastly, some seeds require light to germinate, while others can germinate in the dark. Light-sensitive seeds have a pigment called phytochrome, which triggers germination when it absorbs light. This ensures that the seed only germinates when it's near the soil surface, where it has access to light and can photosynthesise. On the other hand, seeds that can germinate in the dark usually do so deeper in the soil, where they are protected from harsh environmental conditions.