In seed germination, several factors are essential for the process to occur successfully. These factors include water, air, suitable temperature, and sunlight. Water is crucial as it activates enzymes that break down stored food in the seed, providing essential nutrients for growth. Air is needed for respiration, as seeds require oxygen for metabolic processes. Suitable temperature is necessary for optimal enzyme activity during germination.

However, sunlight is not required for seed germination. While sunlight is important for the growth and development of a seedling after germination, seeds themselves do not need sunlight to initiate the germination process. Instead, they rely on other factors such as water, air, and suitable temperature. Therefore, option 3, sunlight, is not required for seed germination.