Requirements for Seed Germination

The germination of seeds is dependent on both internal and external conditions.

External Factors

Water (Moisture) – This is required to trigger the mechanism of germination. Mature seeds are often extremely dry and need to take in significant amounts of water, relative to the seeds dry weight, before cellular metabolism, to resume their growth. When seeds are formed, most plants store food, such as starch, proteins, or oils, to provide nourishment to the growing embryo inside the seed. When seed absorb water, hydrolytic enzymes are activated that break down these stored food resources in to metabolically useful chemicals, allowing the cells of the embryo to divide and grow. Seed coat burst so the seedling can emerge from the seed.

Oxygen – It is essential during germination for respiration and other physiological activities. Some seeds have impermeable seed coats that prevent oxygen from entering the seeds; it is called as seed dormancy.

Temperature – Suitable temperature is important factor for proper seed germination. Temperature affects cellular metabolic and growth rates. Different seeds germinate over a wide range of maximum and minimum temperatures. Seeds of many species prefer temperatures slightly higher than room-temperature, some germinate just above freezing temperature and others respond to alternation in temperature between warm to cool. Some seeds require exposure to cold temperature (vernalization) to break dormancy so they can germinate.

Light or Darkness – It is not considered as essential for seed germination. The seedlings grow more vigorously during darkness rather in light. Light acts as a environmental trigger for germination in seeds. Most seeds are not affected by light or darkness, but many seeds, including species found in forest settings will not germinate until they receive sufficient light for the seedlings to grow.

Internal Factors

Food – Embryo feed on the stored food material, until the young seedlings start to synthesize their own food material.

Auxins – These are growth promoting substances, hence quite essential for germination.

Viability – After the seeds are produced they remain viable for certain definite period that varies from plant to plant or seed to seed. Thereafter embryo becomes dead. Seed viability period depend upon storage conditions, vigour of parents, species etc. generally it is 3 to 5 years, sometimes can be 200 years as in lotus.

DormancySeed dormancy is the failure of fully developed, mature, viable seed to germinate even under favorable physical conditions (moisture and temperature).