Seed vigour, a single concept reflecting several characters, determines the seed quality and uniform emergence potential of plants in the field under variable range of environments. Seed vigour does not reflect a specific property of a seed or seed lot but is still a concept. Several factors like genetic constitution, growth environment and nutrition of the mother plant, maturity at the time of harvest, seed size and weight, mechanical stability, deterioration and ageing and pathogens are responsible for the difference in seed vigour. Vigor testing does not only measure the percentage of viable seed in a sample, it also reflects the ability of those seeds to produce normal seedlings under less than optimum or adverse growing conditions similar to those which may occur in the field. Seeds may be classified as viable in a germination test which provides optimum temperature, moisture and light conditions to the growing seedlings; however, they may not be capable of continuing growth and completing their life cycle under a wide range of field conditions.
Generally, seeds start to lose vigor before they lose their ability to germinate; therefore vigor testing is an important practice in seed production programs. Testing for vigor becomes more important for carryover seeds, especially if seeds were stored under unknown conditions or unfavorable storage conditions. Seed vigor testing is also used as indicator of the storage potential of a seed lot and in ranking various seed lots with different qualities. Cold test, accelerated aging test, electric conductivity test, seedling vigor classification, and seedling growth rate are among the tests that are used to measure seed vigor.
Seed vigour is an important component of seed quality and satisfactory levels are necessary, in addition to traditional quality criteria of moisture, purity, germination and seed health to obtain optimum plant stand and high production of crops. Research is needed to further refine the current seed vigour test methods and to develop new methods which are rapid and more related to field/storage conditions.
Aqief Afzal