Q.How long seeds stay viable/ healthy?

Seed viability, the ability of a stored seed to germinate, varies from a few weeks to many centuries depending on the species and on storage conditions.

A seed is a resting embryo with a food store, and its viability lasts as long as the embryo stays alive inside the dormant seed. Three things decide that:

• The species. Short-lived (recalcitrant) seeds such as Citrus cannot tolerate drying and die within weeks or months. Most cereal and pulse seeds, dried and stored cool, keep good germination for 2-5 years. A few species are extraordinarily long-lived: the textbook cites a seed of the date palm Phoenix dactylifera that grew after about 2,000 years and a seed of Lupinus arcticus reported to have germinated after roughly 10,000 years in frozen ground (the date-palm record is the best documented of the two).
• Storage conditions. Low moisture and low temperature slow the embryo's metabolism and the deterioration of its membranes and enzymes; this is the principle of seed banks that store seeds at sub-zero temperatures for decades.
• Seed structure. A hard, impermeable seed coat and a large food store protect the embryo and extend its life.

Dormancy is the state that allows this waiting: a mature, viable seed will not germinate even under favourable conditions until its dormancy period is over, which spreads germination over time and space and helps the species survive bad seasons.

Maharashtra HSC Biology examiners like this recall point, and it appears in the same form in NCERT Class 12 Biology, which the state syllabus draws from.