The below mentioned article provides a study note on the viability or longevity of seeds.
After their maturation the seeds do not remain viable indefinitely. They have a particular life span during which they must germinate otherwise they lose their viability (or capacity to germinate) first gradually and finally completely. The life span of seeds which may vary from few weeks to many years depends upon (i) species and (ii) the environmental conditions prevailing during seeds storage.
Ewart (1908) divided the seeds into 3 categories depending upon their life span or longevity:
(1) Microbiotic:
Seeds with life span of a few weeks to 4 years.
(2) Mesobiotic:
Seeds with life span ranging from 3 years to 15 years.
(3) Macrobiotic:
Seeds with life span varying from 15 years to 100 years or more. The seeds of most of the crop plants have usually very short life-span and belong to the first category. In such cases the seeds longevity can be increased to a considerable extent by keeping them under suitable storage conditions. On the other hand, seeds of considerable number of wild plants remain viable for 50 years or more because of pronounced dormancy of such seeds caused by the presence of hard seed coats.
Seeds of Cassia bicapsularis and C. multijuga had been found to remain viable even after 100 years. Besides these two legumes, other seeds with a life span of 75 years or more have also been found to be legumes. But the credit for longest life span goes to the viable seeds of Indian lotus (Nelumbo nucifera) which have been found buried under peat and soil in Manchuria. It is believed that these viable seeds must have been at least 130 years old and probably even 200-400 years old.
In recent years, there have been reports of seeds of some plants retaining viability upto many thousand years and even upto 10000 years, but, using 14C-dated techniques most of such reports have been found to be anecdotal and not authentic. However, the oldest 14C-dated seed that has grown into a viable plant was Judean date palm (a cultivar of Phoenix dactylifera) seed about 2000 years old, recovered from excavations at Herod the Great’s palace at Masada in Israel. It was successfully sprouted in 2005 (Sallon et al, 2008).
The second oldest viable 14C-dated recorded seed is now about 1300 years old sacred lotus (Nelumbo nucifera) seed, recovered from a dry lakebed in north eastern China in 1995 (Shen-Miller et al, 1995). Obviously, all these finding pertain to seeds which survived accidental storage followed by controlled germination and are not indicative of the upper survival time limit of properly stored seeds.