I was just looking up the example of the oldest seed that has been germinated and it turns out it is an interesting example of never quite knowing where reasearch might take you (literally and metaphorically).
The oldest seed that has been germinated into a viable plant was an approximately 1,300-yr-old lotus fruit, recovered from a dry lakebed in northeastern China.
Long-living lotus: germination and soil -irradiation of centuries-old fruits, and cultivation, growth, and phenotypic abnormalities of offspringOver this length of time the seeds are subject to natural radiation, in this case from the soil. Although 8 out of 10 seeds germinated, phenotypic abnormalities were observed. Most of the abnormalities resemble those of chronically irradiated plants exposed to much higher irradiances for much shorter time periods.
All seeds presumably repair cellular damage before germination. Understanding of repair mechanisms in the old lotus seeds may provide insight to the aging process applicable also to other organisms.