One of the following plants shows longest seed viability. 

The ability of embryo of seed to develop into seedling is called seed viability. The period is variable in various species of plants. Lupinus arcticus has longest seed viability whose seeds can germinate even after 10,000 years of its formation. Such seeds were excavated from arctic tundra. Phoenix dactylifera has seed viability of 2000 years. Nelumbo and Mangifera have relatively less seed viability. Mangroove plants have very poor or no seed viability as their seeds start germinating when they are still in the fruits of parental plant.