Which of the following seeds have remained alive for the longest period ?

The correct option is Phoenix dactylifera.

Seed viability refers to the ability of a seed to germinate and grow into a normal seedling under favorable environmental conditions. The period for which seeds remain alive or viable varies greatly among different plant species. While some seeds lose viability within a few months, others can remain viable for hundreds or even thousands of years.

Among the given options, the seeds of the date palm, scientifically known as Phoenix dactylifera, have recorded one of the longest periods of viability. A viable seed of Phoenix dactylifera was excavated from King Herod's palace near the Dead Sea. This seed was successfully germinated after remaining dormant for approximately 2,000 years, demonstrating an extraordinary span of viability.

In contrast, another notable example of extreme longevity is Lupinus arcticus (arctic lupine), whose seeds germinated after an estimated 10,000 years of dormancy in the tundra. However, among the choices provided in the question—Phoenix dactylifera, Striga asiatica, Mangifera indica (which has recalcitrant seeds that lose viability very quickly, often within weeks), and Yucca gigantea—the seeds of Phoenix dactylifera have remained alive for the longest period.