Tamara Bonnemaison launches a BPotD series with today’s entry. She writes:
We kick off a series about exceptional seeds with the story of a 2000 year old Phoenix dactylifera seed that was successfully germinated. Thank you to 3Point141@Flickr for submitting this lovely photo of a plant in the cultivated Medjool Group of Phoenix dactylifera. This photo was taken at Excalibur Fruit Trees Nursery in Florida, USA.
Phoenix dactylifera, or the “true” date palm, has played an important role for thousands of years of human history. In 1963, a stash of seeds “dating” (sorry, couldn’t help myself) from AD 70 was discovered in Masada, a fortress in present-day Israel. In 2005, Sarah Sallon of the Hadassah Medical Organization managed to germinate just one of the ancient date seeds, and that seedling has now grown into a palm tree called “Methuselah”. Date palms are dioecious, and it had been hoped that Methuselah would turn out to be female and produce fruit. Unfortunately, this date palm plant is now known to be male, and Sallon and her team will need to undertake careful breeding with modern date palms to produce females that are as close as possible to the ancient cultivated variety. Learn more about Masada and the discovery of these seeds from this National Geographic article: “Methuselah” Tree Grew From 2,000-Year-Old Seed.
The date palm is a 15-25m tall plant that is perhaps native to western India or southern Iraq, but a long history of use and cultivation has made it difficult for botanists to determine its exact place of origin. The fruit of Phoenix dactylifera is likely well known to all BPotD readers; this fruit was cultivated as a staple food and even to make date wine as early as 4000 BCE, and is still commonly eaten today (mmmmm, date squares). Other parts of the date palm may not be as sweet, but are equally useful. For example, palm hearts are used as a vegetable, the fibres can be woven to make a textile, the leaves are used to make mats, and the seeds produce a nutritious oil. For a more comprehensive list, view the Food and Agriculture Organization’s Date Palm Products bulletin.
Although the date palm can be wind-pollinated, the standard practice in cultivation is to hand-pollinate the flowers The flowers are borne at the top of the tree and covered by a protective spathe that splits open when the flowers are mature. The fruit is a one-seeded drupe, which goes from green to yellow to reddish-brown as it ripens. This brings us to the seed. Date seeds are oblong, ventrally-grooved and have a small embryo. A hard endosperm made of cellulose surrounds the embryo, which is surrounded by the mesocarp (the fleshy, sweet part of the date) and finally the epicarp or exocarp (the date’s skin). These are common features of the seeds of many fruits, and my search to uncover just what allowed Methuselah’s seed to remain viable for two millennia revealed little.
Seed longevity is poorly understood by the scientific community, but is gaining more attention with the growing interest in (and need for) seed banks. A 2008 paper by Loïc Rajjou and Isabelle Debeaujon, Seed longevity: Survival and maintenance of high germination ability of dry seeds, sums up our current understanding of the different factors that affect seed longevity. Rajjou and Debeaujon report that seeds are able to protect themselves with their testa (seed coat), antioxidants, and by reducing their metabolic activity; seeds also have the ability to repair their DNA and decontaminate themselves. It is not clear which of the above qualities allowed the Phoenix dactylifera seeds found in Israel to remain viable for such an extraordinary long time, but it is likely that high levels of antioxidants present in date seeds contributed to this high longevity (date seeds are being studied for antioxidant qualities which could be used to improve human health and longevity). The date seeds also benefited from the dry, dark conditions present in Masada Fortress.
Science overload? Have a look at Shevaun Doherty’s artistic exploration of the Methuselah date for an entirely different way of understanding Phoenix dactylifera.