As humans age, our bodies start to slow down and get creaky. But the same doesn't happen with the ginkgo biloba tree.
It's hardly a fair comparison, as these living fossils with the iconic fan-shaped leaves can live more than 1,000 years. Some of the oldest fossilized ginkgo leaves date back to 200 million years ago.
Researchers wanted to know what gives these trees their longevity. They compared dozens of ginkgo trees ranging in age from 15 to 667 years old to see what helped them live so long. Their findings were published in the Proceedings of the National Academies of Science.
"In humans, as we age, our immune system begins to start to not be so good," study coauthor Richard Dixon, a biologist at the University of North Texas, told The New York Times. But in a way, "the immune system in these trees, even though they're 1,000 years old, looks like that of a 20-year-old."
The ginkgo biloba has distinctive, fan-shaped leaves that also explain its other name: maidenhair tree. (Photo: James St. John [CC BY 2.0]/Flickr)
Researchers took thin cores from the trees (which didn't harm them) to examine their growth rings. They particularly studied the vascular cambium, a thin layer of cells underneath the bark that grows each year.
They found that senescence — biological aging and deterioration — was predictable in the expression of genes in the ginkgo's leaves. Leaves grow, they fall off, then new ones grow again. But there was no such difference in the cambium between very young and very old trees.
This suggests that although leaves might die, the trees themselves are unlikely to ever die of old age, according to the findings.
Most trees instead appear to die from stressors such as pests or droughts, the researchers said.
Not needing to be concerned about growing old is "something that for humans is difficult to understand," plant physiologist Sergi Munné-Bosch of the University of Barcelona, told Science. "Aging is not a problem for this species," he says. "The most important problem that they have to deal with is stress."
Researchers believe that studies on similar long-lived trees like redwoods and English yews would yield similar results.
Howard Thomas, plant biologist from Aberystwyth University, tells Science: "The default condition in plants is immortality."