A lifetime ago in January 2020, researchers studying long-lived ginkgo trees found that 600-year-old trees were biologically much the same as 20-year-old whipper snappers. Ginkgoes’ apparent ability to sidestep the usual age-related decline prompted some to wonder whether they might be capable of living forever. Now, a new paper titled, “Long-Lived Trees Are Not Immortal,” aims to set the record straight, reports Cara Giaimo for the New York Times.
The century-spanning ginkgoes featured in the January study aren’t even the oldest known trees. In a stark, rocky landscape east of California’s Sierra Nevada Mountains lives Methuselah, a nearly 4,800-year-old bristlecone pine discovered in 1957 that holds the world title for oldest known living organism.
The paper on gingkoes, published in the journal the Proceedings of the National Academy of Sciences, found that in terms of reproduction and photosynthesis the 600-year-old trees were hale and hearty. The super-old trees’ growth had slowed to a crawl, to be sure, but the cells showed no signs of senescence, which is not quite death but causes cells to stop dividing and eventually results in a loss of function.
But University of Barcelona plant biologist Sergi Munné-Bosch, author of the new commentary about the topic, argues the researchers simply may not have waited long enough to observe the tree’s eventual slide towards death, reports Brooks Hays for United Press International. At 600 years, the ginkgoes in the January study are only about halfway to their maximum lifespan, per Munné-Bosch’s article.
“It is highly probable that physiological senescence occurs in all organisms, but that the limited human lifespan prevents us from properly gauging it in long-lived trees in nature, in real time,” explains Munné-Bosch in the journal Trends in Plant Science.
The authors of the January paper didn’t have multiple trees older than 1,000 years featured in the study, so they couldn’t extrapolate their results to the known age limits of Ginkgo trees, explains Paleobotanist Richard Barclay, who leads the Fossil Atmospheres Project at Smithsonian’s National Museum of Natural History. “It would be great to have been able to study individual Ginkgo plants that were over 1,000 years in age, but replicates at those ages are difficult to find,” he says.
“I think that [the authors of the original paper] might agree with Sergi in that they never suggested that Ginkgo trees were immortal, only that, by 667 years, individual Ginkgo trees still have no detectable levels of senescence,” Barclay says. “This is what good scientists do. They stay within the confines of what their data tells them.”
Furthermore, while the cells inside ginkgo responsible for creating new growth were still happily dividing even in ancient trees, the layer in which those cells reside, called the cambium, gets thinner and thinner over time, Munné-Bosch tells the Times. The cambium is also responsible for producing tissues that aid in the transport of water from the tree’s roots to its shoots, Munné-Bosch writes in his paper. While this thinning wouldn’t exactly be programmed senescence,the cambium could eventually become too thin to function and kill the tree.
Molecular biologist Richard Dixon of the University of North Texas, Denton, who co-authored the January paper documenting the mechanism behind the ginkgoes’ miraculous longevity, tells the Times, “it’s probable that even ginkgo trees may die from ‘natural causes.’”
Barclay hopes to see the methods of the original paper applied to trees that are past the millennial mark and to other species of long-living trees. He wonders, “how universal is this approach to long life, and whether species such as Bristlecone Pine follow a similar approach, or a completely different one.”
Striking a tone more akin to a philosopher than a plant researcher, Munné-Bosch suggests simply existing for such a long time represents a cumulative hardship.
"Time, in some respects, can be considered as a sort of stress," he says in a statement. “Living is stressful, and this very slowly will bring you to death."
And while this idea is certainly true for individuals, Barclay notes that the genus Ginkgo appeared more than 250 million years ago, and shows up in the fossil record in a very recognizable form. Inferences about the way individual plants manage to deal with the stress of time may scale up to geological time, and paleontologists can lean on studies like these for guidelines to use when learning about how Ginkgo lasted through millenia without much visible change.
“We often ponder why different species of plants have longer temporal spans, and plants like Ginkgo have survived through much tumult in the geological past,” he says. “Perhaps it was the strategies that allow Ginkgo to live for a long time as individuals that also allowed them to squeeze through the bottle necks that extinguished other species.”
Rachael Lallensack contributed reporting to this article