Scientists Crack Secrets of Ginkgo Trees’ Near-Immortality
A new botanical scientific study on ginkgo trees highlights the species’ hyper-charged defenses and apparent escalation towards “immortality.”
Native to China, G inkgo biloba, also known as the maidenhair tree, is the only living tree in the Ginkgophyta group and it appears in fossils dating back 270 million years. According to an entry on Red List, the tree was widely cultivated in early human history, and it has various applications in traditional medicine and as a source of food.
Now, the tree is central in what Science Mag call “the most comprehensive plant aging study to date.” Plant biologist Jinxing Lin, of Beijing Forestry University and coauthor of the new study, says the ginkgo tree can live for more than 3000 years and now the “molecular mechanisms” that allow this have been discovered.
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The Immortality of Ginkgo Trees
The new research published in the Proceedings of the National Academy of Sciences provides the first hard genetic evidence that shows as the ginkgo tree ages it gains strength. What’s more, while the annual rings of 600-year-old ginkgos grow thinner, they omit as many defensive and immune-supporting chemicals as their younger relatives. This last observation confirms a long-standing suspicion, in the botanical community, that the default condition in plants “is immortality,” said Dr. Howard Thomas, a plant biologist from Aberystwyth University, reported Science Mag.
The project to examine growth rings was led by Li Wang, a plant molecular biologist at Yangzhou University, and colleagues. The researchers started with collecting thin cores from 34 healthy ginkgo trees in Anlu, in China’s Hubei province, and Pizhou, in Jiangsu province. Among the first observations made was that after hundreds of years ginkgos’ “growth” in certain areas didn’t slow down, and it even speeded up in some instances.
Analyzing Gene Expressions
The photosynthetic ability of a plant relates to its use of sunlight to synthesize nutrients from carbon dioxide and water. The new study showed that the trees’ key indicators of health, including the photosynthetic ability of leaves and the seed quality, “didn’t differ with age.” The study also compared gene expression in leaves and in the cambium, a thin layer of stem cells between the internal wood and external bark that forms throughout the life of a tree. Older trees have only a few layers of cambial cells, said Dr. Wang, and collecting enough material to work with “proved difficult.”
Close up of ginkgo tree leaves. (Profotokris / Adobe stock)
At a genetic level, the trees’ RNA was sequenced, their hormone production was examined, and their miRNA was screened, which are molecules that cause specific genes to turn on and off, in trees ranging from 3 years old to 667 years old. It was discovered that while leaves die, those same genes in the cambium did not, and they were the same as those levels measured in young trees, according to the paper.
Pests and Droughts Defeat Immortality
Plant biologist Jinxing Lin, of Beijing Forestry University, was a coauthor of the study and wrote that evidence was found proving while older trees had lower levels of a growth hormone called indole-3-acetic acid, they had higher levels of abscisic acid, a growth-inhibiting hormone. According to the study, trees aged at 200 years or older saw decreases in gene expression associated with cell division, differentiation, and expansion.
What this means is that the cambial stem cells measured in older trees don ’t divide into new wood and bark as easily as in younger trees. So after thousands of years, of course, ginkgo trees would eventually die of old age. Although most will die from stressors, such as prolonged droughts or infestations of pests.
Shot of a ginkgo tree. (Noel / Adobe stock)
Striking Ability to Fight Stressors
Generally, in wildlife and nature, when animals and plants age, they become increasingly vulnerable to droughts, pests and many other environmental stressors. But the research presented found this tree’s pathogen resistance genes and production of flavonoids (protective antimicrobial compounds) were the same in “all age groups.” This suggests these trees never lose their genetic defenses to fight outside environmental stressors, and those functions only lapse at death, instead of causing or bringing about death.
Author and molecular biologist Richard Dixon of the University of North Texas, Denton, summarized the ginkgo tree’s ability to fight stressors, and to continue to grow healthily for thousands of years in one word – “striking.”
Top image: Group of ginkgo trees in the autumn. Source: nicholashan / Adobe stock
By Ashley Cowie