Ginkgo biloba - the tree that never grows old

The Ginkgo biloba tree can live for thousands years and scientists have recently discovered just how they manage to do it.

The study, by researchers in the US and China, examined healthy ginkgo trees aged 15 to 667 years of age located in Anlu, in China’s Hubei province, and Pizhou, in Jiangsu province. Thin cores were extracted from the trees in order to examine the tree's growth rings and cells, bark, leaves and seeds were analysed.

It was found that the ginkgos’ growth didn’t slow down after hundreds of years, in some cases their growth rates actually sped up. Further to this, the leaf size, photosynthetic ability, and seed quality of the trees, which are all indicators of health, didn’t differ with age.

Study provides first real genetic evidence for how ginkgo achieves immortality 

The scientists looked at gene expression within stem cells found in a layer between the internal wood and the external bark called the cambium and compared it to gene expression within the leaves. The expression of genes associated with the final stage of life increased in dying leaves as expected but within the cambium there was no difference in the expression of those same genes between the young and old trees. 

Jinxing Lin of Beijing Forestry University, an author of the study, says it’s possible that if the division rate of cambial cells continues to decline after thousands of years, tree growth could slow, and ginkgo trees might eventually die of old age however most trees appear to die from pests attacks or droughts.

The researchers also looked at gene expression relating to pathogen resistance and discovered no difference for trees at different ages, in other words the trees do not lose their ability to defend themselves against outside stressors as they get older. This combined with the fact that unlike other plants it's genes are not programmed to trigger unstoppable decline once youth had passed, gives the ginkgo biloba an amazing ability to grow healthily for thousands of years.

Mark Gush, head of horticultural and environmental science at the RHS (Royal Horticultural Society), told the BBC that the oldest living tree in the world - a Bristlecone pine (Pinus longaeva) - is estimated to be more than 4,800 years old.

"Apart from a consistent supply of food, light and water, the ability to live to such a great age is thought to be linked to slow growth rate, cellular adaptations and relative protection from secondary influences such as pest and disease, climate extremes and catastrophic physical damage," he said.

This sort of research is becoming increasingly important as the UK sets about on an ambitious tree planting programme. It all helps to provide an understanding of the mixture of tree species that will deliver the most rewards to the ecosystem in which they are planted over the long term.