The plant biologist Sergi Munné-Bosch, from the University of Barcelona, points out in an article that although the signs of senescence in long-lived trees can be almost imperceptible, this does not mean that they are immortal.
Slow growth, high capacity for regeneration and high tolerance and resilience to environmental stress are the key factors behind the extreme longevity of ancient trees around the world. This is confirmed by an article published in the magazineTrends in Plant Science by Professor Sergi Munné Bosch, from the Faculty of Biology and the Biodiversity Research Institute of the University of Barcelona (IRBio).
Methuselah, a specimen ofPinus longaeva More than 5,000 years old, it is found in the Inyo National Forest (United States) and is considered the oldest tree on the entire planet. In Iran, the Abarkuh cypress is over 4,000 years old. The Vouves olive tree, the most emblematic millennial specimen of the species, are also great giants of survivalOlea europaea(Crete) and the Chestnut of the Hundred Horses (Sicily).
These millennial survivors of ancestral forests around the planet "they are an excellent model of tolerance and resilience to stress”Says Munné-Bosch. "Specifically –precise– they are considered an exception within the respective species on a population scale and are models that help us better understand the importance of interindividual variability in adaptive processes”.
In the plant world, great resilience and tolerance to stress (extreme temperatures, lack of nutrients, drought, etc.) are always linked to slower growths, greater capacity for regeneration and greater longevity. In the case of the oldest trees on the planet, this highly efficient ecophysiological response to external factors is added to a modular growth pattern and a great capacity to regenerate and maintain dormant structures - such as buds - that can restart plant growth during life cycle of the specimen.
The modular growth cycles of ancient trees are sustained around the trunk, and this "gives them greater robustness and the ability to survive longer”, Says the researcher. The log "It is made up of more than 99% dead tissues, and the xylem - a set of vessels in vascular tissue - is also completely dead. The living tissues that make up the phloem - the conducting vessel for the elaborated sap - and the vascular cambium are highly protected by the tree's bark.”.
Herbaceous and shrubs are also perennials that can be very long-lived. With more than three hundred years, theBorderea pyrenaica –An endemic plant of the Pyrenees– is the herbaceous plant with the longest longevity described so far. As a survival strategy, this terrestrial phanerogam sustains its cyclical growth periods on a tuber.
Longevity and senescence
The great capacity of perennial plants to survive in nature is a scientific reference to study the mechanisms related to longevity and senescence. Its potential longevity is so extraordinary that the plant usually dies from external factors long before any physiological decline associated with aging can be observed.
“This is very easy to understand in the case of ancient trees. The probability of dying of any organism, however tolerant and resilient it may be to stress, increases over time. For reasons of chance, it is really very difficult for any organism to survive so many years to different external threats”Clarifies Munné Bosch.
Over time, structural limitations are the main cause of the functional decline of the oldest plant species.
“A tree may reach its maximum height depending on its genome and the environmental conditions of its natural habitat. Later, it will be able to extend its longevity by means of new branches and generating new branches when it suffers damage. But all this has a limit. When the vascular tissue that connects the roots with the aerial part (xylem) or the sources of photoassimilates with their sinks (phloem) suffer a large enough damage, the plant will eventually die.”, Concludes the researcher.
Sergi Munné Bosch. "How Can Millennial Trees Reach Extreme Longevities?"Trends in Plant Science (2020)