Despite debate, even the world's oldest trees are not immortal

Date:
July 27, 2020
Source:
Cell Press
Summary:
The oldest trees on Earth have stood for nearly five millennia,
and researchers have long wondered to what extent these ancient
organisms undergo senescence, physically deteriorating as they
age. Plant biologist now argue that although signs of senescence
in long-lived trees may be almost imperceptible to people, this
does not mean that they're immortal.



FULL STORY ==========================================================================
The oldest trees on Earth have stood for nearly five millennia, and
researchers have long wondered to what extent these ancient organisms
undergo senescence, physically deteriorating as they age. A recent paper studying ginkgoes, one of the world's longest-lived trees, even found
that they may be able to "escape senescence at the whole-plant level,"
raising questions about the apparent lack of aging in centuries-old
trees. However, in a Forum publishing July 27 in the journal Trends in
Plant Science, plant biologist Sergi Munne'-Bosch argues that although
signs of senescence in long-lived trees may be almost imperceptible to
people, this does not mean that they're immortal.


========================================================================== "When we try to study these organisms, we're really astonished that
they live so long. But this doesn't mean that they're immortal," says Munne'-Bosch, professor of plant physiology and leader of the ANTIOX
research group at the University of Barcelona. "They live so long
because they have many mechanisms to reduce a lot of the wear and tear
of aging." Despite trees' well-evolved methods of prolonging the aging process, research has shown that they still undergo physiological stress associated with senescence. "They have limits," says Munne'-Bosch. "There
are physical and mechanical constraints that limit their ability to live indefinitely." However, due to the difficulty of conducting research on
trees with such long lifespans, little is known about what the process
of senescence looks like.

Simply finding enough millennial trees to study can be challenging. "When
a species of tree can live for five millennia, it's very difficult
to find even two trees that are between two and five millennia,"
says Munne'-Bosch. For these long-lived trees, dying of senescence
is a possibility, but the probability of dying from other causes is significantly higher. "They don't have to worry about senescence because
they have other things that worry them more," he says.

Furthermore, because of their extreme lifespans, the aging process of
trees must be studied at a timescale much larger than scientists are
used to. To see the real-time effects of aging on long-lived trees,
scientists would have to conduct studies that last hundreds, if not
thousands, of years: when trees like gingkoes can live for multiple
millennia, even a 667-year-old organism, while undoubtedly long lived,
may not be old enough to see the effects of aging. "The measure of time
is something that we have invented as humans, and to a millennial tree,
it does not matter at all," Munne'-Bosch says.

Trees have a variety of ways to reduce their chances of death from
aging alone, from compartmentalizing risk in complex branch structures to "building life on death" by growing new shoots from trunks composed of 90% nonliving biomass. But in the review, Munne'-Bosch maintains that even
though long-lived trees can survive for millennia through these methods,
the stress associated with aging, although little, will ultimately
prevent immortality. "Time, in some respects, can be considered as a
sort of stress. Living is stressful, and this very slowly will bring
you to death," he says.

While trees may not be immortal, Munne'-Bosch says that studying the ways
trees prolong senescence is important. Research conducted in trees and long-lived plant species can inform other disciplines, like medicine,
in a variety of ways. "We have a lot to learn from them," he says. "For instance, aspects of regenerative medicine are based on mechanisms that
have already evolved in trees." Although aging is not a universal process,
the knowledge that even the oldest species cannot live forever means that "maybe we are not as different as we think," says Munne'-Bosch.


========================================================================== Story Source: Materials provided by Cell_Press. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Sergi Munne'-Bosch. Long-Lived Trees Are Not Immortal. Trends
in Plant
Science, 2020; DOI: 10.1016/j.tplants.2020.06.006 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200727114656.htm

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