At present, The oldest known tree in the world is a large basin in the White Mountains of California, Foxtail Pine . It is believed that this tree has a history of more than 5,000 years.
Foxtail Pine is one of the famous long-lived trees in the world. Others include ginkgo, Bread Tree , Giant Fir , etc. These trees are often found to grow for more than 1,000 years.
Then the question arises, will these trees that have grown for thousands of years show signs of aging, or will the trees die of aging? If it does not age, why is the longest-lived tree only in its 5,000s?
Will trees age?
As we age, for us humans, some simple tasks may become increasingly difficult to complete, and more and more wrinkles will appear on the surface of the skin to indicate that we are really old.
It is obvious that our body has a mechanism of gradually wear and tear, which will cause the body to gradually experience some "failures". This degeneration is called "aging" in Biology .
Aging is not only on the surface, it occurs at the cellular level, Its essence is that cells in our body stop dividing, or division becomes increasingly hasty.
If we want our body to function properly, then we need the cells to continue to divide normally to replace those retired and damaged cells, but this function is limited as we age.
Now, people already know that the reason why our cells cannot divide normally over time is because the telomeres at the end of the chromosome will shorten in each division.
telomeres are a bit like a "shield", which specifically protects genes to avoid problems during replication, but every time it replicates, it will wear out a little until its protective function is lost, and aging occurs.
The cells of trees are very different from us. Most plants have cells in the embryonic state, which means they can keep the length of the chromosome ends the same throughout their life, and these cells can also be transformed into another cell type at any time to supplement or repair different damages.
In other words, In theory, trees are not as aging as we conventionally understand, and they do not have aging at least on the time scale of human lifespan.
However, this does not mean that a tree can grow forever.
What happens when trees are older?
Before we continue our discussion, we need to understand the fact that no organism, whether it is a plant or an animal, will not really die from aging, and aging is not actually a scientifically recognized cause of human death.
As animals, when we die of aging, it is actually due to some diseases related to aging, such as pneumonia , influenza, cancer or liver failure, etc.
For trees, it is indeed difficult for them to experience what we understand as aging at the cellular level, but they also have their own signs of "aging" and they will die from the "complications" of their aging.
The sign of trees "aging" is that they will grow faster , which is somewhat counterintuitive with our cells stopping growth, but it is true, it is just that they are not growing upwards, but they are growing horizontally.
The characteristics of tree cells determine that they can grow all the time, but Some physical properties of the earth and the mechanical structure of the trees themselves limit their growth .
The most important point for the earth's limitations is the influence of gravity. When a tree grows to a certain point, the tree will not be able to transport enough water from the root to the top, thus preventing enough photosynthesis .
At this time, they will reach the limit of height, which varies for different trees.
However, it is surprising that once the trees reach their maximum height, they will expand around at a faster rate. In 2014, a team reported this amazing discovery in the journal Nature [1], which examined the growth of more than 700,000 trees around the world and finally came to this conclusion.
Another limitation will work when a tree starts to grow faster - Mechanical structure As the tree grows, it will not be able to maintain a stable structure.
For a growing tree, They not only have construction costs, but also maintenance costs . As the trees become larger and larger, their maintenance costs will also increase accordingly, which requires more resource quotas.
(This maintenance cost includes resistance to some diseases, repairing insect invasion, natural disaster damage, etc.)
As trees continue to grow, the cost of maintaining trees has increased, and ultimately inevitably puts trees at a point where the cost is far higher than resources.
At this point, trees may die from their own continuous growth .
What does the trees get from longevity?
In fact, trees have made a lot of improvements to longevity, not just the cellular level we mentioned earlier. There are similar cases in the animal world that "immortality" at the cell level of
, that is, lobsters, they have a telomerase - when cells divide , they will block telomeres from becoming shorter, so lobsters are also theoretically "ageless".
However, the situation of lobsters "death" is exactly the same as that of trees. If a lobster has never been eaten by a predator, then their cause of death will be that they cannot be unsheathed .
The growing body needs to change the shells to accommodate it. As the lobster grows, when a critical value reaches, the resources required for the lobster to shed more than the energy they obtain.
For lobsters, this critical point will come very quickly. It may be reached in dozens or hundreds of years, but the trees are obviously far beyond this time scale.
This is because trees have some unique innovations in maintaining longer life.
For example, In the case of trauma or not, the above and underground parts of the trees can directly replace those invigorated, lost or damaged parts;
For example, the formation of asexual systems, they are a fan-shaped vascular system that allows part of the tree to survive alone, while the whole tree does not need to survive;
In fact, there are many trees' unique longevity adaptations, and if you understand it, you will be surprised.
And all these efforts have the result that trees can live very long and maintain their reproductive ability.
So it is not difficult to find that the evolutionary mechanism of longevity is largely to obtain more offspring .
Figure, the oldest turtle is believed to have lived 190 years old
The turtles we are familiar with are also very long-lived, and their lifespan is disproportionate than their size. This actually has a lot to do with the turtle wanting to get more offspring, because the survival rate of the little turtle is really worrying.
Last
For different trees, their lifespan limits will be very different, and those trees that truly live long are difficult to observe with the lifespan scale of our humans.
However, basically no tree can truly reach its limit of lifespan, because the longer it grows, the more likely they will encounter natural disasters, pests and other risks, which will destroy them.
It is precisely because of this that although the trees are "immortal", we now find that the oldest tree is only over 5,000 years old.
Reference:
[1].https://www.npr.org/2014/01/16/262479807/old-trees-grow-faster-with-every-year
