Among the many fascinating things to study in botany, perhaps the most interesting is the stark differences and eerie similarities that plants have to humans and other animals.
In this article from HerbSpeak, you’ll learn about the lifespan of plants, and whether they hold the keys to immortality, or if they die from old age like everything else.
Do Plants Die of Old Age?
It can be hard to answer this question directly because, not only does it touch on a subject that many people are uncomfortable with, but we do not truly understand the implications of death.
We know it to be a fact of life, but to die of old age implies that a lifespan has been fulfilled, and how do you properly define that, especially in something like plants?
As humans, we would typically characterize old age and death by a lack of brain cell function. Plants do not inherently have a brain like humans and animals do, making it an odd topic to broach.
Plants, however, do undergo a process called senescence and it has many similarities to what happens in human cells.
Senescence begins when the plant’s DNA caps, called telomeres, shorten. Eventually, these caps shorten until there is nothing left to protect, which begins a release of proteins within the plant. (1) These proteins cause an arrest of the cell cycle, called apoptosis, which leads to cell death.
(Senescence) can either occur at the cellular level or senescence of the whole organism can take place.
Ultimately, yes, plants die of old age, but some plants have a much longer lifespan than we would typically assign. Much like some animals live for two or three years, while humans live upwards of a hundred, plants can live for millennia if the conditions are right.
Not all plants are limited to the same lifespan.
Some plants, like annuals, only live for a few seasons before dying back and allowing their offspring to grow up in their place. Others go dormant over the winter for several years, never truly dying as the root system remains “alive” and in-tact.
How Long Can Plants Live?
There is no set lifespan for plants. Some plants can survive for hundreds of years or more, while others will die within a few months.
Plants have what is known as indeterminate growth, which means there is no set age or size for a plant to be considered at old age or mature.
There are two limitations to this; the first is that they would no longer be able to send water to all parts of the plant due to a lack of water pressure in the xylem (in vascular plants.) The second is that they would not be able to support the weight of their own bodies at a certain point, which is something we see on occasion with trees that branch out too much.
To try to make broad statements about the lifespan of plants as a whole kingdom is impossible; not to mention that we’ve hardly found all of the plants that exist on the planet. Each year, we discover an estimated 2,000 species of new plants each year.
For example, annuals tend to germinate, grow, and die all within a single year.
Meanwhile, one aspen tree colony in Utah, US, shares identical root systems – making each individual tree one of the same genetically – and has helped the plant stay alive for over 80,000 years and counting.
In terms of survival of an entire species, Ginkgo biloba is known to be one of the longest-living species, with fossils of its leaves dated to an estimated 270 million years ago. This makes it one of the oldest surviving tree species, and it is one of a kind, thanks to careful cultivation, insect-resistant wood, and aerial roots.
Plant cells have the unique ability to divide and become other cell types, which is why it is possible to grow plants from cuttings.
Still, in nature, it is nearly impossible to sustain a single lifeform with everything it needs to warrant its survival forever.
Whether it is the loss of a certain nutrient in the soil, drought, fire, or other environmental hazard, eventually all plants will die.
Do Plants Feel Pain?
This is an interesting subject that warrants its own deep dive into the science and research we’ve done in recent years.
While there is no evidence that they feel pain as we understand it, as they do not have brains or nociceptors – the receptors that allow us to feel pain as humans – they do have a vast number of senses, much akin to our own bodies.
Plants do not communicate with each other the same way with auditory responses. Still, they communicate with each other through mechanical cell signaling, if it is within the same plant, and with phytochemicals to warn other plants.
Grass, for example, has been known to release airborne phytochemicals to warn other grass of an impending attack.
This response to a sensation is not limited to grass. Plants can tell when insects are feasting on their leaves and modulate their phytochemical response. They can “feel” mechanical stimulation and respond to it. They can “remember” when a light was last turned on, or when something last touched it.
…and so much more.
How Can You Tell if Your Plant is Dying?
While these rules apply for plants in nature, it’s difficult to apply it to our potted houseplant that we’ve been struggling to keep alive for some time.
You can often tell if your plant is dying if it is showing atypical behavior. Droopiness, curling leaves, yellowing leaves, drying leaves, or parts of the plant turning grey are generally a good sign that the plant’s needs are not being met.
It is important to note here that regular senescence can happen in plants that are perfectly happy. Sometimes, leaves get too big, or flowers are ready to go dormant.
Normal senescence is generally characterized by yellowing of a small number of leaves and/or stems before they brown and fall off through natural abscission. These leaves will be the largest or “oldest” of the bunch, as it makes way for new, younger leaves on the plant.
Some plants go dormant, which makes it difficult to tell if they are dead or simply “resting”, as they will often die back to the roots, or in woody plants, die back to the bare branches.
The roots are still active, though they will slow their progress. Unfortunately for us, it is difficult to see the roots in action, as they don’t move and flourish the same way leaves will.
The best way to tell if a dormant plant is dead or just resting is to wait for the plant to come up again in the next season. Continue caring for it with the understanding it’s needs have significantly changed as a dormant plant. While you won’t want to let the soil go completely dry, chances are, it needs a lot less water than you were previously giving it.
Which Plants Live for Many Years
While the list is not exhaustive, there are certainly many outliers that have gained popularity for a longer than average lifespan in the plant kingdom. Giant sequoia, bristlecone pine, ginkgo biloba are some examples of plants that live for many years on average.
There is a long list of plants that live for a long time in nature, but perhaps one of the most fascinating to me personally is the Welwitschia mirabilis plant.
This plant is not a tree, like you might expect, and it is still one of the longest living plants in the world. It can live for upwards of 1,500 years without experiencing senescence. Beyond that, it is a desert plant, subsiding in the fog belt of the Namib desert.
The adult plant looks like something that has washed up from the sea, consisting of two leaves, a stem base, and roots. It absorbs moisture through the humid air and dew, rather than from the soil.
- Byjus.com, Senescence, https://byjus.com/biology/senescence/