“This is not our world with trees in it. It’s a world of trees, where humans have just arrived.”
“Ever since the cognitive Revolution, Sapiens have been living in a dual reality. On the one hand, the objective reality of rivers, trees, and lions; and on the other hand, the imagined reality of gods, nations, and corporations. As time went by, the imagined reality became ever more powerful, so that today the very survival of rivers, trees, and lions depends on the grace of imagined entities such as the United States and Google… Since large-scale human cooperation is based on myth, the way people cooperate can be altered by changing the myths - by telling different stories.”
1. Albino Redwoods
There are mutants hiding among the coastal redwood forests of California. The forest ghosts, as they’re often called, exist within the dense old-growth forests of Henry Cowell Redwoods State Park and Humboldt Redwoods State Park. These are the rare albino redwoods and the key to their survival is community.
Like albino animals, albino redwoods lack pigmentation, so their needles are white instead of green. The lack of color comes from a lack of chlorophyll, the substance that allows plants to capture sunlight energy and turn it into food. This genetic disadvantage would lead to a quick death by starvation if not for the assistance of other trees.
Neighboring redwoods can control where they send their sugars, explains Plant Biologist Zane Moore, and they allow sugars to be sent to the roots of the neighboring albino trees in need. At any time, the healthy redwoods could stop sending food to these freeloaders, but they don’t, because the white redwoods do something in return. It isn’t altruism, it’s mutual benefitting.
Albino redwoods are the community’s toxic waste dump. Moore experimented with the toxicity levels of different branches of redwoods, both albino and green. His experiment shows that albino plants are more efficient at absorbing heavy metals and have a higher tolerance for these toxic elements. Once absorbed by the albino trees, the heavy metals become trapped, removed from the environment, and kept away from the roots of the less tolerant green redwoods.
Research is still being done on these mutations and how they may reveal certain human causation. Moore’s website is a good place to continue on with this topic.
Here’s a short video of some of the albino trees in Henry Cowell Redwoods State Park and the man that protects them from people:
2. What a Plant Feels
We're not venturing into the emotional lives of plants (yet), but a plant’s ability to perceive tactile sensations is just as intriguing. As I've done in similar posts, I'm anthropomorphizing here in order to make connections between what humans can easily relate to and what may fall outside the normal modes of our understanding.
Most people think of plants as immobile, so the idea that they are able to reach out and touch something can be perplexing. There is much more movement in the plant world than us humans properly consider - roots reach out for water and nutrient sources, stems stretch upward and outward towards the light, and vines twirl and hurl themselves through the air in search of props. Further, plants aren’t just registering what they touch, they’re very aware of what is touching them.
In the book Brilliant Green, Stefano Mancuso and Alessandra Viola help bridge the gap between plant and human senses. They start the conversation around touch by pointing out that humans are aware of two types of touch: the first is the awareness of touching something outside of ourselves and the second is the awareness of being touched by external objects. In both of these situations, the touch signals the transfer of information that our brains use to produce a reaction. They go one to use these two types of tactile awarenesses to navigate the complex world of plant touch.
But first, how do humans sense touch?
The human sense of touch is controlled by a complex network of nerve endings and touch receptors distributed throughout the skin, muscles, and other tissue. This network is known as the somatosensory system. Our touch receptors are made up of different sensor cells that perceive pain, temperature changes like hot and cold, and pressure.
When touch receptors are stimulated, they send electrical pulses to neurons.
These neurons pass the pulses along, like a relay team handing off a baton, until the signal reaches the spinal cord. From there, the signal travels to the brain. Once received, the electrical signal is interpreted by the brain and the brain reacts to the message. For example, your brain might tell your hand to drop a hot mug if the temperature receptors in that hand send a signal that the heat is too intense.
How do plants sense touch?
This same system of receptors and responses is present in plants. Instead of a central brain, the plant has what is sometimes called distributed consciousness. We’re still in the early days of understanding these complex signaling networks, but there are numerous studies and everyday observations that confirm just how sophisticated the sense of touch in plants is.
In his book What A Plant Knows, Daniel Chomavitz explains that not only do plants feel touch, some feel it more intensely than humans. “Most humans can feel the weight of about two micrograms of a thread going across your skin. Some plants, for example, the burr cucumber tendrils start coiling under the weight of only a quarter of a microgram. That's ten times more sensitive than humans.”
Twining vines are a great example of one of the ways plant touch works. These plants hurl their shoots through the air, twirling them around in concentric circles in search of a prop. They aren’t just aware once they make contact with support structures, they’re actively seeking that touch. There is purpose to the movement. Here’s a cool video of a cucumber tendril seeking and using the contact it makes with a support:
When plant tendrils find a solid surface, they make a few passes at the object. These multiple touches signal to the plant that it can use the stable object as an anchor. The plant then loops its tendril around the support and starts to coil the tendril in a corkscrew fashion, which pulls the plant towards the taller structure, towards the sun.
If you’re as amazed as I am by this engineering, here’s another video that breaks down the mind-boggling way these tendrils work:
Does a plant notice when it has been touched?
Consider the agility of a Venus fly trap snapping shut its leaves on an unlucky organism. These plants can clearly feel when something comes into contact with their leaves, but the mechanics of the sense are more impressive than what can be seen with the naked eye.
The Venus fly trap (Dionaea muscipula) perceives the touch of an insect and responds to this information by rapidly closing its leaves (in one-tenth of a second). This reaction starts with one of the leaf’s “trigger hairs”.
When touched, these small structures on the inner surfaces of the mouth-like leaves set off a multi-step process, according to a 2016 study. The first touch of a trigger hair signals that something has landed on the leaf. An electrical impulse travels through the lobes but the plant waits.
A second touch within 20 seconds of the first touch means the object is most likely alive. The plant snaps its lobes shut. Note that if there is no second touch, the plant does nothing. This, to me, is the most fascinating piece of a Venus fly trap’s sense of touch. It can actually differentiate between dinner from debris! Darwin did a bunch of testing on Venus fly traps and noted his observations in Insectivorous Plants. Besides being able to differentiate edible insects from falling leaf litter, Darwin noted that Venus fly traps were not fooled by the touch of a forceful breeze. “...I blew many times through a fine pointed tube with my utmost force against the filaments without any effects; such a blowing being received with as much indifference as no doubt a heavy gale of wind. We thus see that the sensitiveness of the filaments is of a specialized nature.” Many scientists think that this is likely an evolutionary safety measure, to save the plant from expending precious energy on non-edible leaf litter or rain drops.
A third touch of the trigger hairs signals that the trapped object is definitely alive and edible and causes the closed leaves to hermetically seal together in preparation for digestion. Any more than four touches triggers the production of digestive enzymes - and the more the captive struggles, the more digestive juices are produced.
Similar to the Venus Fly Trap’s differential touch sensors are those of the Mimosa pudica, aka the shy or sensitive plant.
This species folds up its leaves at the slightest touch from a human or animal. The leaves of the Mimosa pudica, when touched, are activated almost instantaneously, a movement facilitated by water moving into and out of the cell vacuoles. Interestingly, Mancuso and Viola note that the leaves are not usually reactive when touched by rainfall or by the blowing wind. This shows that these are not reflexive movements, but a true behavior, and it seems to be a type of self-defense. “Some think this sudden closing frightens any herbivorous insects on the leaf; others think the mimosa has evolved this ability so as to look less appetizing to its predators.”
There have been some incredibly unique experiments to better understand how these plants “think” and sense, each that further proves that Mimosa pudicas are sensing touch and analyzing each stimuli individually. In the early 1800s, a couple of scientists loaded Mimosa pudicas on a cart and pushed them around Paris to see what would happen. At first, all of the plants closed up their leaves at each bump. But after a short while, all the plants reopened, and stayed open, seeming to understand that the cart’s jostling wasn’t a threat, and not worth the energy to keep closing their leaves. In the Smarty Plants episode from RadioLab, Monica Gagliano talks about repetitively shocking Mimosa pudicas with a contraption she calls the “mimosa plant drop box” and finding that not only do these plants have a very advanced sense of awareness, they even have... memories.
What a Plant Remembers coming soon...
3. Describing the Natural World with New Words
thigmotropism [thig-maa-truh-pi-zm]
noun
The movement, growth, or change in orientation of a plant in response to a touch stimulus.
From the Greek words thigma ‘touch’ and tropos ‘turning’
Video examples: vine growth, venus fly trap hunting, sensitivity plant
4. A Poem about Pines
Robert Service was a British-Canadian poet, known during his life as "The Bard of the Yukon" for his extensive travels to and writings from the Yukon Wilderness in the early 1900s. This poem is from The Spell of the Yukon and Other Verses.
/\ /\ /\ The Pines /\ /\ /\
by Robert Service
We sleep in the sleep of ages, the bleak, barbarian pines;
The gray moss drapes us like sages, and closer we lock our lines,
And deeper we clutch through the gelid gloom where never a sunbeam shines.
On the flanks of the storm-gored ridges are our black battalions massed;
We surge in a host to the sullen coast, and we sing in the ocean blast;
From empire of sea to empire of snow we grip our empire fast.
To the niggard lands were we driven, 'twixt desert and floes are we penned;
To us was the Northland given, ours to stronghold and defend;
Ours till the world be riven in the crash of the utter end;
Ours from the bleak beginning, through the aeons of death-like sleep;
Ours from the shock when the naked rock was hurled from the hissing deep;
Ours through the twilight ages of weary glacier creep.
Wind of the East, Wind of the West, wandering to and fro,
Chant your songs in our topmost boughs, that the sons of men may know
The peerless pine was the first to come, and the pine will be last to go!
We pillar the halls of perfumed gloom; we plume where the eagles soar;
The North-wind swoops from the brooding Pole, and our ancients crash and roar;
But where one falls from the crumbling walls shoots up a hardy score.
We spring from the gloom of the canyon's womb; in the valley's lap we lie;
From the white foam-fringe, where the breakers cringe to the peaks that tusk the sky,
We climb, and we peer in the crag-locked mere that gleams like a golden eye.
Gain to the verge of the hog-back ridge where the vision ranges free:
Pines and pines and the shadow of pines as far as the eye can see;
A steadfast legion of stalwart knights in dominant empery.
Sun, moon and stars give answer; shall we not staunchly stand,
Even as now, forever, wards of the wilder strand,
Sentinels of the stillness, lords of the last, lone land?