by Nina Burton
The above-ground parts of plants move just as much as those beneath the surface. If you snap a picture of flowers every twenty seconds and edit the images into a timelapse film you can see how fiercely they work their way out of the ground. The plant follows the path of the sun in furious little spirals even as it shoots up, and it relaxes only at night. Clinging plants go one step further, reaching for and grabbing on to supports, so if you put a rake next to a honeysuckle plant it will find its way there. A carnivorous plant, one that obtains nutrients from insects, can even feel an insect land and quickly close around it.
Maybe plants can also perceive sound. A sort of clicking has been heard at the tips of roots. It probably arises when cell walls burst as they grow, and if other roots can hear this it might provide an explanation for a mystery. A single plant can have a million root ends, but they never get tangled. This suggests that they must somehow know each other’s position. To me this seemed reminiscent of the way each individual in a flock of birds or a school of fish keeps track of their neighbours so they never crash. In any case, it is clear that plants use their roots rather like a brain, to gather information. This is, of course, just what Democritus believed.
The very possibility that roots could react to sound spurred fresh experiments. Under Mancuso’s direction, a stereo system was installed at a vineyard. After five years, it was confirmed that vines close to the music fared better than others. The grapes matured earlier and had more colour and flavour, and as a bonus it seemed that the music confounded harmful insects, so the growers could dial down the pesticides. But the crucial factor for the grapevines wasn’t the melody – it was the sound frequency. Certain intervals in the bass register seemed to support growth, while higher frequencies were inhibitive.
This theory was supported by a Japanese grocery company’s discovery that mushrooms grew better to the sound of drums. Australian researchers picked up the thread – they found that wheat plants reacted to a tapping sound at 220 hertz and oriented their root tips in that direction. Could these organisms have been affected by vibrations? Judging by Mancuso’s findings, plants could sense the Earth’s electromagnetic fields, just like many animals can. Cress plants were happy to align their roots along them.
The questions only multiplied. Could plants’ sensitivity be considered feelings of some sort? According to winegrowers, harvested wine was sometimes disturbed in a baffling way. It happened twice a year, first when the vines were blossoming and then during harvest time. On these occasions, young wines could grow cloudy for a few days, even though they were stored in barrels or bottles far from the harvest site. Was this a lingering, inherited rhythm of life, or an expression of sympathy? If plants had a type of consciousness, it wasn’t unreasonable to inquire about their emotions.
These were the sorts of questions that had prompted us to wonder about everything laid out on the veranda table. If even wine and wheat could sense their surroundings, perhaps awareness is pretty much everywhere. Were we sitting in the midst of a network of plant and animal feelings? Was this, perhaps, a distinguishing feature of life?
The energetic children had been out of sight for a while as they played hide-and-seek, but it was getting near their bedtime. Their dads had adopted the summer tradition my sister and I had once kept, holidaying for a week together without their other halves. Since both the children and the dads would be sleeping in the cottage, a little rearranging ensued as my sister spent some time with the small ones.
Meanwhile, I took an evening jaunt around the property. What was really going on in all those sap-rich trunks, expansive branches and far-reaching root systems? Communication among both tree roots and ants was probably underway beneath my feet, and trees too were strengthened by their contacts. Together they would build forests that were like superorganisms.
Perhaps the same could be said of our cultures and societies. But plants have keener contact with the Earth, given that they literally live within it. And here Mancuso provided words of comfort in keeping with the time; he believed that future technology would transform plants into interpreters, giving humans information about air and soil quality, clouds of toxins or imminent earthquakes. Together, plants would be a ‘Greenternet’.
They had, in any case, proven that they understand quite a bit about the world. They react to light, sonic vibrations and chemicals, and they are constantly in motion. I only perceive them to be standing still because my vision and brain interpret time differently. Plants simply live in a different rhythm of time, world of senses and system of communication, so I should hardly extrapolate my own ways of measuring and expression into a general norm.
Then again, everything alive has a related system of communication deep down. It exists on a cellular level, and it seems that the animal and plant kingdoms nearly meet within it. Animal cells are actually similar to the cells at the outermost edges of plants’ roots.
This discovery was made by Darwin as he compared plant roots to the brains of earthworms. A major part of his research was on these very topics, botany and earthworms, although the latter was only discussed in whispers for a long time. It was bad enough that he thought our forefathers were apes – if the general public had found out that this family tree encompassed worms as well he would have been dismissed entirely. To add insult to injury, he even considered worms to have a certain amount of intelligence. As a result, his research about them was suppressed until the 1930s, when it was unearthed by the American inventor of the steel plough.
It wasn’t news to anyone that earthworms work the soil. In ancient Egypt, Cleopatra forbade their export, for without worms the Nile Valley would never have been fertile enough to birth a prosperous civilisation. Industrious worms can, in just about a decade, turn over a layer of soil a decimetre thick, aerating it and restoring its nutrients.
But Darwin’s interest had nothing to do with the earthworms’ talent for farming. Rather, he was preoccupied by their similarities with plants. He had first noticed these when he tried to understand earthworm senses, testing their sight by placing lamps next to them and studying their hearing by playing instruments for them. Neither the bassoon nor the penny whistle provoked a reaction, nor was there any effect when he shouted at them. But something did happen when he put them in a pot of soil on the piano. The notes caused them to burrow beneath the surface. Like plants, then, they could sense vibrations in the earth. Did the changing tones carry a message? Worms themselves, it turns out, produce faint but regular sounds.
When it came to their sense of smell, they didn’t seem to care about perfume or tobacco smoke. They did, however, react to the smell of their favourite foods, so Darwin was able to ascertain what they preferred to eat. They taste their food just as we do, and they appeared to find leaves of the wild cherry tree even more delicious than hazelnut leaves. Cabbage, carrot, celery and horseradish were other favourites, but they would hardly touch herbs like salvia, thyme and mint.
When Darwin summarised his comparisons, the similarities between worms and plants were striking. Since they both live in the ground, they have similar senses. Like plants, worms have a special sense of touch as well as photoreceptors instead of eyes. Like plants, worms can assess the chemistry of soil without taste buds or noses, and like plants they consist of multiple segments that can survive without one another. Even though worms aren’t grazed like grasses, they’re eaten by everything from badgers to birds and even fish sometimes. It’s not enough, then, for earthworms to produce many young. They must also be able to lose part of their body without dying. In the name of science, these poor critters have been divided almost forty times before giving up.
Their most important parts are their fronts. Like the tips of roots, they are both strong enough to drill through soil and have the ability to release alarm pheromones. Worms release these when they’re in uncomfortable spots they want to avoid in the future, but they also sometimes do so when they’re speared on a fishing hook. On occa
sion, fish can sense this substance and are deterred from biting.
Naturally, though, worms are different from plants. A worm’s red blood, for instance, is pumped around by five hearts, although they’re really more like thickened blood vessels with muscular valves. It also has a brain, and while it’s little more than an enlarged bundle of nerves it functions well enough to allow the worm to make decisions, orient itself and learn new things. Worms carefully select which leaves they want to eat, and when they transport food into their soil tunnels they try out different solutions to find the most effective way. Their smooth bodies have tiny brushes to grip the soil, and once they’ve rolled up a leaf and pulled it in, they plug the opening as protection against early birds.
In other words, those naked little living intestines turned out to be more complex than people expected. What’s more, in the 20th century, it was found that the use of worms in folk medicine was justified. They can be used for pregnancy tests and contain a fever-reducing substance, so their chemistry is far from banal. But even so, their most interesting feature was their similarity with the root tips of plants, since it paved the way for a bigger question. How sharp are the lines between categories in biological taxonomy? After all, plants and animals have a common origin, and some organisms almost seem to have connections to both kingdoms.
A minor incident occurred as the children were being tucked in. A well-trafficked ant path was discovered near one of the bunk beds. Reactions were mixed. One of the children was fascinated and wanted to know all about ants, but the others wanted to get rid of the intruders on the spot. I sympathised with both teams. To start with, I could try to find one of the poison traps I had sent for. They should be somewhere in the carpentry shed.
This was where I had seen something else that might interest the children. One day, a yellow cushion had appeared on the decaying chopping block. At first I thought it was something the fox had brought over but, on closer inspection, it turned out to be a slime mould called scrambled egg slime. It wasn’t hard to understand why this variety was sometimes called ‘troll butter’ in Swedish. The slime mould could move. It’s not typical for fungi to move above ground, so some biologists elected to count slime mould in the animal kingdom. This upset other biologists, for according to them slime mould belonged to the plant kingdom, because it spread spores.
None of the bickering biologists was correct. Slime moulds are neither animals, plants nor fungi. They’re more like amoebas, given that they are made up of a single cell. But even simple cells are capable of many things. They can recognise each other, communicate and remember, and if, like slime moulds, they lack cell walls they can unite into a single cell with many nuclei. As these nuclei stream back and forth, the entire cell clump moves, and as it does so it greedily dissolves all the bacteria it can find. Slime mould can eat. No wonder it confused systematists.
Now that I was looking for the troll butter, it had vanished from the chopping block – and an indolent clump of cells probably wasn’t all that exciting for the children anyway. But for researchers, slime moulds have turned out to provide important information about the evolution of life. Their many nuclei illustrate what can happen when single-celled organisms begin to collaborate. When slime moulds were tested in mazes they showed evidence of a remarkable memory. Like ants, this memory manifested as scent trails they left behind, although the difference was that slime moulds absolutely did not want to return to their own trails. Quite the opposite – if they recognised their own scent, they took a different path to avoid places where they’d already eaten. Still, this provided researchers with a clue. An external memory like this was probably the first step on the path to an internal memory.
It could hardly be called primitive or poor, for our own external memories are the cornerstones of culture. I myself had very recently lost a family game of Memory, but I moved quite freely among such external memories as books. What slime moulds showed us was the very fact that external memory has played an important role in life, even when not in written form.
And what’s more, it seemed to me that the troll butter said more than just something about the evolution of memory. It also proved a point about plants. Even an organism without eyes, a brain and a nervous system could orient itself in its surroundings, and remember.
Once I’d found an ant trap, I lingered outside the cottage for a moment. The honeysuckle had just begun to release its scent, and it billowed forth as luxuriously as the blossoms. Soon the evening moths would rustle and swarm among the nectary grottoes of the unfurled petals.
The scent gave an essence of a summer night and roused half-forgotten memories from past evenings when I had watched the flowers climb up crevices. After all, it wasn’t only among ants and troll butter that scents could conceal memories. My sister still remembered the moment our mother showed her a butterfly orchid: ‘Take a sniff!’ With that, the forest glade opened into a little world that lived on half a century later.
It was really quite astounding that incorporeal scents could reinvigorate something dead and gone. Marcel Proust, with the help of a sweet little sponge cake, unravelled the memories of an entire life. It’s telling that the sense of smell fades in those with dementia, for while scents are as fleeting as the present moment, they can encircle events and places a person left behind long ago. They have guided us through life for millions of years, which is why we, like all mammals, have two nostrils to help us find the source of odours. This became less crucial once we began to draw maps with names for what we had seen, and at that point smells slipped into a more anonymous world of shadows.
But for deaf-blind Helen Keller, the world of smell was still expressive. Based on what she smelled, she could describe landscapes of meadows, barns and pine groves just as surely as if she had seen them. She also characterised people she met by their smells, more or less the way others recognise their friends by voice. She could tell if they had come from the garden or the kitchen, and she identified especially strong smells from those who had great vitality.
The sense of smell was equally important for Kaspar Hauser, who grew up in a dark cell. He could tell fruit trees apart by the subtle scent of their leaves. But for a long time he was helpless when faced with all the impressions that welled forth among humans.
Are the floating molecules of scents perhaps one of the most ancient expressions of life? Like the pheromones of the animal kingdom, smells provide an unadulterated essence of life, and they have been a crucial help for millions of years. Newborns find their mother’s milk by smell, and bad odours warn of spoiled food. Even at a distance, smell can tell us things about others. Was that approaching creature a predator, potential prey or perhaps a partner? Hundreds of thousands of organic molecules surround each being, forming a unique signature.
When smells cross species lines they are interpreted more ambiguously. The aromatic scent of a coniferous forest is a deterrent for microbes, because it contains terpenes; ticks, moths and fleas hate lavender for the same reason. As for us, we appreciate the same fragrances as bees. That’s why we borrow the scents of flowers, more or less as butterflies attract mates by smelling like roses. For thousands of years we have created perfumes out of petals, fruit rinds, seeds and leaves – yes, even from roots and bark. These ethereal essences can be combined just like tones in music, and in fact they are sorted into base notes, heart notes and top notes. A 19th-century perfumer made an entire scale of them, where D was violet, E was acacia, F was tuberose, G was orange blossom, A was freshly mown hay, B was southernwood and C was camphor. Other floral scents could create other scales, for in the world of smell there are just as many variations as there are in music.
The top notes reach the nose first and are first to fade. Heart notes run from jasmine and roses to the dried buds of cloves. Among the base notes, dried oakmoss can smell like the seashore or a rainy forest. But the classic base note is sandalwood. It’s said to be calming and erotically arousing all at once, fo
r tree essences are warm.
There are also animalistic base notes, such as ambergris, that mysterious essence that was once valued as highly as gold and slaves. It retains its scent for years and comes from deep within the sea. It can be found on beaches, but this fatty substance once enveloped the bones of cephalopods in the stomach of a sperm whale.
Faint or flourishing, mild or exciting – the scents of perfumes are gathered from all the varied places where life roils and streams. Like life, and like music, they slowly change and fade away, and still their quietly intense language has always followed us. In our very early days, our sense of smell was just a knot of tissue at the end of a nerve, but eventually it grew into a brain. Thus at one time the hemispheres of our brains were similar to buds on a smell-stalk, not unlike a sprouting flower. It’s even been suggested that thoughts arose by way of our sensing odours. But thoughts certainly don’t belong to the sphere of smell-sense. Their roots are in the ancient limbic system, the emotional centre of the brain, so scents are linked to emotions.
Just like feelings, they can also be difficult to describe. For how do you capture a scent? Roman poet Lucretius believed that the sense of smell could map out the shape of scent particles. A similar theory was suggested in the 1960s, in which the molecules of floral scents were said to be wedge-shaped, those of musky scents disc-shaped and those of camphor ball-shaped. But neither the shapes of scent molecules nor their chemical formulas have made it easier to render essences into words. Perfumers who can differentiate between thousands of smells find themselves at a loss when asked to describe them. Scents belong to a language that has not been tamed by any grammar. They are floating chemistry, spread on the breeze, on moisture and heat, companions of the present and the life of Earth itself.