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17/02/2022

11/01/2022

Can plants think? They could one day force us to change our definition of intelligence
Some might balk at the idea that plants made of roots, stems and leaves could have intelligence or consciousness. But scientists have actually been hotly debating this idea for decades.

A recent paper sought to finally draw a line under this question by dismissing it completely. It argued that the key physical features found in conscious animals are missing in plants. All such species have an information processing network made up of nerve cells arranged into complex hierarchies that converge in a brain. Plants, on the other hand, do not have nerve cells at all, let alone a brain.

But what if assuming that all intelligence has to look like ours were to limit what we could discover about the way plants really work? Plants may have very different physical systems to us, yet they do respond to their environment and use a sophisticated signalling network to coordinate the way all of the different parts of the plant work together. This even extends to other organisms that plants cooperate with, such as fungi. There’s even an argument that such a system could lead to a form of consciousness.

It has long been known that electrical signals which look quite similar to those that carry information in nerve cells are also observed in plants. So it might be possible that these replicate the functions of an animal’s nervous system.

Many of the interesting and complicated things our brain does are due to interconnections between nerves and the chemical signals that carry information from one nerve cell to the next. Evidence that chemical and electrical signals work together in this way in plants is thin, but could a complex communications network be created in a different way?

Some types of electrical signal can travel throughout the plant following its transport system, and the shape of the entire plant and the transport system that connects it reflects a history of responses to its environment and attunement to it. Cells in plant transport systems have structural interconnections which could carry signals in an intricate and flexible way, while the signals themselves seem to have complexity, with different triggers stimulating different and distinctive electrical patterns.

So electrical signals in plants may have the potential to carry and process information. The problem is that, unfortunately, we know little about whether they actually do or what their function might be if so.

One impressive exception is the Venus flytrap. Each trap has a number of minute hairs inside it. Whenever they are touched they generate an electrical impulse. Two pulses close together cause the trap to close, and three more to close further to crush and digest prey.

Electrical signals also trigger the dramatic leaf drooping in Mimosa pudica and guide the bending of sticky “tentacles” to trap prey in the insectivorous plants known as sundews. Perhaps plants can use nerve type signals in an animal-like way when they need to, but are usually doing things that we find less obvious.

Nervous? Marco Uliana/Shutterstock
Indeed, by comparing plants with organisms with mental processes that look like our own, have we made it impossible to recognise a consciousness different to ours? The philosopher Ludwig Wittgenstein said: “If a lion could talk, we would not understand him.” How much stranger would a plant’s “thoughts” be?

Plants certainly respond to their environment in complex and nuanced ways, using information shared between cells in the same plant, and their neighbours. They can respond to sounds, and produce defensive chemicals when they “hear” caterpillars chewing. Sunflowers track the sun each day, but they also “remember” where it will rise each morning and turn to greet it during the night. Trees in a forest coordinate with one another, computing convoluted jigsaw like patterns in the canopy that optimise light gathering.

An important question is whether all of this could a result of simple pre-determined responses. Does this “behaviour” require anything that might be like our intelligence?

Perhaps true intelligence requires a single command centre to collate inputs and decide actions and an animal-type brain is the only way to create complex consciousness. Indeed some definitions of consciousness assume a central identity aware of itself. Are such things possible without a brain? It has been suggested that shoot and root tips do this by pumping out chemical messages that direct the rest of the plant. But while this might work in a small seedling, a large tree has hundreds or even thousands of shoot and root tips.

Decentralised consciousness
Yet what if consciousness can spontaneously emerge from webs of interactions in complex systems? This is speculative but we have seen that plants can use intricate networks of signals to collect and relay information. Without a centralised brain, how strange and incomprehensible such a consciousness might be. Distributed across a federation of cooperating cells rather than controlled by a single general. “We” rather than “I”.

Ultimately, this may all be semantic. Authors Lynn Margulis and Dorion Sagan claimed that: “In the simplest sense, consciousness is an awareness (has knowledge of) the outside world.” If so, it would be universal to all living things. What would differ would be the nature of experience, some simple and others rich and individual. Maybe that is all that we can say.

After all, we cannot “know” even what it feels like to be another human. But the experience of being a plant (or part of a federation of plant cells) would be unimaginably different to ours, and trying to find common terms to describe both is perhaps futile.

11/01/2022

Plants can tell time even without a brain – here’s how
Anyone who has travelled across multiple time zones and suffered jet lag will understand just how powerful our biological clocks are. In fact, every cell in the human body has its own molecular clock, which is capable of generating a daily rise and fall in the number of many proteins the body produces over a 24-hour cycle. The brain contains a master clock that keeps the rest of the body in sync, using light signals from the eyes to keep in time with environment.

Plants have similar circadian rhythms that help them tell the time of day, preparing plants for photosynthesis prior to dawn, turning on heat-protection mechanisms before the hottest part of the day, and producing nectar when pollinators are most likely to visit. And just like in humans, every cell in the plant appears to have its own clock.

Our eyes and brain rely on sunlight to coordinate activity in the body according to the time of day. Yomogi1/Shutterstock
Read more: Can plants think? They could one day force us to change our definition of intelligence

But unlike humans, plants don’t have a brain to keep their clocks synchronised. So how do plants coordinate their cellular rhythms? Our new research shows that all the cells in the plant coordinate partly through something called local self-organisation. This is effectively the plant cells communicating their timing with neighbouring cells, in a similar way to how schools of fish and flocks of birds coordinate their movements by interacting with their neighbours.

Previous research found that the time of the clock is different in different parts of a plant. These differences can be detected by measuring the timing of the daily peaks in clock protein production in the different organs. These clock proteins generate the 24-hour oscillations in biological processes.

For instance, clock proteins activate the production of other proteins that are responsible for photosynthesis in leaves just before dawn. We decided to examine the clock across all the major organs of the plant to help us understand how plants coordinate their timing to keep the entire plant ticking in harmony.

What makes plants tick
We found that in thale cress (Arabidopsis thaliana) seedlings, the number of clock proteins peaks at different times in each organ. Organs, such as leaves, roots and stems, receive different signals from their local micro-environment, such as light and temperature, and use this information to independently set their own pace.

If rhythms in different organs are out of sync, do plants suffer from a kind of internal jet lag? While the individual clocks in different organs peak at different times, this didn’t result in complete chaos. Surprisingly, cells began to form spatial wave patterns, where neighbour cells lag in time slightly behind one another. It’s a bit like a stadium or “Mexican” wave of sports fans standing up after the people next to them to create a wave-like motion through the crowd.

Plant cells communicate between their neighbours to coordinate the time. James Locke, Author provided
Our work shows that these waves arise from the differences between organs as cells begin to communicate. When the number of clock proteins in one cell peaks, the cell communicates this to its slower neighbours, which follow the first cell’s lead and produce more clock proteins too. These cells then do the same to their neighbours, and so on. Such patterns can be observed elsewhere in nature. Some firefly species form spatial wave patterns as they synchronise their flashes with their neighbours.

Local decision-making by cells, combined with signalling between them, might be how plants make decisions without a brain. It allows cells in different parts of the plant to make different decisions about how to grow. Cells in the shoot and root can separately optimise growth to their local conditions. The shoot can bend towards where light is unobstructed and the roots can grow towards water or more nutrient-rich soil. It could also allow plants to survive the loss of organs through damage or being eaten by a herbivore.

This might explain how plants are able to continuously adapt their growth and development to cope with changes in their environment, which scientists call “plasticity”. Understanding how plants make decisions isn’t just interesting, it will help scientists breed new plant varieties that can respond to their increasingly changeable environment with climate change.

11/01/2022

Why do onions make you cry?
Onions are grown and used all over the world, and anyone who has cut into one knows that it can make you cry. This happens because onions release an irritating chemical that makes your eyes sting.

Onions are mostly water, plus some vitamins and sugar compounds. They also contain compounds that include sulfur, a natural chemical found in many smelly substances, such as skunk spray and garlic. This is one way that plants defend themselves – producing substances that repel creatures who might eat them. Other plants have thorns or stinging leaves, or are made of special cells that make them hard to chew.

Red onion plants, showing their roots, stems and developing bulbs. USDA ARS/Stephen Ausmus
One sulfur compound in onions, called propyl sulfoxide, escapes into the air when you slice an onion. When it comes into contact with moisture, such as water v***r in the air or the natural moisture around your eyes, it changes into sulfuric acid. Sulfuric acid has a strong smell and irritates your eyes, so they make tears to wash it away.

There are some tricks to avoid this “emotional” onion experience. Next time you’re getting ready to dice an onion, start by cutting off and throwing away a little bit of the root end, which has lots of stringy little roots hanging from it. This lets most of the noxious sulfuric compounds, which are found in the root, escape. Then you can remove the pointy tip of the onion, peel its skin and slice it with fewer tears.

Some cooks chill onions for 30 minutes before they cut them, which helps because the sulfur compounds don’t escape into the air as easily when they’re cold.

Ornamental alliums (related to onions) are a popular flower for sunny gardens. Mike/Pexels, CC BY
Onions add flavor to lots of our favorite foods, from spaghetti sauce to tuna salad, so don’t let the smell drive you away. And gardeners love to grow ornamental alliums – members of the onion family that are bred for their looks. Many are very attractive, with blooms that make balls of color on long straight stalks. And their onion-y smell helps fend off rabbits, deer and other animals looking for a tasty garden meal.

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And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

11/01/2022

11/01/2022