Notes Around
Doreen said:
But the point was that the information spread out throughout the whole plant.
In this case, I
think the information Phlog was referring to was simple wavelengths, which is, by more common definitions, a strange application of the word. But, as I noted, there are other treatments of the word that make it appropriate.
So we knew already that stimulating one portion of a plant, in this case a leaf, would cause metabolic changes in other portions of the plant - other leaves?
Part of what caught botanists by surprise in this is the
speed by which the plant responded. To reiterate Foyer at University of Leeds: "
What this study has done is link two signalling pathways together ... and the electrical signalling pathway is incredibly rapid ...." (
Gill)
Generally speaking, we can expect plants to develop seasonal rhythms, such as both Foyer and Karpinski—"
Every day or week of the season has ... a characteristic light quality"—refer to. This could be described as an evolutionary outcome. But part of the issue here is deviation from seasonal rhythm. That is, rather than natural cycles coinciding—e.g., the plant's biological functions and the natural seasons—Karpinski and his colleagues are suggesting a very immediate adaptability about some plants.
Additionally, the experiments with light and pathogens seems to suggest plants can in some way remember data, and condition responses to specific stimuli. Such a notion is very nearly Pavlovian.
• • •
Michael said:
No one is going to say a heart is a parallel primitive nervous system or that it "remembers" or "thinks" and to be honest heart tissue is a lot closer in related function to nervous tissue than plants are. I mean, as you know the NS regulated heart rate both indirectly by hormone release and directly by being wired right into it. Even though info flows from the CNS to the heart directly, even still, no one thinks of the heart as parallel NS.
Does that make sense?
I think where your comparison encounters trouble is in the idea that the heart is a
component of a larger system, while the plant is a system within itself. That is, there are additional components and processes between the environment and the heart. The heart responds to specific stimuli becuse the signal has been translated for that purpose. If you drop a heart off a cliff, it will not beat faster. But if you drop a person off a cliff, the eyes and ears, at least, will perceive the motion, the brain will process what that means and respond by sending signals out through pathways that lead to various parts of the body, including the heart, which in turn respond appropriately to their programming.
If you shine a light on the heart, it will not in and of itself respond. But if you shine a light into the eyes, the brain will interpret and respond, and the heart's action will be subject to the brain.
The heart is a component of an organism. The plant is an organism in itself.
In recent times, we have found nature to be far more subtle and complex than previously estimated. And as we find that complexity is not simply reserved to the animal kingdom, but also includes plants, we need to consider both definitions and what those definitions imply. In this case, it is equally possible that both the scientists and the dissent are overstating the implications. However, all things considered, I doubt the degree of overstatement is equal.
• • •
Rebecca Boyle reports for
Popular Science:
Terence Murphy, a plant biology professor at the University of California-Davis who was not involved in the research, said shining light on that first leaf could have any number of effects.
"The leaf would be loaded up with starch, maybe; that's going to have a real effect on how it communicates through the phloem (vascular system) to other leaves. It's not unreasonable that you could illuminate one leaf and affect the other leaves," he said.
The trick is finding out how the other leaves are informed -- and that's what appears to have been done in the Polish study. Bundle sheath cells surround the veins in leaves, stems and roots, so it's reasonable to think they transmit the electrical impulse, Murphy said.
Biologists have long known that plants can remember -- they need to know whether they've gone through a cold season before they can germinate in the spring, for instance. It's not memory as we know it, but a prolonged change in plant internal systems that causes effects later.
What's more, scientists already know plants transmit electrical signals in response to a stimulus, just as nerves do. This is easily measured using a basic electrode setup, according to Murphy.
Karpinski is apparently well-known among biologists for this kind of work, and it doesn't yet seem he is regarded as any particular laughingstock.
But here's the thing: People tend to regard plants as fairly simple evolutionary outcomes. Sunflowers, for instance, are usually explained according to the process that, as they collect sunlight, the plant grows in a certain way that changes the position of the flower such that it
appears to deliberately follow the light. One can assert, in that context, that a sunflower exhibits a coincidence of responses that are evolutionarily favorable.
With arabidopsis plants, at least, the new suggestion is that plants are capable of specific
behavior. This is understandably unsettling to some, though further discussion in the scientific community and future experiments will clarify the details of what, exactly, Karpinski is onto.
William John Lucas, distinguished professor of plant biology at UC-Davis and chair of the plant biology department, said an internal communication system would provide a wealth of information to different parts of the plant.
"A particular tissue within a plant needs to be able to signal to the rest of the plant in terms of what are its conditions, what should you expect," he said. "If a young leaf is emerging out of a plant, it would be nice for that leaf to know about the conditions in which it is going to emerge."
Lucas studies how plants pick up non-biological information, such as water and light, and how they transmit that information so the entire plant knows under which constraints it will grow. Plants can't move to a sunnier, wetter spot, so they need to make the most of their environment.
Tapping into their "nervous system" would help scientists understand how they do that, Lucas said. That knowledge could lead to optimized food crops or hardier trees.
"There are no neurons in plants, but there is a communication network that we don't fully understand," he said. "There are important implications for these kinds of studies."
(ibid)
So far, there isn't a whole lot on the web about this story; most of the early Google returns pertain to the BBC article. It's worth noting, just because, that this thread is number twenty-one in the result at the moment.
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Notes:
Gill, Victoria. "Plants 'can think and remember'". BBC News Online. July 14, 2010. BBC.co.uk. July 16, 2010. http://www.bbc.co.uk/news/10598926
Boyle, Rebecca. "Can Plants Think?" Popular Science. July 15, 2010. PopSci.com. July 16, 2010. http://www.popsci.com/science/artic...em-illuminating-how-plants-remember-and-react