
Plants “panic” when it rains - lelf
https://phys.org/news/2019-10-panic.html
======
breadandcrumbel
Link to the research:

[https://www.pnas.org/content/early/2019/10/25/1911758116](https://www.pnas.org/content/early/2019/10/25/1911758116)

>“As to why plants would need to panic when it rains, strange as it sounds,
rain is actually the leading cause of disease spreading between plants,” said
University of Western Australia’s Professor Harvey Millar, co-author of the
study.

“When a raindrop splashes across a leaf, tiny droplets of water ricochet in
all directions. These droplets can contain bacteria, viruses, or fungal
spores.”

“The sick leaves can act as a catapult and in turn spread smaller droplets
with pathogens to plants several feet away. It is possible that the healthy
plants close by want to protect themselves,

------
kris-s
What is described in the article doesn't fit the definition of panic.

I'm torn because maybe I wouldn't have read the article without the needless
anthropomorphization. Plants are awesome and interesting to me because they're
so planty and not animaly.

~~~
dickeytk
A defense mechanism that is triggered by a hormone? Doesn't seem terribly far
off

~~~
droithomme
He makes an interesting point. Some plants have a response to rain triggered
by a hormone. To ascribe the term panic to it though might possibly be
mischaracterizing the response because of the tendency to anthropomorphize.

~~~
nkrisc
Well we don't really have words to describe plant behavior. I agree, we can't
view plants through an animalian lense, but at the same time we have to use
the words we have to discuss them. I think it's fair to say plant "panic" is
different than animal "panic" but from what I read, panic seems to be the
closest analogue.

~~~
phkahler
Is our immune response to a pathogen considered panic? I think not.

~~~
jadell
A chemical reaction that sets of a string of defensive protection reactions
and behaviors? Sounds quite like panic to me. It's basically "fight or flight"
for plants except plants can't do the "flight" part.

------
codingdave
"Panic" is an anthropomorphism for what is really going on. Plants react to
water. That makes complete sense. Humans react to it when it falls on us as
well. Maybe we go inside. Maybe we open an umbrella. Maybe we go dance through
the fields and enjoy a summer rain. But whatever we do, they are reactions,
not "Panic."

~~~
Enginerrrd
While I mostly agree with you, I just want to play devil's advocate here a
little bit.

Plants and fungi have some very complex interactive networks capable of
various forms of individual, inter-individual, and inter-species communication
and intelligent decision making. From our perspective though, these
interactions and decisions play out over some very different time scales from
our own cognition. Suppose for a second that a tree was intelligent enough to
be sentient, it would be VERY difficult for either the tree or us to recognize
the intelligence and cognition in the other.

"Panic" responses, fear, and the whole manner of physiologic changes that
happen in a human didn't spring up over-night. These pathways evolved a VERY
long time ago. An insect has some obvious "panic" type of responses to
predation attempts that are not so different from our own. As you climb up the
ladder in intelligence to mammals, and then all the way to humans, there is
absolutely no clear line where "panic" suddenly exists as I believe you would
define it. It's a very smooth and gradual transition. Even in a human, if
you've ever watched one come back to consciousness after a seizure or wake up
from anesthesia, you'll see that it's also a very smooth and gradual
transition to what we'd call consciousness and sentience. It's not at all an
on/off switch.

I wouldn't be at all surprised if some of the same neurotransmitters and
hormones fill the same role in a plant response to dangerous conditions as
they would humans. I know many of the same signalling molecules are in use.
Evolution doesn't like to fix what ain't broke.

~~~
JoeAltmaier
Time scale isn't enough to prevent us from recognizing intelligence and
cognition in trees (I can't speak for the trees recognizing us). Look at their
works, their accomplishments, their cooperative social organization. They've
had a long, long time to show us that.

Oh! They've done nothing! No tribes nor social exchanges - never even mention
hospitals and lasers and money and law...

No, trees are not sentient, intelligent nor exhibiting cognition.

~~~
8bitsrule
No grifting, fraud, hoaxes, deceptions, violence, dishonesty -never even
mention atom bombs, firethrowers, IEDs ... Clearly not sentient.

~~~
tempguy9999
Plants can be parasites, practice deceit, produce poisons to kill animals and
other competing plants, kill other plants by strangultion as well (and likely
other ways). Perhaps that was your point and I missed it.

~~~
8bitsrule
"Plants can ...practice deceit"

Sounds almost like intentionality (sentience) there.

Plants sure aren't all sweetness and light. I did suggest that, while
sentience leads to inventions, it also leads to (non-feeding) murder, war
(largely restricted to humans), and possibly extinction. If we 'have' any
advantages on plants, sentience may not be it.

Plants can't move, and can't speak. That may explain why they've been around
for oh, 50 times longer than us. And will _almost certainly_ be around LONG
after we're not. Smart?

~~~
tempguy9999
Not agreeing or disagreeing, just pinning stuff down here...

> Sounds almost like intentionality (sentience) there

Hmm. Clarification needed - does the concept of deceit mean the deceiver
understands what it is doing ie. has theory of mind? If so, I'd guess plants
do not deceive but do something similar driven by evolution[0] that we need a
different word for as it's not sentience-driven.

I'm open to the idea of evolution itself has some sentience but I'd not waste
time on it as I don't see it's a testable hypothesis.

> If we 'have' any advantages on plants, sentience may not be it.

Agreed, but sentience may actually be an advantage. After all it's not the
sentience in mankind that genuinely makes me despair but other features such
as greed and short-termism. Fix those and maybe our chances of racial survival
would be hugely increased. IOW we have many mental aspects and sentience is
only one of them.

> around for oh, 50 times longer than us

Plants separated from aninmls ~1.7 billion years ago (figure from memory),
humans have been around a few hundred thousand years, by various definitions
of 'human'. I guess you dropped a few zeros :)

[0] eg. natural variegation in plants
([https://en.wikipedia.org/wiki/Variegation](https://en.wikipedia.org/wiki/Variegation))
seems to make insects attack them less as discoloration makes the plants look
to the insects less healthy
([https://en.wikipedia.org/wiki/Variegation#Defensive_masquera...](https://en.wikipedia.org/wiki/Variegation#Defensive_masquerade)).

------
dunstad
If you liked this one, you might also enjoy reading about the mycorrhizal
networks some plants can use to communicate between each other:
[http://www.bbc.com/earth/story/20141111-plants-have-a-
hidden...](http://www.bbc.com/earth/story/20141111-plants-have-a-hidden-
internet)

~~~
dickeytk
my favorite radiolab episode is about this:
[https://www.wnycstudios.org/podcasts/radiolab/articles/from-...](https://www.wnycstudios.org/podcasts/radiolab/articles/from-
tree-to-shining-tree)

------
wcoenen
The article talks about signals and proteins that activate genes, but it
doesn't say what actual response of the plant is being implemented by those
genes. I thought maybe this was an omission, but the paper doesn't seem to
talk about that either.

------
lawzup
So, what defenses are triggered? Seems like this article is half written.
Where's the cause and effect? What are these protective effects you mention?

------
adfkbuvasdas
The instruction to pour water straight into the pot, and not onto the plant,
always struck me as odd. Maybe it’s one of those small ancient nuggets of
knowledge that we struggle to justify but just work. Might be a big leap
still, but reactions like the one from this paper could justify not spraying
water all over my house plants.

~~~
mytailorisrich
Tap water is often hard so pouring it on the plant leaves deposits behind.

Another justification is that when it's sunny water droplets on leaves act as
lenses and might burn the leaves.

It is also known that wet leaves increase the chance of fungi, mildew, etc.
taking hold on them. The article shows that plants are also well aware of
that!

~~~
swiley
I was always told that the leaves just don’t need it and it gets in the way.

------
croh
Related -
[https://en.wikipedia.org/wiki/Jagadish_Chandra_Bose#Study_of...](https://en.wikipedia.org/wiki/Jagadish_Chandra_Bose#Study_of_metal_fatigue_and_cell_response)

------
sigmaprimus
It would have been nice to see what particular plants were used in this study.
I somehow doubt that all plants react this way. Considering some plants grow
under water, others such as sequoias are dependent on fog for their
irrigation. Interesting article none the less.

~~~
Thaliana
The plants used in this study are Arabidopsis thaliana, which is a very
commonly used model organism in plant biology.

I think it's not a particularly wild assumption that a lot of plants will
react in this way. The MYC2 protein and jasmonic acid are important regulators
of plant defenses so priming of defenses when it rains makes sense. There are
pathogens (such as Pseudomonas syringae) that can trick a plant into opening
its stomate, which are airholes on the leaves, as a means of gaining access to
the interior of the leaf.

As the paper describes how the mechanical action of rain can wash pathogens
around the leaf or onto other plants I think it's reasonable to think other
plants would react like this.

The interplay between the jasmonic acid pathway and other plant hormone
pathways is super interesting as plants, in general, have two ways of
defending themselves. For pathogens that feed on dead tissue the name of the
game is to keep the cells alive (jasmonic acid can be thought of as generally
responsible for this sort of response), whereas for pathogens that feed on
live tissue then the plant will kill of cells local to the infection site in
order to deny the pathogen food (salicylic acid is largely responsible here).

~~~
sigmaprimus
I still stand by my original comment, it would have been nice to have the type
of plant studied included in the article and or in the synopsis of the paid
article.

"The plants used in this study are Arabidopsis thaliana" was this information
in the story and I just missed it? Or are you making that assumption due to
that being a "very commonly used model organism in plant biology"? The plant
image used at the top of the article looks nothing like rock cres but instead
more like some sort of hosta or lilly pad, I wonder if the image plant is
shaped that way to catch and funnel water away from its roots? Just as a palm
does the opposite? Anyways I could go on, just wish they had included the
species in the article.

~~~
Thaliana
Checking the article again I got it from the "More Information" box at the
bottom of the article. The paper is titled "In vivo evidence for a regulatory
role of phosphorylation of Arabidopsis Rubisco activase at the Thr78 site" so
that means A. thaliana.

The picture is certainly misleading, I guess they just grabbed a generic
"plants in a rainforest" picture for evocative reasons.

------
meigwilym
> "One of the chemicals produced is a hormone called jasmonic acid that is
> used to send signals between plants," Professor Millar said.

Would this be "that smell" that sometimes lingers after rain fall?

~~~
tmshu1
Maybe you’re referring to the smell of “petrichor”, which comes from the soil
getting wet
[https://en.wikipedia.org/wiki/Petrichor](https://en.wikipedia.org/wiki/Petrichor)

------
vorticalbox
What defences do plants use in this case? Article describes why but not what.

------
earthboundkid
Honestly, same.

------
julienreszka
Very funny thought to imagine plants panicking when it rains.

