When you hear the phrase “killer hair,”
you probably picture a sick mullet -
you know, some super cool ‘do.
You’d probably never mistake it for anything literal.
But, if you venture outside the mammalian branch
of the tree of life
and onto another limb,
you’ll find the owners of some truly killer hair.
From switching on the immune system
to fighting off insects
in the most metal way possible,
here’s what plants do with their killer ‘dos.
[intro song]
So what we’re actually talking abou
t here are tiny protrusions called trichomes,
and a wide variety of plants have them on their stems, leaves, and other surfaces.
While they generally resemble tiny hairs,
they come in a handful of varieties–
some even secrete chemicals to help the plant defend itself.
And that’s only the beginning
of what a bunch of teeny tiny hairs can do.
For example,
how does growing more food
with less water sound?
In a 2017 study in the journal Rice –
yes, that’s a journal –
researchers bred a gene
into a domesticated strain of rice
that caused them to grow more trichomes on their leaves.
Their “hairy” strain lost less water
during photosynthesis compared to the original,
though the plants also got hotter during the day.
The researchers think the extra hairs
are affecting something
called the boundary layer,
which is a layer of air around the leaf,
and making it harder for water to pass through
and escape the leaf.
They hope this could help us develop crops that resist drought or require less water,
which could be useful in the future!
But unlike me, if you’ve ever used a blow dryer,
maybe you’re thinking, yeah,
I know hair traps water.
Don’t worry – I’m just getting started.
Trichomes in Arabidopsis,
a plant in the mustard family and darling of the plant genetics world,
not only help the plant detect rain –
they also help it fire up its immune system.
Publishing in the journal Nature Communications in 2022,
researchers showed that trichomes
are able to detect the physical impact of raindrops,
as well as other mechanical signals.
Once the trichomes detect raindrops,
they send out a pulse of calcium
to the surrounding cells
. That pulse cranks up the expression of genes
that help the plant recognize invading pathogens.
But, why rain?
The plant hasn’t detected any viruses or bacteria or fungi,
just a gentle shower.
The researchers emphasize
that a lot of plant pathogens
are spread by raindrops.
Just like how your mom told you not to go ou
t in the rain or you’ll catch a cold,
it seems plants gear up
whenever it rains to protect themselves
from what comes next.
But while that’s cool,
I promised you metal.
And now I’m going to deliver.
The horsenettle plant uses its hairs
to tear apart caterpillars that try to eat it…
from the inside.
These plants have spiky,
resilient trichomes that pass through
the digestive tracts of caterpillars intact.
What’s more, they’re wreaking destruction
as they go.
In a 2017 paper,
researchers documented
the guts of tobacco hornworm caterpillars
being “stretched, punctured, and torn” –
their words!
They also showed that caterpillars preferred
to avoid diets full of spikes,
and it’s no wonder why.
They even went the extra mile
and showed that silverleaf nightshade,
a plant with similar trichomes, produced similar results.
But tobacco, which has different trichomes,
didn’t put them off.
There’s at least one strategy even more brutal
than ripping apart a herbivore’s guts.
See, plenty of plants have defensive trichomes
like the horsenettle.
Some of them are specifically referred
to as hooked trichomes,
and can actually capture insects
that encounter them.
And for a while,
researchers assumed this
was a relatively passive process
that would occur when insects walked across
or bumped into a trichome.
But in yet another study
from 2017 in the journal Frontiers in Plant Science,
one group showed it can be a bit more…
personal.
In the paper, they looked at leafminer flies interacting
with plain, boring old kidney bean plants.
And… some flies’ legs did get trapped,
which is about what fly part
you’d expect to bump into the trichomes first.
What the researchers saw most often,
however,
was that flies became impaled
when they extended their mouthparts to feed.
And second most often after that?
Well, female flies have an organ
called an ovipositor
that they use to deposit eggs.
And when a female fly
went to lay eggs
in the presence of a trichome…
Well, ouch.
These flies remain trapped
until they struggle free,
and that…
That just can’t be comfortable.
Even if they escape,
they’re scarred for life.
On the list of effective predator defenses,
I have to rate this one pretty high.
And pretty hardcore.
So there you have it.
These are only a few examples
of what trichomes can do,
which just goes to show that,
before we invented “the Rachel,”
Mother Nature already came up with totally killer hair.
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Thanks for watching!
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