Climate change threatens to disrupt basically every aspect of our lives,
including what’s on our dinner tables.
Droughts in particular are looking like they’ll be a major threat to our food supply,
especially since crops like maize, wheat and rice
are particularly vulnerable to dry weather.
Which is why researchers have been trying to make plants more drought resistant
for decades, using high-tech approaches like genetic modification.
And while they have been somewhat successful,
genetically modified plants are not the only way to tackle this problem.
It turns out, a simple solution might have been right under our fingernails
this whole time–the soil-dwelling microbes that make up a plant’s microbiome.
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Anyone with the tendency to forget to water their plants
already knows about the damage that drought can do.
And that damage doesn't go away when water the comes back.
While some of the molecular, structural, and physiological changes
caused by drought go back to normal once the rain comes,
in many cases those changes cause physical damage that can’t be repaired.
So even a short-term drought can have long-term consequences.
During drought conditions, plants are not able to
get the nutrients they need from the soil.
Their leaves shrivel up and have less surface area for photosynthesis,
and their cells aren’t able to elongate like usual.
All of that combined means that you get smaller plants
with less edible mass that just don’t taste as good.
So a drought lasting one growing season can
end up impacting the food supply for years.
Population growth is already pushing agriculture to its limits,
and with the frequency and severity of droughts increasing thanks to
climate change, we’re going to find ourselves trying to
feed more people with less food.
And we’re actually already starting to see this play out.
In Europe, heatwaves and droughts have roughly tripled the amount of grain
that isn’t harvestable over the last 60 years,
from 2.2% between 1964 and 1990 to more than 7% between 1991 and 2015.
And the situation is even more dire in developing nations in tropical regions,
with wheat yields predicted to decline by
roughly 15% in African and Southern Asian countries by 2050.
Which is why finding ways to protect plants from droughts
has been on scientists’ radars for decades.
A lot of plants have coping strategies to help them survive droughts,
and there’s been lots of research into genetic modifications
to enhance drought resistance.
But it’s not just their genes that can help plants survive dry times.
It’s also their neighbors.
Microbiomes are the communities of tiny little organisms
that live in an ecosystem, so the bacteria, fungi, algae, all that jazz.
You may have heard about the human microbiome,
but plants have microbiomes, too.
Theirs include microbes that live both on the inside and outside of the plant itself,
and all of the little guys that live in the soil around the roots.
They help promote plant growth, turn nitrogen into forms
that plants can use, and slurp up nutrients to pass along to their host.
And it turns out that some microbes also
release molecules that play a role in drought resistance.
Some of these bacteria release plant growth regulators,
which alter growth by doing things like impacting energy metabolism,
increasing photosynthesis, and boosting the antioxidant system.
Other bacteria produce enzymes that promote growth by
lowering levels of ethylene, a hormone that’s released when plants are stressed.
And some work by secreting molecules called exopolysaccharides,
which provide structure to biofilms that can surround
a plant’s roots and keep them from losing water.
You might think that these are just all-purpose growth-promoting microbes,
but that doesn’t seem to be the case.
Under normal conditions, they don’t seem to
do much for plant growth or crop yield.
They only start to do their thing once droughts hit,
and not all plants seem to have these particular helpful friends.
So scientists have been trying to come up with ways to
harness the powers of drought-resisting microbiomes and
turn them on more consistently, especially for food-producing crops.
In 2017, researchers in China took bacteria from the leaves of a desert plant
species that is super drought-resistant, as you would expect a desert plant to be.
They added that bacteria to the soil that they were growing wheat in,
and after a few days to let the bacteria get settled in,
the researchers withheld water from the plants for a full week.
Even with these simulated drought conditions,
wheat plants grown with the bacteria had less leaf curling,
longer roots and shoots, more chlorophyll and sugars, and higher total weight,
which the researchers took as evidence that the bacteria
was contributing to growth enhancement and water stress tolerance.
And in 2015, researchers in Milan got similar results
when they inoculated pepper plants with bacteria from grapevine microbiomes.
Now, we’re not at the stage of large-scale deployment of plant microbiomes yet,
but it’s an incredibly promising approach.
The idea is that these microbes could just be added to fertilizer or to soil.
Smaller farms and those in developing parts of the world would be
able to use these solutions to improve their yields and their livelihoods.
Which would mean that one answer to a super
big problem could actually be super tiny.
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