trees_memories.pdf
6min_english_trees_memories.mp3
BBC LEARNING ENGLISH
6 Minute English
؟Do trees have memories
Neil
Hello This is 6 Minute English from BBC Learning English I’m Neil
Sam
And I’m Sam
Neil
Over the past 18 months, we’ve heard a lot about the human immune system –
the cells in our bodies that fight diseases like coronavirus We know that in
humans the blood stream carries immune cells around our body
Sam
But what about trees and plants? They don’t have blood, so how do they protect
themselves?
Neil
That’s a good question, Sam, and the answer involves memory Us, humans, store
memories in our brain, but our body also remembers things, including stressful
situations from the past, which it stores in our genes The information gets
passed on to our children genetically
Sam
But surely trees don’t have memories, Neil! I mean, do you think a tree can
remember being young or what it was doing last year?
Neil
Well, not exactly, but trees grow rings – a layer of wood for each year of growth
That could be a kind of memory
Sam
In this programme, we’ll be asking whether trees can remember – and if so, does
it make them stronger and better able to fight disease?
Neil
But before that I have a question for you, Sam As I said, trees grow a new ring
every year and by counting them we can estimate their age One of Earth’s
longest living trees is The Great Bristlecone Pine, found on the west coast of
America But how long can these trees live? Is it:
a) over 1,000 years?
b) over 3,000 years? or
c) over 5,000 years?
Sam
Wow, it’d be a job to count the rings on those trees! I’ll say b) over 3,000 years
Neil
OK, Sam, we’ll reveal the correct answer later
Sam
Unlike us, trees don’t have blood and bones to protect them from outside
attacks, so how exactly does a tree’s immune system work?
Neil
That’s what BBC World Service programme, CrowdScience, asked bioscientist,
Jurriaan Ton Here’s what he said:
Jurriaan Ton
Plants in particular need to have a very efficient immune system for two
important reasons Firstly, they sit at the bottom of the food chain so there are a
lot of opportunistic organisms out there, including insect herbivores and
microbial pathogens who want to tap into that biochemical energy that is stored
in plants The other reason is plants are rooted to the ground – they cannot
escape from the stressful conditions in their environment
Sam
It’s hard for trees to protect themselves Unlike animals, they can’t run away, and
they’re at the bottom of the food chain – the plants and animals linked in a chain
of eating weaker things and then being eaten by stronger ones
Neil
Rabbits eat grass and, in turn, are eaten by foxes
Sam
Right If you are at the bottom of the food chain, everything wants to eat you,
including opportunistic animals If something is opportunistic, it takes
advantage of a situation to gain some benefit for itself Tree leaves are
opportunities for hungry insects and caterpillars to eat
Neil
So, trees need immunity because they’re under attack, either from disease or
from living things wanting to eat them But what about memory, Sam?
Sam
If trees can remember stress - types of insects that eat it, for example – they
might be better prepared in future
Neil
For me, stress is a work deadline or moving house, but for trees it’s more basic,
something like not getting enough water
Sam
Dr Estrella Luna-Diez believes trees record stress in their rings A small ring,
showing that the tree didn’t grow much that year, indicates some outside stress
She explained more to BBC World Service programme, CrowdScience:
Estrella Luna-Diez
Our hypothesis would be that, depending on the level of that stress – if it was a
really long-lasting drought of a few years, then maybe the tree can remember it
for a long time because it needs to adapt to that hostile environment Now,
maybe the hypothesis would be the other way around, maybe if it was a very dry
July for instance, maybe the tree is not even that bothered and then it forgets
within one year because that memory of stress is gonna be holding it back on its
growth, for instance
Neil
Dr Luna-Diez has a hypothesis – an idea that explains how or why something
happens which has yet to be tested to see if it’s correct
Sam
Her hypothesis is that trees remember stressful outside events, something like a
drought – a long period of time with little or no rain
Neil
For a tree which has lived for hundreds of years it might be useful to remember
that 1947 was a very dry summer
Sam
On the other hand, maybe that stressful year is best forgotten Maybe the tree is
not bothered – not worried or concerned because it’s not important to it
Neil
So, trees do have memories - but they don’t let it get them stressed!
Sam
Maybe that’s the secret to a long life! But what’s the answer to your question,
Neil?
Neil
Ah yes, I asked you how long Earth’s oldest trees, Great Bristlecone Pines, can
live
Sam
I said b) over 3,000 years Was I right?
Neil
You were wrong, I’m afraid, Sam They live even longer – over 5,000 years, in fact
– all the way back to the Bronze Age
Sam
What memories those trees must have - if only they could speak! Right, let’s
recap the vocabulary we’ve learned, starting with immune system – the body’s
way of fighting infection and disease
Neil
A food chain describes the ways plants and animals get eaten and eat each
other
Sam
Opportunistic people take advantage of a situation to get some benefit for
themselves
Neil
A hypothesis is an idea to explain how or why something happens that hasn’t
been tested to see if it’s correct
Sam
A drought is a long period of time with little or no rain
Neil
And finally, if you’re not bothered about something, you’re not worried because
it’s not important to you
Sam
Our six minutes are over Bye for now!
Neil
Bye!
VOCABULARY
immune system
cells and organs which protect the human body from infection and disease
food chain
plants and animals that are linked in a chain because each thing eats something
weaker than it, and gets eaten by something stronger
opportunistic
takes advantage of a situation to gain benefit, often without thinking whether
the action is right or wrong
hypothesis
idea that explains how or why something happens which has yet to be tested to
see if it’s correct
drought
long period of time with little or no rain
not bothered (about something)
not worried or concerned because it’s not important to you
