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.
But what about trees and plants? They don’t have blood, so how do they protect themselves?
但是树木和植物呢？他们没有血，那么他们如何保护自己呢？
Neil(尼尔)
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.
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?
但树木肯定没有记忆，尼尔！我的意思是，你认为一棵树能记得年轻的时候，或者它去年在做什么吗？
Neil(尼尔)
Well, not exactly, but trees grow rings – a layer of wood for each year of growth. That could be a kind of memory.
嗯，不完全是，但树木会长出年轮 —— 每生长一年就会有一层木头。那可能是一种记忆。
Sam(山姆)
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?
在这个节目中，我们将询问树木是否能记住 —— 如果可以，它是否使它们更强壮、更能抵抗疾病？
Neil(尼尔)
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?
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.
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.
Rabbits eat grass and, in turn, are eaten by foxes.
兔子吃草，反过来又被狐狸吃掉。
Sam(山姆)
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.
If trees can remember stress - types of insects that eat it, for example – they might be better prepared in future.
如果树木能够记住压力 - 例如，吃它的昆虫类型 - 它们将来可能会有更好的准备。
Neil(尼尔)
For me, stress is a work deadline or moving house, but for trees it’s more basic, something like not getting enough water.
对我来说，压力是工作期限或搬家，但对于树木来说，这是更基本的，比如没有得到足够的水。
Sam(山姆)
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:
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.
Her hypothesis is that trees remember stressful outside events, something like a drought – a long period of time with little or no rain.
她的假设是，树木会记住压力很大的外部事件，比如干旱 —— 很长一段时间很少或没有降雨。
Neil(尼尔)
For a tree which has lived for hundreds of years it might be useful to remember that 1947 was a very dry summer.
对于一棵已经活了几百年的树来说，记住1947年是一个非常干燥的夏天可能会有所帮助。
Sam(山姆)
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.
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.
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