The importance of plants

We still have to live, breathe and eat. Here on Earth, we rely quite heavily on our plant biodiversity. But could we take it with us? Izzie Clarke went for a stroll around Clare College Gardens in Cambridge with Plant Ecologist, Howard Griffiths…

Howard - Welcome to Clare Gardens.

Izzie - I don't think I've ever seen such a beautiful garden in my life. Howard, what have plants ever done for us?

Howard - How can you ask such a question. Plants are the basis of life on Earth. They are the earth's life support system. Everything we do is derived from plants, either in terms of fossil fuels which represent plants that were buried underground in millions of years ago, or in terms of the basis of all the foodstuffs that we consume, or in terms, often, of many of the clothes that we wear. They learnt millions of years ago how to harvest the energy of sunlight and use that to take up an abundant resource within the atmosphere, carbon dioxide, and turn it into organic carbon. And they contain an enzyme which is the only enzyme that has evolved in a large enough scale to be able to do that, to support what we now know as life on Earth in both the oceans and on land.

Izzie - Yes, and quite a vital role then. So if we were to go, say to another planet like Mars, could we bring them with us and try and work it out?

Howard - Absolutely. I mean many experiments are being done in various space flights in order to test out how plants grow under extremely low gravity: whether they can grow, because of course they're going to be slightly disorientated because plants can sense gravity and normally send their roots down and then shoot up. And without that we would need to devise special chambers perhaps to help them simulate which way is up and which way is down.

Izzie - I’m imagining giant pods that look like a beautiful oasis or something like that.

Howard - Well, I think that's a fairly large scale. I suspect the prototypes I've seen have been slightly smaller, more like small chambers but but nonetheless they are thinking about whether we might be able to grow plants. So we would need plenty of water, we would need carbon dioxide in appropriate concentrations together with the additional nutrients that they would need to be able to take up from the soil and grow.

Izzie - Now is this what we categorize as biospheres? Are they the same thing?

Howard - Very similar. One might imagine that a space station as a permanent habitation might look something like a large experiment that was conducted in the Arizona deserts, and is still going on. It's called Biosphere 2. But it had some problems let's say, and there may be lessons from that biosphere that might help us inform what would be needed on another planet.

Izzie - So what were they looking to find with these biospheres?

Howard - Well in Biosphere 2 they first of all set out to try and create a completely self-sustaining environment with oceans and deserts and different habitats into which a number of people were going to try and live for a whole year without any external intervention.

Izzie - Did this include an oxygen supply? How did that work?

Howard - Well the idea was that the plants that they would grow would help to sustain the oxygen supply and provide them also with food to eat.

Izzie - Sounds amazing. Did it actually work? You alluded to some technical problems.

Howard - Well quite apart from the interpersonal problems that are said to have happened, the individuals lost a huge amount of weight because they simply couldn't grow enough food to support them. And there were also terrible problems in terms of maintaining the right balance between carbon dioxide and oxygen inside those biospheres partly because of the materials they used both in the soil which had too much organic material. And so basically the microbes in the soil were just busy consuming oxygen and converting that to carbon dioxide. So the soils were respiring too much. And the other problem was that the concrete that they built the buildings from was also absorbing carbon dioxide and oxygen. So in the end they had to introduce pulses of oxygen to try and sustain the environment.

Izzie - So even then if we were going to try and replicate that, we’d need to get the practice run here on Earth right first.

Howard - Well the idea that plants will give us the oxygen that we can breathe is one of those sort of long standing fallacies. Yes plants did give us the oxygen we breathe. Over the last three billion years or two billion years. Currently they’re in balance. So plants and organic material respires, as much consuming oxygen as it produces every year. So trying to create an environment where plants can produce the oxygen we need to breathe means that we need to take away that carbon and store it somewhere as our fossil fuels did 300 million years ago.

Izzie - It's quite a long wait to to get to that.

Howard - Exactly, it would be a real problem. So you would still have to find a way to manipulate the oxygen concentration independently to keep it at a high enough level. It would take a very long time to build a self-sustaining environment such as we have on Earth.

Izzie - Okay so perhaps we're not quite there yet. What would some of the other challenges be of growing plants on another planet or in space?

Howard - I think overall, creating the correct atmosphere for them, finding enough water, getting enough soil which didn't in itself alter the composition of gases that we were trying to grow these plants in or live in ourselves alongside them, and overcoming other issues like differences in gravitational pull relative to what we have on Earth.