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Why Use Artificial Leaves in Space When Real Leaves Work Just Fine?

As cool as the Silk Leaf is, you can’t eat one.

by Becky Ferreira
Jul 31 2014, 9:00am

Close-up of a grapevine leaf. Image: Zbysek.nemec.

A new trailer for Christopher Nolan's upcoming space epic Interstellar was released today, prominently featuring that weird accent Matthew McConaughey is so fond of these days.

But Nolan isn't the only artist who has been toying with the mechanics of long-term space missions. For the past few days, Royal College of Arts graduate Julian Melchiorri has been riding a jubilant wave of press about his "Silk Leaf" prototype, which he claims is the "first man-made biological leaf" in an interview on

Melchiorri's Silk Leaf promotion video. Credit: Melchiorri/RCA/Vimeo.

Melchiorri's leaf certainly looks sleek and futuristic, but his pitch gets a little hinky once he starts describing its future applications. "Silk Leaf could be used for space exploration, or space architecture, simply because, as you may know, plants [don't] grow in zero gravity," he said in the video.

"NASA is researching different ways to produce oxygen for long-distance space journeys to let us live in space. This material could allow us to explore space much further than we can now," he continued.

There's only one problem: plants most assuredly do grow in zero gravity. One of the most conclusive experiments on this subject was conducted on the International Space Station between October 2009 to September 2010. During that period, a number of Arabidopsis flowers (commonly known as thale cress plants) were successfully grown in closely monitored beds.

"Bottom line is yes, plants can indeed grow in microgravity," the study's lead author Anna-Lisa Paul told me in an email interview. "However, they certainly 'know' that they are in an altered environment, and they compensate by reaching into their metabolic tool box to engage a host of genes that will help them adjust to this new environment."

"Although sometimes space-grown plants are slightly smaller than their comparable controls on the ground, it is not to an extent that compromises the plant's ability to grow," Paul confirmed.

Indeed, the thale cress plants dealt with microgravity so well that NASA plans to land them on the Moon in 2015, to see how they fare with lunar gravity (basil and turnip seeds are also part of this experiment). Meanwhile, the ISS's first fresh food production experiment, appropriately named VEGGIE, has been running smoothly since it arrived in April 2014.

So not only do plants have potential as air-purifying oxygen producers in space, they are shaping up to be a promising food source for long-term missions. As cool as Melchiorri's Silk Leaf is, you can't eat one. Plus, there's no guarantee it actually will work in space. After all, the Silk Leaf is built from chloroplasts embedded into silk proteins. It may breathe in carbon dioxide and breathe out oxygen, but that does not make it sustainably photosynthetic, even on Earth.

Indeed, what Melchiorri leaves out of his description is as important as what he includes. What happens to the glucose byproducts of the photosynthetic conversion? How long can the chloroplasts self-sustain in silk proteins?

Perhaps most importantly: what's the efficiency on this thing? I doubt it can pump out anywhere near the amount of oxygen a real plant can. Not that there's any shame in that. Plants have playing the photosynthetic game for at least 450 million years. It's no surprise that they are total pros at it by now.

My aim is not to dump all over this project, only to reign in the lofty claims Melchiorri laid out in his video. It's a neat idea, and the light fixtures he fashioned out of the leaves do look pretty cool. But it is not the first man-made leaf to produce oxygen, and regardless, no artificial leaf has ever outcompeted the real thing.

If we want to boost oxygen, purify air, and invite nature into our architecture, it'd be better to stick with the organisms with experience dating back to the Ordovician period.