Growing lettuce on mars

Sunday 4 January 2015

Ten finalists remain in the MarsOne competition and "Lettuce on mars" from the university of Southampton could make a great introduction to an IB topic on photosynthesis. The NoS point in the IB guide 2.9 states that, "control of variables in photosynthesis experiments is essential". An understanding of the different wavelengths of light and the action spectrum of chlorophyll is also found in this section of the guide. All of these concepts are important in the Lettuce on mars project.

The first stages of the project relate best to germination, 9.4 in the HL plants topic. The lettuce seeds are frozen during the 7 month voyage. Assuming that the growth chamber lands safely, it will first be heated to 21-24°C and filled with pressurized carbon dioxide. Oxygen will be produced by electrolysis of water. This would be a great stimulus for designing experiments about seed germination. (Frankly, my students don't always naturally get excited about seed germination.) The Lettuce on mars projects may lead students to ask, "why do the seeds need oxygen?".

Lettuce plants have already been grown in space, on the International Space Station. NASA has done a series of experiments germinating seeds, and one astronaut, and NASA has a mission planned in 2015 to germinate seeds and grow seedlings on the Moon.

There is a nice experiment protocol from NASA which was a seed germinating activity related to some earlier experiments on the Mir space station, some years ago. This could easily be adapted to make a nice experimental design.

To link these space lettuce experiments to the IB topic 2 on photosynthesis we need to look at the way plants are grown. Most lettuce grown in space grows well in Red and Blue light. "An eerie purple glow comes from the grow lights... most plants are really just fine with red and blue lights for photosynthesis," says Gioia Massa of NASA. This raises questions about why plants look green, and which colours of light are absorbed by chlorophyll pigments. 

The Lettuce on Mars project proposes to use natural sunlight, (about 50% of the Earth's sun strength) with backup LEDs to boost the light. How much photosynthesis does a plant do under LED lights of different colours? Which colours / intensities are optimum? There are loads of affordable LED growlights available to buy and these might easlily be adapted for photosynthesis investigations in the lab. 

There are more references to growing plants in space in the links below. 


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