Plants are background features in a lot of science fiction as terraformers or oxygen supply. Plants in space sometimes have a lead role, like the tiny, precious seedling in Wall-E or the dead plants in the spaceship greenhouse in Sunshine. In real life, NASA is taking plants seriously as morale-boosters, air filters, and food supplies for astronauts on future long-duration missions.
In 1993 for the first time in history, Hilaire et al. were able to observe plants growing in a completely novel environment, and specifically find out exactly what effect gravity has on plants. A paper published in BMC Plant Biology today continued that research, showing that root growth patterns are not affected by gravity. The paper is open access and you can read it here.
Robert Ferl and his team, all from the University of Florida, analysed Arabidopsis seedlings grown on the International Space Station (ISS) and control seedlings an identical growth chamber in Kennedy Space Center, Florida. Their results demonstrate that Arabidopsis thaliana cultivars WS and Col-0 have phototropic shoots and roots that grow away from the shoot and the light source (negative phototropism), whatever the gravity exerted on them. Neither plants grown on the ISS nor plants grown on earth grew in a straight line directly away from the light source, but those grown in space deviated further from that line. The typical sinusoidal waving of Arabidopsis roots was unaffected by the lack of gravity (above; shown better in other figures in the paper). That gravity has little effect on root development confirmed the results of Millar et al. (2011), who worked on A. thaliana cultivar Landsberg grown in the dark on the ISS.
Despite the confirmation that plant roots grow away from the shoot irrespective of their distance from the Earth’s surface, the paper contains bad news for anyone hoping to escape in a spaceship with plant-based oxygen and food supplies. Plants in grown on the ISS grew more slowly and were smaller than their Earth-bound counterparts (above, Figure 3E in the paper). Some other spaceflight experiments showed similar differences in size, but in other cases the opposite was true. In this case, the authors were able to demonstrate that the small size of the space-grown seedlings was due to limited cell elongation, not a problem with cell division, but could not explain why.
Highlighted article: Anna-Lisa Paul, Claire E. Amalfitano and Robert J. Ferl (2012) Plant growth strategies are remodelled by spaceflight. BMC Plant Biology 12:232.
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