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New research growing cucumbers on ISS has found that the roots of these plants grew in the direction of water in weightlessness.
Plant roots grow to find water, according to a process known as hydrotropism. Roots are also influenced by gravity and tend to grow downwards, called gravitropism. To find out whether gravity or water had the greater influence on root growth, investigators grew cucumber plants in the microgravity environment on board the International Space Station. In their experiments, water (or hydrotropism) had more influence in controlling root growth.
“We will be able to utilize roots’ ability to sense moisture gradients for controlling root growth orientation and efficiently growing plants in future space farms,” said Dr. Hideyuki Takahashi, senior author of the New Phytologist study.
You can read the full science paper here.
This might sound obvious, but it isn’t. Past plant growth experiments on Mir and ISS had tended to show that plant roots did not know where to grow in weightlessness, suggesting that they needed gravity to guide the roots to water. Because of this, later experiments in space provided the roots complicated engineering to guide the roots to the water.
This experiment shows that maybe that complex engineering is not necessary, or at least could be simplified a bit. At a minimum it is crucial information engineers will need to design any future gardens for interplanetary spaceships with long term weightlessness.