Cucumbers in space

Japanese scientists have grown cucumbers in space flight.

Plant roots grow to find water, according to a process known as hydrotropism. Roots are also influenced by gravity and tend to grow downwards — this is called gravitropism.

Studying the effect of hydrotropism on roots on Earth is difficult because of the competing influence of gravitropism. To find out whether gravity or water had the greater influence on root growth, scientists at Tohoku University grew cucumber plants in the microgravity environment onboard the International Space Station.

In their experiments, the scientists were able to untangle the competing effects of water and gravity to show that, in microgravity, water (hydrotropism) had more influence in controlling root growth. Their results were published in the journal New Phytologist.

“We will be able to utilise 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 study.

Cucumbers were chosen for the study as they — like other ‘cucurbitaceous’ seedlings such as melons, pumpkins and squash — feature specialised protuberances, or pegs, whose formation is regulated by gravity. These pegs form during the plant’s early growth stage to help the seedlings emerge from their hard seed coat and anchor the developing plant in the soil while its roots form.

Image caption: Astronaut Dr Ron Garan watering cucumber seedlings onboard the ISS. Image credit: JAXA, NASA.