The International Space Station
Nasa plans to grow lettuce for astronauts on board the International Space Station.Reuters

Nasa has supplied a portable plant growth unit to the International Space Station (ISS) to grow lettuce for astronauts on board.

The deployable chamber called the Vegetable Production System (Veggie) is capable of producing salad-type crops to provide ISS crew with a palatable, nutritious, and safe source of fresh food.

The space agency hopes to grow the first crops in microgravity aboard the orbiting lab by the end of this year, the Observer reported.

The Veggie utilises the cabin environment for temperature control and as a source of carbon dioxide to promote growth.

"If you can get the environmental conditions correct, there's no reason why plants won't grow pretty well in space," Dr Gioia Massa, Nasa payload scientist for Veggie at the Kennedy Space Centre, Florida, said.

The expedition is part of Nasa's Veg-01 experiment to study the in-orbit growth and development of lettuce seedlings in the spaceflight environment.

"Veggie will provide a new resource for U.S. astronauts and researchers as we begin to develop the capabilities of growing fresh produce and other large plants on the space station," Massa said in a statement, adding that the Veggie could also be used by astronauts for recreational gardening activities during long-duration space missions.

Lettuce plants grow inside in a prototype Veggie.NASA/Gioia Massa

The experiment is also focused at studying the effect of spaceflight environment on the microorganisms that grow on lettuce plants as Nasa's priority is to learn more about the food safety of crops grown in microgravity.

"Determining food safety is one of our primary goals for this validation test," Massa added.

A crop of lettuce and radishes was grown in the prototype test unit at Kennedy's Space Life Sciences Laboratory before the Veggie was supplied to the ISS.

"Seedlings were placed in the Veggie root-mat pillows, and their growth was monitored for health, size, amount of water used, and the microorganisms that grew on them," she said.

A 28-day-old lettuce plant that grew in the prototypeNASA/Gioia Massa