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Russian Greenhouse Studies ‘Lettuce’ Know About Plant Growth in Space

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Posted August 7, 2015

Some of the most important tasks in space biology include the creation of reliable and effectively functioning life support systems, and providing sustaining food sources for crew members. For long-term interplanetary spaceflights and planetary bases, the human life support system and food production has to be based on regenerating the living environment from life support products through physical/chemical and biological processes.

Cosmonaut Maxim Suraev, Expedition 22 Flight Engineer, holds Mizun lettuce plants from the BIO-5 Rasteniya-2 (“Plants-2”) experiment in the Service Module during Expedition 20. Credits: NASA

Cosmonaut Maxim Suraev, Expedition 22 Flight Engineer, holds Mizun lettuce plants from the BIO-5 Rasteniya-2 (“Plants-2”) experiment in the Service Module during Expedition 20. Credits: NASA

Greenhouses will most likely be designed for the cultivation of vegetables, primarily greens and herbs. However, in order to implement these plans, plants must grow, develop, and reproduce in spaceflight with cultivation productivity similar to Earth. To address this need, a series of 17 Rasteniya experiments were conducted from 2002-2011 using the Lada greenhouse on the Russian segment of the International Space Station.

Multigenerational studies were carried out to culture genetically tagged dwarf pea plants in the Lada space greenhouse. For the first time in space research, four consecutive generations of genetically tagged pea line seeds were obtained in spaceflight. The growth and development characteristics of various lines of pea plants did not change in a significant way compared to ground control samples. Using molecular methods with random amplified polymorphic DNA (RAPD) primers with 10 markers and analyzing chromosomal aberrations, it was demonstrated that plants having undergone four complete development cycles in spaceflight did not manifest genetic polymorphism. That makes it possible to assert that there is no impact of spaceflight factors on the genetic apparatus of plants in the first to the fourth “space” generations.

Cosmonaut Valery G. Korzun, Expedition Five mission commander, studies mizuna lettuce as part of the Rastenyia-2 investigation. Credits: NASA

Cosmonaut Valery G. Korzun, Expedition Five mission commander, studies mizuna lettuce as part of the Rastenyia-2 investigation. Credits: NASA

To prepare a chain of higher plants for future life support systems of space crews, experiments were carried out to cultivate the leafy vegetable plant mizuna (Brassica rapa var. nipposinica). Results showed that the significant increase in the parameter of total contamination of International Space Station (ISS) air did not result in a decrease in productivity of the leafy vegetable plant; however, the plants responded with a change in gene expression.

A space experiment to grow super dwarf wheat during a complete vegetation cycle showed that the rate ofplant development over 90 days did not differ from data from ground control experiments. When the space-produced seeds were planted on the ground, plants that grew were no different from the control sample.

The work done has great applied value because in the process of creating and operating the space greenhouse, cutting edge equipment and software were developed, making it possible to grow plants automatically. This dual-purpose technology can also improve plant growth on Earth. The psycho-physiological aspect of the interaction between humans and plants in a habitable pressurized volume was studied, and data were obtained on the safety of cultivating plant biomass on a space station for human consumption. These data are of great interest for design work to create productive greenhouses that are part of promising life support systems of any living complexes that are cut off from the Earth’s biosphere.

Scientists have also studied the interaction of plants with the soil. The processes by which plant roots receive water, gases and nutrients are different in space than they are on Earth. On Earth, gravity and surface tension combine to move water through soil, allowing air to move through the pore spaces in the soil to the plant’s roots. In space, soil is replaced with an artificial growth medium, made up of small grains or other porous material. In microgravity, liquid moves through capillary action, where the liquid is attracted to the adjacent surface of a solid material. The surface tension of the liquid pulls additional liquid along as each new surface is wetted.

If the plant is over-watered and all of the surface area and open spaces within the growth medium are filled with liquid, then gas (air) can’t move, and the plant’s roots are deprived of air and oxygen. When properly wetted, as water is used by the roots, surface tension pulls additional liquid along without filling the pore spaces, and therefore without preventing oxygen from diffusing through the open spaces to the roots. Studies in the Lada greenhouse have addressed the importance of root zone media in these extreme artificial conditions. Scientists have studied a variety of root zone substrates—growth media, material particle sizes, and packing structure—and learned which combinations work best.

Knowledge of root zone substrates in space has allowed scientists to improve their predictions of how artificial soils will behave when they’re irrigated—in space and on Earth—and to design specific plant growth media and artificial soils for greenhouses and other large scale plant production facilities on Earth. Models, describing the behavior of water and oxygen learned from these space experiments, have been published in scientific journals, allowing commercial users to access the information without divulging their propriety growth media mixtures. Sensor technology developed to monitor the Lada root zone is being applied to monitor soil properties in a state-of-the-art measurement facility at an experimental forest.

Source: NASA

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