A current investigation, Plant Habitat-07, looks at how plants and their associated communities of microorganisms respond to different levels of water. The study uses 'Outredgeous' red romaine lettuce, a food crop already known to grow well on the International Space Station. Results from this investigation could inform ways to produce healthy crops under different water conditions in space and on Earth.

Multiple studies of plants on the space station have tested a wide range of crops and methods for growing them. Researchers have successfully grown lettuces, Chinese cabbage, mustard greens, kale, tomatoes, radishes, and chile peppers in space. Here are details on results from earlier plant studies.

Plant Signaling, a NASA investigation conducted in cooperation with ESA (European Space Agency), studied the effects of various gravity levels on plant seedlings, and Plant RNA Regulation compared gene expression involved in the development of roots and shoots in microgravity and simulated 1 g (Earth's gravity). Both investigations used the European Modular Cultivation System, a centrifuge that creates 1 g in space and makes it possible to examine the effects of partial gravity. The investigations found increases in the expression of some genes, such as those involved in light response, and decreases in expression of others, including defense response. These findings can help inform design of space-based plant growth facilities.

JAXA's Resist Tubule also studied the mechanisms of gravity resistance in plants. Researchers found that thale cress plants grown in microgravity exhibited reduced levels of sterols, compounds involved in a variety of cellular processes, which could limit plant growth. These findings could help scientists genetically engineer plants that grow better in microgravity.