NASA - National Aeronautics and Space Administration

The relationship between plants and humans has always been a close and interdependent one. Research about basic plant processes helps in understanding and augmenting this interdependence. Ground-based investigations yield information vital to this understanding; however, the knowledge gained from plant research in space is exciting and extends potential for new discoveries beneficial to humans.

Image to right: Biology can be studied in microgravity because of space flight
Credit: NASA

There is abundant evidence that microgravity affects virtually every aspect of plant growth. Space flight provides the only known environment in which fundamental biological processes and mechanisms can be studied in the absence of the sometimes overriding effects of gravity. Removal of the effects of gravity for long periods of time allows new perspectives in the study of plants.

Answers to important questions about the basics of plant growth and development lie in understanding the role gravity has on plant processes and responses to the environment. For example, gravitropism is the bending response of plants to the force of gravity with the roots growing downward and the shoots growing upward. Charles Darwin began experiments on plant gravitropism during the nineteenth century, yet the mechanisms of this process are still not clear. The more knowledge generated about how plants function, the more likely we can adapt that information into practical, useful new applications and products enhancing life on Earth and in space.

NASA's research with plants in space is dedicated to systematic studies that explore the role gravity plays at all stages in the life of higher plants. Research focuses on the interaction of gravity and other environmental factors with plant systems, and uses hypergravity, simulated hypogravity, and microgravity as tools to advance fundamental knowledge of plant biology. Results of the research contribute to NASA's efforts to further human exploration of space and to improve the quality of life on Earth through applications in medicine, agriculture, biotechnology and environmental management.

Image to right: Plants can be grown in microgravity
Credit: NASA

NASA's plant science research questions focus on five objectives:

• to explain the basic mechanism whereby plants perceive, transduce, and respond to gravitational force (example: comparisons of seedling vs. older plant responses to gravity);



• to understand the role of gravity and microgravity in developmental and reproductive processes in plants (examples: flower development and wood formation);



• to learn how metabolic and transport processes are affected by gravity and microgravity (examples: photosynthesis and long and short distance sugar transport);



• to analyze interactions of microgravity with other important parameters of space (examples: cosmic radiation and electromagnetism); and



• to study the role of plants within recycling life support systems for space exploration (examples: carbon dioxide production and oxygen revitalization).

Knowledge of physiology, cell biology, biochemistry and molecular biology of plants coupled with biotechnology advances contributes to our fundamental knowledge of plants and provides impetus for a new era of plant investigations. The opportunity to experiment at a micro level of gravity provides a new dimension that enables interdisciplinary plant research to answer important questions about the plant's reception of the gravity signal, the plant's biochemical interpretation of that signal, and how that interpretation causes a developmental reaction. It appears that this reaction system, in general, interacts with receptor systems that detect both internal and external signals. It is for this reason that understanding the role of mechanical signals, such as gravity, assumes such significance for plant science: these investigations could begin to reveal the precise control mechanisms involved in dictating plant form, structure, and function.

Understanding how basic processes can be manipulated and put into use in new ways that develop new products and increase productivity is the basis for biotechnological applications in agriculture, horticulture, and forestry. For example, understanding the interaction between gravity and light could be the basis for genetic engineering of plants resulting in increased crop productivity while minimizing the required growing space. Application to horticulture could include the ability to control plant form, and forestry could benefit from faster methods of regeneration of lost forest areas.

Image to left: The International Space Station
Credit: NASA

Before the first lunar outpost, the proposed Mars base, and other future missions from planet Earth can become realities, numerous scientific and technological problems remain to be solved. None of these problems is more important than that of supporting human life in space. Extended duration human exploration missions will require life support capabilities beyond those now available. A solution is to develop technologies that integrate physical and chemical processes into a dynamic, recycling life support system.

Studying plants in space will provide the scientific information necessary for development of such a life support system. Plants will be a primary component of atmospheric regeneration: carbon dioxide exhaled by humans will be taken up by plants and used in photosynthesis, in the process returning oxygen and food to the crew. Plants are also important in water regeneration. The productivity of plants relative to the input of energy (light) can be increased by using such techniques as carbon dioxide enrichment and hydroponics. To achieve a controlled life support system, ground-based research in growth chamber facilities will be conducted along with plant investigations in the microgravity environment of space flight.

Why study plants in space? The discoveries made, lessons learned, and technologies developed from these investigations will benefit those of us on planet Earth as we unlock and utilize gravity's mysteries to enhance our journey into space.

Excerpted from Investigating Plants in Space Educator Guide