dioxide and production of oxygen. In addition, the tests that evaluated movement of water via
transpiration are important since they are indicative of the stomatal responses that regulate
photosynthesis. Further, the impact of microgravity on transpiration was significant since plants
can be used to purify water under spaceflight conditions. These studies involving gas exchange
at elevated carbon dioxide concentrations increased our understanding of the biological
impacts of increasing levels of atmospheric carbon dioxide on Earth-based ecosystems.
Furthermore, an understanding of plant responses under a range of carbon dioxide and light
conditions has potential benefits to commercial, controlled environment, agriculture industries.
The growth and development of the dwarf wheat plants on the ISS was similar to the growth
and development of plants on Earth. Analysis of the plants indicated that the microgravity-
grown plants were 10% taller than plants grown on Earth, although the growth rate of dwarf
wheat leaves was very similar to the plants grown on Earth. The near-real-time video data
provided by BPS allowed for validation of the growth data in microgravity when compared to
the controls. Design applications can be made to the BPS to allow for successful plant
production on the ISS and future long-duration missions to the moon and Mars (Stutte 2003).
To effectively farm in space, multiple redundant plant growth chambers are needed to acquire
the maximum yield of food, oxygen, and water. PESTO evaluated the transpiration (water) and
photosynthesis (oxygen) processes of
the dwarf wheat plant in microgravity
and found that microgravity did not
affect either the transpiration or the
photosynthesis processes of the plants
(Monje 2005).
When environmental controls such as
temperature, relative humidity, carbon
dioxide, and water are effectively
maintained, microgravity does not
affect canopy growth of dwarf wheat
plants. Slight differences in
photosystem I (photosynthesis in which
light of up to 700 nm is absorbed and
reduced to create energy) and
photosystem II (photosynthesis in which light of up to 680 nm is absorbed and its energy is used
to split water molecules, giving rise to oxygen) were noted and are being evaluated further
(Stutte 2005).
When conducting biological studies, it is important to maintain the integrity of the samples. The
standard method to preserve samples is quick freezing at low temperatures (-80°C (-112°F) and
below), but strict temperature control of samples on station is not always uniform or possible.
Therefore, a preservative is needed that will maintain the integrity of biological samples before
cooling. RNAlaterTM was used to preserve some of the PESTO samples on station. The viability
ISS004E10128 – Close-up view of Apogee Wheat Plants
grown as part of the Photosynthesis Experiment and System
Testing and Operation investigation during International Space
Station Expedition 4.