Submitted to: Planta
Publication Type: Peer reviewed journal
Publication Acceptance Date: 3/23/2006
Publication Date: 9/1/2006
Citation: Stutte, G.W., Monje, O., Hatfield, R.D., Paul, A.-L., Ferl, R.J., Simone, C.G. 2006. Microgravity effects on leaf morphology, cell structure, carbon metabolism and mRNA expression of dwarf wheat. Planta. 224:1038-1049. Interpretive Summary: It has been proposed to use plants as the basis for a biological life support system that regenerates the atmosphere, purifies water, and produces food for long duration space missions. However, it is not known how plants will respond to growing in space where they will be exposed to low gravity. Experiments were conducted on the space shuttle and the space station to determine the impact of low gravity upon plant growth and development. The central question was “As plants evolved to deal with gravity, are they now dependent upon it for proper growth and development?” Results from these experiments clearly show that plant growth and development are not affected by low gravity conditions. To utilize plants as a biological support system in space will require the development of specialized crop plants that can take advantage of the unique growth environments found in confined areas such as on the space station (low light, high carbon dioxide, high humidity). However since plant growth and development are not affected by gravity, selection of unique materials can begin with highly productive plants already used for food and fiber here on earth. Selection of plants here on earth that would focus on plant traits that would make them the most efficient in dealing with the specialized environments required in space travel and colonization and allow the development of efficient biological life support systems.
Technical Abstract: The use of higher plants as the basis for a biological life support system (BLSS) that regenerates the atmosphere, purifies water, and produces food has been proposed for long duration space missions. Successful development of a BLSS depends on the photosynthetic apparatus of tissues to be performing properly. The objective of these experiments was to determine what effects microgravity had on chloroplast development, carbohydrate metabolism and gene expression in devlopoing leaves of Triticum aesativum L. cv. USU Apogee. Gravity näive wheat plants were sampled from a series of seven 21-day experiments conducted during Increment IV of the International Space Station. These samples were fixed in either 3% gluteraldehyde or RNAlatertm or frozen at -25 deg C for subsequent analysis. In addition, leaf samples were collected from 24-day-old and 14-day-old plants that were returned to Earth at the end of the mission. Plants grown under identical light, temperature, relative humidity, photoperiod, and CO2 conditions were used as ground controls. At the morphological level, there was little difference in the development of cells of wheat under microgravity conditions. Leaves developed in micro-g environment have thinner cross-sectional area than the 1g grown plants. Ultrastructurally, the chloroplasts of micro-g grown plants were more ovoid than those developed at 1g, and the thylakoid membranes had a trend to greater packing density. No differences in the starch, soluble sugar, or lignin content of the leaves grown in micro-g or 1g conditions. Further, no differences in gene expression were detected in sampled collected at micro-g from 24-day-old leaves.