Sweetpotato is being studied at Tuskegee University as a potential crop for use in the U.S. National Aeronautics and Space Administration's Advanced Life Support program to provide food for long-term space exploration missions. Stem cuttings are commonly used in the propagation of sweetpotato. Although seeds of several crops have been grown in microgravity and their growth compared with ground-based controls (Cowles et al., 1994; Levine and Krikorian, 1991), plants that have been propagated vegetatively have not been studied under these conditions. Sweetpotato stem cuttings offer distinct advantages for space flight studies, especially those of short duration. Cuttings develop roots easier and quicker than seeds and the genetic makeup can be maintained from one initial planting.
Levine and Krikorian (1991) initiated roots of the monocot Hemerocallis (Baker.) M. Hotta and three populations of the dicot Haplopappus gracilis (Nutt.) Gray during a 5-d shuttle flight and reported greater overall root production compared with ground controls. Abrahamson et al. (1991) exposed eight sprouted seedlings [six alfalfa (Medicago sativa L.) and two white clover (Trifolium repens L.)] to microgravity for 6 d on a shuttle flight and found that root length:shoot length and root length:total length were greater compared with ground controls.
Plant regeneration from seeds during space flight studies has shown a decrease in the level of amyloplasts and a disorientation of root growth resulting from the absence of a strongly dominant gravity vector (Smith and Luttges, 1994). In addition, decreases in plant tissue starch from space flight have been one of the most consistent responses to microgravity (Brown et al., 1996). Musgrave et al. (2005) evaluated seed storage reserves and glucosinolates in Brassica rapa L. grown on the International Space Station and reported that deposition of storage reserves was more advanced in ground controls, whereas glucosinolate accumulation was enhanced by microgravity. They concluded that the spaceflight environment adversely influenced the overall flavor and nutritional quality of this crop by its direct impact on metabolite production. In contrast, Stutte et al. (2006) reported that there were no differences in the content of starch and soluble sugars in the leaves of flight and ground-based wheat (Triticum aestivum L.) plants grown for 21 d. They also found very little difference in cell development except that chloroplasts in the leaves of the plants grown in microgravity were more ovoid and the thylakoid membranes trended toward greater packing density. The researchers concluded that the space flight environment exerted minimal impact on wheat metabolism.
There is evidence that indicates plant responses when grown in space may be influenced by the gaseous environment. For example, Musgrave et al. (1998, 2000) obtained smaller seeds and variable weight in space experiments and have hypothesized that the composition of the gaseous environment changed as a result of the lack of buoyancy-driven convection in microgravity. Ground-based studies by Blasiak et al. (2006) reported that accretionary seed growth in pepper (Capsicum annum L.) was limited by the availability of oxygen and suggested that the variation in seed quality could be attributed to localized limitations in oxygen supply. Shoots of B. rapa grown in microgravity had greater sucrose and total soluble carbohydrates compared with ground control shoots, and it was suggested that this response was the result of root zone hypoxia caused by microgravity-induced changes in fluid and gas distribution (Stout et al., 2001).
Successful root growth is the all-important first step in the establishment of a sweetpotato crop in a closed environment. Of particular importance to this crop is the rapid growth of adventitious roots because these will influence the eventual development of storage roots. If sweetpotato is to be used successfully in future bioregenerative systems that recycle wastes into food, water, and oxygen, reliable plant propagation and growth in microgravity must be demonstrated necessitating a comprehensive understanding of the effects of gravity on both the plant's physiology and environment (Stout et al., 2001).
The primary objective of this experiment was to demonstrate the feasibility of the use of stem cuttings for plant propagation in microgravity. The root growth, distribution of amyloplasts in the root cells, and carbohydrates in the stems were examined and compared with their ground-based counterparts.
Abrahamson, K.S. , Lisec, J.T. , Derby, J.A. , Simske, S.J. & Luttges, M.W. 1991 Effect of weightlessness on leguminous sprouts Amer. Soc. Gravitational Space Biol. Bul. 5 59
Blasiak, J. , Kuang, A. , Farhangi, C.S. & Musgrave, M.E. 2006 Roles of intra-fruit oxygen and carbon dioxide in controlling pepper (Capsium annum L.) seed development and storage reserve deposition J. Amer. Soc. Hort. Sci. 131 164 173
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Blasiak, J. Kuang, A. Farhangi, C.S. Musgrave, M.E. 2006 Roles of intra-fruit oxygen and carbon dioxide in controlling pepper (J. Amer. Soc. Hort. Sci. Capsium annumL.) seed development and storage reserve deposition 131 164 173 10.21273/JASHS.131.1.164
Brown, A.H. , Chapman, D.K. & Liu, S.W.W. 1974 A comparison of leaf epinasty induced by weightlessness and by clinostat rotation Bioscience 24 518 520
Brown, C.C. , Tripathy, B.C. & Stutte, G.W. 1996 Photosynthesis and carbohydrate metabolism in microgravity 127 134 Sige H. Plants in space biology Tohuku University Press Tokyo
Castonguay, Y. , Nadeau, P. & Simard, R.R. 1993 Effects of flooding on carbohydrate and ABA levels in roots and shots of alfalfa Plant Cell Environ. 16 695 702
Cowles, J. , Lemay, R. & Jahns, G. 1994 Seedling growth and development on space shuttle Adv. Space Res. 14 3 12
Croxdale, J. , Cook, M. , Tibbitts, T.W. , Brown, C.S. & Wheeler, R.M. 1997 Structure of potato tubers formed during space flight J. Expt. Bot. 48 2037 2043
Daugherty, C.J. & Musgrave, M.E. 1994 Characterization of populations of rapid- cycling Brassica rapa L. selected for differential waterlogging tolerance J. Expt. Bot. 45 385 392
Dionex Corp 1989 Analysis of carbohydrates and anion exchange chromatography with pulsed amperometric detection Tech. Note 20. Dionex Corp Sunnyvale, CA
Hall, A.J. & Milthorpe, F.L. 1977 Assimilate source-sink relationships in Capsicum annum L. III. The effects of fruit excision on photosynthesis and leaf and stem carbohydrates Aust. J. Plant Physiol. 4 771 783
Johnson, S.P. & Tibbits, T.W. 1968 The liminal angle of a plagiotropic organ under weightlessness BioScience 18 655 661
Karnovsky, M.J. 1968 A formaldehyde-glutaraldehyde fixation at high osmolality for use in electron microscopy J. Cell Biol. 27 137A 138A
Kordyum, E. , Baranenko, V. , Nedukha, E. & Samoilov, V. 1997 Development of potato minitubers in microgravity Cell Physiol. 38 1111 1117
Leather, G.R. , Forrence, L.E. & Abeles, F.B. 1972 Increased ethylene production during clinostat experiments may cause leaf epinasty Plant Physiol. 49 183 186
Levine, H.G. & Krikorian, A.D. 1991 Shoot growth, root formation and chromosome damage results from the chromax I Experiment (Shuttle Mission STS-29) Amer. Soc. Gravitational Space Biol. Bul. 5 28
Mortley, D.G. , Bonsi, C.K. , Hill, J.H. & Hill, W.A. 2001 Nutrient management of sweetpotato grown in nutrient film technique Acta Hort. 548 567 574
Mortley, D.G. , Bonsi, C.K. , Loretan, P.A. , Hill, W.A. & Morris, C.E. 1994 Relative humidity influences yield, edible biomass and linear growth rate of sweetpotato HortScience 29 609 610
Mortley, D.G. , Hill, W.A. , Loretan, P.A. , Bonsi, C.K. & Morris, C.E. 1996 Growth responses of hydroponically grown sweetpotato tolerant and intolerant of a continuous daily light period HortScience 31 209 212
Musgrave, M.E. , Kuang, A. , Brown, C.S. & Matthews, S.W. 1998 Changes in Arabidopsis leaf ultrastructure, chlorophyll and carbohydrate content during spaceflight depend on ventilation Ann. Bot. (Lond.) 81 503 512
Musgrave, M.E. , Kuang, A. , Tuominen, L.K. , Levine, L.H. & Morrow, R.C. 2005 Seed storage reserves and glucosinolates in Brassica rapa grown on the International Space Station J. Amer. Soc. Hort. Sci. 130 848 856
Musgrave, M.E. , Kuang, A. , Xiao, Y. , Stout, S.C. , Bingham, G.E. , Briarty, L.G. , Levinskikh, M.A. , Sychev, V.N. & Podolski, I.G. 2000 Gravity independence of seed-to-seed cycling in Brassica rapa Planta 210 400 406
Porterfield, D.M. , Barta, D.J. , Ming, D.W. , Morrow, R.C. & Musgrave, M.E. 2000 Astroculture root metabolism and cytochemical analysis Adv. Space Res. 26 315 318
Plaut, Z. , Mayoral, M.L. & Reinhold, L. 1987 Effect of altered sink: Source ratio on photosynthetic metabolism of source leaves Plant Physiol. 85 786 791
Reynolds, E.S. 1963 The use of lead citrate at high pH as an electron opaque stain in electron microscopy J. Cell Biol. 17 208 212
Setter, T.L. , Brun, W.A. & Brenner, M.L. 1980 Effect of obstructed translocation on leaf abscisic acid associated stomatal closure and photosynthesis decline Plant Physiol. 65 1111 1115
Setter, T.L. , Water, I. , Greenway, H. , Atwell, B.J. & Kupkanchanakul, T. 1987 Carbohydrate status of terrestrial plants during flooding 411 433 Crawford R.M.M. Plant life in aquatic and amphibious habitats Blackwell Scientific Oxford, UK
Smith, J.D. & Luttges, M.W. 1994 White clover growth and root tip cell morphology under three gravity conditions: Spaceflight, clinorotation, and nominal Amer. Soc. Gravitational Space Biol. Bul. 8 15
Spurr, A.R. 1969 A low-viscosity epoxy resin embedding medium for electron microscopy J. Ultrastruct. Res. 26 31 43
Stout, S.C. , Porterfield, D.M. , Briarty, L.G. , Kuang, A. & Musgrave, M.E. 2001 Evidence of root zone hypoxia in Brassica rapa L. grown in microgravity Int. J. Plant Sci. 162 240 255
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
Watson, M.L. 1958 Staining of tissue sections for electron microscopy with heavy metals J. Biophys. Biochem. Cytol. 4 475 478
Wheeler, R.M. , White, R.G. & Salisbury, F.B. 1986 Gravitropism in higher plant shoots. IV. Further studies on participation of ethylene Plant Physiol. 82 534 542