Biological Sciences in Space

原著論文

Analysis of Experimental and Quantitative Parameters Employed to Assess the Effects of Novel Gravity Forces on the Amphibian Egg

Hiroki Yokota, Anton W. Neff, George M. Malacinski

原稿種別: Others
専門分野: Others
1993 年 7 巻 2 号 p. 85-100
発行日: 1993年
公開日: 2005/05/20

DOIhttps://doi.org/10.2187/bss.7.85

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The amphibian embryo provides a convenient model system for studying a variety of early morphological processes which are affected by novel gravity forces. Suitable descriptions of many of the so called “gravity effects” on amphibian eggs are available. In order to extend those morphological observations to subcellular and molecular levels of investigation, a more thorough understanding of experimental design and measurement methodology is desirable. Accordingly, several of the ground-based techniques, including clinostation and centrifugation are analyzed from both theoretical and practical points of view. The measurements often carried out to quantitate gravity effects are also considered. Analyses of cleavage furrowing and egg cytoplasmic viscosity are presented.

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シンポジウム記録

Plant Growth and Development under Microgravity Conditions

Y. Masuda

原稿種別: Others
専門分野: Others
1993 年 7 巻 2 号 p. 101-102
発行日: 1993年
公開日: 2005/05/20

DOIhttps://doi.org/10.2187/bss.7.101

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The Gravitropic Response Chain of Roots: New Perspectives

A. Sievers, Z. Hejnowicz

原稿種別: Others
専門分野: Others
1993 年 7 巻 2 号 p. 103-106
発行日: 1993年
公開日: 2005/05/20

DOIhttps://doi.org/10.2187/bss.7.103

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The interaction between the cytoskeleton and statoliths as well as the involvement of cytoskeletal tension modulated by the interaction must be kept in mind when considering the perception of gravity. Signals of unknown nature but having an electrical component which can be detected extracellularly propagated with a velocity of 3-9 mm/s along an intrasymplasmic continuous system may be involved in the transmission of the gravity effect perceived in the root cap and during the graviresponse in the elongation zone. This fast signal may precede a hormone effect on cell elongation so that the graviresponse begins with a curvature in a relatively small part of the elongation zone.

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Automorphogenesis of Plant Seedlings under Simulated Microgravity on a 3-D Clinostat

T. Hoson, S. Kamisaka, B. Buchen, A. Sievers, M. Yamashita, Y. Masuda

原稿種別: Others
専門分野: Others
1993 年 7 巻 2 号 p. 107-110
発行日: 1993年
公開日: 2005/05/20

DOIhttps://doi.org/10.2187/bss.7.107

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We developed a three-dimensional (3-D) clinostat equipped with two motors and studied the changes in different growth processes of higher plants under this condition. On the clinostat, morphogenesis of seedlings changed dramatically. Shoots and roots exhibited a spontaneous curvature as well as an altered growth direction. The curvature occurred at different portions of seedlings. Maize shoots exhibited the curvature in the transition zone connecting roots and mesocotyls, coleoptile nodes, and coleoptiles. Maize roots bent in the most basal region, the region between the mature and the elongating zone, and the elongating zone. The curvature became larger with their growth. Such an automorphogenesis may play an important role in regulation of life cycle of higher plants under a microgravity environment.

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Development of Statocyte Polarity under Simulated Microgravity on a 3-D Clinostat

B. Buchen, T. Hoson, S. Kamisaka, Y. Masuda, A. Sievers

原稿種別: Others
専門分野: Others
1993 年 7 巻 2 号 p. 111-115
発行日: 1993年
公開日: 2005/05/20

DOIhttps://doi.org/10.2187/bss.7.111

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The development and ultrastructure of cress root statocytes grown on the 3-D clinostat have been compared to ground controls and to roots grown under real microgravity during the Spacelab D-1 mission. Roots grown for 24 h on the clinostat develop a normal root cap. The statocytes show the typical polar organization except a random distribution of statoliths. Thus, the cell polarity of gravity-sensing cells is genetically determined and expressed on the 3-D clinostat. However, the starch content of the statoliths is significantly decreased and the total area of the ER complex is increased in clinostatted statocytes compared to ground controls. The number of enlarged lipid bodies is higher. These structural parameters are similar to results obtained under real microgravity. Thus, the 3-D clinostat has been proven as a useful device to mimic microgravity.

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Plant Growth under Clinostat-Microgravity Condition

M. Yamada, Y. Takeuchi, H. Kasahara, S. Murakami, M. Yamashita

原稿種別: Others
専門分野: Others
1993 年 7 巻 2 号 p. 116-119
発行日: 1993年
公開日: 2005/05/20

DOIhttps://doi.org/10.2187/bss.7.116

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A three-dimensional clinostat which controlled by computer programs was developed to examine the effects of microgravity on the growth and differentiation of higher plants. In clinostat-grown seedlings of garden cress, Lepidium sativum L., the growth of cotyledons was promoted, but that of hypocotyl was not, compared to the earth-grown control. Photosynthetic activity per mg chlorophyl in cotyledons was unchanged, but the amount of photosynthesis per cotyledon increased in clinostat-grown seedlings compared to the control. Use of an appropriate computer program was pointed out for better simulation of microgravity condition.

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Rice Coleoptile Growth under Water and in Air - Possible Effect of Buoyancy on Growth and Cell Walls

S. Kamisaka, K.-S. Tan, T. Hoson, Y. Masuda

原稿種別: Others
専門分野: Others
1993 年 7 巻 2 号 p. 120-123
発行日: 1993年
公開日: 2005/05/20

DOIhttps://doi.org/10.2187/bss.7.120

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Rice seedlings were grown under water, under water with air bubbling, and in air. Maximum growth was achieved in coleoptiles grown under water. Differences in coleoptile growth were detected between air bubbling and air conditions, which could be due to buoyancy effect under water. Promoted growth under water was due to an increase in the cell wall extensibility. The increase in the cell wall extensibility correlated with a decrease in the amount of diferulic acids bound to cell walls, suggesting that the enhancement of the formation of diferulic acid bridges in hemicelluloses in air or under water with air bubbling makes cell walls mechanically rigid, thereby inhibiting cell elongation in rice coleoptiles. Differences in the cell wall extensibility and the amount of diferulic acid in cell walls existed between air bubbling and air conditions. These differences seem to be due to buoyancy effect.

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Gravity and Evolution of Cucurbitaceae Plants: Peg Formation Regulated by Gravity

H. Takahashi, H. Suge, T.K. Scott

原稿種別: Others
専門分野: Others
1993 年 7 巻 2 号 p. 124-132
発行日: 1993年
公開日: 2005/05/20

DOIhttps://doi.org/10.2187/bss.7.124

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It has been suggested that peg formation on the transition (TR) zone between hypocotyl and root in Cucurbitaceae seedlings is regulated by gravity. We have examined whether the TR zone of cucumber seedlings possess a gravity-sensing apparatus which might be involved in peg formation. The results showed that there are sedimentable amyloplasts in the sheath cells and adjacent cells to them in the TR zone, which appear well before negative gravitropic bending of the hypocotyl occurs. Because the cortical cells do not have significant number of sedimenting amyloplasts, the gravity-sensing mechanism for peg formation may be similar to that for gravitropism. Some chemical stimulus may migrate from the gravisensing cells to the cortical cells which are destined to become a peg by the alteration of growth polarity. An increased auxin level in the cortical cells appears to be a direct cause of peg formation. Thus, peg formation of Cucurbitaceae seedlings may be a pleiotropic response to the graviperception and physiological changes that function in shoot gravitropism.

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Comparative Growth and Gravitropsim Studies in Auxin Response Mutants of Arabidopsis thaliana

H. Ishikawa, M. Evans

原稿種別: Others
専門分野: Others
1993 年 7 巻 2 号 p. 133-140
発行日: 1993年
公開日: 2005/05/20

DOIhttps://doi.org/10.2187/bss.7.133

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We used a video digitizer system to measure the kinetics of promotion and inhibition of root elongation by applied auxin in roots of intact seedlings of Arabidopsis thaliana. We determined the dose response relationship for auxin action on elongation in roots of wild type seedlings and seedlings of four mutants with altered auxin responsiveness. Roots of all four mutants maintained more rapid rates of elongation in the presence of inhibitory concentrations of auxin than did roots of the wild type. The latent period preceding the change in elongation rate after auxin application was the same in the mutants as in the wild type indicating that the differences in the auxin response between the wild type and the mutants are not due to differences in hormone uptake. Low concentrations of auxin induced substantial promotion of root elongation in the wild type and in the mutants aux1-7 and axr2 but not in axr1-3 or axr1-12. The mutants aux1-7 and axr2 showed no gravitropic curvature when stimulated at 90°. The mutants axr1-3 and axr1-12 exhibited rates of gravitropism intermediate between the non-responsive mutants and the wild type. For these intermediate mutants there was an inverse relationship between growth rate and rate of gravitropic curvature.

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Recent Directions in Life Sciences Research at NASA

T.K. Scott

原稿種別: Others
専門分野: Others
1993 年 7 巻 2 号 p. 141-147
発行日: 1993年
公開日: 2005/05/20

DOIhttps://doi.org/10.2187/bss.7.141

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Since the date of the Second Symposium on Space Botany at Tezukayama University, NASA and the Life Sciences Division have undergone vast organizational and management alterations. What follows in this paper is a brief summary of remarks made at that Meeting. However, for a variety of reasons, many of the changes at NASA are not yet fully reconciled; therefore much of the content should be considered for its historical perspective rather than for its current relevance.

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