巻号一覧
24 巻 (2010)
- 3_4 号 p. 121-
- 2 号 p. 67-
- 1 号 p. 3-
24 巻, 3_4 号
選択された号の論文の5件中1～5を表示しています
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Yoshiaki Kitaya, Hiroaki Hirai, Toshio Shibuya2010 年 24 巻 3_4 号 p. 121-128
発行日: 2010年
公開日: 2012/06/27
ジャーナル フリーThe present paper aims to outline problems for growing healthy plants over a complete ontogenetic cycle in space farming. Possible effects of sub-gravity or microgravity conditions on suppression of plant growth and reproduction were summarized in a view of heat and gas exchanges between leaves and reproductive organs of plants and atmosphere. It is concluded that proper control of air movement would be essential to make the environmental variables uniform inside the plant canopy and to enhance the heat/gas exchange between plants and the ambient air and thus promote growth of healthy plants under microgravity conditions in space farming.抄録全体を表示PDF形式でダウンロード (643K) -
Kouichi Soga2010 年 24 巻 3_4 号 p. 129-134
発行日: 2010年
公開日: 2012/06/27
ジャーナル フリーGravity resistance is a response that enables the plants to develop against the gravitational force. We have analyzed the nature and mechanisms of gravity resistance using both hypergravity conditions produced by centrifugation and microgravity conditions in space. As the final step of gravity resistance, plants develop a short and thick body and increase the cell wall rigidity in response to the magnitude of the gravitational force. Prompt reorientation of cortical microtubules is involved in the modification of body shape. The regulation of the cell wall rigidity is brought about by modification of the metabolisms of anti-gravitational cell wall polysaccharides and changes in the pH of cell wall fluid. Plants may perceive the gravitational force independently of the direction of stimuli by mechanoreceptors on the plasma membrane in gravity resistance. The development of gravity resistance may serve an important function in the transition of plant ancestors from an aquatic environment to a terrestrial environment.抄録全体を表示PDF形式でダウンロード (256K) -
Yoshinobu Ohira, Fuminori Kawano, Xiao Dong Wang, Naoya Nakai, Takashi ...2010 年 24 巻 3_4 号 p. 135-144
発行日: 2010年
公開日: 2012/06/27
ジャーナル フリーRoles of mechanical load and satellite cells in the regulation of morphological properties of soleus muscle fibers were reviewed. Gravitational unloading by exposure to microgravity and/or by hindlimb suspension causes passive plantarflexion of ankle joints, which then shortens the length of muscle fibers and sarcomeres. Such phenomena cause the decrease of tension development. Atrophy of muscle fibers caused by inhibited protein synthesis is induced in association with decreased number and increased size of myonuclei. Distribution of satellite cells, which serve as a source of new myonuclei during regeneration after a muscle injury and/or atrophy, also decreases in response to lowered mechanical load. However, these responses are generally reversible, when the mechanical load applied to muscle fibers is increased, suggesting that satellite cells play important role(s) in the regulation of muscle fiber properties. The data also indicated that one of the satellite cell-related regulations of muscle fiber was mechanical load-dependent, which was influenced by the sarcomere length.抄録全体を表示PDF形式でダウンロード (776K) -
Chiharu Hosoya, Asuka Akiyama, Azusa Kage, Shoji A. Baba, Yoshihiro Mo ...2010 年 24 巻 3_4 号 p. 145-152
発行日: 2010年
公開日: 2012/06/27
ジャーナル フリーChlamydomonas is known to form bioconvection as the result of its gravitactic swimming behavior. Several mechanisms have been discussed as the main cause of the preferential reorientation of the microorganisms with respect to gravity vector. In this study, we assessed the gravitactic orientation mechanism of Chlamydomonas by observing the bioconvective motion in the hyper-density medium containing Percoll. Observation of the bioconvection at the right angle to the convective motion (vertical observation) revealed that Chlamydomonas formed the reverse bioconvection in the hyper-density medium. Cells accumulated at the bottom of the chamber and then formed upward-moving plumes from the bottom accumulation. This reverse bioconvection indicates that the gravitactic orientation of Chlamydomonas is primarily due to the torque generated by the morphological fore-aft asymmetry of the cell. It is, therefore, highly likely that the orientation mechanism based on the drag-gravity model makes greater contribution in the gravitactic orientation of Chlamydomonas than other mechanisms, which include gravity sensing and gravity-buoyancy torque.抄録全体を表示PDF形式でダウンロード (1089K) -
Yuko Sasagawa-Saito, Daisuke Kitazawa, Yutaka Miyazawa, Nobuharu Fujii ...2010 年 24 巻 3_4 号 p. 153-162
発行日: 2010年
公開日: 2012/06/27
ジャーナル フリーWhen cucumber (Cucumis sativus L.) seeds germinate in a horizontal position, seedlings develop a specialized protuberance (or peg) on the lower side of the transition zone between the hypocotyl and the root. Gravistimulation induces asymmetric auxin distribution and auxin-inducible gene expression, so that peg formation is suppressed on the upper side of the transition zone. However, we know little of transcriptional regulation of auxin-inducible genes in the transition zone. We demonstrated that Auxin Response Factor 5 (CsARF5) protein functions as a transcriptional repressor of auxin-inducible gene in protoplasts. Our immunoblot analysis suggested that CsARF5 protein is more abundant on the upper side that suppressed peg formation than on the lower side that induced peg formation in the transition zone. When collar-like pegs were induced by exogenous application of auxin to intact seedlings, accumulation of CsARF5 protein decreased substantially. By contrast, exogenous auxin application to segments of the transition zone neither induced collar-like pegs nor decreased CsARF5 proteins. These results suggested that less auxin suppresses peg formation and then indirectly induces accumulation of CsARF5 protein to ensure repression of transcription of auxin-inducible genes.抄録全体を表示PDF形式でダウンロード (1509K)
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