title: A hypergravity environment increases chloroplast size, photosynthesis, and plant growth in the moss Physcomitrella patens.
abstract: The physiological and anatomical responses of bryophytes to altered gravity conditions will provide crucial information for estimating how plant physiological traits have evolved to adapt to significant increases in the effects of gravity in land plant history. We quantified changes in plant growth and photosynthesis in the model plant of mosses, Physcomitrella patens, grown under a hypergravity environment for 25 days or 8 weeks using a custom-built centrifuge equipped with a lighting system. This is the first study to examine the response of bryophytes to hypergravity conditions. Canopy-based plant growth was significantly increased at 10×g, and was strongly affected by increases in plant numbers. Rhizoid lengths for individual gametophores were significantly increased at 10×g. Chloroplast diameters (major axis) and thicknesses (minor axis) in the leaves of P. patens were also increased at 10×g. The area-based photosynthesis rate of P. patens was also enhanced at 10×g. Increases in shoot numbers and chloroplast sizes may elevate the area-based photosynthesis rate under hypergravity conditions. We observed a decrease in leaf cell wall thickness under hypergravity conditions, which is in contrast to previous findings obtained using angiosperms. Since mosses including P. patens live in dense populations, an increase in canopy-based plant numbers may be effective to enhance the toughness of the population, and, thus, represents an effective adaptation strategy to a hypergravity environment for P. patens.
authors.affiliation: Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Takemura
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama, 930-8555, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Kamachi
authors.affiliation: Faculty of Agriculture, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka, 812-8581, Japan.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kume
authors.affiliation: Faculty of Science, Hokkaido University, Kita-ku, Sapporo, 060-0810, Japan.
authors.forename: Tomomichi
authors.initials: T
authors.lastname: Fujita
authors.affiliation: Graduate School of Science and Engineering, University of Toyama, 3190 Gofuku, Toyama, 930-8555, Japan.
authors.forename: Ichirou
authors.initials: I
authors.lastname: Karahara
authors.affiliation: Department of Applied Biology, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, Kyoto, 606-8585, Japan. hanba@kit.ac.jp.
authors.forename: Yuko T
authors.initials: YT
authors.lastname: Hanba
mesh_terms: D019068:Bryopsida / Q000254:growth & development / Q000502:physiology* / Q000648:ultrastructure; D002245:Carbon Dioxide / Q000378:metabolism; D002473:Cell Wall / Q000502:physiology / Q000648:ultrastructure; D002498:Centrifugation; D002736:Chloroplasts / Q000502:physiology / Q000648:ultrastructure; D004777:Environment; D018471:Hypergravity; D010641:Phenotype; D010788:Photosynthesis; D018515:Plant Leaves / Q000254:growth & development / Q000502:physiology / Q000648:ultrastructure
chemical_list: D002245:Carbon Dioxide
keywords: Bryophyte; CO2 diffusion; Cell wall; Evolution; Gametophore