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.

Allelic Variation in the Chloroplast Division Gene FtsZ2-2 Leads to Natural Variation in Chloroplast Size

“…Natural variation in chloroplast size or other aspects of chloroplast morphology has rarely been systematically investigated within a single species (Jellings et al, 1983). However, such differences have been reported between species (Honda et al, 1971;Jellings and Leech, 1984;Pyke and Leech, 1987), in different cell and tissue types within a species (Dengler et al, 1996;Pyke, 1997;Ahmadabadi and Bock, 2012;Stata et al, 2014;Swid et al, 2018), and under different environmental conditions (Boardman, 1977;Tsuji et al, 1979;Possingham et al, 1988;Filek et al, 2010;Li et al, 2013b;Takemura et al, 2017). Chloroplast size differences have been particularly well documented in response to light conditions.…”

Comparisons of the Effects of Vibration of Two Centrifugal Systems on the Growth and Morphological Parameters of the Moss <i>Physcomitrella patens</i>

“…A centrifugal hypergravity experiment is useful to investigate gravitational effects on plant growth on Earth (Herranz et al, 2013;Manzano et al, 2012;Nava et al, 2015;Soga et al, 2006;Takemura et al, 2017;Tamaoki et al, 2014). However, a rigorous 1-G control experiment is difficult to perform, because several factors (vibration, pressure, gas circulation, humidity and temperature) are presumed to change during centrifugation in addition to gravity.…”

“…Given that MK-3 generated little vibration, we used it as a vibrational control experiment. In this work, we adopted the 10 G condition for the experiments because growth of P. patens was significantly influenced at 10 G: increases in canopy-based biomass and plant numbers, rhizoid length and stem (caulid) diameter, and decreases in shoot length and leaf cell wall thickness (Takemura et al, 2017). After cultivation for 4 weeks at 10 G, the gametophore explants properly proliferated, showing similar features of the canopies between the gametophores cultivated with MIJ-17 and MK-3 (Fig.…”

“…Thus, mosses are key organisms for space development and terraforming of the Moon or Mars where gravity is different from that of Earth's, so that their growth responses to different gravity conditions (microgravity or hypergravity) will be an important subject to investigate. Nevertheless, few experiments have examined the effects of gravitational change on the growth of mosses (Kern et al, 2005;Takemura et al, 2017).…”

2018 Awards in the Journal of Plant Research

“…Kaori Takemura and Yuko T. Hanba in the Department of Applied Biology at the Kyoto Institute of Technology, Hiroyuki Kamachi and Ichirou Karahara in the Graduate School of Science and Engineering at the University of Toyama, Atsushi Kume in the Faculty of Agriculture at Kyushu University, and Tomomichi Fujita in the Faculty of Science at Hokkaido University have studied responses of growth and photosynthesis in bryophytes to hypergravity conditions (Takemura et al 2017). In the evolutionary history of plants, bryophytes are the oldest plant groups to expand their habitats from aquatic to land environments.…”