Chapter 5
Gravitropism in Fungi, Mosses and Ferns
Donat-Peter Häder
Abstract Motile pseudoplasmodia of cellular and acellular slime molds show
gravitaxis while unicellular Dictyostelium amoebae do not. Fungi display
gravitropism of their fruiting bodies which is thought to facilitate spore dispersal.
Caulonemata and sporophytes of liverworts and mosses show negative gravitropism
which is a also observed in sporophytes of ferns. Several hypotheses have been
proposed to explain the mechanism for graviperception but none has been
proven yet.
Keywords Slime molds · Fungi · Liverworts · Mosses · Ferns · Gravitaxis ·
Gravitropism
5.1 Introduction
Terrestrial organisms including fungi, mosses, ferns and higher plants use the gravity
vector of the Earth to optimize their position in their environment (Blancaflor and
Masson 2003). It is obvious that photosynthetic organisms orient their shoots
upwards in order to maximize photosynthesis (negative gravitropism). Leaves or
leaflets are often oriented at an oblique angle, which exposes the laminas perpendicular to the incident sun rays (Franklin and Whitelam 2004; Mano et al. 2006).
Roots or rhizoids are usually oriented downwards (positive gravitropism or at an
angle to the gravity vector to anchor the plant in the substratum (Cove 1992; Aloni
et al. 2006). Even though fungi are not photosynthetic organisms, gravitropic
orientation is beneficial to bring the fruiting bodies above the soil’s surface and to
facilitate the spreading of the spores.
As detailed in the introductory chapter of this volume, gravitropism—as well as
gravitaxis in motile microorganisms–is based on a gravireceptor, a structure which
senses the pressure of a heavy element, which, under the effect of gravity, exerts
pressure on the sensitive element. The pressing element can be a statolith—a heavy
organic or inorganic particle such as an amyloplast or an organelle containing bariumsulfate crystals (Sack 1997; Braun 2002). Alternatively, the whole cytoplasm of a cell
© The Author(s), under exclusive licence to Springer International Publishing AG,
part of Springer Nature 2018
M. Braun et al., Gravitational Biology I, SpringerBriefs in Space Life Sciences,
https://doi.org/10.1007/978-3-319-93894-3_5
67
Gravitropism in Fungi, Mosses and Ferns
Donat-Peter Häder
Abstract Motile pseudoplasmodia of cellular and acellular slime molds show
gravitaxis while unicellular Dictyostelium amoebae do not. Fungi display
gravitropism of their fruiting bodies which is thought to facilitate spore dispersal.
Caulonemata and sporophytes of liverworts and mosses show negative gravitropism
which is a also observed in sporophytes of ferns. Several hypotheses have been
proposed to explain the mechanism for graviperception but none has been
proven yet.
Keywords Slime molds · Fungi · Liverworts · Mosses · Ferns · Gravitaxis ·
Gravitropism
5.1 Introduction
Terrestrial organisms including fungi, mosses, ferns and higher plants use the gravity
vector of the Earth to optimize their position in their environment (Blancaflor and
Masson 2003). It is obvious that photosynthetic organisms orient their shoots
upwards in order to maximize photosynthesis (negative gravitropism). Leaves or
leaflets are often oriented at an oblique angle, which exposes the laminas perpendicular to the incident sun rays (Franklin and Whitelam 2004; Mano et al. 2006).
Roots or rhizoids are usually oriented downwards (positive gravitropism or at an
angle to the gravity vector to anchor the plant in the substratum (Cove 1992; Aloni
et al. 2006). Even though fungi are not photosynthetic organisms, gravitropic
orientation is beneficial to bring the fruiting bodies above the soil’s surface and to
facilitate the spreading of the spores.
As detailed in the introductory chapter of this volume, gravitropism—as well as
gravitaxis in motile microorganisms–is based on a gravireceptor, a structure which
senses the pressure of a heavy element, which, under the effect of gravity, exerts
pressure on the sensitive element. The pressing element can be a statolith—a heavy
organic or inorganic particle such as an amyloplast or an organelle containing bariumsulfate crystals (Sack 1997; Braun 2002). Alternatively, the whole cytoplasm of a cell
© The Author(s), under exclusive licence to Springer International Publishing AG,
part of Springer Nature 2018
M. Braun et al., Gravitational Biology I, SpringerBriefs in Space Life Sciences,
https://doi.org/10.1007/978-3-319-93894-3_5
67