Chapter 6
Gravitropism in Higher Plants: Cellular
Aspects
Dennis Said Gadalla, Markus Braun, and Maik Böhmer
Abstract Due to their sessile life style, an important ability of plants is to adjust
their growth towards or away from environmental stimuli. Plant responses that
involve directed movements are called tropisms. Among the best-known tropisms
are phototropism, the response to light, and gravitropism, the response to gravity.
Gravity is one of the major factors that govern root growth in plants. Since the
emergence of land plants, gravitropism allowed plants to adjust root growth to
maximize access to water and nutrients, and shoots to explore and exploit space
on and above the surface of the Earth. In this chapter we discuss current knowledge
and point out open questions like the nature of the gravireceptor, the role of
secondary messengers, hormones and the cytoskeleton. We review the history of
plant gravitropism research, from early experiments performed by naturalists like
Charles Darwin to the utilization of clinostats, centrifuges and experimentation in the
almost stimulus-free environment of microgravity provided by drop towers, parabolic flights of aircrafts and rockets, satellites and low earth orbit space stations,
which are increasingly contributing to our understanding of plant gravity sensing
and orientation.
Keywords Auxin · Clinostat · Gravitropism · Gravity · Microgravity · Roots ·
Statolith
6.1 Introduction
All organisms on Earth are subject to the continuous influence of gravity. In a
process called gravitropism, plants perceive the direction of gravity and can adjust
their growth accordingly (Fig 6.1). Most plant organs are actively positioned at
various defined angles from the gravity vector, the gravitational set point angle
(GSA; Digby and Firn 1995).
This allowed plants to leave the water and conquer land, enabling them to explore
and exploit space below, on and above the surface of the Earth in a most beneficial
way and, thus, to provide food and resources for all animal and human life on
© 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_6
75
Gravitropism in Higher Plants: Cellular
Aspects
Dennis Said Gadalla, Markus Braun, and Maik Böhmer
Abstract Due to their sessile life style, an important ability of plants is to adjust
their growth towards or away from environmental stimuli. Plant responses that
involve directed movements are called tropisms. Among the best-known tropisms
are phototropism, the response to light, and gravitropism, the response to gravity.
Gravity is one of the major factors that govern root growth in plants. Since the
emergence of land plants, gravitropism allowed plants to adjust root growth to
maximize access to water and nutrients, and shoots to explore and exploit space
on and above the surface of the Earth. In this chapter we discuss current knowledge
and point out open questions like the nature of the gravireceptor, the role of
secondary messengers, hormones and the cytoskeleton. We review the history of
plant gravitropism research, from early experiments performed by naturalists like
Charles Darwin to the utilization of clinostats, centrifuges and experimentation in the
almost stimulus-free environment of microgravity provided by drop towers, parabolic flights of aircrafts and rockets, satellites and low earth orbit space stations,
which are increasingly contributing to our understanding of plant gravity sensing
and orientation.
Keywords Auxin · Clinostat · Gravitropism · Gravity · Microgravity · Roots ·
Statolith
6.1 Introduction
All organisms on Earth are subject to the continuous influence of gravity. In a
process called gravitropism, plants perceive the direction of gravity and can adjust
their growth accordingly (Fig 6.1). Most plant organs are actively positioned at
various defined angles from the gravity vector, the gravitational set point angle
(GSA; Digby and Firn 1995).
This allowed plants to leave the water and conquer land, enabling them to explore
and exploit space below, on and above the surface of the Earth in a most beneficial
way and, thus, to provide food and resources for all animal and human life on
© 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_6
75