the vector information of the gravitational force as a reliable and constant guide for
orientation. Space-related experiments including those with centrifuges, clinostats
and especially those that have been performed in the almost stimulus-free microgravity environment in parabolic plane flights and sounding rocket flights as well as
on Space Shuttle missions have greatly improved our knowledge on the role of the
cytoskeleton and associated proteins in the early processes of plant gravity sensing.
The wealth of findings and valuable data from space-related research made
gravitropic tip-growing rhizoids and protonemata of characean algae the best understood model cell types for gravity-sensing phenomena in the plant kingdom. The first
research project in a microgravity environment heralded an era of breakthroughs in
our understanding of the decisive primary phases of gravity sensing in plants.
References
Bartnik E, Sievers A (1988) In-vivo observation of a spherical aggregate of endoplasmic reticulum
and of Golgi vesicles in the tip of fast-growing Chara rhizoids. Planta 176:1–9
Braun M (1996a) Anomalous gravitropic response of Chara rhizoids during enhanced accelerations. Planta 199:443–450
Braun M (1996b) Immunolocalization of myosin in rhizoids of Chara globularis Thuill.
Protoplasma 191:1–8
Braun M (1997) Gravitropism in tip-growing cells. Planta 203:S11–S19
Braun M (2001) Association of spectrin-like proteins with the actin-organized aggregate of
endoplasmic reticulum in the Spitzenkörper of gravitropically tip-growing plant cells. Plant
Physiol 125:1611–1620
Braun M (2002) Gravity perception requires statoliths settled on specific plasma-membrane areas in
characean rhizoids and protonemata. Protoplasma 219:150–159
Braun M, Limbach C (2006) Rhizoids and protonemata of characean algae – model cells for
research on polarized growth and plant gravity sensing. Protoplasma 229:133–142
Braun M, Richter P (1999) Relocalization of the calcium gradient and a dihydropyridine receptor is
involved in upward bending by bulging of Chara protonemata, but not in downward bending by
bowing of Chara rhizoids. Planta 209:414–423
Braun M, Sievers A (1993) Centrifugation causes adaptation of microfilaments; studies on the
transport of statoliths in gravity sensing Chara rhizoids. Protoplasma 174:50–61
Braun M, Sievers A (1994) Role of the microtubule cytoskeleton in gravisensing Chara rhizoids.
Eur J Cell Biol 63:289–298
Braun M, Wasteneys GO (1998a) Reorganization of the actin and microtubule cytoskeleton
throughout blue-light-induced differentiation of characean protonemata into multicellular thalli.
Protoplasma 202:38–53
Braun M, Wasteneys GO (1998b) Distribution and dynamics of the cytoskeleton in graviresponding
protonemata and rhizoids of characean algae: exclusion of microtubules and a convergence of
actin filaments in the apex suggest an actin-mediated gravitropism. Planta 205:39–50
Braun M, Wasteneys GO (2000) Actin in characean rhizoids and protonemata. Tip growth, gravity
sensing and photomorphogenesis. In: Staiger CJ, Baluska F, Volkmann D, Barlow PW (eds)
Actin: a dynamic framework for multiple plant cell functions. Kluwer, Dordrecht, pp 237–258
Braun M, Buchen B, Sievers A (2002) Actomyosin-mediated statolith positioning in gravisensing
plant cells studied in microgravity. J Plant Growth Regul 21:137–145
References
63
orientation. Space-related experiments including those with centrifuges, clinostats
and especially those that have been performed in the almost stimulus-free microgravity environment in parabolic plane flights and sounding rocket flights as well as
on Space Shuttle missions have greatly improved our knowledge on the role of the
cytoskeleton and associated proteins in the early processes of plant gravity sensing.
The wealth of findings and valuable data from space-related research made
gravitropic tip-growing rhizoids and protonemata of characean algae the best understood model cell types for gravity-sensing phenomena in the plant kingdom. The first
research project in a microgravity environment heralded an era of breakthroughs in
our understanding of the decisive primary phases of gravity sensing in plants.
References
Bartnik E, Sievers A (1988) In-vivo observation of a spherical aggregate of endoplasmic reticulum
and of Golgi vesicles in the tip of fast-growing Chara rhizoids. Planta 176:1–9
Braun M (1996a) Anomalous gravitropic response of Chara rhizoids during enhanced accelerations. Planta 199:443–450
Braun M (1996b) Immunolocalization of myosin in rhizoids of Chara globularis Thuill.
Protoplasma 191:1–8
Braun M (1997) Gravitropism in tip-growing cells. Planta 203:S11–S19
Braun M (2001) Association of spectrin-like proteins with the actin-organized aggregate of
endoplasmic reticulum in the Spitzenkörper of gravitropically tip-growing plant cells. Plant
Physiol 125:1611–1620
Braun M (2002) Gravity perception requires statoliths settled on specific plasma-membrane areas in
characean rhizoids and protonemata. Protoplasma 219:150–159
Braun M, Limbach C (2006) Rhizoids and protonemata of characean algae – model cells for
research on polarized growth and plant gravity sensing. Protoplasma 229:133–142
Braun M, Richter P (1999) Relocalization of the calcium gradient and a dihydropyridine receptor is
involved in upward bending by bulging of Chara protonemata, but not in downward bending by
bowing of Chara rhizoids. Planta 209:414–423
Braun M, Sievers A (1993) Centrifugation causes adaptation of microfilaments; studies on the
transport of statoliths in gravity sensing Chara rhizoids. Protoplasma 174:50–61
Braun M, Sievers A (1994) Role of the microtubule cytoskeleton in gravisensing Chara rhizoids.
Eur J Cell Biol 63:289–298
Braun M, Wasteneys GO (1998a) Reorganization of the actin and microtubule cytoskeleton
throughout blue-light-induced differentiation of characean protonemata into multicellular thalli.
Protoplasma 202:38–53
Braun M, Wasteneys GO (1998b) Distribution and dynamics of the cytoskeleton in graviresponding
protonemata and rhizoids of characean algae: exclusion of microtubules and a convergence of
actin filaments in the apex suggest an actin-mediated gravitropism. Planta 205:39–50
Braun M, Wasteneys GO (2000) Actin in characean rhizoids and protonemata. Tip growth, gravity
sensing and photomorphogenesis. In: Staiger CJ, Baluska F, Volkmann D, Barlow PW (eds)
Actin: a dynamic framework for multiple plant cell functions. Kluwer, Dordrecht, pp 237–258
Braun M, Buchen B, Sievers A (2002) Actomyosin-mediated statolith positioning in gravisensing
plant cells studied in microgravity. J Plant Growth Regul 21:137–145
References
63