caa a22 4500 47710150X CHVBK 20180405111543.0 cr unu---uuuuu 170330e19960701xx s 000 0 eng 10.1007/BF00195738 doi (NATIONALLICENCE)springer-10.1007/BF00195738 Braun Markus Botanisches Institut, Universität Bonn, Venusbergweg 22, D-53115, Bonn, Germany aut Anomalous gravitropic response of Chara rhizoids during enhanced accelerations [Elektronische Daten] [Markus Braun] Centrifugal accelerations of 50-250 g were applied to rhizoids of Chara globularis Thuill. at stimulation angles (α) of 5-90° between the acceleration vector and the rhizoid axis. After the start of centrifugation, the statoliths were pressed asymmetrically onto the centrifugal flank of the apical cell wall. In contrast to the well-known bending (by bowing) under 1 g, the rhizoids responded in two distinct phases. Following an initial phase of sharp bending (by bulging), which is similar to the negatively gravitropic response of Chara protonemata, rhizoids stopped bending and, in the second phase, grew straight in directions clearly deviating from the direction of acceleration. These response angles (β) between the axis of the bent part of the rhizoid and the acceleration vector were strictly correlated with the g-level of acceleration. The higher the acceleration the greater was β. Except for the sharp bending, the shape and growth rate of the centrifuged rhizoids were not different from those of gravistimulated control rhizoids at 1 g. These results indicate that gravitropic bending of rhizoids during enhanced accelerations (5° ≤ α ≤ 90°) is caused not only by subapical differential flank growth, as it is the case at 1 g, but also by the centripetal displacement of the growth centre as was recently discussed for the negative gravitropism of Chara protonemata. A hypothesis for cytoskeletally mediated polar growth is presented based on data from positive gravitropic bending of Chara rhizoids at 1 g and from the anomalous gravitropic bending of rhizoids compared with the negatively gravitropic bending of Chara protonemata. The data obtained are also relevant to a general understanding of graviperception in higher-plant organs. Springer-Verlag, 1996 Chara (rhizoids, protonemata) nationallicence Gravitropism nationallicence Growth centre nationallicence Statoliths nationallicence Polarity nationallicence α : stimulation angle between the rhizoid axis and the acceleration vector nationallicence β : response angle between the axis of the bent part of the rhizoid and the acceleration vector nationallicence ER : endoplasmic reticulum nationallicence g : gravitational acceleration (9.81 m·s−2) nationallicence TEXUS : technologische Experimente unter Schwerelosigkeit (experiments under reduced gravity) nationallicence Planta Springer-Verlag 199/3(1996-07-01), 443-450 0032-0935 199:3<443 1996 199 425 https://doi.org/10.1007/BF00195738 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00195738 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Braun Markus Botanisches Institut, Universität Bonn, Venusbergweg 22, D-53115, Bonn, Germany aut NATIONALLICENCE 773 0- Planta Springer-Verlag 199/3(1996-07-01), 443-450 0032-0935 199:3<443 1996 199 425 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer