Which cells respond to gravitropic stimulus in the lentil root?

Darbelley, Nicole; Perbal, Patrick; Perbal, Gérald

doi:10.1111/j.1399-3054.1986.tb05763.x

Cited by 8 publications

(3 citation statements)

References 14 publications

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“…Les mecanismes de Ia courbure gravitropique sont maintenant mieux connus grace aux analyses morphometriques (Barlow et Rathfelder, 1985 ;Selker et Sievers, 1985 ;Zieschang et Sievers, 1991) ou cytologiques (Darbelley et al, 1986). La croissance cellulaire au niveau du meristeme et de Ia zone d'elongation a ete analysee par Darbel- (Fig.…”

Section: La Reaction Gravitropiqueunclassified

“…Lorsque l'axe primaire d'une plantule change d'orientation dans Ie champ gravitationnel terrestre, l'extremite racinaire se courbe et se replace dans Ia direction de Ia gravite (Audus, 1962 ;Larsen, 1962 ;Perbal, 1978;Volkmann et Sievers, 1979). La reaction gravitropique resulte d'un phenomene de croissance asymetrique qui s'etablit rapidement dans les moities inferieure et superieure de Ia racine (Barlow et Rathfelder, 1985 ;Darbelley et al, 1986;Selker et Sievers, 1987 ;Zieschang et Sievers, 1991). Ainsi, apres 1 h de stimulation en position horizontale, Ia courbure atteint deja 15 a 20°.…”

Section: Introductionunclassified

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Microgravité et gravitropisme racinaire

Perbal

Driss‐Ecole

1993

Acta Botanica Gallica

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Space experiments permit to understand better some phases of the gravitropic reaction which occurs when the orientation of the root changes in the gravitational field. In gravisensing cells (statocytes in the root cap), the nucleus is attached to the cell periphery, close to the plasma membrane, by actin filaments. The location of the amyloplasts (statoliths) depends also greatly on these elements of the cytoskeleton. A short period in microgravity (5 min.) modifies the location of the nucleus and of the amyloplasts in the statocytes. The tensions exerted by these very dense organelles on the actin network disappear and this network undergoes a relaxation. The kinetics of gravitropic curvature is also better understood. In fact, gravitropic reaction is regulated by a mechanism depending on gravity. In roots grown in space, then stimulated for 1 h on a 1 g centrifuge, and replaced in microgravity, the regulation limiting the curvature does not occur. It is hypothesized that the sedimentation of the amyloplasts on the endoplasmic reticulum placed at the basal pole of the statocytes could be responsible for this regulation. The contacts between these two organelles should have also a role in root growth. This hypothesis will be tested in our next space experiment (July 94). The experiments in near weightlessness also permit to determine the presentation time which is the duration of stimulation necessary to evoke a slight but significant curvature. Presentation time is 27 s. This short period allows a slight movement of the amyloplasts only (around 0.45 micrometer). The sequence of events leading to the curvature of the root is now well established: the first signal is the separation of the endoplasmic reticulum and the amyloplasts, when the root is subjected to a change in orientation. It is followed by the pressure of these organelles on the actin network which transmits this mechanical effect to the plasma membrane. The transduction of the effect occurs then by the activation of the ions channels (Ca++) and the carrier of a growth inhibitor (auxin), both located in the plasma membrane. This growth inhibitor provokes an asymmetrical growth in the distal part of the meristem and the proximal part of the cell elongation zone. At last, when the root tip reaches the direction of gravity, the amyoloplasts sediment on the endoplasmic reticulum and induce a signal of termination of the curavature.

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Section: La Reaction Gravitropiqueunclassified

Section: Introductionunclassified

Microgravité et gravitropisme racinaire

Perbal

Driss‐Ecole

1993

Acta Botanica Gallica

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“…A variety of changes in growth patterns during the gravitropic response has been reported in different species; these changes are reflected at the cellular level as differential stimulation or inhibition of cell elongation during gravireaction (Pilet and Ney 1981;Barlow and Rathfelder 1985;Darbelley et al 1986). By examining the kinetics of growth rate changes during gravitropism in Lepidium roots (Selker and Sievers 1987) and in maize (Ishikawa et al 1991), it was shown that the pattern of differential growth changes during the gravitropic reaction and involves changes in the position of the elongation zone.…”

Section: Introductionmentioning

confidence: 98%

The response to auxin of rapeseed (Brassica napus L.) roots displaying reduced gravitropism due to transformation by Agrobacterium rhizogenes

Legué

Driss‐Ecole

Maldiney

et al. 1996

Planta

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It has recently been documented that, compared to untransformed controls, the roots of oilseed rape (Brassica napus L. CV CrGC5) seedlings transformed by Agrobacterium rhizogenes A4 show a reduced gravitropic reaction (Legue et al. 1994, Physiol Plant 91: 559-566). After stimulation at 90 degrees C or 135 degrees, the transformed root tips curve. but never reach a vertical orientation. In the present study, we investigated the causes of reduced gravitropic bending observed in stimulated transformed root tips. First, we localized the gravitropic curvature in normal and in transformed roots after 1.5 h of stimulation. The cells involved in root curvature (target cells) corresponded at the cellular level to the apical part of the zone of increasing cell length. In transformed roots grown in the vertical position, these cells showed a reduction in cell length compared to controls. Because auxin is considered to be the gravitropic mediator, the response of normal and transformed roots to exogenous auxin was studied. Indole-3-acetic acid (IAA) was applied along the first 3 mm using resin beads loaded with the hormone. In comparison to normal roots, transformed roots showed reduced bending toward the bead at all points of bead application. Moreover, the cells which responded to IAA corresponded to the target cells involved in the gravitropic reaction. The level of endogenous IAA was lower in transformed roots. Thus, it was concluded that the modified behavior of transformed roots during gravitropic stimulation could be due to differences either in IAA levels or in reactivity of the target cells to the message from the cap.

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Development and Gravitropism of Lentil Seedling Roots Grown in Microgravity

Perbal¹,

Driss‐Ecole²

2007

Biology in Space and Life on Earth

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Which cells respond to gravitropic stimulus in the lentil root?

Cited by 8 publications

References 14 publications

Microgravité et gravitropisme racinaire

Microgravité et gravitropisme racinaire

The response to auxin of rapeseed (Brassica napus L.) roots displaying reduced gravitropism due to transformation by Agrobacterium rhizogenes

Development and Gravitropism of Lentil Seedling Roots Grown in Microgravity

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