L'action des statolithes dans la r ponse g otropique des racines de Lens culinaris

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Abstract
The possibility of a relationship between the geotropic response and the sedimentation of amyloplasts was studied. In the first experiment the geotropic curvature and the statolithic apparatus of the roots were defined individually. Statistical analysis showed no correlation between curvature (in its initial phase) and the average number of amyloplasts per cell in section, their average volume and the space that they occupy in the statocyte. These findings seem to exclude the possibility of the statoliths acting by pressure on some sensitive surface. In the second experiment the initial rate of curvature and the percentage of amyloplasts along the longitudinal wall were analysed as a function of the angle of inclination relative to direction of gravity (45–150°). The results obtained show that at the various angles the initial rate of curvature is not dependent on the percentage of amyloplasts which are in contact with a sensitive surface. Nor can the displacement of the amyloplasts caused by the change of orientation explain the relationship between the degree of curvature and the angle of inclination. It seems that no direct link can be found between the sedimentation of the amyloplasts and the geotropic reaction in its initial phase. These results are discussed in reference to recent literature on the existence of growth inhibitors that could be responsible for the geotropic response.