Lack of gravitropic response of tumour roots of Forsythia intermedia: cytological evidence for this behaviour

Abstract

Tumours of Forsythia intermedia Zab. consist of clusters of roots characterized by limited growth. These roots are agravitropic and have a nontypical cap without starch. Placed in moisture, the roots elongate in the same direction as they had on the plant, without any gravitropic curvature. Elongated roots have a caplike area, the cells of which exhibit amyloplasts. The absence of gravitropic response of the elongated roots was confirmed experimentally. Amyloplasts of the columella cells do not sediment in the direction of gravity, even after modification of the position of the root with respect to gravity. The reason for this agravitropism of Forsythia intermedia tumour roots is discussed in relation to their cytological features.