Elimination of Geotropic Responsiveness in Roots of Cress (Lepidium sativum) by Removal of Statolith Starch

Roots of garden cress (Lepidium sativum L.) seedlings were made starch-free by treatment with gibberellic acid and kinetic for 29 hours at 35°C in the dark. After 3 hours of temperature adaptation at 21°C the starch-depleted roots were unable to respond to gravity, but elongated 0.48 mm por hour. Under the same conditions control roots pretreated in plain water at 21 and at 35°C elongated 0.64 and 0.33 mm per hour, respcetively (at 21°C). When the hormone-treated seedlings were illuminated, their roots reformed starch after 20 to 24 hours; simultaneously the geotropic responsiveness was restored. The results are interpreted in support of the statolith theory.