INFLUENCE OF ZINC TOXICITY ON GRAVITROPIC RESPONSE OF TOMATO (Lycopersicon esculentum Mill.) ROOTS

Abstract

In this study, primary roots sprouting from Lycopersicon esculentum Mill. (tomato) seeds, germinated in Hoagland's nutrient solution containing different amounts of ZnCl(2) (1, 3 and 5 mM), were observed. Primary roots have shown negative geotropic behaviour at ZnCl(2) levels of 3 and 5 mM, instead of positive tropism. This effect was much obvious in the plants grown in Hoagland solution containing 5 mM ZnCl(2). On the other hand, the addition of 100 mg/L triiodobenzoic acid (TIBA) into imbibition and growth medium containing 3 or 5 mM ZnCl(2) eliminated negative gravitropic behaviour of primary roots and induced positive tropism of roots which were oriented to embryo axis, and gave rise to root elongation.