EFFECTS OF FLURIDONE AND ABSCISIC-ACID ON LATERAL ROOT INITIATION ANDROOT ELONGATION OF EXCISED TOMATO ROOTS CULTURED IN-VITRO

Roots of tomato (Lycopersicon esculentum Mill. cv. Bonny Best) were ex cised and cultured in the presence of the abscisic acid synthesis inhi bitor fluridone, and with concentrations of exogenous abscisic acid ra nging from 10(-10) to 10(-4) M to determine the effects of abscisic ac id and its synthesis inhibition on the development of lateral roots in in vitro cultured tomato roots. Exogenous abscisic acid inhibited lat eral root initiation and emergence at concentrations of 10(-6) M and g reater. Fluridone (10(-6) M) enhanced the formation of lateral roots e ven in the presence of abscisic acid, at all concentrations tested exc ept 10(-4) M. Abscisic acid increased apical distance, and fluridone r educed it up to 10(-5) M abscisic acid. Both fluridone and abscisic ac id reduced lateral and primary root lengths. It was concluded the endo genous abscisic acid is probably involved in the regulation of lateral root initiation and root apical dominance, and that abscisic acid may affect lateral root initiation differently than lateral root emergenc e.