APPLIED ABSCISIC-ACID, ROOT-GROWTH AND TURGOR PRESSURE RESPONSES OF ROOTS OF WILD-TYPE AND THE ABA-DEFICIENT MUTANT, NOTABILIS, OF TOMATO

Abscisic acid (ABA) applied to the rooting medium of intact, hydroponi cally-grown tomato (Lycopersicon esculentum) seedlings severely inhibi ted root growth at concentrations greater than or equal to 0.5 mmol m( -3). At 1.0 mmol m(-3) the effect was more apparent in the ABA deficie nt mutant notabilis (not) than in Ailsa Craig (wild-type) seedlings. A pplication of 1.0 mmol m(-3) ABA to wild-type roots resulted in reduct ions in turgor pressure within 72 h. In contrast, little if any effect on turgor pressure was observed with not roots at the same concentrat ion. That turgor pressure was more strongly influenced in the wild-typ e, but that growth was more strongly influenced in not, suggests that 1 mmol m(-3) ABA has independent effects on turgor pressure and growth rate.