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, hydroponically-grown tomato (Lycopersicon esculentum) seedlings severely inhibited 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 deficient mutant notabilis (not) than in Ailsa Craig (wild-type) seedlings. Application of 1.0 mmol m(-3) ABA to wild-type roots resulted in reductions in turgor pressure within 72 h. In contrast, little if any effect on turgor pressure was observed with not roots at the same concentration. That turgor pressure was more strongly influenced in the wild-type, 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.