Abstract
Diurnal changes in the concentration of abscisic acid (ABA) which occur in leaves of droughted, field-grown plants of pearl millet (Pennisetum americanum (L.) Leeke) are not always correleated with changes in bulk leaf water potential ( psi ). A rapid decline in ABA content of the leaves following its rise to a peak level in mid-morning, was observed in several time-course studies despite continued water stress. The possibility that the reduction in ABA in leaves was due to an elevated rate of its export was examined. The decrease in ABA that occurred despite the block to export and despite continuing stress was, attributed to changes in the synthesis or metabolism of ABA within the leaf.