Diurnal changes of leaf water potential, abscisic acid, phaseic acid and indole-3-acetic acid in field grown Sorghum bicolor L. Moench

Summary Diurnal changes of leaf water potential, abscisic acid, phaseic acid and indole-3-acetic acid were studied in field grown sorghum. Leaf water potential fluctuated over a range of -0.84 to -1.82 MPa with two distinct low value peaks at 10.00 and 16.00 h. Abscisic acid exhibited a distinct diurnal variation and fluctuated over a range of 45–110 ng g -1 fresh wt. with two distinct peaks at 08.00 and 18.00 h. Abscisic acid levels, except those from 10.00 to 17.00 h were, negatively correlated with leaf water potential and began to increase at leaf water potential values around -1.0 MPa. Phaseic acid levels were low compared to abscisic acid levels, but fluctuated in a manner similar to abscisic acid with peaks at 10.00 and 18.00 h. Fluctuations in indole-3-acetic acid levels were very small.