EFFECT OF PACLOBUTRAZOL ON ABSCISIC-ACID LEVELS IN WHEAT SEEDLINGS

Contradictory results have been reported for the effects of triazoles on abscisic acid (ABA) levels in plants. Paclobutrazol reduced the height, fresh weight, and ABA levels of wheat seedlings. The magnitude of the inhibitory effect of paclobutrazol on ABA levels was dependent on the length of time after application. ABA levels in plants as determined by gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) were reduced by 50-60% 2 days after soil application. A further 15% reduction occurred by the seventh day after treatment. ABA level analyses began at the time of treatment with 4-day-old seedlings and continued until 21 days after treatment when only a 20% reduction was detected. These determinations using GC-SIM-MS should increase the understanding of triazole effects on ABA levels.