Effect of Pod Removal on Abscisic Acid Levels in Soybean Tissue1

The seasonal profiles of free and conjugated abscisic acid (ABA) in seed, pod wall, and leaf tissue were determined using field‐grown control and depodded ‘Clay’ soybean (Glycine max (L.) Merr.) plants. Total seed ABA was initially high (13.0 /µg/g fresh weight) but decreased to 0.4 µg/g at maturity. The pod wall contained much less ABA than did seeds (ca. 0.5 µg/g). Pod wall ABA level was constant during development except for a twofold increase during final pod maturation. Leaves also contained much less ABA (< 1 µg/g) than did seeds. Upper canopy leaves contained more ABA than did lower canopy leaves. Depodding had no consistent effect on leaf ABA levels. Water stress caused an increase in ABA content in leaf tissue with no effect on pod wall tissue, while senescence increased ABA content hi pod walls with little effect on leaf tissue.