Abstract
Auxin, cytokinin, and abscisic acid levels were measured and compared at similar stages after pollination in immature corn ( Zea mays L.) kernels of two inbred varieties, A188 and MO-17, and one hybrid, DeKalb XL-12. Kernels from XL-12 were examined 3, 12 and 15 days after pollination. The general trend in the hormone profiles of XL-12 corn kernels was one of rapid accumulation of growth promoting hormones, auxins and cytokinins, and a decline of growth inhibiting hormones, abscisic acid (ABA) and ABA-ester(s). For all three varieties, the auxin accumulation (free indole-3-acetic acid (IAA) and esterified IAA) was by far the most pronounced change among the hormone groups observed. A188 corn kernels containing 1-mm embryos (12 days after pollination) had 20-fold less auxin than Missouri-17 kernels containing 0.8-mm embryos (15 days after pollination) and 16-fold less auxin than XL-12 kernels containing 0.5-mm embryos (15 days after pollination). Since literature reports have correlated corn embryo size with the ability of embryo derived callus to regenerate in culture, it is hypothesized that endogenous kernel auxin levels may be a major regulatory hormone component of corn embryo callus regeneration. Procedures for the measurement of auxin, cytokinins, and abscisic acid using high performance liquid chromatography are also described.
Published Version
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