Hormones in wheat kernels during embryony

Abscisic acid (ABA), indole-3-acetic acid (IAA) and six cytokinins in wheat (Triticum aestivum L.) grain components were extracted, from 0 to 25d post anthesis (DPA), and quantified by noncompetitive indirect ELISA. At 3 DPA, which coincides with early embryo and endosperm cell divisions, whole kernel hormone levels in μmolkg–1 dry mass (DM) were: zeatin (Z) 30, IAA 4, zeatin riboside 1.8, ABA 1.0, other cytokinins < 0.6. Endosperm Z content declined from about 13μmol kg–1 DM at 6 DPA to 0.1μmolkg–1 DM by 9 DPA and remained low thereafter. Generally by 9 DPA, embryo differentiation is nearly complete, and the endosperm mitotic index has decreased to near zero. At 13 DPA, Z content in embryos was 0.9μmol kg–1 DM, and then decreased to 0.3μmol kg–1 DM by 25 DPA. Endosperm IAA content remained low through 9 DPA (about 6μmolkg–1 DM) and then increased sharply to about 38 μmol kg–1 DM by 19 and 25 DPA. In contrast, embryo IAA content decreased from about 34μmolkg–1 DM at 13 DPA to about 15μmolkg–1 DM at 19 and 25 DPA. Endosperm ABA content fluctuated between 1.0 and 4.5 μmol kg–1 DM between 6 and 25 DPA while embryo ABA content fluctuated between 3.4 and 4.8μmol kg–1 DM between 13 and 25 DPA. These hormone changes may be involved in the coordinated development of embryos in ovulo.