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 25 d 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 μmol kg−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 13 μmol kg−1 DM at 6 DPA to 0.1 μmol kg−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 0.9 μmol kg−1 DM, and then decreased to 0.3 μmol kg−1 DM by 25 DPA. Endosperm IAA content remained low through 9 DPA (about 6 μmol kg−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 34 μmol kg−1 DM at 13 DPA to about 15 μmol kg−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 4.8 μmol kg−1 DM between 13 and 25 DPA. These hormone changes may be involved in the coordinated development of embryos in ovulo.