Hormones in wheat kernels during embryony

Abstract

Summary 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 0.1µmol 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