Submitted to: Journal of Plant Physiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/19/2001
Publication Date: 6/30/2002
Citation: Hess, J.R., Carman, J.G., Banowetz, G.M. 2002. Hormones in wheat kernels during embryony. Journal of Plant Physiology.159:379-386. Interpretive Summary: A set of hormones control the development of the wheat kernel, but the specific changes in hormone levels that accompany each stage of kernel development were not understood. This lack of understanding has prevented informed genetic manipulation of wheat development to improve kernel size and quality. This study quantified changes in three groups of hormones during development of the wheat kernel. This work was significant because changes in these hormones have not previously been related to specific stages of kernel development.
Technical Abstract: 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 umol 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 umol kg**-1 DM at 6 DPA to 0.1 umol 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 umol kg**-1 DM, and then decreased to 0.3 umol kg**-1 DM by 25 DPA. Endosperm IAA content remained low through 9 DPA (about 6 umol kg**-1 DM) and then increased sharply to about 38 umol kg**-1 DM by 19 and 25 DPA. In contrast, embryo IAA content decreased from about 34 umol kg**-1 DM at 13 DPA to about 15 umol kg**-1 DM at 19 and 25 DPA. Endosperm ABA content fluctuated between 1.0 and 4.5 umol kg**-1 DM between 6 and 25 DPA while embryo ABA content fluctuated between 3.4 and 4.8 umol kg**-1 DM between 13 and 25 DPA. These hormone changes may be involved in the coordinated development of embryos in ovulo.