Physiological and morphological characteristics during development of pedunculate oak (Quercus robur L.) zygotic embryos |
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Authors: | Christine Prewein Michaela Endemann Vilem Reinöhl Jan Salaj Vanda Sunderlikova Eva Wilhelm |
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Institution: | (1) ARC Seibersdorf Research GmbH, Division of Biogenetics & Natural Resources, 2444 Seibersdorf, Austria;(2) Department of Botany and Plant Physiology, Mendel University of Agriculture and Forestry, Zemedelska 1, 61300 Brno, Czech Republic;(3) Institute of Plant Genetics and Biotechnology, Slovak Academy of Sciences, Nitra, Slovakia |
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Abstract: | The developmental stages of oak zygotic embryos (ZEs) are characterized here according to morphological and physiological
features. Seeds were harvested from June to September in 1-week intervals. Excised embryos were classified into four stages
of development by using growth parameters. For physiological characterization, endogenous levels of abscisic acid (ABA), indole-3-acetic
acid (IAA), l-proline, starch content and water status were determined. The expression of the oak legumin storage protein gene was tested
in immature cotyledonary ZEs before and after ABA treatment. The ABA levels of the embryos showed a significant peak during
the intermediate stage of maturation (stage III) and then decreased again at the end of the late maturation phase (stage IV).
Concomitant with ABA, the moisture content declined with the maximum embryo size. High IAA levels were found at the beginning
of embryo enlargement as exponential growth occurred (stage II) but decreased during further development. Starch accumulated
gradually in the course of maturation, whereas significant values were found in stage IV ZEs near shedding. Proline, on fresh
weight basis, was high during stages I and II. Osmotic potential increased when, by rapid dry matter accumulation, stage II
ZEs reached their maximum size during early intermediate development. Expression of precocious germination was higher on hormone-free
medium, in particular, among stage II and stage III ZEs. Variations in phytohormone levels in combination with changes in
tissue water status seem to be important factors for oak ZE development. |
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Keywords: | Oak Seed physiology Abscisic acid Indole-3-acetic acid Starch |
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