© 2004 Heron Publishing—Victoria, Canada
Changes in water status and proline and abscisic acid concentrations in developing somatic embryos of pedunculate oak (Quercus robur) during maturation and germination
Christine Prewein (1), Martin Vagner (2) and Eva Wilhelm (1, 3)
1. ARC Seibersdorf Research GmbH, Environment and Life Sciences, Department of Biotechnology, A-2444 Seibersdorf, Austria / 2. Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Rozvojova 135, 165 02 Prague 6, Czech Republic / 3. Corresponding author (eva.wilhelm@arcs.ac.at) / Received November 18, 2003; accepted May 29, 2004; published online September 1, 2004
Summary
Somatic embryos of oak (Quercus robur L.) were matured on P24 media differing in gel strength (0.8, 0.9 and 1.0% (w/v) agar). Viscosity and osmotic potential (Ψπ,medium) of the media were determined. Developing cotyledonary embryos were analyzed at maturity Stages I–III for water content,
osmotic potential (Ψπ,embryo) and concentrations of abscisic acid (ABA) and proline. Proliferation of embryogenic tissue, germination rates and the number
of embryos formed were also determined in order to relate embryo quality to physiological parameters. Viscosity increased
with agar concentration, a phenomenon apparently related to water availability. Many Stage III embryos with high germination
potentials were obtained on P24 medium containing 1.0% agar. Embryo water content decreased progressively from 94 to 80% during embryo maturation. Stage
I and II embryos that matured on media containing 0.8 or 0.9% agar had similar values of Ψπ,embryo, whereas Ψπ,embryo of Stage III embryos that matured on medium containing 1.0% agar was significantly lower, although Ψπ,medium was unaffected by gel strength. Stage III embryos showed a nearly 16-fold increase in proline concentration and a 50% decrease
in ABA concentration compared with Stage I embryos. We conclude that tissue water status and a complex relationship between
ABA and proline concentrations, modulated by medium gel strength, are important factors in the maturation process and the
quality of oak somatic embryos.
Keywords:
Fagaceae, forest tree, hardwood, micropropagation, somatic embryogenesis, tissue culture.
