© 2007 Heron Publishing—Victoria, Canada
Storage lipid dynamics in somatic embryos of Norway spruce (Picea abies): histochemical and quantitative analyses
Magdalena Grigová (1), Martin Kubeš (1, 2), Nikola Drážná (1), Tomáš Řezanka (3) and Helena Lipavská (1, 4)
1. Department of Plant Physiology, Faculty of Science, Charles University, Viničná 5, 12844 Prague 2, Czech Republic / 2. Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Rozvojová 263, 16502, Prague 6, Czech Republic / 3. Institute of Microbiology, Academy of Sciences of the Czech Republic, Vídenská 1083, 14000, Prague 4, Czech Republic / 4. Corresponding author
(lipavska@natur.cuni.cz
) / Received November 23, 2006; accepted March 12, 2007; published online August 1, 2007
Summary
Adequate storage compounds are a prerequisite for successful development during the later stages of somatic embryogenesis;
however, the critical amount of reserves below which somatic embryos fail to mature and germinate has not been determined.
We analyzed storage lipids during Norway spruce (Picea abies (L.) Karst.) somatic embryogenesis. As maturation progressed, lipids, which were stored as lipid bodies in the cytoplasm,
were localized first in suspensor cells of the early embryos, and later in the embryonic root pole, superficial layers of
the hypocotyl and in cotyledons. The concentration of total lipids exhibited marked variation, with values peaking during
cotyledon development and then decreasing during maturation. Linoleic (18:2), oleic (18:1), palmitic (16:0) and 5,9-octadecenic
(5,9-18:2) acids were the most abundant fatty acids in embryos. As embryos developed, linoleic acid concentration increased
slightly, whereas oleic acid concentration decreased. Oleic acid was the most prominent component of the fatty acid spectrum
in isolated dormant zygotic embryos and megagametophytes. Addition of 5% polyethylene glycol to the medium during somatic
embryo maturation caused a shift in the fatty acid spectrum toward that of zygotic embryos. During maturation, changes in
the exogenous carbohydrate supply had no significant effect on total lipid concentration in mature embryos. A marked decrease
in lipid concentration was detected during desiccation, indicating the importance of adequate lipid reserves during this developmental
stage. The lipid content of zygotic embryos differed considerably with harvest year and location, suggesting that zygotic
embryo data cannot be an indicator of somatic embryo quality.
Keywords:
embryo maturation, fatty acid composition, histochemistry, oil bodies, zygotic embryo.
