Abstract

Reliable methods of culturing isolated immature soybean embryos under stringent environmental controls are available, but have not been used to study factors affecting soybean seed lipid biosynthesis. This study compared the changes in lipid composition during seed maturation in planta and in two in vitro culture systems and evaluated both culture systems for studying the developmental regulation of lipid biosynthesis. Immature soybean [Glycine max (L.) Merr. cv. McCall] embryos from three developmental stages (seed length = 2–3, 5–6, or 8–9 ram) were cultured for 5, 15, or 45 d in LSG (modified Linsmaer-Skoog salts, 50 g kg⁻¹ sucrose) or SHGM (Schenk-Hildebrandt salts, 10 g kg⁻¹ sucrose) liquid culture media. Lipid concentrations of the cultured embryos ranged from 10 to 179 g kg⁻¹ dry wt. and were consistently lower than that of mature seed (185 g kg⁻¹ dry wt.). Regardless of stage at excision, the mole percent (mol %) of palmitic and linolenic acids declined and the mol % linoleic acid increased when embryos were cultured in LSG. This pattern is consistent with that observed during maturation in planta. In contrast, the mol % of palmitic and stearic acids increased when embryos were cultured in SHGM and the resulting fatty acid profiles bore little resemblance to those of mature seed. Immature embryo culture in LSG medium provides a viable system for examining lipid biosynthetic processes and, with discriminant function analysis of storage lipid composition, can provide a useful estimate of embryo maturation.

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