PYROLYSIS MASS-SPECTROMETRY OF DEVELOPMENTAL STAGES OF MAIZE SOMATIC EMBRYOS

The diversity in biopolymers such as Polysaccharides, (poly)phenols, n ucleic acids and lipids in the developmental stages of two types of hi stologically different somatic embryos of maize was investigated, usin g in-source pyrolysis low voltage electron impact mass spectrometry (P yMS) and the data were compared with those obtained for zygotic embryo s. The first type of somatic embryo is attached to callus tissue and s hows the same histo-differentiation characteristics as zygotic embryos . The second type grows from clusters of cells in liquid culture and i ts shoot meristem is blocked in development (Emons & Kieft 1991). In-s ource pyrolysis low voltage electron impact mass spectrometry shows th at during callus initiation from young zygotic embryos the relative ab undances of di- and triglycerides decrease, but increase again after e stablishment of the.embryogenic callus. During callus initiation mass peaks for ferulic acid appear. The embryogenic cell clusters contain m ore pentosans and hexosans than the non-embryogenic elongated cells. I n the globular stage, the hexosans increase. At the ovoid stage, when the first cells with vascular thickenings are observed in the sections , which are brightly fluorescent and can be stained with phloroglucino l, mass peaks for lignin are observed in the mass spectrum. The mass s pectra of the developmental stages of somatic embryos grown attached t o callus are quite comparable to those of zygotic embryos. Both struct ures contain far less phenolics, no lignin-like polyphenols, and a muc h higher amount of polysaccharides than the single somatic embryos.