Mature seed coats of representatives of all three genera of Musaceae were analysed for macromolecular composition with various mass spectrometric techniques and compared with scanning electron microscopy and light microscopy in combination with histochemical techniques. Mass spectrometric techniques are more sensitive and more specific in identifying macromolecular compounds than histochemical methods. The macromolecular ' fingerprint ' of the seed coats of Musaceae showed unique components of aromatic phenols. The seed coat structure of all three genera is homogeneous within the Musaceae. It is characteristic at the family level and most complex within the Zingiberales. Very remarkable are the separation of the outer cell walls from the exotestal layer, exposing a secondary surface with silica crystals, and the relatively thick mesotesta which protects the seed, e.g. against the biting forces and passage through the digestive tracts of dispersing agents. Germination takes place with an operculum and is facilitated by a predetermined rupture layer in the micropylar collar. The musaceaous seed presents a good example of the solution of conflicting demands of protection and germination.
Cannaceae seeds have been analysed regarding seed coat structure, germination and macromolecular composition of the seed coats. Data of several mass spectrometric techniques were combined with those of microscopic and histochemical techniques to acquire insight into the functions of the seed coat. Cannaceae seeds have an exotestal layer of Malpighian cells with a hydrophobic and a hydrophilic part. The hydrophobic part is mainly responsible for the impermeability of the seed and contains silica, callose, lignin as water repellent substances. Water can only enter the seed after a certain temperature-induced opening of an imbibition lid. During imbibition the hydrophilic part of the Malpighian cells swells and the seed coat ruptures due to differences in pressure in the upper and lower part of the Malpighian cells.Within the order Zingiberales there are still unsolved questions about the relations between seed coat structure, macromolecular composition and germination. Because there is a dearth of reliable data on the macromolecular components, the functional interpretation of seed coat has remained an almost unexplored field of research. The family Cannaceae has a somewhat distinct position within this order, having seeds with an exotesta of Malpighian cells, a long life time, and germination with an imbibition lid. Most taxa of the Zingiberales have an endotestal seed coat and germination with a seed lid.
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