title: Ultrastructure and elemental composition of dormant and germinating Diplodia maydis spores.
abstract: The ultrastructure of Diplodia maydis spores was studied in thin sections with a transmission electron microscope. Storage vacuoles were evenly distributed in the two cells. Some of the vacuoles that contained a dense osmiophilic sphere(s) were surrounded by a membrane, and had membranous aggregates around their periphery. The sport wall was composed of an electron-dense layer and an electron-translucent layer. An inner cytoplasmic membrane was present. Dormant and germinating spores were studied with scanning electron microscopy and also with a Si (Li) energy-dispersive X-ray analyzer. The dormant spore was ovate and usually two-celled with a central septum. Germination proceeded via a germ tube from the side of one end of the cell. Of several methods for preparation of specimens for X-ray analysis studied, freeze-dried spores mounted on carbon stubs and then further carbon coated gave the best results. X-ray analyses revealed that spore populations contained large amounts of Si, P, Cl, and K, smaller amounts of S and Ca, and trace amounts of Mg and Al. Analyses of single spores revealed high K and Cl and low P and Mg at one end of the cell with concomitant low K and Cl and high P and Mg in the central portion and other end of the cell. In two-celled germinating spores, high K and Cl occurred in the end of the nongerminating spore cell, whereas the germinating cell contained high P and Mg and low K and Cl. X-ray image maps revealed that K and Cl were located together at one end of the spore.
mesh_terms: D002118:Calcium / Q000032:analysis; D002467:Cell Nucleus / Q000648:ultrastructure; D002713:Chlorine / Q000032:analysis; D008928:Mitochondria / Q000648:ultrastructure; D003904:Mitosporic Fungi / Q000032:analysis / Q000502:physiology / Q000648:ultrastructure*; D011188:Potassium / Q000032:analysis; D012825:Silicon / Q000032:analysis; D013172:Spores, Fungal / Q000032:analysis / Q000502:physiology / Q000648:ultrastructure*; D013455:Sulfur / Q000032:analysis; D014617:Vacuoles / Q000648:ultrastructure
chemical_list: D002713:Chlorine; D013455:Sulfur; D011188:Potassium; D002118:Calcium; D012825:Silicon