Abstract. Cell cultures of Lycopersicon peruvianum L.stressed with CdSO 4 (10-3M) show typical changes in the ultrastructure, starting with the plasmalemma and later on extending to the endoplasmic reticulum and the mitochondrial envelope. Part of the membrane material is extruded, with the formation of osmiophilic droplets which increase in size and number during the stress period. After 4 h, about 20% of the cells are dead. A short heat stress preceeding the heavy-metal stress induces a tolerance effect by preventing the membrane damage. The cells show a normal ultrastructure with one exception: cytoplasmic heat-shock granules are formed. This protective effect can be abolished by cycloheximide. Cadmium uptake is not markedly influenced by the heat stress. Cadmium is found together with sulfur in small deposits in the vacuoles of stressed cells. The precipitates contain an excess of sulfur, evidently due to the stress-induced formation of phytochelatins. The role in heavy-metal tolerance of heat-shock proteins in the plasmalemma (HSP70) and in cytoplasmic heat-stress granules (HSP17, HSP70) is discussed.

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The synthesis of trimethylsilyl-substituted poly(titaniumcarbodiimide) as a novel precursor for titanium carbonitride based ceramic materials is described. The precursor and the subsequent processing steps (cross-linking and pyrolysis) are characterized by IR and Raman spectroscopy, thermal gravimetric analysis and simultaneous mass spectroscopy, electron microscopy and powder X-ray diffraction measurements. The novel polymer is formed by the reaction of TiCl 4 or Ti(NEt 2 ) 4 with bis(trimethylsilyl)carbodiimide. Subsequent pyrolysis at 1000°C in argon results in the formation of a ceramic composite material consisting of nanocrystalline TiCN and amorphous SiCN as constituting phases. Using Ti(NEt 2 ) 4 as a starting reagent instead of TiCl 4 , chlorine contamination of the ceramic material can be avoided. The different molecular vibration modes of the metal-nitrogen, metal-carbon and nitrogencarbon bonds in poly(titaniumcarbodiimides) with trimethylsilyl substituents were calculated using quantum mechanical methods, providing a comprehensive understanding of the measured spectra.

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