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SUMMARYNumerous metachromatic vacuolar granules occur in the hyphae of the fungal symbiont of Taxus baccata mycorrhizas. These granules exist in the trunks and in proliferating arbuscules but they are absent in lysed arbuscules. Direct microanalysis with an electron probe shows that they have a high phosphorus and calcium content. Potassium and magnesium are also present but in lesser quantities. The concentration of phosphorus and calcium is higher in the granules than in the light part of the vacuoles. The concentration of phosphorus also is higher in the granules than in the nuclei of the root, cells and the concentrations of calcium are greater than those measured in the pecto-cellulosic wall of root cells. The role of calcium in the metabolism of phosphorus within the tissues of mycorrhizas still remains unknown.

A dominant genetic male sterility trait obtained through transformation in rapeseed (Brassica napus) was studied in the progenies of 11 transformed plants. l h e gene conferring the male sterility consists of a ribonuclease gene under the control of a tapetumspecific promoter. Two ribonuclease genes, RNase T1 and barnase, were used. The chimaeric ribonuclease gene was linked to the bialophos-resistance gene, which confers resistance to the herbicide phosphinotricine (PPT). l h e resistance to the herbicide was used as a dominant marker for the male sterility trait. l h e study presented here concerns three aspects of this engineered male sterility: genetics correlated with the segregation of the 1-DNA in the progenies; expression of the male sterility in relation to the morphology and cytology of the androecium; and stability of the engineered male sterility under different culture conditions. Correct segregation, 50% male-sterile, PPT-resistant plants, and 50% male-fertile, susceptible plants were observed in the progeny of seven transformants. l h e most prominent morphological change in the male-sterile flowers was a noticeable reduction i n the length of the stamen filament. l h e first disturbances of microsporogenesis were observed from the free microspore stage and were followed by a simultaneous degeneration of microspore and tapetal cell content. At anthesis, the sterile anthers contained only empty exines. In some cases, reversion to fertility of male-sterile plants has been observed. Both ribonuclease genes are susceptible to instability. lnstability of the RNase TI-male sterility trait increased at temperatures higher than 25°C. Our results do not allow us to confirm this observation for the barnase male-sterile plants. However, the male-sterile plants of the progeny of two independent RNase T I transformants were stably male sterile under all conditions studied.