TRANSLOCATION AND METABOLISM OF PHOSPHATE FOLLOWING ABSORPTION BY THEASCOCARPS OF TUBER-MELANOSPORUM AND T-AESTIVUM

The capacity of the tufts of hyphae which sprout from the scales of th e peridium of the ascocarps of Tuber aestivum and Tuber melanosporum t o absorb phosphate has been confirmed using labelled phosphate. The de tailed distribution of the tracer was determined from autoradiographs and these and the corresponding photographs were studied using image a nalysis. The aim of this investigation was to identify the conduction pathways of absorbed [P-32]phosphate; these were found to be the ferti le veins of the gleba, and in particular the sterile hyphae adjacent t o the paraphyses. Some of the compound was metabolised rapidly by the ascocarp. These results provide additional evidence that the ascocarp may become nutritionally autonomous at some stage in its development. In addition, the role of the tufts of hyphae in the physiology of the ascocarp suggests a link between its mode of growth and its external f orm. The distribution of absorbed phosphate was heterogeneous even aft er a 24 h incubation period. The similarity of the distribution profil es of the isotope across fertile veins, both with and without incubati on, suggests that translocation continues throughout the incubation pe riod, and that metabolised phosphate may be remobilised.