N-14 AND N-15 IMAGING BY SIMS MICROSCOPY IN SOYBEAN LEAVES

The distribution of N-15 and N-14 compounds in cryofixed and resin emb edded sections of soybean (Glycine max L) leaves was studied by SIMS m icroscopy. The results indicate that, with a mass resolution M/DELTA-M higher than 6000, images of the nitrogen distribution can be obtained from the mapping of the two secondary cluster ions (CN-)-C-12-N-14 an d (CN-)-C-12-N-15, in samples of both control and N-15-labeled leaves. The ionic images were clearly related to the histological structure o f the organ, and allow the detection of N-14 and N-15 at the subcellul ar level. Furthermore, relative measurements of the (CN-)-C-12-N-14 an d (CN-)-C-12-N-15 beams made possible the quantification of the N-15 a tom% in the various tissues of the leaf.