Use of ICP‐MS and¹⁰B to trace the movement of boron in plants and soil

Of all the plant essential elements, boron (B) is the least understood. This lack of understanding is due in part to the unavailability of a suitable isotope to trace the movement of B. With the introduction of the inductively coupled plasma mass spectrometry (ICP‐MS) in the mid 1980s, it is now possible to utilize the stable isotope 10B as a tracer of B. The low detection limits of the ICP‐MS also allow determination of B concentrations in small samples such as membrane or cell wail preparations. In this paper, we describe the use of enriched 11B and 10B to trace B uptake in intact plants (soil and nutrient solution application), isolated protoplasts, leaf and stem tissue (foliar application). Results suggest that stable isotope labelling is an effective and inexpensive method of monitoring B movement in plants and soil. The recovery of enriched B in fruit and nut tissue suggests B may be at least partially phloem mobile. Enriched B isotopes were effectively used to monitor B uptake into isolated protoplasts and whole plants. Monitoring soil B movement was also accomplished using this procedure. Differences in the natural abundance of B isotopes (10B:nB ratio) at different locations and in different soil types is discussed. Description of ICP‐MS instrumental parameters, digestion techniques, isotopic enrichment and ratioing parameters is included.