Status of sulphur in the foliage of Norway spruce (Picea abies (L.) Karst.) in relation to the mode of contamination

For decades, trees have been exposed to atmospheric S pollution (acid rains). They can thus fulfil their S requirements not only via the roots, but also via their needles. However, whether leaf-absorbed S has a different fate from that of root-absorbed S, or may be toxic to the plant, remains uncertain. Norway spruce trees have been contaminated with (35)SO(4)(2-) either via a nutrient solution, or via a spray, and their (35)S distribution has been analysed. In the case of foliar contamination, a high percentage of (35)S(-) was present in the form of SO(4)(2-), both on the surface and inside the youngest needles. In the case of root contamination, the (35)S of the youngest leaves was mainly incorporated into insoluble organic compounds. Older needles showed a different S distribution.