Redistribution of sulphur during generative growth of barley plants with different sulphur and nitrogen status

The effect of S and N application on the distribution and redistribution of S compounds in spring barley (Hordeum vulgare L.) was investigated in pot experiments by determination of changes in the content of total-, sulphate- and thiol-S in leaves, ears and stems during the grain-filling period. Nit rogen and sulphur had a clear interactive effect on the yield of all plant parts with little or no effect of S at low N application rates and similar low effect of N without S application. The sulphate concentration in the di fferent plant parts was markedly affected by the S application rate. This e ffect was most pronounced in leaves, less in stems and least in ears. In S- replete plants, leaf S decreased during grain development by an average of 28%, while in S-deficient plants the leaf S content did not change during t he grain-filling period. About 70% of leaf N was redistributed to the ears in plants growing at adequate S supply compared with about 35% of leaf N in S-deficient plants. The proportion of ear N and S originating from the red istribution of leaf N and S was 49% and 23%, respectively. This study verif ies that S is relatively immobile in plants as the proportion of S redistri buted from leaf tissue was considerably smaller than that of N. The results suggest that the availability of soil or root S during grain-filling is im portant for an adequate S supply to the developing grains as the distributi on of S to the ears considerably exceeded the amount exported from the leav es.