A glasshouse experiment in 1997 at Wye College, University of London, investigated the uptake of
35S-SO4 at two growth stages. When labelled S was applied at growth stage 24 on 20 January only
14% of available sulphur was detected in the plant parts. There was a progressive increase in uptake
into the newly emerged leaves. The leaves, which emerged after the application of the radiolabelled
sulphur solution was complete, imported sulphur from other parts of the plant. At final harvest the
ears had become a major new sink and had imported 68% of the labelled sulphur.
When labelled sulphur was applied on 7 March at growth stage 41–45, an average of 93% of
available sulphur was taken up during the 3 days exposure period. The major portion was quickly
translocated and recovered from the aerial parts. At final harvest 53% appeared in the grain. The
experimental results demonstrated that sulphur reserves can be remobilized to developing sinks. It is
suggested that sulphate ions can be retained as a reserve pool by the plant until they are required by
actively developing sinks.