Sulphur nutrition changes the sources of S in vegetative tissues of wheat during generative growth

During generative growth, developing wheat grains require nitrogen and sulp hur to synthesize storage proteins. The hypothesis that the S required for grain growth can be derived from vegetative tissues was examined by growing plants in nutrient culture containing either 50 mu M S (low-S) or 200 mu M S (high-S) and terminating the nutrient supply at various times during gen erative growth, After terminating the nutrient supply, high-S plants redist ributed soluble S to developing grains from pools in roots and leaves, wher eas low-S plants remobilized insoluble S (protein-S) from the leaves to the grains. A model for the cycling of S within mature leaves during generativ e growth is presented.