The association of gibberellin-like activity with the chloroplast fraction of leaf homogenates.

Significant gibberellin-like activity has been detected in the 1000xg fraction of leaves of Brassica oleracea var. acephala (Canson kale) and Hordeum vulgare (cv. "Himalaya"). In kale and barley the qualitative pattern of activity found in the chloroplast fraction differs from that normally seen in total-leaf extracts. When expressed on a total chlorophyll or sample fresh-weight basis, approximately 16% of the gibberellin-like activity found in the leaf can be accounted for in the 1000xg or chloroplast fraction. The physiological implications of this finding are discussed.