Thesis

Changes in gibberellin content during Phaseolus vulgaris germination

Gibberellin-like activity from cotyledons, sead-coats and embryonic axis of Phaseolus vulgaris was measured by the barley reducing sugar assay and the dwarf pea stem assay during germination. In the first 48 hours of germination the amount of gibberellin-like substance decreases 1000 fold in the cotyledons and 10 fold in the axis when measured with the barley assay. This assay reveals significant activity from unimbibed seed coats. The activity increases in the initial stages of germination, and then decreases. When measured by the pea assay, no activity is detected from unimbibed.seed coats although small amounts of activity are obtained for a short period following the onset of germination. These decreases in levels of gibberellin- like material during germination could reflect its utilization and conversion to less active forms, the accumulation of inhibitors which mask activity of the hormone, or exudation into the medium. Comparison of results from the two assays suggests qualitative changes in gibberellin- like material, or the accumulation of inhibitors with different effects in the two assays.

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