Wild cucumber, Echinocystis

Both the endosperm and cotyledons of the wild cucumber, Echinocystis macrocarpa Greene, have been shown to contain gibberellin-like substances. The... 

At first glance, it is difficult to recognize the gibberellins as diter-penes. However, any element of doubt about this has been dispelled by isotope experiments in vivo and in a cell-free system. In the fluid endosperm of the wild cucumber Echinocystis macrocarpa the following synthetic pathway has been demonstrated (Fig. 85) geranylgeranyl pyrophosphate—(—) kaurene—(—) kauren-19-ol —gibberellin A5. Presumably the synthesis then proceeds via Aj to gibberellic acid. 

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