A re-examination of the reputed control of cotyledonary metabolism by the axis.

A re-examination has been made of the supposed regulation by the axis of cotyledonary isocitrate lyase (EC 4.1.3.1) activity in Cucumis sativas L. and Cucurbita maxima Duch. and greening in cucumis. When precautions are taken to ensure that isolated cotyledons and cotyledons attached to the axis have equal access to oxygen and/or water no axis effects can be observed. The results underline the importance of maintaining excised plant parts in comparable physical conditions if meaningful physiological measurements are to be made. Previous reports describing a controlling role for the axis are therefore most probably incorrect, although alternative regulatory mechanisms mediated by the axis are still possible.