The Chemistry and Microstructure of Protein Bodies in Celery Endosperm

Anatomical variations in regions of the endosperm and the structure and composition of protein bodies of ungerminated celery (A pium graveolens) fruits were examined by histochemistry, light microscopy, electron microscopy, and X-ray analysis. Protein bodies contained either phytin globoids with Mg and P and lesser amounts of Ca and K or Ca oxalate druse crystals that had only Ca peaks. Most of the Ca in the fruit is stored in the druse crystals, which are broken down more slowly than the globoids during germination. Cells in the central region of the endosperm, distal to the cotyledons, contained enlarged protein bodies and other cellular features, indicating that they had already undergone some autolysis prior to the onset of germination. Such cells would be expected to appear to respond earlier to the application of exogenous gibberellin than more peripheral cells in the endosperm. The apparent early response of central cells in isolated endosperm halves may therefore not depend on an inherent difference in the response time of these cells, but rather on the fact that they had already been exposed to a gibberellin-like stimulus earlier in fruit development.