Endosperm Structure and Storage Reserve Histochemistry in the Palm, Washingtonia filifera

Abstract

The endosperm of Washingtonia filifera consists of living cells with the same general cellular structure throughout the seed. The major storage reserves are carbohydrate, stored in the form of thickened walls; lipid, stored as numerous small lipid bodies which fill the cytoplasm; and protein, stored as large, but variably-sized, protein bodies. The protein bodies contain two types of inclusions: prismatically-shaped denser protein crystalloids and small crystalline deposits presumed to be phytic acid. The X-ray microanalysis shows these crystalline inclusions do contain P, Ca, Mg, and Fe. Protein bodies are positively stained with PAS. Nuclei are present in all cells, but stain very palely. Plastids and mitochondria are present, but infrequently seen. The plastids have few, poorly developed membranes. Endoplsasmic reticulum and dictyosomes are lacking. The cell wall is thick except in areas of pit fields and consists of three layers which differ in their staining with toluidine blue and in their ultrastructural characteristics: middle lamella, thickened outer wall, and thin inner wall. All wall layers are positively stained with PAS and calcofluor. Although general structural features of the endosperm in Washingtonia filifera are similar to those in date seeds, the composition of the wall polysaccharides and protein bodies appear to differ somewhat.