A HISTOLOGICAL AND STRUCTURAL STUDY OF PHACELIA-TANACETIFOLIA ENDOSPERM IN DEVELOPING, MATURE, AND GERMINATING SEED

The ruminate endosperm of developing, mature, and germinated seed of P hacelia tanacetifolia was investigated with light and scanning electro n microscopy and energy dispersive spectroscopy. At each of the three stages examined, large numbers of calcium oxalate crystals were visibl e in the endosperm epidermis and in a few cells of the outermost endos perm layers. In developing seeds the endosperm cells were characterize d by a large number of starch grains interspersed with some protein bo dies of small size, while in the mature seeds, there were few small st arch grains and a large number of big protein bodies. The globoids obs erved within protein bodies could be ascribed to the ''type 1'' phytin inclusions and showed considerable P and Ca levels, some K, and only traces of Mg and S. During germination we observed vacuolation and ini tial digestion of the protein bodies, which was indicated by periphera l pitting. Digestion started from the endosperm epidermis and continue d toward the inner endosperm. The Ca contained in globoids, mobilized at germination together with protein reserves, is probably the Ca sour ce used by P. tanacetifolia seedling during early growth. The role of Ca-oxalate crystals in the endosperm is briefly discussed.