Gross morphology, ultrastructure and distribution of minerals in sound and severely heat-damaged, elevator-stored rapeseeds (Brassica napus L.) were studied by electron microscopy and X-ray microanalysis. Sound seeds had surface reticulations and a thick seed coat of five layers: epidermis, palisade, crushed parenchyma, aleurone and inner crushed parenchyma. The aleurone cells in the seed coat and the embryonic cells contained many lipid droplets and protein bodies among the cytoplasmic organelles. Severely heat-damaged seeds had a more compressed, electron-dense seed coat with much surface debris which obscured the reticulations; embryonic tissues appeared distorted and shrunken. Aleurone cells in the seed coat and most embryonic cells were necrotic and had large structureless areas and abnormal protein bodies. In the coat of sound seeds, calcium, potassium, sulphur, silicon, magnesium and phosphorus were found in decreasing order of proportional amounts. In cotyledonous tissue the sequence was phosphorus, potassium, sulphur, magnesium and silicon with phosphorus in highest relative proportion. In severely heat-damaged seeds, cotyledonous protein bodies had lower proportions of phosphorus and sulphur, while the seed coat had a higher proportion of phosphorus and lower calcium when compared to sound seeds.
Localization of a thrombin-sensitive calcium pool in platelets.