Effect of electron microscopy fixation pH on the ultrastructure of soybean protein bodies

Cotyledon tissues from mature soybeans were systematically prepared for transmission electron microscopy employing fixation buffer pH's of 7.2, 6.4, and 5.6. Tissue fixed at pH 7.2 showed few membrane-bound internal protein body structures. Portions of the same tissue fixed at pH 6.4 revealed numerous membrane-bound crystalloid structures and stacks of membranous sacks. Tissue prepared at pH 5.6 also contained numerous membrane-bound crystalloid structures and examples of membrane-bound globoid structures. This is the first investigation to document the effect of fixation pH on the subcellular structure of soybean protein bodies and the first to show membrane-bound crystalloid or globoid structures in soybeans.