Seaweeds are very rich in inoriganic and vitamins, this being one of the characteristics, in comparison to other vegetables in general. Although many analytical reports have involved the quantities of the inorganic constituents, little is known about their distribution in the tangle tissues and the effects of cooking on the changes in the constituents. The purpose of the present study is to investigate the softening mechanisms of the tangle and changes in the nutritive value during cooking. Fresh tangles Laminaria japonica Areschoug of the second year were used, and the distribution and changes in inorganic constituents in the tissues before and after cooking were observed by an energy dispersive X-ray microanalytical electron microscope. Results are summarized as follows:
1. Inorganic constituents of the tangle leaves were mainly C1, K, Na, Ca, Mg and P, and a trace of Fe, Zn and Cu.
2. The quantities of inorganic constituents were varied among the tangles from different districts.
3. Chloride ions were mostly distributed at the center part of the leaf; potassium at the leaf apex; and phosphorus, sulfur and calcium at the basal part of the leaf around the growth points.
4. Main constituents of the leaf cooked in water were potassium, chloride and sodium, and in the cell wall calcium and potassium.