Location of reserves of mineral elements in seed protein bodies: macadamia nut, walnut, and hazel nut

Abstract

This paper presents the results of thin-section, freeze-fracture, energy dispersive x-ray (EDX) analysis, and chemical analysis studies of cotyledon tissue from dry seeds of macadamia nut (Macadamia integrifolia), walnut (Juglans regia), and hazel nut (Corylus avellana). Studies concentrated on mineral elements in the storage protein bodies. Protein bodies of macadamia nut contained no protein crystalloids but did contain some globoid crystals. Aqueous fixation of macadamia tissue appeared to result in a rapid solubilization of proteinaceous matrix material. EDX analysis of macadamia nut globoid crystals revealed the presence of P, K, and Mg in most cases but the occasional crystal was very high in calcium. Walnut protein bodies often contained many large protein crystalloids. Globoid crystals were present between the protein crystalloids and in the proteinaceous matrix. EDX analysis indicated the presence of P, K, and Mg as the main elements in walnut globoid crystals. Hazel nut protein bodies contained one or more small protein crystalloids, globoid crystals of various sizes, and proteinaceous matrix. Some protein bodies contained druse crystals. EDX analysis showed that the druse crystals were rich in calcium and thus are presumably calcium oxalate. EDX analysis of globoid crystals revealed the presence of elements consistent with the phytin-rich nature of globoid crystals. Variations in globoid crystal composition are discussed.