The seeds of Cucwubit maximas contain protein bodies with electrondense globoid crystals. Because of their density globoid crystals are ideal material for energy-dispersive x-ray (EDX) analysis studies of elemental composition. Fixation trials were carried out to test globoid crystal extraction during glutaraldehyde fixation, water washing, and ethanol dehydration. Glutaraldehyde fixation without subsequent washing or dehydration alone produced no significant changes in elemental composition of cotyledon globold crystals. If glutaraldebyde fixation was followed by water washes or ethanol debydration there was some loss of the major globoid crystal elements but the relative percentages of the elements P, K, Ca, and Mg remained relatively unchanged. In this paper results of a study of the P, K, Mg, and Ca content of globold crystals in different tissues of squash embryos are presented. The globoid crystals in the radicle were found to be the least dense in the embryo. Globoid crystals from all embryo regions contained P, K, and Mg. In the various embryo regions P and Mg maintained relatively constant proportions of the globoid crystal composition while K and Ca varied. Of particular significance is the distribution of Ca which is generaly an immobile element. Calcium was found in highest amounts in the globoid crystals of the radicle and stem regions while globoid crystals in much of the cotyledon contained little, if any, Ca. The Ca storage thus seems to be spatially arranged in a manner that would aid early growth of the root-shoot axis.In order for us to understand the nutritional state GLOBOID CRYSTAL COMPOSITION tained from a single fruit grown at CSIRO, Adelaide, South Australia.Two seeds of similar size from the Stoke's seed supply (seeds I and 2) and two seeds from a fruit grown at CSIRO (seeds 3 and 4) were selected for EDX2 analysis. The seed coats were removed and tissue was sampled from the radicle, stem, cotyledon base, cotyledon center, cotyledon side, and cotyledon tip of each seed. Since the embryo axis of squash is very short, the stem sample was selected as the portion of the axis to which the cotyledons were attached. The cotyledon base sample was that portion of the cotyledon immediately adjacent to the cotyledonary node. A 3-mm2 region at the center of the cotyledon was used as the cotyledon center sample. The cotyledon side sample came from a region (2 x 5 mm) at the edge of the cotyledon, midway between the cotyledon base and the cotyledon tip. For the cotyledon tip sample a 2-mm2 region of tissue was taken from the edge of the cotyledon in the region furthest removed from the cotyledonary node.Tissues from the cotyledon and stem regions were sliced 0.5 to 1 mm thick prior to fixation. The samples were prepared for EDX analysis according to the method of Lott (11). Tissues from the dry seeds were fixed in 5% glutaraldehyde in distilled H20, dehydrated, infiltrated with Spurr's low viscosity epoxy resin, and polymerized. Sections, 150 to 170 nm thick, were mounted on copper grids ha...

Elemental composition and distribution of the mineral reserves in the endosperm and embryo tissues of Ricuis commwus cultivars Hale and Zanzibarensis were investigated. Energy dispersive x-ray analysis was used to determine the elemental composition of the globoid crystals, while atomic absorption spectrometry allowed quantification of the elements, particularly Ca, in various seed regions. No major differences were found between the two cultivars with regard to the elemental distribution in globoid crystals. While the majority of globoid crystals contained P, K, and Mg, the occasional one also contained Ca. In extremely rare instances, Fe was detected in globoid crystals. Ca-containing (2,4,8,9,12,15,22). The protein bodies of castor bean endosperm have been studied previously (18,23,26)

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Previous energy-dispersive x-ray analysis studies of globoid crystal composition in seed protein bodies gave an indication that there might be a correlation between seed size and the type of elements stored in globoid crystals. This possibility was tested by conducting energy-dispersive x-ray analysis studies of P, K, Mg, and Ca levels in gioboid crystals of four embryo regions (radicle, stem, cotyledon center palisade mesophyll, cotyledon center spongy mesophyli) in each of five different Cucurbita species (C. mixts, C. mschats, C. foeddissim, C. pepo, and C.). The species were chosen to provide a range of seed size and weight. Globoid crystals from all embryo regions in all five species contained P, K, and Mg.Some variations in the levels of these elements did occur but there was no consistent pattern with regard to area of the seed or with regard to seed size. Calcium distribution showed significant variations. In species with large seeds (C. mrita, C. mosehata) Ca was mainly found in globoid crystals in the radicle. Globoid crystals in species with small seeds (C. foetidissima, C. pepo, C.) contained Ca in all embryo regions tested. The results of this study support the concept that Ca distribution in globoid crystals can be correlated with seed weight.The protein bodies in seeds of most plant species contain mineral reserves in addition to proteins. These mineral reserves are generally thought to occur mainly as phytin, a cation (K, Mg, Ca) salt of inositol hexaphosphoric acid (see review in 6). In many species the phytin reserves are concentrated into electron-dense regions called globoid crystals (6,9,10,12). The bulk of a seed's available reserves of several important macronutrients are thus found in globoid crystals inside protein bodies.Lott et al. (8) carried out the first studies in which elemental composition of globoid crystals from different parts of a dicot embryo was studied with energy-dispersive x-ray analysis. Globoid crystals from all embryo regions of Cucurbita maxima were found to contain P, K, and Mg. The distribution of Ca was of particular interest since there was a definite spatial arrangement.Globoid crystals of the radicle and stem regions contained considerable Ca while globoid crystals in much of the cotyledon contained little, if any, Ca.Globoid crystals of protein bodies in the main storage organ of various oil seeds have been studied with EDX2 analysis (2, 3, 6, 7). Lott and Buttrose (6) observed that where Ca distribution was concerned there seemed to be an effect not only due to area of the embryo in question but also due to seed size. Globoid crystals from large cotyledons (sunflower, cashew, pistachio, walnut, hazel nut, jojoba) were found to contain either no Ca or only traces of

Protein bodies in seeds are important for seedling growth because they provide necessary nitrogenous compounds. It is often overlooked that protein bodies also function as the subcellular location of much of a seed's reserves of macronutrients such as P, K, Ca, and Mg. Structural investigations of storage tissue from several cucurbit seeds have revealed that protein bodies often consist of proteinaceous matrix, protein crystalloid, soft globoid, and globoid crystal regions (2, 8, 9). The protein reserves are thought to be located primarily in the proteinaceous matrix and protein crystalloid regions. The mineral reserves usually occur in the electron-dense globoid crystals and are generally considered to be largely phytin, a cation (K, Mg, Ca) salt of inositol hexaphosphoric acid (3,4,(11)(12)(13).Recently, Lott et al. (7) published results of an energy-dispersive x-ray analysis study of globoid crystal composition in 10 different regions of Cucurbita maxima embryos. Although P, K, and Mg were commonly found in globoid crystals in all squash embryo regions, the Ca distribution showed definite differences between embryo regions. Ca was common in globoid crystals of the radicle and stem regions. In the cotyledon, Ca levels were on average much lower than those of the root-shoot regions. Most globoid crystals from spongy or palisade mesophyll cells lacked any detectable Ca. The bulk of the Ca values for the cotyledon samples thus came from a fraction of the globoid crystals present. In this paper we report the results of EDX2 analysis studies designed to discover where globoid crystals with relatively high Ca levels are located within Cucurbita cotyledons.