CHANGES IN THE ELEMENT COMPOSITION OF GLOBOIDS FROM CUCURBITA-MAXIMA AND CUCURBITA-ANDREANA COTYLEDONS DURING EARLY SEEDLING GROWTH

Energy dispersive X-ray analysis was used to study the element composi tion of globoids from the cotyledons of Cucurbita maxima and Cucurbita andreana seeds and seedlings at various stages of growth. The influen ce of light and mineral nutrient conditions on changes in globoid comp osition was also investigated. The element composition of globoids cha nged markedly during early seedling growth. In both species, regardles s of light and mineral nutrient conditions, K decreased markedly, Mg, Ca, Fe, Mn, and Zn generally increased, and P remained relatively cons tant. There were differences in globoid composition changes between th e two species that could be attributed, at least in part, to differenc es in the Ca content of the mature, dry embryos. In C. andreana, which had a higher initial Ca content, there was a large increase in the Ca content of the globoids during seedling growth and no significant inc rease in Mn. In C. maxima globoids, there was only a slight increase i n Ca, but there was a much larger increase in Fe, Zn, and Mn than occu rred in C. andreana. Light conditions alone did not have a significant influence on the changes in globoid composition. Light, in combinatio n with mineral nutrients, resulted in a more rapid degradation of glob oids in the later stages of growth. Mineral nutrient conditions affect ed mostly elements that were initially present in large amounts. There were very large, globoid-like particles present in some later stage s amples of both species, from each of the different growth conditions. These particles had element compositions that were consistent with the ir being composed of phytate.