Mineral nutrition in white spruce (Picea glauca [Moench] Voss) seeds and somatic embryos; II. EDX analysis of globoids and Fe-rich particles

The elemental compositions of globoids and Fe-rich particles were investiga ted in white spruce (Picea glauca [Moench] Voss) somatic embryos, zygotic e mbryos and female gametophytes using energy dispersive X-ray analysis. Glob oids, phytate deposits in seed protein bodies, were found throughout the fe male gametophyte of seeds and in the ground meristem and procambium from al l regions of both somatic and zygotic embryos. Iron-rich particles, believe d to be Fe-associated phytate deposits in seed proplastids, were found thro ughout the female gametophyte of seeds and in the protoderm, ground meriste m, and procambium from all regions of both somatic and zygotic embryos, Glo boids in somatic and zygotic embryos ranged from 0.5-3.0 mu m in diameter, but globoids typically ranged from 1.5-2.0 mu m in diameter in somatic embr yos and from 2.0-3.0 mu m in diameter in zygotic embryos. Globoids in femal e gametophyte tissue ranged from 0.5-6.0 mu m in diameter. All Fe-rich part icles studied from somatic embryos and from seeds ranged from 0.14-0.25 mu m in diameter. Globoids in somatic embryos and seeds contained high P, mode rate K and Mg with occasional traces of Fe and little if any Ca and Zn. Glo boids in the zygotic embryo cotyledon procambium tissue also contained mode rate levels of Fe and had significantly higher Fe:P ratios, which were not found in any other regions in seeds or in somatic embryos. Iron-rich partic les in somatic embryos and seeds contained high P and Fe, moderate K and Mg , and little if any Ca and Zn. Typically, spectra of Fe-rich particles in s omatic embryos had P peaks higher than Fe peaks and spectra of Fe-rich part icles in seeds had P peaks lower than Fe peaks. Overall, the composition of globoids and Fe-rich particles in somatic embryos and zygotic embryos were very similar with only minimal differences found. (C) 1999 Elsevier Scienc e Ireland Ltd. All rights reserved.