Iron-rich particles and globoids in embryos of seeds from phyla Coniferophyta, Cycadophyta, Gnetophyta, and Ginkgophyta: characteristics of early seed plants

Abstract

For the first time, iron-rich particles were discovered in embryo-axis tissue from dry seeds of genera in four phyla of seed-producing plants. Iron-rich particles were present in dry seeds of phyla Ginkgophyta (Ginkgo), Cycadophyta (Dioon), Gnetophyta (Ephedra), and within the Coniferophyta, representatives of the families Araucariaceae, Cephalotaxaceae, Cupressaceae, Podocarpaceae, Sciadopityaceae, and Taxaceae. These iron-rich particles were determined by energy dispersive X-ray analysis to be rich in phosphorus and iron, but generally contained considerable potassium, some magnesium, and perhaps calcium, chlorine, manganese, and (or) zinc. Transmission electron microscopy revealed that these particles were often less than 0.33 μm in diameter and were naturally electron dense. These particles differed from the globoids that were present in the same cells. Globoids were rich in phosphorus, potassium, and magnesium, but lacked high levels of iron. Globoids sometimes contained calcium and perhaps traces of iron, manganese, and zinc. Frequently, globoids were more electron-dense and more regularly spherical in shape. Iron-rich particles and globoids are apparently common features in embryos of the early seed plants.Key words: iron-rich particles in seeds, Ginkgophyta, Cycadophyta, Gnetophyta, Coniferophyta, globoids in seeds.