Sieve-Element Characters of the Proteaceae and Elaeagnaceae: Nuclear Crystals,Phloem Proteins and Sieve-Element Plastids

The sieve-element characters of 34 species from the Proteaceae and Elaeagnaceae have been studied by transmission electron microscopy. While nondispersive protein bodies and dispersive P-protein are typical components of both families, specific forms and/or their distinctive origin accentuate some taxa. Within the Grevilloideae, subfamily of Proteaceae, a number of Australian species and genera contain protein crystals of nuclear origin arranged into rosette-like bodies, while in the other members studied from the same subfamily no nondispersive protein bodies were found. Several Australian and South African genera of the Proteoideae contain compound-spherical nondispersive protein bodies that reside in the cytoplasm from their very beginning. In the Elaeagnaceae three different P-protein bodies are present of which one is tubular and dispersing, another is nondispersive and of irregular-stellate form, and a third is globular (resembling a P-protein from Cucurbita). The great majority of the species studied from the Proteaceae contains form-Ss sieve-element plastids, Lomatia ilicifolia and Macadamia ternifolia are distinct in having form-Pcs plastids. The average diameter of stem sieve-element plastids in the family is 1.38 μm. The Elaeagnaceae (three species investigated) is a pure form-So family (average diameter: 0.8 μm). There are no specific sieve-element characters that would support any relationship between the Proteaceae and Elaeagnaceae. While affinities of the former to pre-Gondwanan parts of the Rosanae/Myrtanae are discussed, a reconsideration of the Elaeagnaceae as a possible member of the Violanae (identical features with Cucurbitaceae) is proposed.