Sieve-tube plastids and plastid filaments of caryophyllales

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Abstract
Comparative investigations of 20 Centrospermae from 12 families revealed that a plastid with an electron-dense core and/or annular plastid filaments is typical for Caryophyllales. When the plastid membrane breaks down — it is most probable that this takes place artificially during the process of preparation and fixation — the plastid inclusions (core and annulus) disintegrate and in a whirl set free numerous 40–60 Å wide filaments. These so-called plastid filaments spread over the sieve-tube lumen and through the sieve pores, but they always remain discernable from the plasmatic filaments of the sieve tubes. There is a theory on how the somewhat different inclusions of various species could have been differentiated in an ontogenetic and phylogenetic process. Sieve-tube plastids of Polygonum and Rumex (Polygonales) and of Plumbago have no plastid filaments. They contain starch.