[Sieve-tube plastids and plastid filaments of caryophyllales : On the fine structure and distribution of a further specific plastid].

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.