Do plastids inDendrobiumcv. Lucky Duan petals function similar to autophagosomes and autolysosomes?

Ultrastructure of autophagy in plant cells

“…Preliminary evidence was found for complete degradation of the cytoplasmic material inside the plastids. 78 In many plastids the (granular) structure of the contents of the intraplastidial space is very similar to the cytoplasm, whereas in other plastids the intraplastidial spaces show lower electron density than the cytoplasm, but still a granular structure. In still other plastids the intraplastidial space has a uniform (nongranular) structure either with low electron density or completely translucent.…”

“…74 In Dendrobium petal cells the opening of the plastid interior to the cytoplasm is approximately circular and less than 0.2 μm in diameter, which is small compared with the size of the plastid. 78 It is not yet known whether this opening closes. Preliminary evidence was found for complete degradation of the cytoplasmic material inside the plastids.…”

“…[75][76][77][78] According to the interpretion of Ragetli et al 74 their data showed chloroplasts sending out a protrusion that swirls around a portion of the cytoplasm, then encloses this cytoplasmic portion as it merges with the main plastid body again. An alternative interpretation suggested that the two outer membranes of the plastids invaginate (move inwards), thereby forming a space inside the plastid that is contiguous with the cytoplasm.…”

“…In still other plastids the intraplastidial space has a uniform (nongranular) structure either with low electron density or completely translucent. 78 These differences in structure suggested a series of increasing states of degradation. These data have been interpreted to indicate autophagy by plastids, but more work is required to substantiate this idea.…”

“…While this invagination occurs, a portion of the cytoplasm moves into the plastid interior. 78 Whatever the correct interpretation, structures in the sequestered portion of the cytoplasm included at least ribosomes, membranes, and vesicles 74,78 and possibly also mitochondria. 74 In Dendrobium petal cells the opening of the plastid interior to the cytoplasm is approximately circular and less than 0.2 μm in diameter, which is small compared with the size of the plastid.…”