Ribosomes and DNA in chloroplast
The chloroplast, having multiple circular copies of its chromosome and its own tRNA and ribosome genes more resembles the bacterial systems it is descended from.  See @A.Kennard comment 

Polysomes being found in bacteria frequently are single mRNA to which are attached multiple ribosomes.  This paper shows that chloroplast polysomes were observed in the mid 1960s by centrifugal sedimentation.