Julie Beth Wood wrote:
>But then there is a botany text (Worth, Botany of Plants), that defines a
>plastid simply as an "organelle in the cells of certain groups of
>eukaryotes that is the site of such activities as food manufacture and
>storage; plastids are bounded by a double membrane."
Defining plastids as plant organelles only may have been a bit simplistic
as certain animals (hydra and corals spring to mind) sequester chloroplasts
from ingested plant material if I remember correctly. Then there are all
the photosynthetic protists (Euglena, dinoflagellates, Chlorarachnion,
chromists, etc) where the plastid was most likely acquired through secondary
endosymbiosis of another eukaryote (photosynthetic alga) and also the
plastid remnants in Plasmodium and other Apicomplexa. It is likely that all
plastids are of 'plant' origin but certainly the organelles are no longer
restricted to plants!
>However, in all my enormous experience, i've never heard the word plastid
>used to describe mitochondria. :)