1. One of the differentiated structures in cytoplasm of plant cells where photosynthesis or other cellular processes are carried on; plasid contain DNA and are self-replicating. SYN: trophoplast. 2. One of the granules of foreign or differentiated matter, food particles, fat, waste material, chromatophores, trichocysts, etc., in cells. 3. A self-duplicating viruslike particle that multiplies within a host cell, such as κ particles in certain paramecia. [G. plastos, formed, + -id]
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plas·tid 'plas-təd n any of various cytoplasmic organelles of photosynthetic cells that serve in many cases as centers of special metabolic activities
plas·tid·i·al pla-'stid-ē-əl adj
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plas·tid (plasґtid) any of the specialized organelles in plant cells other than the nucleus and centrosome, such as chloroplasts.Medical dictionary. 2011.