A membrane-bound organelle and the site of photosynthesis. Most diatom plastids appear golden brown due to carotenoid pigments (beta-carotene, diatoxanthin, diadinoxanthin, fucoxanthin), which mask the color of the chlorophyll molecules (chlorophylls a, c2, and c1 or c3)
chromatophore
an older term, often used more in European literature
chloroplast
while plastid includes non-photosynthic plastids, a chloroplast has chlorophyll and, therefore, is photosynthetic