Definition of photosystem
: either of two photochemical reaction centers consisting chiefly of photosynthetic pigments complexed with protein and occurring in chloroplasts: a : one that absorbs light with a wavelength of about 700 nanometers —called also photosystem I b : one that absorbs light with a wavelength of about 680 nanometers —called also photosystem II
First Known Use of photosystem
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