a photosystem is an organized aggregation of photosynthetic pigments, electron carriers and ions in thylakoid membrane as ultramicroscopic granule, concerned with entrapment of solar energy, activation of pigments, emission and transport of electrons, photolysis of water and photophosphorylation collectively constituting the light independent phase of photosynthesis. there are two types of photosystem in higher plants- photosystem I and photosystem II.
