They do even synthesize some more amino acids. We will meet several of them in the following sections. Some of these intermediates are starting points of amino acid biosynthetic pathways.
Plants take up nitrogen as nitrate, in smaller amounts also as ammonium ions.
A few species, mainly of the leguminosa family, live in symbiosis with nitrogen-fixing bacteria that are able to reduce atmospheric nitrogen. In the second step is nitrite reduced to ammonium by nitrite reductase, an enzyme that is located in plastids. Each type of plastid has its own assimilatory nitrite reductase. In photosynthetic tissues functions reduced ferredoxin as the electron donor that is produced in photosynthesis. The reactions are part of an electron transport chain that involves both NADP and FAD .