Any process that stops, prevents or reduces the frequency, rate or extent of photosynthesis. [ http://www.ncbi.nlm.nih.gov/pubmed/7592491 http://purl.obolibrary.org/obo/go/references/0000058 GOC:TermGenie ]
Synonyms: downregulation of photosynthesis down-regulation of photosynthesis down regulation of photosynthesis