photomorphogenesis Syllabification: (pho·to·mor·pho·gen·e·sis)Pronunciation: /ˌfōtōˌmôrfəˈjenəsis/Definition of photomorphogenesis noun Botany development of form and structure in plants that is affected by light, other than that occurring for photosynthesis. photomorphogenesis in other Oxford dictionaries Definition of photomorphogenesis in the British & World English dictionary