IPA: /ˌfoʊtəʊbaɪəˈlɒdʒɪkəl/
KK: /foʊtoʊbaɪˈoʊlədʒɪkəl/
Relating to the study of how light affects living organisms.
The photobiological effects of sunlight on plants are crucial for their growth.
Photobiological → It is formed from "photo-" (from Greek "phōs", meaning light) and "biological" (from Greek "bios", meaning life, and "logia", meaning study). The word refers to the study of life processes that are influenced by light.
Think of 'light' ('photo-') affecting 'life' ('biological') — that's what photobiological means.