Photobiology and photosynthesis
As, photo biology is the study of effect of light on organisms, and hence relates to photosynthesis as it requires sunlight to occur. Photosynthesis is the phenomenon by which plants make their food in presence of sunlight and release energy, water and oxygen as by-product. The way plants respond to sunlight and process energy is all combined with photobiology and its related aspects and knowledge about them can explain other processes in plants relating to response with light