Photosynthate translocation from leaves to fruits is an important determinant of crop yield and quality. In protected cultivation, environmental control based on photosynthate translocation is indicative for realising high-yield and high-quality production. However, there are few studies on the environmental response of photosynthate translocation. In this study, we focused on light intensity as a key environmental factor to steer translocation. We fed ¹¹CO₂ to a leaf of strawberry plant (Fragaria × ananassa Duch.) and analysed real-time dynamics in ¹¹C-labeled photosynthate translocation from a ¹¹CO₂-fed leaf to individual fruits on an inflorescence of intact plants by using positron emission tomography (PET) under different light intensities (50, 100, 200 and 400 μmol m^-2 s^-1). A poor relationship was obtained between ¹¹C-photosynthate translocation and light intensity according to the results that ¹¹C-photosynthate translocation rates into the fruits was highest under the light intensity of 100 μmol m^-2 s^-1 followed by those of 200, 400 and 50 μmol m^-2 s^-1. On the other hand, there was a strong negative correlation between transpiration rate of the ¹¹C-fed leaf and ¹¹C-photosynthate translocation rate. These novel findings indicate that transpiration, which controls the leaf moisture status, is one of the main drivers for photosynthate translocation towards fruits.