Dynamics of Photosynthate Loading in Strawberries Affected by Light Condition on Source Leaves

In greenhouse production of strawberries (Fragaria×ananassa×Duch.) during winter season in Japan, unsuitable climate condition (low solar radiation, low temperature, etc.) for strawberry growth causes serious problems such as yield depression and low quality of fruits. For sustainable production with high profitability, it is keenly desired to establish a system for efficient environmental control based on physiological functions of crops. Translocation of photosynthate from leaves to fruits is a major physiological determinant for size and sugar content of strawberries. It is therefore essential to clarify the response of photosynthate loading to surrounding environment. In this study, we focused on light condition which strongly influences the photosynthesis, and analyzed effects of irradiation on dynamics of photosynthate loading. Furthermore, aiming at the estimation of dynamics of photostnthate loading in cultivation field, we simulated daily amount of photosynthate loading by kinetic model using a saturable Michaelis-Menten component in combination with an unsaturable component obeying first-order kinetics.