Dynamics of carbon export from leaves as translocation affected by the coordination of carbohydrate availability in field strawberry

Abstract

Carbon export from leaves as translocation is a result of plant coordination of leaf carbohydrate availability. Carbohydrate availability coordination is actively studied in model plants (Arabidopsis) under regulated conditions and can be optimized to increase productivity. However, in horticultural crops grown under field conditions, carbon export dynamics and coordination are poorly understood. The objective of this study was to analyze the dynamics of carbon export from leaves and the effects of carbohydrate availability coordination on these dynamics in strawberry grown under field conditions. Through three different day/night cycles, we measured leaf carbohydrate concentrations and photosynthetic rates and evaluated the dynamics of carbon export based on the leaf carbon balance. During the daytime, when carbon resources are almost entirely supplied by photosynthesis, strawberry leaves stored sucrose and starch. Starch synthesis was remarkable when sucrose concentration exceeded 150 mmol m−2, and the carbon export rate tended to increase. In the nighttime, when carbon resources are supplied by leaf sucrose and starch stored during the daytime, the starch concentrations decreased linearly and the carbon export rate was lower than the daytime level. These results indicate that in the daytime, the coordination of leaf carbohydrate availability for starch storage and carbon export was affected by leaf sucrose concentration, whereas, at night, it was regulated by leaf carbon storage levels at dusk rather than sucrose concentration. Thus, this study elucidates the basis of carbon export dynamics in strawberry leaves under field conditions, advancing our understanding of the role of leaf carbohydrates in translocation.