Starch and the clock: the dark side of plant productivity

Efforts to improve photosynthetic efficiency should result in increased rates of carbon assimilation in crop plants in the next few decades. Translation of increased assimilation into higher productivity will require a greater understanding of the relationship between assimilation and growth. In this review, we discuss new progress in understanding how carbon is provided for metabolism and growth at night. In Arabidopsis leaves, the circadian clock controls the rate of degradation of starch to ensure an optimal carbon supply and hence continued growth during the night. These discoveries shed new light on the integration of carbon assimilation and growth over the light–dark cycle. They reveal the importance of considering the carbon economy of the whole plant in attempting to increase crop productivity.