Biochemical assays
Leaf samples were harvested at the time points indicated, immediately frozen in liquid nitrogen, and stored at -80°C until further analysis. Extraction was performed by rapid grinding of tissue in liquid nitrogen and the immediate addition of ethanol as described in Gibon et al. (2004). Photosynthetic pigments were determined as in Porra et al. (1989). The levels of starch, sucrose, glucose, and fructose were determined exactly as described previously (Fernie et al., 2001). Malate and fumarate contents were determined as described before (Nunes-Nesi et al., 2007). Protein and amino acid contents were determined as described previously (Cross et al., 2006).