Figure 8.

Summary of the distinctive responses of carotenoid pigments during short- and long-term acclimation in avocado leaves. The schematic shoot shows the relative positions and sizes of young and mature leaves in the canopy. Relative changes in pigment pools are represented by the approximate length and direction of the vertical arrows. Horizontal arrows indicate transitions from short- to long-term acclimation. Young leaves stand out due to the reversal of the Lx cycle in the light, with small but rapid synthesis of Lx in the light and decrease in the dark. This is in marked contrast to the rapid deepoxidation of Lx in mature leaves and its very slow recovery of Lx on return to shade. De novo synthesis (de novo) increases total Lx+L and V+A+Z pools during sun acclimation, whereas pigment degradation (degrad) occurs during long-term shade acclimation. The α-C and β-C pools fluctuate in size independent of changes in the derived xanthophylls (Lx+L and V+A+Z, respectively). Young leaves show the fastest and largest absolute changes in α- and β-branch pools, but the ratios of total change in carotenoids and xanthophylls in each branch were close to 1.