“…Using time-lapse imaging, two spatial waves of clock gene expression were observed in roots, one up from root tip and the other one down from hypocotyl junction, suggesting that the Arabidopsis clock has multiple coordination points [154], and a less hierarchical clock structure than that suggested from grafting experiments. Furthermore, rhythm analyses across entire seedlings demonstrated period and phase differences between organs, as the cotyledons and hypocotyl exhibited shorter periods and an earlier peak than the root, but oscillations in the root tip ran faster than the middle region of the root [160] (Figure 2). These observations are also qualitatively similar to the periods and phases previously observed in isolated organs [153,155,157], suggesting intra-organ heterogeneity in clock function.…”