Figure 2.

A simplified outline of the circadian system of Populus showing inputs, central clock (oscillator) and outputs. The clock ensures that growth and other processes are synchronized with the local environment, time of day and season. LHY1, LHY2 and TOC1 are core components of the oscillator whose functions are complemented by additional elements. Cell proliferation is controlled by the morning clock components LHY1 and LHY2 via cytokinin biosynthesis and CYCLIN D3; auxin is regulated in the evening. EBI1a and/or EBI1b are likely to act at night, restricting LHY1 and LHY2 expression. Arrows show positive effects; bars show negative effects. Black text and lines show pathways with experimental support; grey text and lines show tentative pathways.