|The day/night cycle of light and darkness make a predictable event, which plants and other organisms have developed means to anticipate. To be able to synchronise life processes with the environment, an endogenous, biological clock drives the rhythmic regulation of many plant processes. The same clock controls crucial seasonal events, such as flowering, dormancy and tuber formation via the measurement of day length. By using the latest technology, we aim to deepen the knowledge of the light regulation of the clock by studies of the light receptor phytochrome B. We will also identify and characterise new genes coding for proteins that restrict the timing of the clock to keep a 24-hour cycle. This will be obtained by the identification and characterisation of mutants impaired in this function. The results from the proposed project will ultimately be applicable in agriculture and forestry by enabling means to extend the geographic range of crops. At present many crops are geographically restricted since their growth are adapted to their local environmental conditions. The means to genetically adapt crops to other environmental conditions by resetting their clock functions will bring a larger diversity of crops. This would profit farmers, since they would find new produce, and consumers would have a greater choice of locally grown varieties. Increased diversification would also give means for a more sustainable agricultural practise.