Expression of circaseptan and circannual rhythmicity in the imbibition of dry stored bean seeds.

Water uptake of seeds of Phaseolus vulgaris L. cv Limburg was monitored in a controlled atmosphere every day at solar noon for a period of 2 years. The imbibition rate, determined as the mean of five replicas, was related to the lunar cycle, maximal water uptake occurring between the new phases of the cycle. The monthly mean value of imbibition rate, calculated from the daily measurements, displayed a circannual rhythm reaching maximal values in August-September and minimal values in February-March. These monthly values were positively correlated with the mean of the maximal temperatures recorded daily outside.