Improving quantitative flowering models through a better understanding of the phases of photoperiod sensitivity.

A quantitative understanding of the phases of sensitivity to photo-thermal environment is important if the accuracy of flowering models is to be improved and if the timing of long and short day treatments in protected cropping is to be optimized. A simple method of quantifying the duration of the phases of sensitivity to photoperiod is through the use of reciprocal transfer experiments where plants are transferred between long and short days at regular intervals throughout development. The advantages and disadvantages of different analytical approaches used to analyse such data sets are examined. Inconsistencies between the approaches are highlighted, as are differences in the way authors have interpreted data. The problem of confounding the effects of photoperiod and light integral is considered, as is the need to separate the number of inductive cycles needed for flower commitment from the length of the juvenile phase. The effects of photo-thermal environment on the duration of these phases of photoperiod sensitivity are discussed, together with topics requiring further development.