ISHS Acta Horticulturae 718: III International Symposium on Models for Plant Growth, Environmental Control and Farm Management in Protected Cultivation (HortiModel 2006)
THE PHYSIOLOGY OF FLOWERING: QUANTIFYING THE EFFECTS OF PHOTO-THERMAL ENVIRONMENT |
| Author: | S.R. Adams |
| Keywords: | modelling, temperature, photoperiod, light integral, reciprocal transfer, phases, temperature integration |
| Abstract:
This paper reviews approaches taken to modelling time to flowering and assesses some of the underlying assumptions that are often made. A popular approach is to describe the effects of temperature, photoperiod and light integral as linearly related to the rate of progress to flowering (the reciprocal of the number of days to flower). This approach can easily incorporate both sub- and supra-optimal temperatures and critical and ceiling photoperiods and can be modified to include interactions where appropriate. Other workers have concentrated on modelling temperature x photoperiod interactions using a range of mathematical functions. Temperature averaging is discussed as this is becoming an increasingly important part of energy saving strategies in greenhouse production. Depending on the way in which temperatures are averaged and models are fitted, plants are often assumed to respond to either the average or instantaneous temperature. Neither assumption would appear to be entirely correct when plants are exposed to both sub- and supra-optimal regimes. Furthermore, most models ignore the different phases of flowering. Plants have distinct developmental phases and hence show changes in their sensitivity to environmental stimuli. Many plants are photoperiodic but yet are insensitive to daylength when juvenile and during the latter stages of flower development. Reciprocal transfer experiments provide a means of quantifying the phases of photoperiod sensitivity and an analytical approach to analyse such data sets is described. | |
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