Analysis of reciprocal-transfer experiments to estimate the length of phases having different responses to temperature.

BACKGROUND AND AIMS

The responsiveness of plant ontogeny to temperature may change with plant age. These changes may best be identified by experiments in which individual plants are transferred in a time series from low temperature (LT) to high temperature (HT), and vice versa. Any change in the value of the slope for a plot of the duration taken to complete a developmental phase against time of transfer (either LT to HT or HT to LT) will indicate a change in the temperature responsiveness of development, and the time at which this change occurs. The analysis of this type of reciprocal-transfer experiment is usually performed by regression for each of the visually identified linear sub-phases, separately for the data for LT-to-HT and for HT-to-LT transfers. Here, a mathematical approach is presented using a single curve-fitting procedure.

METHODS

Both LT-to-HT and HT-to-LT transfers are combined in a single curve-fitting procedure. This new, combined approach is illustrated using a published data set for three rice (Oryza sativa) cultivars, where the pre-flowering duration is divided into three sub-phases, and temperature responsiveness is generally stronger during the second than the first and third sub-phases.

RESULTS AND CONCLUSIONS

This new model approach provides an objective method, relative to the separate analyses, for assigning data points to a particular sub-phase. Plausible parameter values can be obtained from capturing the whole data of both sets of transfers, which otherwise could not be obtained from the separate-analysis method. Furthermore, the length of sub-phases identified from the LT-to-HT transfers is consistent, in terms of its response to temperature, with that identified from the HT-to-LT transfers. Re-analysis of the published rice data using the new approach reveals that in addition to temperature sensitivity, the optimum temperature of pre-flowering development may vary with plant age. The new approach gives rise to a generalized model for the analysis of reciprocal transfer experiments to quantify age-dependent changes of response of plants (and potentially insects) to any environmental variables that have a significant impact on their development.