Plants are highly sensitive to temperature, and appear to use temperature signals to control development in several ways. We have seen that some plants require a long period of cold (vernalization) in order to become competent to flower. Another influence of temperature is the ambient growing temperature. Plants are able to sense as little as a 1ºC difference in temperature. Among many of the plants studied, increasing ambient temperature accelerates flowering. Remarkably, climate change has already caused a significant change in the flowering times of wild plants. Flowering in response to warm temperature is dependent on the expression of FT, because in the absence of FT, ambient temperature increases do not accelerate flowering. The activation of FT by temperature is mediated by the PHYTOCHROME INTERACTING FACTOR 4 (PIF4) transcription factor. This protein binds the FT gene in a temperature-dependent manner, switching the gene on in warm temperatures.

It appears that different species have different sensitivities to ambient temperature, some plants responding very little and others much more. This has important implications for how species will adapt to climate change. It has been shown that those plants which respond to ambient temperature appear to have been able to extend their range as the climate has changed, while those plants that do not use ambient temperature as an important developmental cue have stayed put and are much more likely to go extinct. Finally, it is particularly important to remember that plants growing in the field are exposed to a wide range of signals, and predicting how they respond to this information from lab-based experiments, usually designed to minimize variables, is complex. Indeed, comparing the response of plants to warming in the laboratory with plant phenology data collected in the field has shown that plants in nature have much stronger responses to climate change than would be predicted from experimental data.