Application of the thermal death time model in predicting thermal damage accumulation in plants.

The thermal death time (TDT) model suggests that the duration for which an organism can tolerate thermal stress decreases exponentially as the intensity of the temperature becomes more extreme. This model has been used to predict damage accumulation in ectothermic animals and plants under fluctuating thermal conditions. However, the critical assumption of the TDT model, which is additive damage accumulation, remains unverified for plants. We assessed thermal damage in Thymus vulgaris under different heat and cold treatments, and used TDT models to predict time to thermal failure of PSII. Additionally, thermal tolerance estimates from previous studies were used to create TDT models to assess the applicability of this framework in plants. We show that thermal damage is additive between 44 °C and 47 °C and between -6.5 °C and -8 °C, and that the TDT model can predict damage accumulation at both temperature extremes. Data from previous studies indicate a broad applicability of this approach across plant species and traits. The TDT framework reveals a thermal tolerance landscape describing the relationship between exposure duration, stress intensity, and percentage damage accumulation. The extreme thermal sensitivity of plants emphasizes that even a 1 °C increase in future extreme temperatures could impact their mortality and distribution.