Gradual vs rapid losses in PSII maximum quantum yield

A negative relationship between the Fv/Fm breakpoint temperature, T5 and decline width was observed (R2 = 0.68 p =0.02) (Figure 4A). Moreover, species that sustain QYmax levels to a high breakpoint temperature show sudden and steeper QY decline with a narrow DW . Conversely, in cases where the QY decline started at lower temperatures, the decline was gradual (widerDW ). A. guianensis and H. courbaril showed the highest seasonal variation in DW compared to other species and showed similar response over both seasons. C. echinocarpus showed the lowest T5 and widest DW . To further expand this analysis, we also included an as yet unpublished dataset for four evergreen species from a Cerradão (savannah forest) about 50 km from our study site and data from three Panamanian tropical forest species (Slot et al., 2018). The results from this additional analysis (Figure 4B) showed a similar negative relationship betweenT5 and decline width (R2 = 0.96p <0.001) consistent with results from our dataset.Calophyllum inophyllum and Inga spectabilis from Panama, showed similar response to A. guianensis in our measurement with much narrower DW; A. guianensis however, remained the species with highest T5 in our combined analysis.