Photosynthetic heat tolerances and extreme leaf temperatures

Photosynthetic heat tolerances (PHTs) have several potential applications including predicting which species will be most vulnerable to climate change. Given that plants exhibit unique thermoregulatory traits that influence leaf temperatures and decouple them from ambient air temperatures, we hypothesized that PHTs should be correlated with extreme leaf temperatures as opposed to air temperatures.
We measured leaf thermoregulatory traits, maximum leaf temperatures (TMO) and two metrics of PHTs (Tcrit and T50) quantified using the quantum yfield of photosystem II for 19 plant species growing in Fairchild Tropical Botanic Garden (Coral Gables, FL, USA). Thermoregulatory traits measured at the Garden and microenvironmental variables were used to parameterize a leaf energy balance model that estimated maximum in situ leaf temperatures (TMIS) across the geographic distributions of 13 species.

T MO and TMIS were positively correlated with T50 but were not correlated with Tcrit. The br...