Little is known about photosynthetic thermotolerance (PT) of tropical and sub-tropical wild plants and its association with leaf phenology and persistence. Zhang et al. use the temperature-dependent increase in minimum fluorescence to assess PT for a total of 24 woody species differing in leaf flushing time in a valley-type savanna in south-west China. They find that PT is positively associated with leaf life span and foliar calcium concentration but is independent of leaf mass per unit area. The current maximum leaf temperature during extreme heat stress (44.3 °C) is close to the critical temperature of photosystem II (45.2 °C), and thus future global warming may increase the risk of heat damage to the photosynthetic apparatus of these species.