Abstract - Foliar water uptake by plants has been found to occur in several biomes where drought or cloud cover are frequent, but not for tropical rainforest. The absorption of water through leaves, by bypassing the principal plant hydraulic network, enables plants to scavenge water from minor precipitation events. This may temporarily alleviate the water stress caused by low soil moisture, hydraulic resistance in the xylem and the effect of gravity on the water column. In doing so, this phenomenon may play an important role in determining the response of plants to a drying climate or to climatic extremes. I am going to present data indicating this effect in six hyper-dominant genera in the Amazon, and examine a first approximation of the magnitude of this phenomenon at the canopy scale. The measurements and calculations suggest that the night-time input of dew in the dry season typically ‘pays’ for the first hour of transpiration in Manilkara bidentata, raising the possibility that conditions favourable to dew formation could substantially affect survival during drought extremes and may influence overall carbon exchange. I will compare these results to recent data collected in Australian rainforest (Daintree) and discuss the implications.