Responding to the first question is not easy, as it is necessary to identify what are the main physiological changes in papaya in terms of gas-exchange measurements when this plant is subjected to deficit-irrigation regimes. Under a situation of water scarcity,many crops have a high capability of regulating leaf transpiration through stomata, reducing water loss from the plant tissues, and thereby avoiding severe plant dehydration or the total or partial embolism in the xylem vessels (Chaves et al., 2010). Because of this, there is a decline in CO2 fixation declines, and therefore sodoes the photosynthetic activity of the plant (Chaves et al., 2007).Associated with lower transpiration levels, the process of evaporative cooling diminishes, raising leaf temperatures typically several degrees above the air temperature (Fuentes et al., 2012). These relationships establish the basis for monitoring the crop–water status using thermal information, since any situation that triggers a partial closing of the stomata (for example by a water-stress situation more or less prolonged) will result in a significantly higher leaf temperature.