Associated with the leaf-transpiration process, a phenomenon known as evaporative cooling occurswherebyheatis dissipated by water-vaporloss from the stomata. With lower transpiration levels, the evaporative-cooling process is significantly reduced,raising the leaf temperature (Tleaf) typically several degrees above the air tem- perature (Jones, 1999; Jones et al., 2002; Araus et al., 2008; Fuentes et al., 2012). These relationships establish the basis monitoring the crop–water based on leaf/canopy temperature, since any situation that causes a partial closing of the stomata (for example by a more or less prolonged water-stress situation) will result in a significant rise in leaf temperature. Therefore, Tleaf can be used as an indica- tor of the degree water stress with the advantage that it can be remotely measured and in plants of different sizes under field as well as controlled conditions.