This study was carried out in a commercial orchard of papaya in the Savanna region of Bahia state where there are two distinct seasons: dry season, from May to September and a rainy one from October to March. Two genotypes, one from 'Solo' group (Sunrise Solo) and another from 'Formosa' group (Tainung 01) were used. Net CO2 assimilation rate (A), stomatal conductance (g s), instantaneous transpiration (E), air temperature inside the chamber (Tar) and photosynthetic photon flux density (PPFD) were measured at one hour interval in a fully expanded sun-exposed leaves in two season, one characterized as dry season (July and September) and another one as rainy season (November and January). Intrinsic water use efficiency (IWUE) was calculated using A and g s (A/g s). In both genotypes, the reduced g s due to high VPD in July and September contributed to reduce A. The behavior was similar in the two studied genotypes. In the dry season, reduced g s triggered a higher IWUE.
photosynthesis; stomatal conductance; photosynthetic photon flux density; vapor pressure deficit
