In arid and semi-arid lands one of the factors that limits pecan trees production is the low water availability. Regardless its low quality caused by salinity. In pecan orchards management has been observed increment of ions (carbonates, bicarbonates, chlorides and sodium). The effects knowledge of NaCl on photosynthesis and stomata conductance are important to identify tolerance levels of pecans to NaCl. The aim of this study was to evaluate the photosynthesis and stoma conductance on pecan seedlings subjected to different concentrations of NaCl. This study was carried out in an experimental greenhouse of the URUZA-UACh, (25º North Latutude and 103º West Longitude and 1,115m) where 60 gavels with pecan seedless were settled. A complete random design with different NaCl treatments (0, 750, 1000 and 1250 ppm) was established. The study included 10 evaluations with an infrared gas analyzer device (IRGA-6400, Li-COR Inc.). of photosynthesis (μmol CO2 m-2 s-1)and stoma conductance (mol H2O m-2 s-1). Plant high, trunk diameter and number of leaves plant were also recorded. Photosynthetic activity within treatments varied due possibly to different response capacities because pecans seedlings. Photosynthesis decreased significantly (P

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