Gas exchange in bacurizeiro (Platonia insignis Mart.) genotypes in the dry and rainy seasons in the Middle North region of Brazil

The bacurizeiro (Platonia insignis Mart.) is a species of great economic and social importance in the North and Middle North regions of Brazil. However, little is known about the environmental effects on its physiological characteristics. The objective of this work was to determine the gas exchange of genotypes of bacurizeiro in the dry and rainy seasons in the Middle North region of Brazil. The experiment was conducted in the Embrapa Meio Norte experimental field, located in Teresina-Piauí. A completely randomized design in a 7x2 factorial scheme was used, with seven genotypes and two seasons (dry and rainy), with three replications. The genotypes were M1MP14p12f1, M1MP14p13f1, M2PP2p18f5, M3MP6p14f1, M3MP6p15f1, M4MP6p7f4 and M7PP5p18f3 from the improvement program of Embrapa Meio Norte. Liquid photosynthesis, stomatal conductance, transpiration and internal CO2 concentration, ratio between internal CO2 concentration and ambient CO2 concentration, intrinsic water use efficiency and instant water use efficiency were evaluated. The environmental variation affects the plasticity of the bacurizeiro genotypes. There is less efficiency in the use of water in the dry period in all genotypes of bacurizeiro, with values between 1.20 and 1.55 µmol CO2 m-2 s-1 / µmol H2O m-2 s-1, respectively. The genotypes M1MP14p13f1, M2PP2p18f5 and M7PP5p18f3 are the most stable in the face of environmental variations, since in both seasons they are in the same formed groups