Physiological and agronomical responses of common bean subjected to tryptophol

With the increasing global demand for food, fuel and fibre, the use of plant growth regulators in agriculture has become an agricultural practice aimed to improve physiological and productive responses. Our work aimed to evaluate the effect of tryptophol (Tol), a precursor of auxin, on common bean (Phaseolus vulgaris L.). The experiment was conducted in pots under greenhouse conditions, where we evaluated the Tol effect on bean crop under two different application forms: T-Soil-soil application of Tol (4.10(-4) mg L-1) and T-Leaf-leaf tryptophol application (4.10(-4) mg L-1), plus a reference treatment (0 mg L-1 of Tol). We analysed the variables: shoot fresh and dry matter; root dry matter, area and volume; leaf macro and micronutrients; CO2 net assimilation rate (A); stomatal conductance (g(S)); internal CO2 concentration (C-I); foliar transpiration (E); photosynthetic pigment content and some crop production attributes. The application of Tol through the foliar pathway proved to be more advantageous because it improved the shoot fresh and dry matter, increased the root volume and area, favoured less foliar transpiration and improved the length of pods, while the application of Tol in soil induced higher nitrogen accumulation in leaves. Our observations allow the characterization of Tol as a bioactive metabolite, suggesting an important potential for use in agricultural systems.