Abstract

Luminosity and temperature are factors that directly act in photosynthetic process, in which the elevation of the light intensity may provoke reduction in the assimilation of carbon, impairing the development of the soybean culture. This work aimed to know physiological parameters of soybean (Glycine max L. Merr.) under different intensities of artificial light. The experiment was carried out in randomized blocks, in a factorial scheme 2 × 5, being two soybean cultivars (Potência and NS6700) and five densities of light: 0 (control), 500, 1000, 1500 and 2000 μmol m^-2 s^-1 of photosynthetically active radiation (PAR) provided by LED bulbs, with 4 repetitions, in total of 40 plots. The following variables were set: rate of CO₂ assimilation (A), transpiration (E), stomatal conductance (gs), inner CO₂ concentration in the substomatic chamber (Ci) and water use efficiency (WUE) in which a portable device of gas exchange was used (Infra-Red Gas Analyzer-IRGA, marca ADC BioScientific Ltd, modelo LC-Pro). Seedlings of soybean positively responded under different intensities of artificial light till reach the maximum saturation point between 1400 and 1600 µmol m^-1 s^-1 of light, which promoted a better rate of A, Ci andWUE. E and gs presented positive linear responses by increasing the intensity of artificial light. The ideal light intensity to the use of Infra-Red Gas Analyzer-IRGA between 1400 and 1600 µmol m^-1 s^-1 to the soybean culture.

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