Photosynthetically active radiation intensity used as an extended photoperiod to increase quality in basil seedlings

The use of a protected environment for vegetable seedling production has become one of the best alternatives to minimize the adverse micrometeorological effects of the external environment and guarantee quality and production throughout the year. Inside the protected environment, it is essential to study the physiological responses of plants to the wavelength, periodicity, intensity, and direction of light in the photosynthetic process. Thus, the aim of this study was to investigate the effect of different intensities of photosynthetically active radiation (PAR) used as an extended photoperiod in a greenhouse on the production of basil seedlings. A completely randomized design, in a 2 × 4 factorial scheme, with four replications of 20 seedlings per plot was used. Two basil varieties, sweet basil (green color) and purple basil (purple color), were evaluated under three intensities of supplementary PAR, which were 375, 411, and 438 µmol m-2 s-1, and control, in the absence of supplementary PAR. The seedling height, stem diameter, shoot dry matter, root dry matter, total dry matter, leaf area, ratio between plant height and stem diameter, ratio between plant height and shoot dry matter, ratio between shoot dry matter and root dry matter, and Dickson quality index were evaluated. Results show that higher intensities of PAR used as an extended photoperiod favor the quality of basil seedlings produced in a protected environment.