2018 ASHS Annual Conference

Under indoor sole-source lighting (SSL), light intensity and carbon dioxide (CO₂) can be precisely controlled to influence growth, development, and volatile oil content. However, there is currently limited information on physiological and biochemical responses of culinary herbs to varying light intensities and CO₂ concentrations under SSL. Due to increased plant densities during seedling production, fewer inputs per plant are required, creating the potential to increase production efficiency. Therefore, the objectives of this research were to: 1) quantify if light intensity and CO₂ concentration under SSL influence volatile oil content of sweet basil seedlings and if differences remain present through subsequent greenhouse finishing; and 2) determine if light intensity and CO₂ during seedling production influence morphology and yield at harvest. Sweet basil (Ocimum basilicum) ‘Nufar’ seeds were sown in rockwool cubes and placed in a growth chamber with CO₂ concentrations of 500 or 1,000 µmol·mol^‒1. Broad spectrum white light-emitting diodes (LEDs) provided 19:39:39:3 blue:green:red:far-red light ratios (%) and light intensities of 100, 200, 400, or 600 µmol·m^‒2·s^‒1 for 16-h to create daily light integrals (DLIs) of 6, 12, 23, or 35 mol·m^‒2·d^‒1. After two weeks, seedlings were transplanted into deep flow technique (DFT) hydroponic systems in a greenhouse with an average daily temperature of 23 °C and DLI of 14 mol·m^‒2·d^‒1. At transplant and three weeks after transplant, height, leaf area, stem diameter, node and branch number, and fresh and dry mass were recorded and tissue samples were frozen -80 °C for volatile analysis. Relative linalool, eugenol, methyl eugenol, methyl chavicol, and 1,8-cineole concentrations were analyzed using SPME and GCMS. Carbon dioxide and the interaction of CO₂ and DLI did not have an effect on growth or development. However, DLI affected height, leaf area, stem diameter, and fresh and dry mass of seedlings at transplant and height, branch and node number, leaf area, and fresh and dry mass of plants three weeks after transplant. For example, the fresh mass of seedlings increased by 287% as light intensity increased from 100 to 600 µmol·m^‒2·s^‒1 while subsequent greenhouse grown plant fresh mass increased by 80%. Therefore, environmental parameters under SSL production of seedlings can be used to increase quality and yield.