The Effect of Different Levels of Carbon Dioxide and Ethanol Spraying on The Growth, and Physiological and Biochemical Characteristics of Basil

One of the research requirements in agriculture is to find a new and practical method for sustainable production that brings the highest efficiency and the least harm to humans and the environment. In order to investigate the effect of different levels of carbon dioxide and ethanol foliar spraying on the physiological and biochemical characteristics of basil (Ocimum basilicm cv. Keshkeni luvelou), a factorial pot experiment based on a completely randomized design with three replications was conducted in the research greenhouse of the Department of Horticultural Sciences and Landscape of Ferdowsi University Mashhad in 2018. The factors included ethanol spraying at 4 levels (0, 10, 20, and 30% v/v) and carbon dioxide at 3 levels (380, 700, and 1050 µmol mol−1). The results showed that the highest relative water content (RWC) of leaf, photosynthesis rate, transpiration rate, stomatal conductance, and leaf protein were observed in the treatment of 20% v/v ethanol foliar application with the application of 700 µmol mol−1 of carbon dioxide, as they increased by 45%, 295%, 684%, 83%, and 328% compared to the control, respectively. Fresh and dry biomasses of shoot parts increased significantly with increasing carbon dioxide concentration and ethanol spraying. Thus, the highest fresh and dry biomasses of shoot parts were obtained in foliar spraying of 30% v/v of ethanol and 700 µmol mol−1 of carbon dioxide which increased by 176% and 76%, respectively, compared to the control. The highest activity of polyphenol oxidase and guaiacol peroxidase, stomatal resistance, and electrolyte leakage were related to spraying 30% v/v of ethanol with an application of 1050 µmol mol−1 of carbon dioxide which showed an increase of 2%, 4%, 65%, and 76%, respectively, compared to the control. Overall, the results showed that foliar spraying of 20 and 30% v/v of ethanol along with the application of 700 µmol mol−1 carbon dioxide had the greatest effect in increasing photosynthesis and finally the fresh and dry biomasses of basil.