Interaction Effect of CO2 Enrichment and Nutritional Conditions on Physiological Characteristics, Essential Oil and Yield of Lemon Balm (Melissa officinalis L.)

Carbon dioxide enrichment and nutritional improvement can increase photosynthesis and growth of different crops. The aim of the present study was to assess interaction effects of CO2 enrichment and fertilizer on physiological characteristics and lemon balm essential oil. Experimental units were composed of CO2 at 380, 700, and 1050 ppm with and without manure and N fertilizer application. A continuous increasing trend of individual plant leaf area, total dry weight accumulation and relative growth ratio were recorded with CO2 enrichment. When CO2 was elevated from 380 to 1050 ppm, the values of height (24.3%), SPAD reading (2.7%), essential oil yield (26.3%) and final yield (65.3%) were increased, unlike, stomatal conductance (35.2%) and essential oil percentage (53%) were decreased. The highest and the lowest values (except for oil percentage) were obtained under N and no fertilizer application, respectively. Except for SPAD, interaction between CO2 enrichment and each fertilizer on all measured characteristics had a significant effect, so that CO2 effect was intensified by applying each fertilizer. Therefore, it can be concluded that when temperature increase caused by rising CO2 is not considered or there is not a limitation for resources, CO2 enrichment will improve lemon balm biomass and essential oil yield.