Effects of concentration and growth stages of thiamine foliar application on morphological characteristics, yield and essential oil yield of fennel (Foeniculum vulgare Mill.)

Vitamins affect many metabolic and biological processes in plants and participate in the synthesis of enzymes, nucleic acids, and proteins as coenzyme in their metabolic pathways. In order to evaluate the effect of foliar application of thiamine on growth, yield, yield components and essential oil of fennel (Foeniculum vulgare Mill.), a field experiment was conducted as factorial on the basis of a randomized complete block design with three replications at the Faculty of Agriculture, University of Maragheh, Iran in 2015. The treatments were included three levels of thiamine foliar application (zero; distilled water), 50 and 100 μm/l) and foliar application stages in four levels of stem elongation, flowering, grain filing, and all three stages. The results showed that the effect of thiamine on all traits was significant. The concentration of 50 μm/l thiamine had the maximum increasing effect on the number of sub stems, number of umbels per plant, number of umbelets per umbel, number of grains per umbelet, grain yield, and essential oil yield and the concentration of 100 μm/l thiamine had the maximum increasing effect on the plant height, 1000-grain weight, biological yield, and essential oil percentage,compared to control. The effect of foliar application stages on the number of umbelets per umbel, number of grains per umbelt, and 1000-grain weight were significant and their highest values were obtained by thiamine foliar application in all three stages (stemming, flowering, grain filing). The interaction effects of the treatments were not significant on any of the traits. In general, results of this experiment showed that the foliar application of 50 and 100 μm/l thiamine at stemming, flowering, and grain filing stages can improve the seed yield and essential oil yield of fennel.