The present study was conducted to examine the interactive effects of water deficit and foliar-applied Zn on morpho-physiologic, grain yield and essential oil attributes of 12 fennel genotypes consisting Urmia, Hamadan, Kerman, Shiraz, Birjand, Yazd, Ardabil, Avicenna, Kashan, Mashhad, Bushehr and Isfahan in 2014 at the Lavark Research Farm, Isfahan University of Technology, Isfahan, Iran as a split-split-plot 3-replicate randomized complete block design. Two levels of irrigation (40% and 80% depletion of available soil water) were chosen as main-plots, the 12 genotypes as sub-plots and two Zn levels (0 and 4 g kg -1 of ZnSo 4 ) as sub sub-plots in a field study.Drought tolerance index was determid and the genotypes were discriminated in three groups namely drought-tolerant (Shiraz, Urmia, and Kashan), drought-sensitive (Kashan, Birjand, Hamedan, Yazd, Isfahan and Ardabil), and moderately-tolerant (Avicenna, Mashhad and Bushehr). Water deficit led to significant decreases in leaf water potential, relative water content (RWC) and chlorophyll concentration, in contrary to significant increases in leaf proline concentration and antioxydative enzymes activities, i.e. superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). Genotypic differences in growth, dry mass and grain yield and physiological responeses to water deficit wree detected, i.e. genotype “Kashan” out-performed the other genotypes in terms of physiological characteristics and grain yield under water deficit conditions. Foliar-applied Zn led to increases in physiological characteristics including leaf water potential, relative water content, leaf proline, chlorophyll a, chlorophyll b, and carotenoids concentrations, seed yield, seed essential oil content and yield and seed Zn concentration of fennel in general and the drought-stricken fennel plants in particular. Genotypes differed in their response to the Zn, genotype “Kashan” was found more responsive to the Zn, compared to the remaining genotypes. Findings of our study confirm that water deficit may cause serious decreases in fennel dry mass and grain yield but foliar application of Zn may ameliorate, at least in part, the adverse effect ot this abiotic stressor. Keywords : Drought, antioxidative enzymes, water potential, foliar-applied Zn, essential oil
