the effect of melatonin on quality and growth characteristics of ajowan (carum copticum l.) to irrigation cut-off the development of different periods

The study was carried out to explore the influence of varying melatonin concentrations on the improvement of morphological, biochemical, and yield parameters of ajowan under conditions of irrigation cut-off at various stages of plant growth. the experimental treatments included irrigation cut-off at various stages of the plant: control (full irrigation), vegetative stage, flowering, and vegetative + flowering, as well as three levels of melatonin foliar spraying (0, 0.5, and 1 mm). the experiment was carried out in a split plot arrangement based on a completely randomized blocks design, in the research farm of the university of jiroft in 2023. the results showed that drought stress in different stages of plant growth caused a decrease in plant height, stem diameter, number of umbels per plant, number of seeds per umbel, weight of 1000 seeds, percentage of oil, seed yield, biomass yield, oil yield. melatonin foliar spraying enhanced evaluated parameters under drought circumstances. melatonin at 1 mm concentration exhibited the most favorable influence on photosynthetic pigments, morphological traits, yield components, seed yield, and biological yield. only plant height, proline content, percentage of oil, biological yield, and essential oil yield were affected by the interaction of irrigation cut-off and melatonin treatment. the maximum plant height, biological yield, and essential oil yield were achieved with 0.5 foliar spraying and 1 mm melatonin concentration under full irrigation. in addition, the maximum concentration of proline was found when irrigation was halted during vegetative + flowering without melatonin. the highest percentage of essential oil (4.3%), biomass yield (14.65 kg ha^-1) and seed yield (19.56 kg ha^-1) were obtained in the treatment of full irrigation and melatonin foliar. in general, foliar spraying with melatonin increased resilience to drought stress and enhanced performance in ajowan seedlings, and the treatment with a 1 mm concentration of melatonin was more beneficial.