Effect of melatonin on morphological and physiological parameters of Anise hyssop under water deficit stress conditions

In the present study to investigate the effect of melatonin on morphological and physiological parameters of Agastache under different water-deficit stresses used factorial experiment in the form of Randomized Completely Block Design with three replications in the commercial greenhouse, Urmia in 2019. The first factor was the levels of water deficit stress (non-stress, water deficit stress with depletion 40% and 70% FC) and the second factor was the different concentrations of melatonin (0, 50, and 100 µM) on Agastache. Results indicated that Applying stress, especially moderate stress, increases plant pigments, proline content, total sugar, number and length of lateral branches , and ultimately increases the dry weight of shoot. Foliar application of various melatonin concentrations, especially 100 μM, caused an increase of 11.58% in carotenoids and 43.35% in shoot proline content, and a decrease of 29.23% H2O2 contents. Melatonin may have increased Agastache tolerance to water deficit stress by protecting against oxidative damage and scavenging free radicals through stimulating the enzymatic and non-enzymatic systems, resulting in increased growth and yield.