Effect of Drought and Humic Acid on Morphological Traits and Essential Oil Content of Thymus Kotschyanus

Abstract

The study was conducted to investigate the effect of Humic Acid organic fertilizer on the performance of Thymus Kotschyanus populations under the influence of drought stress. This experiment was performed as a three-factor factorial in the form of a completely randomized design (CRD) for 5 replications (pots) in the greenhouse of Pardisan Research Station belonging to Qom Agricultural and Natural Resources Research and Training Center. Three factors include 5 top accessions of T. Kotschyanus (factor A), irrigation levels at 80% crop capacity (control), irrigation at 60% crop and irrigation capacity at 40% crop capacity (FC) (factor B); and different levels of Humic acid including 3 Levels of 0, 1500 and 3000 mg/l were dissolved in irrigation water twice after full establishment of the plants and twenty days after the first iteration (factor C). The results of trait variance analysis showed that there was a significant difference at the level of possible error of 1% or 5% between the top accessions of T. Kotschyanus and between different irrigation levels in terms of all traits under study. Effectiveness of accession × irrigation levels were also significant in most traits at the level of 1% or 5% probability of error. In other words, the behavior of different Thymus accessions at different irrigation levels was significantly different and the effect of irrigation levels on different irrigations was not similar. These results are consistent with the reports of many researchers on the effect of drought stress on morphological traits as well as increasing essential oil content in drought stress conditions in medicinal plants. Hassani et al. (2006) reported on the effect of different levels of water stress on growth, performance, and essential oil content of Dracocephalum moldavica. Many traits, such as aerial organ length, wet and dry weight of aerial organ were reduced in dry stress conditions, and the highest percentage of essential oil was obtained for 70% crop capa