Document Type : Research Article
Authors
1 Department of Horticultural Science, Faculty of Agriculture and Animal Science, University of Torbat-e Jam, Torbat-e Jam, Khorasan Razavi, Iran.
2 Department of Water Science and Engineering, Faculty of Agriculture and Animal Science, University of Torbat-e Jam, Torbat-e Jam, Khorasan Razavi, Iran
Abstract
Introduction
Moldavian balm (Dracocephalum moldavica L.) is an annual herbaceous plant that belongs to the Lamiaceae family. It is known for its production of essential oils and its medicinal-aromatic properties. Moldavian balm’s essential oil is used for food, cosmetics, flavorings, and pharmaceutical purposes. Abiotic stresses include drought, soil salinity, flooding, extremes of temperature, and contamination with organic pollutants and heavy metals hamper plant growth and productivity. In recent decades, heavy metal (HM) pollution has spread across natural and anthropic ecosystems posing inevitable, serious health risks. Soil microbiota plays an important role in the sustainable production of the different types of agrosystems. Mycorrhizae (a combination of mycelium of the fungus and the roots of the plant) form networks that capture water and nutrients from the soil, which facilitate the acquisition of the plant. Arbuscular Mycorrhizal (AM) Fungi play a crucial role in mitigating the oxidative damage caused by heavy metal stress in different plant species. Thus, interaction between mycorrhizae, and plants can be an excellent strategy for sustainable agricultural production The aim of this study was to determine the effects of mycorrhizal arbuscular on improving heavy metal tolerance in moldavian balm, a medicinal and aromatic plant.
Material and Methods
An experiment was conducted to study the effect of mycorrhizal arbuscular fungi on growth characteristicsas, quantitative and qualitative yield of Moldavian Balm, under heavy metals stress at Research Greenhouses of College of Agriculture, University of Torbat-e Jam. Treatment included mycorrhiza (inoculated and non-inoculated) and heavy metals including lead (0, 150 and 300 mg/kg) and cadmium (0, 40 and 80 mg/kg) Which arranged in factorial based on completely randomized design whit 4 replications. Growth criteria, yield components, essential oil content and photosynthetic pigments were evaluated. In this study, different morphological traits (plant height, root length, root volume, stem diameter, Leaf length, Leaf width, Leaf area, stem diameter, Number of branches), vegetative parameters (Biomass fresh and dry weight, root fresh and dry weight), photosynthetic pigment concentrations and essential oil content were measured analyzed. Data analysis of variance (ANOVA) was performed using IBM SAS software (Version 9.1) and the differences between means were assessed using Duncan’s multiple range tests at p≤ 0.05.
Results and Discussion
Results showed that with increasing the concentration of heavy metals in the soil especially that of Cd, most of the growth characteristics and yield components of these plants were significantly reduced as compared to those of controls. Mycorrhizal inoculation improved these traits where plants were grown under heavy metals stress. The highest biomass fresh and dry weight was observed in mycorrhizal plants grown in non-contaminated medium, which was significantly higher than those of other treatments. The highest biomass fresh weight was measured in non-stressed mycorrhizal plants. Biomass fresh weight in non-mycorrhizal plants of Pb150 did not differ significantly from that of mycorrhizal plants of Pb150. biomass fresh weight in mycorrhizal and nonmycorrhizal plants stressed by Cd40 or Cd80 was lower compared to mycorrhizal and non-mycorrhizal plants grown in non-contaminated media or contaminated media with Pb150 or Pb300. Furthermore, the lowest biomass fresh weight was observed in non-mycorrhizal plants stressed by Cd80. Root fresh and dry weight of mycorrhizal plants was significantly higher than that of non-mycorrhizal plants. With increasing Cd or Pb concentration in soil, Root fresh and dry weight was decreased as compared to that of controls. Inoculation with mycorrhizal improved the photosynthetic pigment concentrations under heavy metals stress. The highest percentage of essential oil content (1.3% v/w) was observed in mycorrhizal plants stressed by Pb150, while the lowest percentage (0.53% v/w) was evident in non-mycorrhizal plants polluted with Cd80, With increasing concentration of the heavy metals, essential oil of moldavian balm was significantly decreased, but the essential oil content in mycorrhizal plants was significantly higher than that measured in non-mycorrhizals.
Conclusion
Arbuscular Mycorrhizal (AM) Fungi are widely believed to support plant establishment in soils contaminated with heavy metals, because of their potential to strengthen defense system of the AM mediated plants to promote growth and development. Overall, mycorrhizal inoculation of moldavian balm has promoted plant growth and, in addition, mycorrhization has enhanced yield as well as active substances in moldavian balm grown in the heavy metals stress condition. However, these approaches show promise in mitigating the adverse effects of heavy metals stress and improving the overall health and productivity of plants. Based on the enhanced physiological and biochemical responses, as well as increased essential oil content, it is recommended to use arbuscular mycorrhizal fungi fertilization under heavy metals.
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