Document Type : Original Article
Authors
1
Former Master's student, Department of Horticultural Sciences, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran
2
Professor, Department of Horticultural Sciences, Faculty of Agriculture, Bu-Ali Sina University, Hamedan, Iran
3
Associate Professor, Department of Horticultural Sciences and Engineering, Faculty of Agricultural Sciences and Engineering, Campus of Agriculture and Natural Resources, Razi University, Kermanshah, Iran
Abstract
Extended Abstract
1. Introduction: Water deficit is one of the major abiotic stresses that adversely affects crop growth and yield. Drought stress occurs when the available soil-water becomes scanty and atmospheric conditions cause continuous loss of water by transpiration or evaporation. Arbuscular mycorrhizal fungi, the most important root endophytes, are extensively studied and well documented for their role in promoting resistance to drought stress, nutrient uptake, and improvement in plant development. Furthermore, drought stress adversely affects the physiology, biochemistry, growth, and development of plants worldwide. It leads to the accumulation of reactive oxygen species (ROS) in plants, destroys cell membranes, and disrupts the dynamic balance of active oxygen content. These physiological and biochemical responses of plants under drought stress cause growth inhibition and even death. Many studies have shown that the inoculation of mycorrhizal fungi initiates morphological, nutritional, and physiological changes in host plants to counter biotic and abiotic stresses and enhance plant growth. Approximately 72% of the known vascular plants can act as hosts for arbuscular mycorrhizal fungi, and such mutually beneficial mycorrhizal associations have key roles in maintaining plant productivity in natural and agricultural habitats.
2. Materials and Methods: To investigate the symbiosis of mycorrhizal fungi and drought stress on the growth and biochemical characteristics of tarragon plant, a factorial pot experiment (with two factors) was conducted in the form of a completely randomized design in the research greenhouse of Razi University in 2021. The first factor was drought stress in two levels, including control (full irrigation) and irrigation up to 50% of the pot capacity, and the second factor included inoculation of tarragon rhizomes with mycorrhizal fungi from the genus Glomus in 5 levels (G.hoi + G. mosseae, G.hoi + G. intraradices, G. mosseae + G. intraradices, G.hoi + G. mosseae + G. intraradices, and the control (no inoculation). During the cultivation of rhizomes, fungi inoculation was done, and the amount of mycorrhizal fungi used for each pot was 100 g. After the rhizomes were cultivated and the plants were fully established, drought stress was applied. In order to prevent sudden stress and osmotic stress in plants, drought stress was applied gradually over a period of two months. Drought stress was applied by weight, and two months after the application of drought stress, some growth characteristics (leaf dry weight and root length) and physiological characteristics (relative water content, photosynthetic pigments, electrolyte leakage, proline, total soluble sugars, soluble protein, and antioxidant capacity) were measured.
3. Results and Discussion: The results showed that in tarragon plants, drought stress caused a decrease in leaf dry weight, root length, photosynthetic pigments, relative water content, and soluble protein. While the amount of proline, total soluble sugars, and antioxidant capacity has increased. The use of mycorrhizal fungi improved the studied characteristics under drought stress conditions. In the conditions of drought stress, the application of mycorrhizal fungi led to a decrease in electrolyte leakage. In response to drought stress, osmotic regulation processes were activated in tarragon plants. Inoculation with mycorrhizal fungi significantly increased vegetative growth indicators, relative content of plant water, proline, and total soluble sugars of tarragon plants under drought stress conditions in comparison with non-inoculated plants. In general, the use of mycorrhizal fungi increased the resistance to drought stress in tarragon plants. The lowest amount of leaf dry weight (0.65 g) and root length (14.65 cm) was observed in the treatment of 50% FC. Contrary to drought stress, the use of all three types of mycorrhizal fungi increased the dry weight of the leaf (0.83 g) and root length (17.57 cm). In the conditions of drought stress, the application of mycorrhiza improved the amount of photosynthetic pigments compared to the control. The highest amount of proline (18.33 μmol g-1 FW) was in the treatment of drought stress with three species of mycorrhizal fungi. The highest amount of total soluble sugar (49.00 mg g-1 FW), soluble protein (0.352 mg g-1 FW), and antioxidant activity (96.06%) was observed in the full irrigation treatment with three species of mycorrhizal fungi.
4. Conclusion: Under drought conditions, mycorrhizal fungi can enhance seedling survival, promote absorption and transportation of water by the host plant, change the root morphology, improve the gas exchange ability and water use efficiency, regulate the plant endogenous hormone levels, and accelerate reactive oxygen species removal, all of which are aimed at reducing the negative impact of drought on plants. The results showed that the application of G. intraradices +G. hoi + G. mosseae had a better effect on the growth, physiological, and biochemical characteristics of tarragon under drought stress. The above results showed the positive effect of mycorrhiza in increasing the drought tolerance of the tarragon plant and better inhibition of free radicals produced in the presence of this stress. Accumulation of organic molecules in the vacuoles of leaf cells under drought stress is more common in mycorrhizal plants and causes a decrease in the osmotic potential of leaf cells. All these changes change the ratio of water in mycorrhizal plants. In this study, the use of all three species of mycorrhizal fungi improved stress tolerance in tarragon plants more than the control.
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