Medicinal Plants
Esmaeil Nabizadeh; Masud Haghshenas; Khadijeh Ahmadi
Abstract
Introduction
Stevia (Stevia rebaudiana) is one of the medicinal plants of the Asteraceae family that contains natural compounds, especially stevioside and ribaodioside A, which are estimated to be 150 to 400 times sweeter than sucrose. Plants are exposed to various environmental stresses during growth ...
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Introduction
Stevia (Stevia rebaudiana) is one of the medicinal plants of the Asteraceae family that contains natural compounds, especially stevioside and ribaodioside A, which are estimated to be 150 to 400 times sweeter than sucrose. Plants are exposed to various environmental stresses during growth and development under natural and agricultural conditions. Among these, drought is one the most severe environmental stresses affecting plant productivity. About 80–95% of the fresh biomass of the plant body is comprised of water, which plays a vital role in various physiological processes including many aspects of plant growth, development, and metabolism. Stevia is susceptible to various environmental stresses but the major effects are contributed by drought. Today, the fungal species Stevia rebaudiana is used as a biofertilizer and increases the production of secondary metabolites of economically valuable plants and also increases the growth and seed production of many plants. This fungal endophyte produces a significant amount of acid phosphatase for mobility in a wide range of insoluble or complex forms of phosphate, enabling the host plant to have adequate access to inactive phosphorus reserves in the soil. However, medicinal plants that are cultivated have often been reported to have lower abundance of arbuscular mycorrhizal fungi in the rhizosphere, which significantly reduces plant survival. Considering the coexistence role of mycorrhizal fungi in modulating the effects of drought stress, the aim of this study was to investigate the morphological, physiological and biochemical traits of stevia in response to the effects of mycorrhizal inoculation and drought stress.
Materials and Methods
This experiment was conducted to investigate the effect of P. indica endophytic fungus under water stress conditions on vegetative characteristics, physiological parameters and micronutrients of stevia. A factorial experiment was employed based a completely randomized design with four replications in the research greenhouse of Islamic Azad University, Mahabad Branch in 2017. The first factor was drought stress at four levels (25, 45, 60 and 80% of field capacity) and the second factor was inoculation of seedlings with fungus at two levels (no inoculation and inoculation with P. indica). Water stress was applied based on a combination of plant appearance symptoms (no wilting to severe wilting) and soil moisture. Investigated traits included root colonization, dry weight, leaf number, plant height, stem diameter, chlorophyll a, b, total chlorophyll, carotenoids, proline, soluble sugars, antioxidant power and micronutrients including copper, iron, zinc and manganese. To analyze the data variance, SAS 9.1 statistical software was used to analyze the variance of the data.
Results and Discussion
The results showed that the evaluated traits in the present study were affected by the main treatments of fungus and drought stress. Seedlings inoculated with P. indica endophytic fungi had the highest percentage of root colonization, growth parameters, photosynthetic pigment content, soluble compounds and micronutrients compared to no inoculation. Drought stress increased soluble sugars, proline content and antioxidant power of stevia leaves and decreased the other traits by increasing the stress level from 25 to 80%. The highest rate of root colonization (26.90%), stem diameter (3.21 mm) and carotenoid content (1.71 μg/ml) was observed in the treatment of plant inoculation with fungi and 25% drought stress. While the highest antioxidant power was found in the treatment of plant inoculation with fungi and 80% drought stress. According to the results of the present study, use of P. indica fungus had the most positive effect on the quantitative and qualitative characteristics of stevia medicinal plant compared to no fungus inoculation.
Conclusion
This study showed the positive effect of P. indica endophyte inoculation on quantitative and qualitative characteristics of root colonization, dry weight, number of leaves, plant height, stem diameter, chlorophyll a, b, total chlorophyll, carotenoids, proline, soluble sugars, antioxidant power and The micronutrients of calcium, iron, zinc and manganese showed stevia, and drought stress reduced the studied traits except for proline content, soluble sugars and antioxidant power. Inoculation of stevia seedlings with P. indica endophytic fungi at drought stress levels had the highest rate of root colonization, stem diameter, carotenoid content and antioxidant power compared to non-fungal inoculation. Therefore, due to the effect of biological compounds of natural origin and the production of plants with healthier active secondary compounds, the use of P. indica endophytic fungi can be recommended.
Seyyed Mousa Mousavi; Mehrangiz Chehrazi; Esmaeil Khaleghi
Abstract
Background and objectives: Water stress is one of the most important environmental stresses in agriculture and urban landscape management. Water stress has been defined as the induction of turgor pressure below the maximal potential pressure. Previous studieshave showed that drought had been negative ...
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Background and objectives: Water stress is one of the most important environmental stresses in agriculture and urban landscape management. Water stress has been defined as the induction of turgor pressure below the maximal potential pressure. Previous studieshave showed that drought had been negative effects on morphological, physiological and biochemical characteristics of plants. Changes in protein expression, accumulation, and synthesis have been observed in many plant species as a result of plant exposure to drought stress during growth plants. The maintenance of plant water potential during water deficit is essential for continued growth and can be achieved by osmotic adjustment mechanisms resulting from the accumulation of compatible solutes such as proline in the cytoplasm. Proline acts as a "compatible solute", i.e. one that can accumulate to high concentrations in the cell cytoplasm without interfering with cellular structure or metabolism. Proline has a protective action which prevents membrane damage and protein denaturation during water stress. Accumulation of sugars in different parts of plants is enhanced in response to the variety of environmental stresses. Marigold(Tagetesspp.) is a genus of annual or perennial, belonging to the Asteraceaefamily, that is used as a marginal flower in the landscape.Due to the fact that drought stress is one of the most important problems especially in the agricultural industry and also in the landscape, it is necessary to study the damaging effects of drought stress on plant characteristics. Therefore, the aim of this study was to investigate the effect of different levels of water stress on physiological and biochemical characteristics of two types of pot marigold.
Materials and Methods: A research was conducted in order to investigate the effect of different levels of water deficit (100 as control, 75 and 50 percent of potential evapotranspiration (ETcrop)) on trend changes of leaf proline, total soluble sugars, relative water content and soluble protein changes in two species of pot marigold (French and African) as a factorial experiment based on a randomized complete block design with three replications. In this experiment, two species of pot marigold seeds (African and French) were planted in the trays including cocopeat. Then seedlings were transplanted to pots with 19 × 16 cm dimensions. After transplanting, the seedlings were irrigated well for 3 weeks. Then plants were irrigated with 100%, 75% and 50% ETcrop. Parameters such as leaf proline and total carbohydrates content, leaf relative water content were measured three times at intervals of once every 21 days but the amount of soluble proteins was measured one time in 63 days after treatment. Data analysis was performed using MSTATC software and mean comparison was done by Duncan's multiple range test at 5% and 1% probability.
Results: The results showed that leaf proline and total soluble sugars increased with incrementin levels of water deficit and the trend changes of leaf traits were increased with the passing of time. So that, in 43 days after water stress treatment, leaf proline content had an increase of 3 or 4 times in 50% Etcrop irrigation treatment compared with the control and 75% Etcrop irrigation treatment, respectively. The highest levels of leaf proline (119.28 mg per gram of fresh weight) and total soluble sugars content (1.8 mg per gram of fresh weight) was related to 50% ETc treatment. The amount of leaf total soluble sugars was also higher in African species compared with French species. The results showed that the leaf soluble proteins and relative water content decreased with reducingirrigation, so that the lowest amount of relative water content (57.9%) and soluble protein (31.57mg per g fresh weight) were obtained in 50% ETc treatment.
Conclusion: When the plants were exposed to progressive drought stress, changes appeared earlier in relative water content, whereas later effects in the levels of free proline, total soluble sugar, total soluble protein. The results showed that irrigation had significant effects on all evaluated parameters such as leaf proline, total soluble sugers, RWC and soluble proteins. Our findings also showed that there was no significant difference between control treatment and 75% ETcrop treatment in the measured indices and it's importancfor optimal management of water in landscape couldbe considered. Finally, it can be expected that African species is better than French species for planting in landscape.
