Seyyed Mousa Mousavi; Mehrangiz Chehrazi; Esmaeil Khaleghi
Abstract
Introduction: With regard to decrease of precipitation and poor distribution of rainfall during the dry phenomenon of urban, green spaces face problems. In fact, one of the most important environmental stress is drought stress at different stages of plant growth such as seed germination, seedling establishment ...
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Introduction: With regard to decrease of precipitation and poor distribution of rainfall during the dry phenomenon of urban, green spaces face problems. In fact, one of the most important environmental stress is drought stress at different stages of plant growth such as seed germination, seedling establishment and crop production. The effect of drought stress, plants photochemical activity ceased Calvin cycle enzymes and chlorophyll content also varies in the process of photosynthesis under drought stress. Under drought stress, reactive oxygen species (ROS) such as hydrogen peroxide (H2O2), superoxide radicals (O2 • -) and hydroxide (OH •) increase their accumulation in cells that can lead to oxidative stress. To neutralize ROS, antioxidant enzymes systems in plant such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) are active. The response of antioxidants depends on the lack of water, the intensity of the stress and the type of plant species. Also, it is well known that photosynthetic systems in higher plants are most sensitive to drought stress. Indeed, drought is one of the factors affecting photosynthesis and chlorophyll content. Some of researchers reported that chlorophyll might estimate influence of environmental stress on growth because these parameters were closely correlated with the rate of carbon exchange. The aim of this study was an investigation of effect of water deficit different levels on antioxidant system and lipid peroxidation in two species of marigold. Therefore, an experiment was carried out as factorial in a randomized complete block design with three replication at Shahid Chamran University of Ahvaz in 2014 year.
Materials and methods: Experimental treatments were irrigation with three levels: 100% ETcrop (no stress), 75% ETcrop (moderate stress) and 50% ETcrop (severe stress) and two species of marigold (African and French). Catalase activity decreased absorption at a wavelength of 240 nm through catabolizing on the basis of H2O2 according to Beers and Sizer (1952). Peroxidase activity decreased absorption at a wavelength of 470 nm that was measured by using Hemeda and Kelin (1990). Ascorbate peroxidase enzyme extracted from leaf based on defects in the wavelength of 290 nm that was measured by Nakano and Asada (1987). The final product of membrane lipid peroxidation malondialdehyde concentration as the reaction thiobarbituric acid (TBA) was measured. Also, chlorophyll a, b and total chlorophyll were calculated by Arnon’s equations and chlorophyll content index (C.C.I) was measured by chlorophyll content meter (SPAD-502).
Results and discussion: Results of analysis of variance showed that irrigation treatment had significant effect on chlorophyll a, total chlorophyll (Chl a+b), chlorophyll content index and catalase peroxidase, ascorbate peroxidase enzymes activity and malondialdehyde while there was not significantly difference between two species of marigold on any of the measured biochemical characteristics. Also, results revealed that amount of leaf chlorophyll a and total chlorophyll (chl a+b) were reduced by increasing water deficit. In fact, amount of total chlorophyll, chlorophyll a, b and chlorophyll content index were higher in plants that were received 100% ETcrop than 75 and 50% ETcrop. ,The results of enzyme activity were similar to total chlorophyll and chlorophyll a and b. Amount of decreased chlorophyll a and total chlorophyll in plants were received 50% ETcrop were 24% and 47.46%, compared with 100% ETcrop, respectively.
Conclusion: Result showed that different levels of irrigation were significantly different at 5% level on catalase, peroxidase, ascorbate peroxidase enzymes activity and malondialdehyde concentration. Catalase, peroxidase, ascorbate peroxidase enzymes activity and malondialdehyde concentration were increased by reducing the amount of irrigation while there were no different between two species of marigold and interaction between species and irrigation was not effective on measured indexes.
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.
