1- Department of Forestry, Faculty of Natural Resources and Marine Sciences, Tarbiat Modares University, Noor, Iran
2- Department of Rangeland Management, Faculty of Natural Resources and Marine Sciences, Tarbiat Modares University, Noor, Iran
2- Department of Rangeland Management, Faculty of Natural Resources and Marine Sciences, Tarbiat Modares University, Noor, Iran
Abstract: (821 Views)
Extended Abstract
Background: Drought is one of the most important factors affecting plant survival that can have significant effects on their growth, development, and productivity, especially in arid and semi-arid regions where climate change has exacerbated this phenomenon. The black hawthorn (Crataegus pentagyana Waldst. & Kit. ex Willd.) is one of the valuable medicinal plants in the forests of northern Iran, which plays an important role in maintaining biodiversity and sustainability of forest ecosystems due to its ability to adapt to different habitats. Due to its high ecological values, including the protection of biodiversity and wildlife, this plant is also known as a pioneer and nurse species for the establishment of plants in the primary succession stage and is of particular importance in terms of its ability to control urban pollution; also, it is known not only as a valuable medicinal source, but also helps to strengthen the soil and restore degraded environments. In general, considering its importance in the protection and restoration of degraded forest areas in mountainous regions and arid to semi-arid valleys in the north of the country, and on the other hand, the emergence of drought and global warming phenomena in recent years, studying the responses of this plant to drought stress can provide a solution for protecting this species against climate change and also for managing water resources in seedling production nurseries and restoring degraded forests. In fact, the aim of this study is to investigate the effect of drought stress on the ecophysiological traits of the leaves of this species in order to identify the reactions related to gas exchange, water relations, and its photosynthetic pigments under conditions of long-term irrigation interruption and its consequences on seedling health and survival.
Methods: To conduct this study, in late winter 1401, 54 two-year-old and homogeneous potted seedlings of the medicinal plant Crataegus pentagyana (50 ± 5 cm in height and 2 ± 5 mm in diameter) were obtained from the Lajim Savadkouh Forest Seedling Production Nursery. After being transferred to the greenhouse, the seedlings were subjected to a drought stress experiment as withholding irrigation in six treatment levels and three four-fold replications in a completely randomized design. Then, the seedlings were measured on the third, seventh, fourteenth, twenty-first, twenty-eighth, and thirty-fifth days (following withholding irrigation) for gas exchange traits, water relations, and photosynthetic pigments. To measure photosynthesis and transpiration, the leaves of the upper one-fifth of the seedlings were used by Photosynthesis Meter under natural conditions of temperature, light, and relative humidity (from 9.5 to 11 am). Then, three of the most developed and mature leaves were selected from each seedling, and after undergoing the necessary processes and drying in an oven (70°C for 48 hours), the relative water content of the leaves was calculated using the determined formula. The electrolyte leakage content (used as an indicator of cell membrane damage) was also determined by preparing 1 cm2 samples from the middle part of newly mature leaves, then measuring their initial electrical conductivity and placing them in a bain-marie bath (80 °C) for 12 hours and measuring the total electrical conductivity, according to the relevant formula. To measure photosynthetic pigments, the leaves were frozen after extraction and centrifugation steps, and the absorbance of the supernatant solution was read at wavelengths of 470, 645 and 663 nm using a spectrophotometer. Thus, the content of chlorophyll a, chlorophyll b, total chlorophyll and carotenoids was determined in mg/g fresh weight using the proposed equations. Data analysis was performed using SPSS 26 software and graphs were drawn using Excel software. The Kolmogorov-Smirnov test was used to examine the normality of the data, one-way analysis of variance (one-way-ANOVA) was used to determine the significance of the data, and the Tukey test was used to compare the means (at 5% and 1% confidence levels).
Results: With increasing drought intensity, photosynthesis, transpiration, and relative water content decreased significantly. In other words, photosynthesis decreased by 62% and 90.5% on days 14 and 35 of withholding watering compared to day 3 of withholding watering. This decrease was 12.5% and 68% for transpiration, 19% and 60.6% for relative water content, and 22.7% and 68.2% for total chlorophyll, respectively. Meanwhile, electrolyte leakage increased by 8% and 14.4% on days 14 and 35 of withholding watering, respectively. The content of chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, and the ratio of total chlorophyll/carotenoids decreased under the influence of drought, such that they decreased significantly in severe stresses (withholding watering on days 21, 28, and 35).
Conclusion: The present study shows that drought as one of the main stress factors has significant effects on the ecophysiological traits of Crataegus pentagyana seedlings, so that its severity can have a negative effect on the overall health of the plant. In fact, this research revealed that an imbalance in the photosynthetic system and disruption in chlorophyll production and synthesis, and in general, a significant vulnerability of Crataegus pentagyana seedlings to drought stress occurs when the seedlings are deprived of water for more than 14 days. Also, this study emphasizes the importance of water resource management in forest nurseries and urban and suburban green spaces and a better understanding of the response of seedlings of this plant to drought stress in order to improve their performance and also protect them against climate change.
Background: Drought is one of the most important factors affecting plant survival that can have significant effects on their growth, development, and productivity, especially in arid and semi-arid regions where climate change has exacerbated this phenomenon. The black hawthorn (Crataegus pentagyana Waldst. & Kit. ex Willd.) is one of the valuable medicinal plants in the forests of northern Iran, which plays an important role in maintaining biodiversity and sustainability of forest ecosystems due to its ability to adapt to different habitats. Due to its high ecological values, including the protection of biodiversity and wildlife, this plant is also known as a pioneer and nurse species for the establishment of plants in the primary succession stage and is of particular importance in terms of its ability to control urban pollution; also, it is known not only as a valuable medicinal source, but also helps to strengthen the soil and restore degraded environments. In general, considering its importance in the protection and restoration of degraded forest areas in mountainous regions and arid to semi-arid valleys in the north of the country, and on the other hand, the emergence of drought and global warming phenomena in recent years, studying the responses of this plant to drought stress can provide a solution for protecting this species against climate change and also for managing water resources in seedling production nurseries and restoring degraded forests. In fact, the aim of this study is to investigate the effect of drought stress on the ecophysiological traits of the leaves of this species in order to identify the reactions related to gas exchange, water relations, and its photosynthetic pigments under conditions of long-term irrigation interruption and its consequences on seedling health and survival.
Methods: To conduct this study, in late winter 1401, 54 two-year-old and homogeneous potted seedlings of the medicinal plant Crataegus pentagyana (50 ± 5 cm in height and 2 ± 5 mm in diameter) were obtained from the Lajim Savadkouh Forest Seedling Production Nursery. After being transferred to the greenhouse, the seedlings were subjected to a drought stress experiment as withholding irrigation in six treatment levels and three four-fold replications in a completely randomized design. Then, the seedlings were measured on the third, seventh, fourteenth, twenty-first, twenty-eighth, and thirty-fifth days (following withholding irrigation) for gas exchange traits, water relations, and photosynthetic pigments. To measure photosynthesis and transpiration, the leaves of the upper one-fifth of the seedlings were used by Photosynthesis Meter under natural conditions of temperature, light, and relative humidity (from 9.5 to 11 am). Then, three of the most developed and mature leaves were selected from each seedling, and after undergoing the necessary processes and drying in an oven (70°C for 48 hours), the relative water content of the leaves was calculated using the determined formula. The electrolyte leakage content (used as an indicator of cell membrane damage) was also determined by preparing 1 cm2 samples from the middle part of newly mature leaves, then measuring their initial electrical conductivity and placing them in a bain-marie bath (80 °C) for 12 hours and measuring the total electrical conductivity, according to the relevant formula. To measure photosynthetic pigments, the leaves were frozen after extraction and centrifugation steps, and the absorbance of the supernatant solution was read at wavelengths of 470, 645 and 663 nm using a spectrophotometer. Thus, the content of chlorophyll a, chlorophyll b, total chlorophyll and carotenoids was determined in mg/g fresh weight using the proposed equations. Data analysis was performed using SPSS 26 software and graphs were drawn using Excel software. The Kolmogorov-Smirnov test was used to examine the normality of the data, one-way analysis of variance (one-way-ANOVA) was used to determine the significance of the data, and the Tukey test was used to compare the means (at 5% and 1% confidence levels).
Results: With increasing drought intensity, photosynthesis, transpiration, and relative water content decreased significantly. In other words, photosynthesis decreased by 62% and 90.5% on days 14 and 35 of withholding watering compared to day 3 of withholding watering. This decrease was 12.5% and 68% for transpiration, 19% and 60.6% for relative water content, and 22.7% and 68.2% for total chlorophyll, respectively. Meanwhile, electrolyte leakage increased by 8% and 14.4% on days 14 and 35 of withholding watering, respectively. The content of chlorophyll a, chlorophyll b, total chlorophyll, carotenoids, and the ratio of total chlorophyll/carotenoids decreased under the influence of drought, such that they decreased significantly in severe stresses (withholding watering on days 21, 28, and 35).
Conclusion: The present study shows that drought as one of the main stress factors has significant effects on the ecophysiological traits of Crataegus pentagyana seedlings, so that its severity can have a negative effect on the overall health of the plant. In fact, this research revealed that an imbalance in the photosynthetic system and disruption in chlorophyll production and synthesis, and in general, a significant vulnerability of Crataegus pentagyana seedlings to drought stress occurs when the seedlings are deprived of water for more than 14 days. Also, this study emphasizes the importance of water resource management in forest nurseries and urban and suburban green spaces and a better understanding of the response of seedlings of this plant to drought stress in order to improve their performance and also protect them against climate change.
Keywords: Black hawthorn, Carotenoids, Electrolyte leakage, Photosynthesis, Relative water content, Withholding watering
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