عنوان مقاله [English]
Sumac (Rhus coriaria L.) is one of the valuable and multi-purpose medicinal plants native to Iran.Sumac is known to be useful in the treatment of many diseases due to its rich antioxidant and phenolic and tannin content in this plant. Cultivation of sumac is very important in the livelihood of farmers in the region. Every year its fruits are harvested in the traditional way. Environmental stress is one of the most important factors limiting the growth and development of plants. Drought stress has different effects on plants and reduces the quality and yield of agricultural products. Photosynthesis is one of the first processes that are damaged under drought stress. Investigating the fluorescence kinetics of Chlorophyll a can provide useful information about the structure and function of the photosynthetic apparatus. In order to identify drought resistant cultivars, an experiment was conducted with four cultivars of sumac from two regions in the northwest of the Iran. Most of the parameters related to chlorophyll a fluorescence in different varieties showed significant results. Our data showed that the FV/FM ratio decreased in drought-exposed plants. The reduction of PIabs under drought stress was due to a decrease in the photochemical efficiency of photosystem II reaction centers and the rate of electron transfer (ETo/RC), accompanied by an increase in energy loss (DIo /RC). Among the cultivars studied, Aqboraz cultivar was reported to be resistant in all traits.
The origin of the sumac plant is in the Middle East region, including Iran. Sumac is a valuable medicinal plant that is cultivated in the northwestern region of Iran. With the increase in the global average temperature, the frequency of drought events and heat waves increases, this issue has significant negative consequences for the production It will have agricultural products. Drought is considered one of the most important environmental stresses that plants are repeatedly exposed to periods of water deficit, which affects the growth and development of plants and subsequently the yield of agricultural products. Photosynthesis is one of the key processes that it is significantly affected by drought stress. The primary effect of water shortage is stomatal closure, which allows plants to limit transpiration. In addition, a decrease in relative water content (RWC) and leaf water potential has also been reported in case of water deficit. Photosynthesis is one of the most sensitive processes to drought, which by limiting the release of carbon dioxide in the stomata and mesophyll cells, reducing stomatal conductivity and changes in carbon absorption leads to a decrease in the internal concentration of CO2. In recent years, the measurement of chlorophyll fluorescence, especially the OJIP test, has become a popular method to evaluate the stability of photosynthesis under the influence of various stress factors from biotic and abiotic factors. Chlorophyll a fluorescence is a natural phenomenon that describes the loss and radiation of heat or the re-emission of a part of the absorbed energy that is not used to drive photosynthesis. Measurement of chlorophyll a fluorescence provides information on changes in photosynthetic efficiency and heat dissipation. It is an extremely simple, non-invasive, highly sensitive, rapid and accurate method that provides a quantitative assessment of oxygenic photosynthesis. Photosynthetic organisms change their photosynthetic activity to adapt to stressful conditions such as drought. When the protein-chlorophyll complexes of thylakoid membranes are damaged by stress or normal physiological changes (ripening, senescing, etc.), the fluorescence changes as a natural process of chlorophyll molecules. Chlorophyll fluorescence can be easily measured and analyzed by various techniques. One of the widely used techniques is the OJIP test, which provides parameters based on the theory of energy flux in thylakoid membranes. OJIP parameters describe photosynthetic reactions through algebraic equations and quantify the characteristics of the structure and function of photosystems. JIP parameters detect changes in photosynthetic efficiency at the cellular level even before visible signs of stress appear.In order to investigate the response of sumac leaves to the drying of leaf water content, this experiment was carried out in the physiology laboratory of the Faculty of Agriculture of Tabriz University in the summer of 2022. The leaves of sumac plant collected from Arsbaran (Aqboraz and Horand) in East Azerbaijan province and Sardasht (Yasinabad and Mavolo) in West Azerbaijan province were used to assess their tolerance to drought stress. From each region, 50 fully developed sumac leaves were randomly selected and after being placed in insulated boxes with relative humidity close to 100%, they were transferred to the laboratory. The leaves were measured for chlorophyll fluorescence parameters after at least 30 min adaptation to darkness. This measurement was done every two hours up to 3 times. In all three periods, the weight of the leaves was measured in milligram with a three-zero scale. Chlorophyll fluorescence analysis test called OJIP was measured by Handy PEA fluorimeter (Hansatech, UK). The parameters obtained from the fluorimeter are listed in Table No. 1. Abiotic stresses such as drought have a destructive effect on the physiological characteristics and growth of plants. Closing the stomata to prevent water loss is one of the primary responses to drought stress. Drought stress causes the destruction of one chlorophyll through premature leaf senescence, and as a result, photosynthesis affects the most important photochemical process of the plant. The main aim of this research was to measure and investigate the water loss of sumac plants and its effect on the photosynthetic system of the plant. The obtained data showed that the OJIP test parameters, including density of reaction centers per photosystem II antenna chlorophyll, energy dissipation flux per reaction center showed an increasing trend based on previous studies. The Maximum quantum yield of photosystem II photochemistry, electron transport flux per reaction center, and performance index of photosystem II based to absorption also showed a decreasing trend according to previous researches and the findings of this research follow the previous studies. In general, the samples collected from Aqboraz region showing a better ability to cope with drought stress when compared to other cultivars. Making them promising candidates for use in future breeding programs. These results show that Aqboraz sumac landraces have a high resilience to water stress, opening new perspectives for screening landraces sumac cultivars for drought tolerance.