جستجوی مقالات مرتبط با کلیدواژه « water stress » در نشریات گروه « باغبانی »

The ever-increasing tendency to the use of medicinal plants in the world has grown concerns about their cultivation and production processes. As medicinal plants are more compatible with the nature, special interest and attention has recently been given to herb therapy, and use of medicinal plants, being limited by the rise of pharmaceutical drugs, has become again common and widespread due to a number of reasons. Nigella sativa L. is one of the herbs that has a variety of uses and has been being used in iran’s traditional medicine since old times. Today this plant is considered as one of the most important kinds of medicine. Therefore, it is of great importance to conduct some researches on the herbs around the country due to different ecological requirements. N. sativa belonging to buttercup family, with the scientific name of Ranunculaceae, is an annual, dicotyledonous, herbaceous plant. In several studies, N. sativa has been reported to have anti-oxidative, anti-inflammatory, strengthening of immune system, and anti-histamine and oil extract properties. Furthermore, several effects such as lowering blood sugar, lipids, and hypertension, excretion of bile and uric acid, protection of liver, kidney and cardiovascular tissues as well as anti-seizure, anti-cancer, anti-microbial and anti-parasitic effects related to this plant have been reported. The aim of the present study is to improve the yield and yield components and oil of medicinal plant N. sativa by anti-transpiration compounds under drought stress conditions.                       

An experiment was conducted at Research Station,Faculty of Agriculture, Ferdowsi University of Mashhad, in 2012-2013. The research was performed using a split plot experiment based on a randomized complete block design with three replications. The irrigation intervals (8 and 16 days) in main plots and anti-transpiration compounds of chitosan (0.25, 0.5 and 1%), Plantogopsyllium mucilage (0.5, 1 and 1.5%) and arabic gum (0.25, 0.5 and 0.75 %) were put in subplots with three replications. Also, the distance between the main plots in each block and distance between the two blocks were assigned as 100 cm and 200 cm, respectively; so that the moisture content of a plot had no effect on the adjacent plots. Planting date was April16 and planting was performed by hand in 0.5cm-deep furrows. Throughout the growing season, anti-transpiration compounds were applied concurrently with the imposition of drought stress, administered weekly at sunset until the flowering stage. Subsequently, yield, yield components, and oil content were measured.

Results showed that irrigation intervals had significant effects on all studied characteristics with the exception of 1000 seed weight. ncreasing irrigation intervals reduced percentage yield and yield components and oil of black cumin grains. Anti-transpirants compounds did have significant effects on percentage of oil and yield and yield components of black cumin grains. There were significant difference between different anti-transpirants compounds in terms of oil and yield components yield and of black cumin grains. The 8 days irrigation interval produced more grain yield compared with 16 days irrigation intervals (621.56 vs. 484.23 kg/ha). The highest oil (27.74%) and lowest (21.74%), respectively, at treatment anti-transpirants compound chitosan1 percent With 8 days irrigation interval and gam arabic 0.25 percent was obtained with 16 days irrigation interval and chitosan stimulating abscisic acid synthesis in the treated plant would result in stomatal closure, reduction of stomatal conductance, transpiration rate and water content. They also pointed out that the anti-transpiration effect of chitosan was because of its stimulatory effect in increasing abscisic acid concentration in the treated leaves of bean plant. As the above compounds are natural and biodegradable, as well as safer and less expensive than other chemical anti-transpiration compounds, they can serve as a good alternative to the chemical compounds. Cognition and expertise in water relations of plant and drought stress tolerance is considered as the main program in agriculture and the ability to withstand this stress is of great economic importance.

The anti-transpiration compounds led to significant changes in terms of all the studied traits compared to the control, indicating the effectiveness of theses natural compounds. Providing the appropriate conditions, 1% chitosan treatment can enhance the yield under drought stress. Spraying by arabic gum did not improve the growth conditions. According to this experiment, 1% chitosan treatment and 1.5% Plantago psyllium mucilage is considered the most appropriate strategy to enhance the yield of Nigella sativa under drought stress.

Water stress is one of the most important abiotic stresses limiting growth and plant yield under dryland conditions, which affects the morphological and physiological characteristics of plants. To evaluate morphological characteristics, yield, mucilage, and seed oil of Lallemantia iberica (M.B.) Fisch. & C.A. Mey. ecotypes [Kerman (Kerman province), Naein (Isfahan province), Sanandaj (Kurdistan province), Mashhad (Razavi-Khorasan province), and Malekan (East-Azerbaijan province)] under dryland conditions, an experiment was conducted as a randomized complete block design with three replications in the medicinal plants research farm of Yasouj Agricultural Research Center and Natural Resources in the 2016-2017 crop year. The results showed that ecotype significantly affected morphological traits, seed yield, mucilage yield, and oil yield. The highest seed yield was obtained from Kurdistan (529 kg ha-1) and Mashhad (515 kg ha-1) ecotypes. The highest and lowest oil yield was related to Kurdistan (211 kg ha-1) and Kerman (189 kg ha-1) ecotypes, respectively. Mashhad (22.7 kg ha-1) and Malekan (18.2 kg ha-1) ecotypes had the highest and lowest seed mucilage yield, respectively. Although there was no significant difference between the oil and seed mucilage percentage of the ecotypes, the highest (41.3%) and lowest (39.9%) oil content was found in Kerman and Kurdistan ecotypes and the highest (4.4%) and lowest (3.7%) mucilage percentage belonged to Mashhad and Kurdistan ones, respectively. Overall, the results showed that Kurdistan and Mashhad ecotypes are suitable for cultivation under dryland conditions of Yasouj due to higher yield of seeds, mucilage, and seed oil.

Recently, the use bioregulators to ameliorate the effects of environmental stresses on agricultural products has been considered. This split plot experiment was conducted as a randomized complete block design to investigate the moderating effect of some bioregulators on vegetative, biochemical and yield characteristics of greenhouse tomatoes under drought stress in the research greenhouse of University of Hormozgan. Experimental factors were three drought stress levels as the main factor, were include full irrigation as control, moderate and severe drought stress, respectively, irrigation of plants based on providing 100, 75 and 50% readily available water, and foliar application of 0.5 g per plant of biological compounds (the first time one day before applying drought stress and the second time before flowering begins) as a sub-factor including control (without the use of compounds), proline, chitosan and N-Succinyl and N, O dicarboxymethylate chitosan (NSC and NOC, respectively). Application of bioregulators at each water stress level increased the of proline content and catalase and peroxidase enzymes activity in comparison with the control, which in most cases the highest increase in enzyme activity related to NSC. Chitosan derivatives, on the other hand, were able to reduce the amount of malondialdehyde (MDA) and hydrogen peroxide in tomato leaves. Among the biological compounds, NSC and chitosan had the greatest improving effect on the fruit yield via increasing the number and diameter of fruit. So that foliar application with NSC increased fruit yield in control, moderate and severe water stress by 5.33, 17.91 and 33.24%, respectively. Therefore, according to these results, under deficit irrigation conditions, chitosan and its derivatives can reduce the effects of drought stress on tomatoes more efficiently than proline.

The ability of phenological adjustment and accelerate maturation is one of the most drought tolerance mechanisms in crops. Tall fescue is one of the valuable forage and turf grasses that is used to prevent soil erosion and produce forage in pastures and is compatible with most soils and climates. In this research, yield potential and genetic variation of three phenological groups including mid-flowering group (parental group), early and late flowering groups each containing 25 genotypes, selected from a poly cross community, were studied under non-stress and water deficit conditions in the research farm of Isfahan University of Technology for two years. Irrigation was applied when 90 and 50% of available soil water were depleted for stress and normal environments, respectively. The results showed that there was considerable variation in the studied germplasms in terms of all studied traits and responses to water deficit stress. The highest value of genetic variation belonged to forage yield. The results showed that dry forage yield in the first and second harvest stress decreased by 17% and 52% due to water deficit, respectively. The highest estimate of heritability was related to the trait of day to anthesis and the lowest was related to the percentage of dry matter and forage yield. The results showed that the highest dry forage yield under non-stress conditions belonged to the late flowering group. Means comparison of genotypes showed that the highest dry forage yield under normal and water stress belonged to genotypes 10 (from America with 209.50 g/plant) and 3 (from Yasouj with 142.25 g/plant), respectively, in the late flowering group, genotypes 25 (from Shahrood with 383 g/plant) and 22 (from Poland with 178.50 g/plant), respectively in early flowering group and genotypes 25 (from Shahrood) with 222.50 and 182.25 g/plant in the parental group, respectively. The results indicate that the studied genotypes may have incomplete summer dormancy that should be investigated in future studies. Considerable genetic diversity between and within phenological groups and their different responses to drought stress can be used to develop and produce suitable synthetic varieties for soils with limited water resources.

Root exudates and morphological root traits play an important role in plant species’ response to drought. However, the functional consequences of these drought-induced changes for rhizosphere microbial communities are unknown. We hypothesized that drought-sensitive and -tolerant grass genotypes widely differ in the quality of root exudates, growth strategies, and root systems, which may affect rhizosphere microbial communities. Therefore, we examined microbial biomass carbon and nitrogen in the rhizosphere of drought-sensitive and -tolerant genotypes of Bromus inermis, Dactylis glomerata, and Festuca arundinacea species under four years water stress treatments at Lavark Farm of the Isfahan University of Technology. Responses of the rhizosphere microbial communities to the water stress varied by the plant genotypes. Water stress increased rhizosphere microbial biomass carbon in the drought-sensitive and -tolerant genotypes of Bromus inermis species. In contrast, water stress treatment significantly reduced microbial biomass in the rhizosphere of Dactylis glomerata genotypes. The effect of water stress on rhizosphere microbial biomass carbon was positive in the drought-sensitive genotypes of Festuca arundinacea species, while conversely, this effect was negative in the drought-tolerant genotypes. We found a similar pattern across two drought-sensitive and -tolerant genotypes of Bromus inermis species to the water stress, which could be an evolutionary strategy to overcome drought conditions through the stimulation of microbial biomass and activity and the subsequent mineralization of nutrients. Higher microbial biomass carbon in the rhizosphere soils relative to those in the control (bulk soil) were observed, regardless of the moisture treatment. Under the water stress, microbial biomass carbon were almost simillar in the rhizosphere of drought-sensitive and -tolerant genotypes but were higher in the drought-tolerant genotypes without the stress.

 Cucumber is one of the important greenhouse vegetables in Iran and the world. This product, in Iran, has the largest area under cultivation in comparison with other greenhouse vegetables, and according to the statistic in 2020, the Office of herbs, vegetables and ornamental plants Ministry of Agriculture, the greenhouse cucumbers area under cultivation in Iran is 15000 ha. Cucumber is the product of warm and temperate season (with mild winters) and is very sensitive to adverse environmental conditions and even rare changes in soil moisture content will have a significant adverse effect on its growth and yield. Cucumber root is shallow, it is fibrous, and its shallow root causes its sensitivity to drought so that its main root penetrates 5–10 cm in heavy soil and 20-30 cm in light soils. This plant has an extensive and almost thin root system that has the possibility of expansion in a wide range horizontally, and, therefore, it can produce mass root, at the depth of 30 cm. In order to study the effect of grafting and water stress on morphological characteristics greenhouse cucumber (Cucumis sativus L), an experiment was conducted as complete randomized block design with three replications.
 This research has been carried out in the city of Pars-Abad, Ardabil province, Iran. The longitude of Pars-Abad is 47°55ʹ E, latitude is 39°38ʹ N, and its height distance sea level is 32 meters. This research was done in the greenhouse of the Moghan Agriculture and Natural Resources Faculty in a complete randomized block arranged in split plot with three replications. To determine the characteristic curve of soil moisture, soil samples was selected and the weight moisture percentage at pressures of -0.3, -5, -10 and -15 bar, which include the important potential of the soil, was determined by using Pressure plate’s apparatus and soil moisture characteristic curve was mapped and soil parameters characteristic curve was determined. this study, the main factor included water stress in three levels of 90, 60 and 40% field capacity and the secondary factor included three rootstocks of Shintoza cucurbits (Cucurbita moschata × Cucurbita maxima), Flexi Fort cucurbits (Cucurbita moschata × Cucurbita maxima, cucumber varieties Nagen 972 (Cucumis sativus L.) self-grafted and check (ungrafted) cucumber varieties Nagen was studied as a scion. In this study, the grafting method of hole insertion was used as the best grafting method for Cucurbitaceous.
 Duncan test results showed that with increasing stress, the diameter of the main root, at the rootstocks of Shintoza and Flexi Fort, increased almost twice as much as the control. The results showed an approximately 3 times increase in the yield, at the rootstocks of cucurbits at different levels of stress and it had a significant positive relationship at 1% level with the length, diameter and weight of root. The highest yield related to the Flexi Fort rootstocks was obtained 2.99 kg per plant in the water stress condition 90% of field capacity and then Shintoza rootstocks ranked second with 2.617 kg per plant, at 60% water stress. The maximum water use efficiency related to Shintoza rootstocks was at 32% and Flexi Fort rootstocks, Nagen and control, were respectively 30, 22 and 36% of Potential evapotranspiration.
 The results showed that, with increasing water stress, unlike the control, which was associated with decreasing linear trend of yield, Treatments with cucurbits grafting at Shintoza and Flexi Fort rootstock, faced with increased water stress, from 40 % to 90 % of field capacity by minor reducing of product. This can be due to increasing root uptake parameters such as length, weight and length of the main root in these Treatments. Correlation analysis showed a significant relationship at **P<0.01 level between a percentage of roots and yield. The results in all applied water stress also showed a high yield of grafted treatments about three times more than the control. Reducing the yield sensitivity factor in cucurbits Treatments, causes the plant could maintain its performance in irregular watering that encounter the plant with tension. The high water use efficiency in cucurbits Treatments shows that it is possible to perform economic optimization in the production based on water consumption scarcity of water.

Water is a main factor in agriculture activities and almost 70 percent of world water resources are consumed in agriculture. Drought consist the most important environmental restriction to plant growth and production. Drought stress is known to change a range of physiological processes such as photosynthesis, stomatal conductance and transpiration rate. Citrus are one of sub-tropical and tropical fruits and the most important horticultural products in the world that tolerate low temperature and weak drainage but as regards Citrus growing in sub-tropical and tropical regions that often expose drought. Drought is one the environment stress factors that is caused changes in plants morphological and physiological characteristics. Study of survival time in the three citrus rootstocks in sever stress circumstances showed that this time in rootstocks poncirus, cleopatra mandarine and former-alkaeid 5 were 11, 13 , 20 days, respectively  while survival time in valencia on the rootstocks was 21, 26 and 29 days, respectively. This study was performed in order to study drought tolerant in natural genotypes with the poncirus and rough lemon. And so, morphological and physiological characteristics were investigated in this genotypes. 
This research was performed in separately two tests in Citrus and subtropical fruits research center on 2016. In the first test, survival time and total transpiration and in the second test, organs fresh and dry weight, ion leackage and leaf relative water content were assessed in factorial experiment based on randomized completely design in nucellar seedlings of 8 Citrus natural genotypes (G10, G11, G12, G16, G18, G22, G23, G25) poncirus and rough lemon under glasshouse conditions (with temperature 26-28 degree centigrade in day and 20-22 degree centigrade in night and 80-85 percent relative humidity). Factors were 10 Citrus genotypes and two treatment of irrigation (optimum irrigation and withholding irrigation for six weeks) in the second test and 10 Citrus genotypes in the first test. In this study, medium weight moisture is calculated and due to the soil moisture characteristics curve was obtained medium matric potential. The matric potential rate was in control -0.03 megapascal and in sever stresss -1.5 megapascal. Organs fresh and dry weight were measured on digital balance with accuracy 0.01 gr. (model GM 6101, Germany). S amples were dried in oven (70 degree centigrade and for 48 hours). RWC is measured by using of fresh weight, dry weight and turgid weight in this formula: RWC= [(FW-DW) / (TW-DW)] × 100. Ion leackage was determined by use of 4 equal leaf segments and measuring of primary and secondary ion leackage in this fomula: EL (%) = (EL1/EL2) × 100. The first research was included of 10 treatment, six replication and one seedling in every plot and the second research was included of 20 treatment, three replication and two seedlings in every plot. SAS software (ver. 9.1) and Duncan test were used to variance analysis and mean comparison. Excel software was used to graphs drawing.
The results showed that in first test, poncirus (with 125 days) and G11 (with 78 days) have longer survival time and are more tolerant and so rough lemon (with 38 days) and G12 (with 44 days) were more susceptible. Others were intermediate. Slowest of water consumption time in poncirus and the most quick in rough lemon, and so maximum of total transpiration in G25 and minimum in poncirus was observed. In second test, decrease maximum of leaf, shoot and total fresh weight in G22 (arranged by 0.37, 0.47 and 0.42) and decrease minimum in G11 (arranged by 0.48, 0.54 and 0.52), decrease maximum of root fresh weight in G22 (with 0.35 fold) and decrease minimum in G18 (with 0.52 fold), decrease maximum of root/shoot fresh weight in G18 (with 0.61 fold) and decrease minimum in G23 (with 0.65 fold) and increase maximum of root/shoot dry weight in G16 (with 1.56 fold) and increase minimum in poncirus (with 1.3 fold) was observed in compared with control. In stress, G18 (with 32.32 percent) and G12 (with 34.37 percent) had leaf relative water content minimum in compared with control. G12 (with 78.59 percent) and G18 (with 73.16 percent) had maximum and poncirus (with 31.85 percent) minimum ion leackage percent in compared with control. Therefore, rough lemon, G12 and G18 as susceptible and poncirus and G11 as tolerant to drought were introduced.
In stress conditions, poncirus has longer survival time, slower water consumption time, minimum total transpiration and minimum ion leackage percent and is most tolerant. Rough lemon has shower survival time, more rapid water consumption time and is most susceptible. Other genotypes locate in after grades. Therefore poncirus and rough lemon can be used as rulers in tests of drought study.

In order to study the effects of water deficit stress and salicylic acid application on morphological and physiological characteristic of Ziziphora clinopodioides Lam. a factorial experiment based on a complete randomized block design with four water deficit stress levels (100%, 75%, 50% and 30% FC) and three levels of salicylic acid (0, 0.5 and 1 mM) in three replications was performed in greenhouse condition. Water deficit stress decreased plant, leaf and stem dry weight, leaf area, chlorophyll a, b and total chlorophyll content, carotenoids content and essential oil yield, while these traits increased by application of SA. Total phenol content was increased by water deficit stress and SA application. The highest level of plant (18.2g), leaf (6.6g), and stem (8g) dry weight were observed in 100% FC with 0.5 mM SA. Essential oil yield was decreased by water deficit stress and the highest level of this character was obtained in 100% FC with 0.5 mM SA application. According to the obtained results, Z. clinopodioides needs to irrigate at field capacity along with  0.5 mM SA in order to reach to the highest growth and chemical yields.

Water deficit is one of the most important challenges for the agriculture, especially in the arid and semi-arid regions of the world.Due to the high potential of some medicinal plants for cultivation under environmental stresses, cultivation of these plants in the low-yield fields can be considered. Therefore, to reduce the negative effects of water deficit on the growth of Hibiscus sabdariffa L., a factorial experiment was conducted in a completely randomized design with three replications in the research greenhouse of agriculture faculty, Birjand University in 2017. The experimental treatments included the amount of irrigation water at four levels (100, 80, 60, and 40% of the field capacity) and irrigation treatment with magnetic water at three levels (non-magnetic water (control), magnetized water with one, and two times passing through the magnetic field). The results showed that the effects of irrigation water amount treatments on the all measured traits and magnetic irrigation treatments on the all traits except leaf number were significant. Also, the interaction effects of irrigation water amount × magnetic irrigation treatments were significant on the plant height, number of bolls per plant, fresh and dry weight of aerial parts, dry weight of roots, and dry weight of sepals. Reducing the amount of irrigation water from 100 to 40% of field capacity caused a decrease in the spade number, stem diameter, number of leaves, and fresh root weight by 34.7%, 23%, 40.6%, and 27.6%, respectively. The mean comparison of interaction effects of irrigation water amount × magnetic irrigation treatments showed that irrigation with double-magnetized water improved all the traits compared to the irrigation with non-magnetic water. Therefore, it seems that the application of magnetic irrigation can be considered as one of the strategies to reduce the negative effects of water deficit.

A greenhouse research was carried out to study the simultaneous effect of hydropriming and water stress on the yield and yield components of sweet pepper (Padra var.) in Ferdowsi University of Mashhad. The experiment was performed as a factorial arrangement of two factors in a completely randomized design with three replications. Hydro-priming consisted of two levels (non-hydropriming and hydropriming) and the water stress included three levels (100, 75 and 50 percent of water requirement), which were applied in a silty clay soil. The results showed that the effect of seed hydropriming on shoot fresh weight and electrical conductivity (EC) of fruit water were significant (P<0.01). The effects of deficit irrigation on the fruit fresh and dry weights, fruit number, plant height, and stem diameter were significant at 1 percent level (P<0.01), while the effects on shoot fresh and dry weights were significant at 5 percent level (P<0.05). Interaction effects of the treatments were significant on EC of fruit water at the 1 percent level (P<0.01), while the effects were significant on the fruit number, shoot dry weight, plant height, and pH of fruit water at the 5 percent level (P<0.05). The results also showed that the highest fruit number (4.34 per plant) was recorded in the 100 percent plant water requirement and seed hydropriming, while the lowest fruit number (2.0 per plant) was found in the 50 percent plant water requirement and seed hydropriming treatment. The highest and lowest fruit fresh weights (i.e., 191.4 and 82.1 g per plant) were observed in water stress treatments of 100 and 50 plant water requirement percent, respectively. The results also revealed that the fruit number changed in 75 and 50 percent water requirement treatments + non-hydropriming conditions by 11.3 and –11.0 percent, while under hydropriming conditions, fruit number was reduced by –16.5 and –50 percent, respectively. Overall, in this study the best treatment was 100 percent water requirements + seed hydropriming in greenhouses conditions. Deficit irrigation and hydropriming levels were applied on this plant in the Mashhad region in field conditions and recommended for future research.

In this study, the effects of deficit irrigation along with a foliar application of silicon on growth, yield, and quality of tomato (Lycopersicon esculentum L. cv BHN) were evaluated. This experiment was conducted as a factorial arrangement in a completely randomized design with three replications. Tomato plants were planted in pots containing coco-peat and perlite (80:20 v/v). The plants were treated with different irrigation levels (60, 80, and 100% full irrigation) and different levels of silicon (0, 100, and 200 mg L-1). Results showed that with an increase in irrigation levels vegetative growth and fruit quality was improved. The highest plant height and fruit number were found in 100% water requirement. Application of 200 mg L-1 silicon significantly increased fruit number and yield in 60% deficit irrigation. Deficit irrigation significantly increased catalase and peroxidase enzyme activity. The application of 100 mg L-1 silicon could increase TSS in 80% deficit irrigation. Overall, it seems that foliar application of silicon (200 mg L-1) could alleviate the negative effects of drought stress in tomato and improved growth, yield, and fruit quality under drought stress conditions.

A rapid, complete, and uniform seed germination is important to establish a healthy seedling that is a critical key to successful crop production. Therefore, identification of effective factors on germination and plant response to various conditions are important to use an appropriate agronomic managements. Temperature and water are the most important environmental factors controlling seed germination in plants. The crop growth models are among the most effective tools for using in crop management decisions. The response of seed germination to temperature and water potential can be simulated by thermal time, hydrotime and hydrothermal time models. Regarding the importance of watermelon production in Iran, this study was conducted to determine the cardinal temperatures of germination in watermelon plant, and also to quantify its germination in response to the temperature and water potential interaction. .

In order to investigate the effects of temperature and drought stress on seed germination and quantifying the germination responses; a factorial experiment was conducted with seven  levels  of temperature including  10, 15, 20, 25, 30, 35 and 40 °C and  the  six levels of water potential including 0, –0.25, –0.5, −0.75, –1.0, and –1.25 MPa, respectively. A Ψ of 0 MPa was obtained using distilled water. The negative Ψ levels were prepared by polyethylene glycol (PEG 6000; Merck, Germany) according to Michel and Kaufman (1973). For each treatment, four 25-seed replicates were placed in 9-cm petri dishes containing one disk of Whatman No. 1 filter paper, with 7 mL of test solutions. Cumulative germination percentage was transformed to probit regression against time log (Finney, 1971; Steinmaus et al., 2000), and the time taken for cumulative germination (tg) to reach subpopulation percentiles (10–90%) was estimated from this function according to Steinmaus et al. (2000). Then the germination rates (GR) were calculated as the inverses of the germination times for each percentile at each T or Ψ. The preliminary estimation of the parameters in the TT, and HT models were obtained by plotting GR versus T and Ψ for each percentile. Then using repeated probit analysis developed by Ellis et al. (1986), the exact parameters for the TT, HT and HTT models were determined for the whole seed population. All statistical procedure were done by SAS and Excel software, and the figures were drawn by SigmaPlot10 software.

The analysis of variance showed that the temperature, water potential and their interaction had significant effect on the germination percentage of the watermelon plant. Seed germination of watermelon was about 96 % under the optimal conditions. However, the germination ability was affected by the temperature and water potential of the seedbed. The results showed that the germination was decreased by decreasing water potential, at all temperature levels. The seeds of watermelon germinated over a range of water potentials from 0 to -1 MPa. Furthermore, the lowest germination loss associated with decreasing water potential observed at temperature range of 20-30 °C (compared to temperatures below and above this range). The maximum percentage of germination was recorded at 20-30 °C, while no seeds germinated at 10 and 40 ° C. The results also showed that the highest germination rate was obtained at 25 °C and the germination rate decreased at lower and higher temperature than this range. While watermelon seeds were grown under no water stress condition, the estimated base and ceiling temperatures of germination by a linear regression method were 10.7 and 40.0 °C, respectively. However thermal time model was used, but the base and the maximum temperatures were estimated as 11.5 and 40.1 °C, respectively. Furthermore, an optimum temperature of 25.2 °C was predicted by hydrothermal time model for watermelon germination. The results showed that the base temperature and median thermal time to germination were varied with changing water potential. The hydrotime analysis showed that the base water potentials was in a range from -0.45 to -1.23 Mpa, that differed with changing water potential. Watermelon seeds had higher base water potential and also required a longer hydrotime for germination under non-optimal temperature. Hydrothermal time analysis showed that seed germination responses to temperature and water potential might as well quantified by parameters derived from hydrothermal time models (R2= 0.90-0.92). The amount of hydrothermal time required to germinate was 40.5 MPa °C days on the suboptimal and supra optimal temperature ranges. The HTT model showed that the Ψb(50) increased by 0.09 MPa with every degree increase in temperature above optimum temperature.

The thermal time, hydrotime and hydrothermal time models well described germination time course of watermelon seeds in response to temperature and water potential.Thus, the estimated parameters of these germination models allowed us to characterize the germination behavior of watermelon seeds under varying environmental conditions and global warming.

In order to study the effects of drought stress on polyphenolic compounds of pomegranate juice (Punica granatum L.) (total phenol, total flavonoid and cyanidin 3-glocoside content) as well as  fruit yield, an experiment was carried out as split plot based on a randomized complete block design with three replications (irrigation levels in main plots and pomegranate genotypes in subplots). Results showed that drought stress increased the content of juice polyphenolic compounds (P <0.05) and decreased fruit yield (P <0.05) in comparison with non-stress conditions (75±5% FC). However, mild stress (55±5% FC) caused a lower yield loss (P <0.05) compared to severe stress (35±5% FC). The results also showed that the genotypes studied could be considered as a rich source of phenolic compounds; however, the highest difference among the genotypes was found for cyanidin 3-glocoside content at different irrigation levels. On the other hand, based on the principal component analysis, under non-stress and mild stress conditions, genotypes Agha Mohamad Ali (AMA), Pust Sefid Torsh (PST), Malas Torshe Saveh (MTS), and Malas Shirine Saveh (MSS) could be recommended in food and pharmaceutical industries as superior and natural antioxidant-rich genotypes due to the high fruit yield and polyphenolic compounds. Generally, because of the importance of yield potential under drought stress, the mild drought stress treatment (55±5% FC) could be introduced as the optimum condition to obtain acceptable level of secondary metabolites, particularly cyanidin 3-glocoside, and fruit yield in Saveh region.

In order to study the effect of water deficit and foliar application of salicylic acid and spermine on the phenological stages and caffeic acid derivatives yield of Echinacea purpurea L., a three replicated split- plot experiment was conducted based on a randomized complete block design during 2016 and 2017 growing seasons at the research field of Research Institute of Forests and Rangelands, Iran. In this experiment, three irrigation regimes (irrigation after 20, 40 and 60% depletion of soil available water) were accommodated in main plots and salicylic acid (SA) and spermine (SPM) spray treatments (Control (no spray), spray at five levels of 75 mg/l SA, 150 mg/l SA, 75 mg/l SPM, 75 mg/l SA+75 mg/l SPM and 150 mg/l SA+75 mg/l SPM) were considered in subplots. The exogenous SA and SPM were applied on the foliage at two steps, 10-days apart and at the beginning of stem elongation stage. The effects of irrigation regime and spray treatments were significant on the traits studied. Drought stress decreased the number of days to phenological stages, the yield of echinacoside and cynarin in flower and cichoric acid, and caftaric acid and cynarin in leaves, but increased the yield of chlorogenic acid in flowers and caffeic acid derivatives (cichoric acid, echinacoside, chlorogenic acid, caftaric acid and cynarin) in roots. The foliar application of salicylic acid and spermine increased all studied traits. The interaction between water deficit and foliar spray was significant on the yield of caffeic acid derivatives in roots. The highest yield of cichoric acid (9.49 kg/ha), echinacoside (0.67 kg/ha), chlorogenic acid (0.26 kg/ha), caftaric acid (7.31 kg/ha) and cynarin (0.27 kg/ha) in roots was obtained at irrigation after 60% depletion of soil available water and simultaneous application of high concentrations of SA and SPM. Based on the results of the present study, the foliar application of SA and SPM improved the yield of caffeic acid derivatives in coneflower under both normal and water stress conditions.

Water supply in arid and semiarid regions of the world is a serious problem in crop production. Grafting may enhance water stress resistance and plants growth. In order to evaluate the effect of different cucurbit rootstocks (Flexifort, Shintoza and ungrafted cucumber) and water stress (40, 60, 90% of field capacity) on morphologic traits and yield of greenhouse cucumber (Cucumis sativus L. var. Nagen 792), an experiment was conducted as split plots design based on randomized complete blocks with three replications in 2016. Results showed that plant dry weight, leaf and stem fresh weight, number of nodes and root moisture content in Flexifort rootstock as compared to ungrafted plants was increased by 91, 53, 58, 28 and 7%, respectively. Root volume in the Shintoza and Flexifort rootstocks was almost twice as much as the ungrafted plants and its volume decreased with increasing water stress. Plant dry weight, leaf and stem fresh weight, number of nodes, root volume and leaf and root moisture content were decreased significantly with increasing water stress. Maximum leaf area and marketable yield were obtained in Flexifort rootstock irrigated with 90% of field capacity and minimum leaf area and marketable yield were obtained in ungrafted plants irrigated with 40% of field capacity. These results suggest that grafted plants on Flexifort and Shintoza have better growth and yield than ungrafted plants under water stress conditions

Water is a main factor in agriculture activities and almost 70 percent of world water resources are consumed in agriculture. The present research has been done to investige response of Citrus rootstocks to drought as factorial test based on randomized completely design with three replications. Factors included rootstocks in 10 levels [Poncirus (PT), Troyer citrange (TC),Citrumello (CR),Sour orange (SO),Cleopatra mandarin (CM), Rough Lemon (RF), Bakraii (B), Chang-sha (CH), Machrophylla (M) and Mexican Lime (ML)] and irrigation in two levels [optimum irrigation (fixed in field capacity) and withholding irrigation]. Results showed that drought induced increament of ion leackage percentage in all of the rootstocks and  the root to shoot dry weight ratio in PT, M and B and decrease of leaf water relative content in all of the rootstocks, leaf fresh weight in SO, stem fresh weight in CR, root fresh weight in TC, SO, CR and M, shoot fresh weight in SO and CR, total fresh weight in SO, CR and M, root to shoot fresh weight ratio in TC, CR, M and CM. Therefore, TC, CH and PT had good tolerance to drought because of lower ion leackage in TC, higher water storage in CH leaves and the higher root to shoot dry weight ratio in PT.

Nigella sativa L. is one of the herbs that has a variety of uses and has been used in Iran’s traditional medicine since old times. Today this plant is considered as one of the most important kinds of medicine. Almost all the metabolic activities of plant cells, including the construction of active ingredients in medicinal plants, depend on lack of absorbable water by plants can lead to the morphological, physiological and biochemical changes, including decrease of cell swelling and growth and thus reduction of leaf area and plant height, stomatal closure and photosynthesis restriction, increase of soluble compounds for regulating the osmotic pressure, reduction of nutrient absorption and ultimately reduction of crop production. The use of anti-transpiration compounds is considered as a promising tool for the regulation of transpiration in respect of water conservation at an optimal level, where the strategies such as the use of anti-transpiration compounds have the potential for transpiration regulation. The aim of the present study is to improve the yield and yield components of medicinal plant N. sativa by anti-transpiration compounds under drought stress conditions.

The research was done using a split plot experiment on a randomized complete block design with three replications. The irrigation intervals (8 and 16 days) in main plots and anti-transpiration compounds of chitosan (0.25, 0.5 and 1 %), Plantago psyllium mucilage (0.5, 1 and 1.5 %) and arabic gum (0.25, 0.5 and 0.75 %) were put in subplots with three replications. Also, the distance between the main plots in each block and distance between the two blocks were assigned as 100 cm and 200 cm, respectively; so that the moisture content of a plot had no effect on the adjacent plots. Planting date was April 16 and planting was performed by hand in 0.5cm-deep furrows. Anti-transpiration compounds were sprayed simultaneously with applying drought stress till the flowering stage once a week at sunset. Plant height, leaf area index, irrigation water efficiency index, leaf temperature and stomatal conductance were measured.

The results showed that there were significant differences between treatments in all studied traits. The best rate of the measured traits was observed at 8-day irrigation interval and chitosan treatment. Providing plant favorite conditions such as reducing plant temperature, increasing morphological traits comparing to rainfed at 16-day irrigation interval. Applying arabic gum did not improve growth but acted as a growth inhibitor. Anti-transpiration compounds led to significant changes in all the studied traits compared to the control, indicating the effectiveness of these natural compounds. Chitosan stimulating abscisic acid synthesis in the treated plant would result in stomatal closure, reduction of stomatal conductance, transpiration rate and water content. It also pointed out that the anti-transpiration effect of chitosan was because of its stimulatory effect in increasing abscisic acid concentration in the treated leaves of bean plant. As the above compounds are natural and biodegradable, as well as safer and less expensive than other chemical anti-transpiration compounds, they can serve as a good alternative to the chemical compounds. Cognition and expertise in water relations of plant and drought stress tolerance is considered as the main program in agriculture and the ability to withstand this stress is of great economic importance.

The important processes, including nutrition, photosynthes is, stomatal opening and closure and growth are all influenced by water. In this study, it was observed canopy temperature and stomatal conductance would increase at 16-day irrigation interval, where the increase is considered as a drought tolerance mechanism. Also, the anti-transpiration compounds led to significant changes in terms of all the studied traits compared to the control, indicating the effectiveness of theses natural compounds. Providing the appropriate conditions, 1% chitosan treatment can enhance the yield under drought stress. Spraying by arabic gum did not improve the growth conditions. According to this experiment, 1% chitosan treatment and 1.5% Plantago psyllium mucilage is considered the most appropriate strategy to enhance the yield of Nigella sativa under drought stress.

Effect of deficit irrigation on evapotranspiration, yield, water use efficiency and some growth parameters of Hamadanian pepper (Bivar) using a completely randomized design (CRD) with a full irrigation treatment (FI) and three deficit irrigation treatments (85, 70 and 55% application of water requirement; DI85, DI70, and DI55, respectively) in five replications was examined. Evapotranspiration in the FI, DI85, DI70, and DI55 treatments during the 66 days of the deficit irrigation application, were 337.8, 307.5, 281.1 and 244.2 mm and in the whole growth period were 396.2, 365.9, 339.5 and 302.6 mm, respectively. The plant’s morphological characteristics were decreased with decreasing the soil water content. However, in 79% of the cases, the difference between FI and DI85 treatments was not significant. Whereas, in all the cases, the difference between DI55 treatment and FI and DI85 treatments was significant. Applying deficit irrigation decreased the number of good-shaped fruits from 33.0/plant in the FI treatment to 15.6/plant in the DI55 treatment and similarly increased the number of bad-shaped fruits from 5.4 to 18.0 per plant. Crop yield and water use efficiency in the FI treatment were 18.98 ton/ha and 4.79 kg/m3, which did not have significant difference with the DI85 treatment (which had a yield of 17.75 ton/ha and a water use efficiency of 4.85 kg/m3). While there is not a statistically significant difference between the crop yields of FI and DI85 treatments, the DI85 treatment uses less water and gives crop yield very close to that of full irrigation treatment. Hence, the DI85 treatment can be recommended in the cultivation of Hamadanian pepper. In the severe water-scarce conditions, the DI70 treatment could be used to yield 13.48 ton/ha, which is 29% less than the FI treatment. Also, water use efficiency in the DI70 treatment was decreased by 17% compared to the FI treatment. Irrigation efficiency was 61.9, 65.3, 69.6 and 73.4% in the FI, DI85, DI70, and DI55 treatments, respectively

Soil amendments have been widely used in greenhouse cultivation. Cucumber, as an important summer crop, has the highest area under cultivation in the greenhouses of Iran. For this reason, in the present research, effect of applying zeolite and drought stress on cucumber growth and its fruit parameters (number, weight, length and diameter of the fruit) was investigated in a split-plots experiment, based on completely randomized design, with 9 treatments and 3 replications, in Arian city, Southern Khorasan province, Iran. Three levels of drought stress (0, 25% and 50% of water requirement), as the main plots, and three levels of zeolite (0, 5 and 10 grams per kg of soil), as the sub-plots, were applied during the plant’s growing season. Results showed that application of zeolite didn’t have significant effect on number of fruits; but its effect on other yield parameters (fruit weight, fruit length and fruit diameter) was significant at 5% level. Interaction between water stress and zeolite was significant. Application of 10 grams of zeolite per kg of soil resulted in the highest yield, number of fruits and fruit length. Increasing the amount of zeolite, increased fruit yield..