جستجوی مقالات مرتبط با کلیدواژه « دماهای کاردینال » در نشریات گروه « زراعت »

Bitter apple (Citrullus colocynthis) is one of the medicinal plant that grows in semi-arid and desert condition which have been used in traditional medicine. There is a few research on cardinal temperatures of Bitter apple in the literature. In order to determine Germination characteristics and cardinal temperatures for Bitter apple, a laboratory experiment was down in petri dish based on completely randomized design with four replications. The experimental treatments were nine different temperatures (5, 10, 15, 20, 25, 30, 35, 40, 45 °c). The measured traits were germination percentage, germination rate and mean germination time. Cardinal temperature was calculated using dental, dual, and beta functions. The results showed that with increasing temperature up to 30 ° C, percentage and germination speed increased. The highest germination percentage (70%) and germination rate (2.8 seeds / day) were observed at 30 ° C. The lowest germination time (4.48 days) was observed at 30°C. The base, favorite and maximum temperatures (cardinal temperatures) for this plant were12, 30 and 45 °c, respectively.

Purple nutsedge (Cyperus rotundus L.) is one of the problematic weeds worldwide prevalent in tropical and subtropical regions. Tubers are major tools through which purple nutsedge is propagated, whereas its seeds have a low ability to germinate. Therefore, evaluation of the response of tubers against environmental agents is great of importance to know the germination and emergence time. Germination, in turn, is mostly affected by temperature, among other environmental factors. Various models that are recognized as the Thermal Time model have been introduced to describe the seed germination pattern against temperature. Since predicting the emergence of reproductive organs through the modeling is great of importance for improving the control strategies; the present study was carried out to investigate the response of tuber sprouting of purple nutsedge (Cyperus rotundus) against temperature using thermal time models.

The experiment was carried out as a randomized complete block design with three replications in a germinator. Each replicate was placed on a separate shelf. For each replicate, 15 tubers were placed inside a 20 cm Petri dish on a filter paper and then 100 ml of water was added. The experiment was performed separately for constant temperatures of 10, 15, 20, 25, 30, 35, and 40 °C in absolute darkness. To analyze the data as modeling, five thermal time models were evaluated based on the statistical distributions of normal, Weibull, Gumble, logistic and log logistic. Indices such as R2, RMSE, RMSE%, and AICc were used to evaluate the models.

The results showed that all models predicted the germination response of purple nutsedge tuber with high accuracy (R2 = 0.95). A comparison of models based on AICc values showed significant superiority of the Gumble model over other models. According to this index, there was no difference between logistic and log logistic models with normal. Among the models, Weibull was identified as the most inappropriate model. Different models estimated the final germination (Gmax) between 0.93 to 0.94 (93 to 94%). The base temperature was estimated through different models from 7.10 to 7.47 °C. Among the models, the model based on the Gumble distribution proved the skew to the right of the thermal time and Tm. According to the Gumble model, the thermal time parameters required to reach 50% germination (θT (50)) equals 123.8 ° C day and the maximum temperature for germination at 50% probability (Tc (50)) was estimated to be 46.10 ° C.

the thermal time model based on the Gumble probability distribution was most plausible among the models. Also, a distributed right skewness related to the thermal time and Tm was proved through the Gumble model. The parameters obtained from the Gumble model can be used to predict the sprouting of purple nutsedge tubers. 

Thermal time models were evaluated for prediction of tuber sprouting of purple nutsedge. The thermal time model based on the Gumble distribution was superior over the normal distribution. Thermal time and Tm for tuber sprouting of purple nutsedge were distributed as right skewness.

Recognition of Eryngium caeruleum germination biology can provide the possibility of forecasting the seed dormancy and germination level in various conditions. This study was conducted as factorial experiment based on completely randomized design with three replications in the laboratory of Agronomy and Plant Breeding Department, College of Agriculture and Natural Resources, University of Tehran, to understand Eryngium caeruleum seed dormancy and response of germination thermal parameters. The experimental factors were included three levels of gibberellic acid (0, 250, 500 mg/l), six chilling time (1, 3, 5, 10, 15, 30 days) and seven temperatures (5, 10, 15, 20, 25, 30, 35°c). Germination parameters were obtained by the segmented model under the influence of gibberellic acid and chilling treatments. The results of this study showed that, the best treatment for reducing dormancy level, cardinal temperatures for germination including base, optimum and ceiling temperatures was obtained 1.81, 22.31, and 34.10°c respectively. Increasing of the chilling time and the gibberellic acid concentration from 0 to 250 mg/l, decreased the base temperature, and increased optimum temperature. Ceiling temperature, at first was increased and then decreased.

Temperature is one of the primary environmental regulators of seed germination. Seed priming technique has been known as a challenge to improving germination and seedling emergence under different environmental stresses. Quantification of germination response to temperature and priming is possible, using non-liner regression models. Therefore, the objective of this study was to evaluate the effect of temperature and priming on germination and determination of cardinal temperatures (base, optimum and maximum) of Brassica napus L.

Treatments included priming levels (non-priming, priming with water, gibberellin 50 and 100 mg/l) and temperature (5, 10, 15, 20, 30, 35 and 40 °C). Germination percentage and time to 50% maximum seed germination of Brassica napus L. were calculated for different temperatures and priming by fitting 3-parameter logistic functions to cumulative germination data. For the purpose of quantifying the response of germination rate to temperature, use was made of 3 nonlinear regression models (segmented, dent-like and beta). The root mean square of errors (RMSE), coefficient of determination (R2), CV and SE for the relationship between the observed and the predicted germination percentage were used to compare the models and select the superior model from among the methods employed.

The results indicated that temperature and priming were effective in both germination percentage and germination rate. In addition, the results showed that germination percentage and rate increase with increasing temperature to the optimum level and using priming. As for the comparison of the 3 models, according to the root mean square of errors (RMSE) of germination time, the coefficient of determination (R2), CV and SE, the best model for the determination of cardinal temperatures of Brassica napus L. for non-primed seeds was the segmented model. For hydro-priming and hormone-priming with 50 mg/l GA, the best models were segmented and dent-like models and for hormone-priming with 100 mg/l GA,  the dent-like model was the best. The results showed that for non-priming, hydropriming with water, gibberellin 50 and 100 mg/l treatments, the segmented model estimated base temperature as 3.54, 2.57, 2.34 and 2.34 °C and dent-model estimated base temperature as 3.34, 2.45, 2.21 and 2.83 °C, respectively. The segmented model estimated optimum temperature as 24.62, 23.23, 23.69 and 24.38 °C. The dent-model estimated lower limit of optimum temperature and upper limit of optimum temperature as 20.01, 19.62, 16.25, 19.87 and 28.81, 27.38, 29.58 and 27.31 °C.

Utilizing non-liner models (segmented, dent-like and beta) for quantification of germination of Brassica napus L. response to different temperatures and priming produced desirable results. Therefore, utilizing the output of these models at different temperatures can be useful in the prediction of germination rate in different treatments.

Conditional dormancy (CD) is a dynamic state between dormancy (D) and nondormancy (ND). Seeds at the conditional dormancy stage germinate over a narrower range of temporal conditions. Conditional dormancy is usually observed in seeds with physiological dormancy. However, primary conditional dormancy has also been seen in some freshly harvested seeds. The purpose of the present study was to investigate whether freshly harvested oilseeds have non-dormancy or conditional dormancy.

A factorial experiment was conducted based on a completely randomized design with four replications at Seed Technology Laboratory of Aburaihan Campus, University of Tehran, Iran, in 2018. In this experiment, seeds of rapeseed were collected from 20 different locations in Golestan and Mazandaran provinces. Following that, a germination test was carried out at different temperatures (5, 15, 20, 30, 35°C), and the germination percentage and seed germination rate were recorded. In order to break seed dormancy, two treatments were used: gibberellic acid and after-ripening. For after-ripening treatment, seeds were stored in a paper bag in a dry and dark environment for 6 months. For gibberellic acid treatment, a solution of 100 parts per million (PPM) of gibberellic acid was prepared and added to the Petri dishes. Subsequently, the percentage and rate of germination were recorded.

The results showed that freshly harvested seeds had primary conditional dormancy and germinated in a narrow range of temporal conditions. In addition, cardinal temperatures for freshly harvested seeds were 4.45 and 27.8 for bases and ceilings, respectively. Following gibberellic acid and after-ripening treatments, seeds germinated in a wider range of temperatures and base and ceiling temperatures reached 1.74 and about 40°C, respectively. Thus, germination percentage of seeds treated with gibberellic acid and after-ripening increased at both high and low temperatures. However, the increase in germination percentage was higher at high temperatures than low temperatures. In addition, the effect of gibberellic acid treatment was more than that of after-ripening treatment on the release of dormancy, and after-ripening treatment had an intermediate effect between the gibberellic acid and freshly harvested seeds.

Based on the results of this experiment, the application of gibberellic acid and after-ripening treatments resulted in breaking the dormancy of freshly harvested seeds and increased germination temperature range at high and low temperatures.  Of the two treatments, gibberellic acid had the greatest effect on breaking dormancy and increasing temperature range. Among the cultivars, these changes were maximum in the germination capacity of Hyola 50 and Trapar cultivars and Trapar cultivar had minimum changes.

In order to evaluate germination behavior of Colchicum seed, an experiment was conducted as factorial based on a randomized complete design with four replications. The experimental treatments were all combination of priming at three levels (warm stratification, cold stratification, control), gibberellic acid at two levels (0,500 ppm) and incubation temperatures at 8 levels (2, 5, 10, 15, 20, 25, 30, 35). After applying the priming treatments, gibberellic acid treatment was applied and then the response of seed germination at constant temperatures were assessed in the germinator. The effect of temperature on germination components was significant. Germination was occurred only in warm stratification. Generally, germination was started by a very slow trend and after seeds were set at incubation temperatures, at least 40 days were lasted to germination occurred. There was no germination at 2°C. By increasing temperature at a range of 5-15°C, germination percentage was increased and then was stopped at 25°C. Germination uniformity at 20°C was more than other temperatures. The meanest germination time was observed at 20°C and the least mean germination time was at 15°C. Gibberellic acid (single application) had no effect on seed germination. Based on two regression models, the cardinal temperatures (Tbase, Topt, Tmax) were (1.38-1.72°C), (12.7516.10°C) and (24.12-25.65°C), respectively.

Medicinal plants are one of the important economic plants that are used raw or processed in traditional or modern industrial medicine. Nowadays, this increasing demand has caused the extraordinary and inappropriate harvesting of these plants, which is due to the destruction of the natural habitat of these plants and the presence of a number of them at risk of extinction and destruction. Therefore, in order to prevent the extraction of these plants in the natural habitats, it is necessary to cultivate and domesticate these plants. One of the primary problems in the domestication of medicinal plants is the presence of dormancy in the seeds of these plants. Milk thistlel is a medicinal herb from the Asteraceae family, whose seeds contain valuable medicinal compounds. Primary problems in the domestication of this plant are the presence of a dormancy in its seeds, which leads to the non-uniformity of germination and its emergence in the field. Hence, the first step in the domestication of wild plants is to identify the type of dormancy with the aim of choosing the most effective method to solve it. Therefore, the study was conducted with the aim of: 1) determining the type of dormancy; 2) studying the germination reaction of milk thistle seeds to different levels of gibberellic acid and after ripening under different temperature conditions.

This research was carried out in two separate experiments on fresh and after- ripe milk thistle seeds, with the aim of investigating the effects of various concentrations of gibberellic acid on dormancy removal and germination of this plant at different temperatures. In each experiment, the germination test was carried out at 5, 10, 15, 20, 25, 30 and 35 ° C temperatures on fresh and after-ripe milk thistle seeds with different levels of gibberellic at five levels 0, 500, 1000, 1500 and 2000 ppm. In each experiment, traits such as percentage, rate and uniformity of germination, along with time to germination, were determined in different treatments. The response of these traits toafter-ripening, temperature and gibberellic acid was investigated.

The results showed that fresh and after ripe seeds of milk thistle could not germinate at any temperature, and using gibberellic acid, seeds could germinate at different temperatures. But the response of the fresh and after ripe seeds to gibberellic acid was different. In fresh seeds, percentage, rate, and uniformity of germination were less than the after ripe seeds. Also, the time to start germination in after ripe seeds was less than fresh seeds. In other words, it can be said that although the after-ripening did not remove the seeds dormancy of milk thistle, but increased the susceptibility to gibberellic acid, so that the percentage after ripe seeds and germination rate at lower concentrations of gibberellic acid (500 ppm) was observed. It also after ripening increased the optimum temperature and seed germination ceiling of this plant compared to fresh seeds. The optimum temperature for fresh and after ripe seeds was 10 ° C and 25 ° C, respectively, and the temperature was 30 ° C and 35 ° C, respectively. However, there was no significant difference between the fresh and after ripe seeds at the base temperature In other words, it can be said that the after ripening increases the germination temperature of the milk thistle seeds with gibberellic acid.

  oilseed rape has a wide range of adaptation and grows well in many regions under variable temperatures. However, the ability of the varieties varies in response to the favorable and unfavorable conditions. Temperature stresses (high or low temperatures) have harmful effects on crops. Generally, temperatures below 10 ° C can damage germination and emergence. Low temperatures can also have a negative effect on the post-emergence stages of crops. The high temperatures can also reduce the total dry matter produced, the number of pods under development, the number of seeds per pod, the weight of seeds, and, finally, the yield of the plant. Also, high temperatures affect the development and maturity of the seeds, resulting in a higher level of yield. Identifying high or low tolerant cultivars can help researchers improve the new cultivars and increase the flexibility of selecting the right cultivar for farmers. There are several methods for evaluating cultivars at low and high temperatures based on farm or laboratory surveys. Field surveys are difficult, unsustainable and seasonal. Because in field conditions, temperatures and humidity fluctuate a lot. Various studies have been done to evaluate the variation of germination in heat or cold stress in different plants such as lettuce, alfalfa, sorghum, cotton, sesame, etc. However, there is not much information on canola cultivars in Iran. The aims of this study was to determine the cardinal temperatures (2) evaluate the tolerance of different genotypes at high or low temperatures and (3) and to study the secondary dormancy potential in Iranian genotypes. In order to, germination tests were conducted in fixed temperatures incubators with 5, 10, 15, 20, 25 and 30 oC on 10 oilseed rape genotypes, in 4 replications with 50 seeds. Finally, cardinal temperatures were estimated using segmented (for germination rate) and beta (for germination percentage) functions. The tolerance of genotypes to high or low temperatures were determined using estimated cardinal temperatures. Also, an experiment was conducted to investigate the potential of different cultivars for induction of dormancy, in which seeds of 10 oilseed rape genotypes were subjected to drought stress conditions to determine the percentage of total induction due to drought for each genotype. The percentage of germinated seeds, the percentage of seeds with dormancy and dead seeds can be determined. Finally, the percentage of induction of the secondary dormancy was calculated for each genotype. Statistical analysis was performed using SAS software. Marshall and Squire (1996) showed that the minimum temperature (Tb) for oilseed rape germination was about 3 °C. Soltani et al. (2013) showed that the minimum temperature for oilseed rape germination was 2.7 °C and under dry conditions up to 6.7 °C at -0.8 MPa increased. Also, they showed that the average thermal time for germination (TT50) increased from 29.5 °C/day at 0 MPa to 57.9 °C/day at -0.8 MPa. Results indicated that mean of base (Tb), optimum (To) and ceiling (Tc) temperatures for germination percentage were 4.99, 18.23 and 34,20 oC and also mean of base (Tb), optimum (To) and ceiling (Tc) temperatures for germination rate were 6.18, 24.76 and 39.40 oC. The Heat and Cold tolerance indexes were also different in different cultivars. Okapi cultivar was the most tolerant in heat tolerance index (5.95) and in cold tolerance index (8.48). X-Power had the lowest tolerance to heat (4.78) and cold (6.50). The potential of secondary dormancy induction also was at the highest level in Okapi (about 40 %). It seems that there was connection between secondary dormancy induction and tolerance to temperature stresses which needs more studies.

In order to examine the germination response of basil medicinal plant’s seeds (Ocimum basilicum L.) to temperature and determination of cardinal temperatures for germination percentage and rate, a compound decomposition experiment was performed through a fully random design with four reptile and six thermal levels (8, 15, 20, 25, 30, and 35 degree centigrade) in seed technology laboratory of Abou-Reyhan campus in Univerity of Tehran. In this study, 22 Basil masses were evaluated including “Tehran”, Green Shahr-e-Rey”, “Green Birjand”, “Purple Birjand”, “Green Shiraz”, “Green Zabol”, “Zahedan”, “Green Zahedan”, “Kermanshah”, “Green Pishva”, “Purple Pishva”, “Green Malayer”, “Khash”, “Local green Tonekabon”, “Green Isfahan II”, “Purple Isfahan II”, “Green Isfahan III”, “Green Isfahan IV”, “Green Mash’had”, “American green Napolta”, “Italian Genovese”, and “Switzerland” . Based on the results of variance analysis, temperature impact, genotype, and their interaction on germination percent and germination rate was significant at the 5% level. Optimal range of temperature for germination percent and germination rate was obtained as 19.10-27.78 and 20.32-29.89 degrees centigrade, respectively. In most masses, the highest germination rate was observed at 25 degrees centigrade. Among all evaluated masses in current research, Isfahan III was appropriated the highest germination rate in all temperatures. The results of experiment showed that the response of germination percentage and germination rate to temperature was well described through Beta function and segmented function, respectively, and cardinal temperatures can be determined for Basil using these two models.

IntroductionSeed germination is a complex biological process that is influenced by various environmental and genetic factors. Temperature and water potential are two primary environmental regulators of seed germination. Quantification of germination response to osmotic potential and temperature is possible using non-liner regression models. Tall mallow (Malva sylvestris) is an important invasive weed in southwest Iran and also a medicinal plant. ). Tall mallow is native home in Western Europe, North Africa and Asia. This plant frequently found in cultivated fields, orchards, gardens, farmyards near manure piles, along roadsides, in towns, and in waste places and, can grow anywhere from 60 to 120 cm in length. Not published information exists concerning effect of osmotic potential on cardinal temperatures, Therefore, the objective of this research was to evaluate the effect of osmotic potential and different temperatures on germination and determination cardinal temperatures (base, optimum and maximum) of Malva sylvestris under osmotic stress.
Material and methodsIn this study germination response to water potential in different temperature were studied. Treatments included osmotic levels (0, -0.2, -0.4, -0.6 and -0.8 MPa) and temperature (5, 10, 15, 20, 30, 35 and 40 °C). Cumulative germination response of seeds to differential water potential and temperature were quantified using three-parameter sigmoidal model. For quantifying response of germination rate to temperature for different osmotic potential were used of 3 non-linear regression models (segmented, dent-like and beta). The root mean square of errors (RMSE), coefficient of determination (R2), CV and SE for relationship between the observed and the predicted germination percentage were used to select the superior model from among the employed methods. Germination percentage and time to 50% maximum seed germination of Malva sylvestris were calculated for the different temperatures and osmotic potential by fitting 3-parameter sigmoidal functions to cumulative germination data.
ResultsResults indicated that temperature in addition to germination percentage also on germination rate was effective. Also results showed that germination percentage and germination rate increased with increasing temperature, while germination percentage and germination rate reduced as a result of water potential increment. Results indicated that under different osmotic potential as 0, -0.2, -0.4, -0.6 and -0.8 MPa, the segmented model estimated base temperature as 1.46, 1.82, 1.29, 0.43 and 4.06 °C, the dent model estimated base temperature as 1.23, 1.82, 3.04, 2.63 and 4.07 °C, the beta model estimated base temperature as -4.32, 4.46, 1.86, 1.61 and 4.13 °C, the segmented model estimated optimum temperature as 28.29, 27.58, 22.24, 22.51 and19.69 °C, the optimum temperature using beta model as 27.89, 25.41, 23.18 and 21.05 °C, the dent-like model estimated lower limit of optimum temperature and upper limit of optimum temperature as 23.16 and 33.58, 16.86 and 30, 16.1 and 25, 15.81 and 25, 19.51 and 1987 °C, ceiling temperature using segmented model were 42.9, 40, 40, 40 and 34.96 °C, using dent-like model were 42, 40, 40, 40 and 34.96 °C, using beta model were 42.01, 40.02, 39.96, 39.98 and 34.83 °C, the segmented model estimated fo as 13.87, 18.45, 19.43, 25.24 and 36.13 h, the dent-like model estimated as 16.65, 23.28, 23.43, 30.48 and 36.56 h and using beta model were 16.06, 21.34, 22.21, 28.92 and 42.89 h, respectively. In compared 3 models according to the root mean square of errors (RMSE) of germination time, the coefficient of determination (R2), CV and SE the best model for determination of cardinal temperatures of Malva sylvestris for 0 to -0.6 MPa was dent-like model and for -0.8 MPa was segmented model. In general, results indicated that lower limit of optimum temperature and upper limit of optimum temperature and ceiling temperature reduced but fo increased as a result of water potential increment.
ConclusionGermination of Malva sylvestris response to different temperatures and osmotic potentials, led to acceptable results. Utilizing the output of non-liner models at different temperatures can be useful in prediction of germination rate in different water potential.

This study was conducted to quantify germination response of onion (Allium cepa) to temperature. For this purpose, seeds were exposed to Various constant temperatures (5, 10, 15, 20, 25, 30, 35 and 40ºC) treatments in seed lab, the university of Tehran, in 2015. The effects of temperatures on rate and percentage of germination was significant. With temperature increasing from 5 to 30ºC, both germination percentage and rate increased, while it decreased with increasing temperature from 30 to 35ºC. Cardinal temperatures of seed germination were estimated by using four regression models including dent-like, segmented, beta modified and beta Models. The best model for estimating cardinal temperatures was dent-like and beta modified models that by used dent-like model The base, under optimal, upper optimal and ceiling temperatures were 0.3, 24.99, 33 and 35.89 °C, respectively, and following beta modified model, The base, optimal and ceiling temperature were 0.2, 26.87 and 35.51°C. For predicting time of germination at different constant temperatures used Thermal-time that constant coefficient of Thermal-time was 3191.43 (°Cd).

Determination of response function of seed germination and seedling emergence to temperature and obtaining cardinal temperatures (base, optimal and maximum) and biological day requirement (minimum day number for seed germination and seedling emergence under optimal temperature and moisture conditions) for emergence is important for crop simulation modeling. This study was carried out to survey seedling emergence response to temperature in five rapeseed cultivars that were sown on 12 sowing dates under Gorgan environmental conditions (2013-2014). Three regression models including beta, segmented and dent-like were used to describe the response of seedling emergence rate to temperature. Root mean square of error, coefficient of determination, correlation coefficient and regression of predicted versus observed values were used to develop the appropriate model. Segmented model was superior compared to beta and dent-like models to achieve the objective of this study. Estimated cardinal temperatures using appropriate model were 3.2, 26.8 and 40˚C for base, optimum and maximum temperatures, respectively. Estimation of biological day requirement in sowing depth of 2 cm showed 4.5 days. The result showed that there is no significant difference for cardinal temperatures and biological day requirement among cultivars. It was concluded that segmented model can be used to quantify the response of rapeseed sedling emergence to temperature and to obtain cardinal temperatures of emergence and thermal time or time to emergence. These parameters are required to develop prediction models for rapeseed seedling emergence under diverse temperature conditions.

This study was conducted to evaluate the effects of water potential and temperature on seed germination rate of lemon balm (Mellissa officinalis L.). The seeds were incubated in various temperatures of 20, 23, 25, 27, 30 and 32ºC and water potentials of 0, -0.2, -0.4, -0.6 and -0.8 MPa in three replications. This study was conducted in Seed Laboratory, College of Agriculture and Natural Resources, University of Tehran in Karaj in 2015. Data were analyzed using combined statistical design in a completely randomized design in several places. Segmented function was evaluated to describe cardinal temperatures. The base, optimum and ceiling temperatures of lemon balm were 17.30, 30.9 and 35ºC under optimum conditions of water potential, respectively. The base temperature increased gradually with decreasing water potential and increased to 21.25°C in -0.8 MPa water potential. The optimum temperature decreased to about 28°C by decreasing water potential to -0.6 MPa. Lemon balm seeds did not germinated in 5, 10, 15 and 35°C in any moisture levels. The R2 value of hydrothermal time model was 0.55. The hydrothermal value was 71.41 MPa oday and According to this model seed germination of lemon balm needs to 71.41 MPa oday. The results can be used for future studies on the seed biology and ecology of lemon balm.

Access to weed distribution maps can be very useful in planning their management. Locating areas prone to infection with new entrant weeds is needy to knowledge of ecological characteristics of these plants such as cardinal temperatures, EC and pH. In order to investigate the effects of temperature on germination and determine the main germination temperatures (base temperature, optimum and ceiling for germination) of ivy-leaved morning glory, seeds incubated at 10, 15, 17, 20, 25, 30, 35 and 40 0C. To determine the cardinal temperatures, Original beta, Modified beta, segmented and dent like models were used. The results indicated that the original beta model was superior than the other models and base, optimum and ceiling temperatures for seed germination were 10, 25.91 and 41.22 0C respectively. The results showed that ivy-leaved morning glory has high tolerance ability to soil salinity. So, germination percent of this plant can be reduced by 50% in salinity of 45dS.m-1. In addition, germination present of these plants in acidic pH was higher than the alkaline pH. Distribution maps indicated that there were no limitations regarding temperatures and EC for germination and establishment of this weed through the Golestan Province. But regarding pH, there is a major in increasing distribution extent in the province. So that only a small section of Kalaleh and Galikesh lands are suitable in this regard.

A laboratory study was conducted at Golestan plant protection management in 2013 to determine the effect of temperature and water potential on seed germination of tall morning-glory. Treatments were consisted of seven levels of temperatures (10, 15,25,30,35 and 40 0C) and six levels of water potential in (0, -0.2, -0.4, -0.6, -0.8 and –1.0 MPa). Seed germination began at 100C up to 250C, and then started to decrease. The highest seed germination (84%) was obtained at alternating temperatures of 25:35 °C. By reducing water potential from 0 to -1.0 MPa, seed germination percentage was decreased from 80% to 0. On the basis of three- parameter logistic model, the salt concentration required for 50% reduction of seed germination was -6.5 MPa. The Segmented model used to determine cardinal temperatures of tall morning-glory. Based on this model, base, optimum and ceiling temperatures of the plant in control treatment were 8.3, 25, 40 0C respectively. In general, the optimal temperature range, germination occurred in less water potential. By reducing water potential, base, optimum and biological hours for germination was increased.

Germination and seedling establishment are two critical and important stages during plants growing season. From seed technology viewpoint, germination refers to emergence and development from seed embryo, so that could produce normal seedling. Many studies have been done to determine germination cardinal temperatures and required thermal time for emergence occurrence, but there's not a lot of information about the sunflower cultivars. This study was aimed to investigate the germination response of three sunflower varieties (Farrokh, Hisan and Progress) and assessment of nonlinear regression models to determine cardinal temperatures and required biological days for germination of three aforementioned varieties. For this, Farrokh, Hisan and Progress varieties seeds were exposed to five constant temperatures (15, 25, 30, 35 and 40 0C) in Seed Research Lab., Gorgan Univ. Agric. Sci. and Natur. Res. (GUASNR) in 2012. Germination duration and percentage were measured, germination rate was calculated and biological time and thermal time for germination were estimated. In order to quantify cardinal temperatures, three nonlinear regression models (segmented, dent-like and beta) were used. Results indicated that temperature and variety simple and interaction effects had significant effect on maximum germination percentage (MGP), germination rate (reciprocal time to 50% germination), and time to 10, 50 and 90% germination. Assessment of three nonlinear regression models including segmented, dent-like and beta models revealed that segmented and beta had the same quality and selected as appropriate models for Farrokh, while dent-like model was selected as the superior model for Hisan and Progress varieties. For Farrokh, base, optimum and ceiling temperatures were estimated as 8.51, 33.26 (lower and upper optimum were 30.44, 37.05) and 48.47 0C, respectively. the base, lower optimum, upper optimum and ceiling temperatures were estimated as (8.9, 30.41, 37.77 and 45 0C) and (9.85, 28, 38 and 47 0C) for Hisan and Progress, respectively. Biological time for 50% germination for Farrokh, Hisan and Progress also were estimated as 18.14 (20.47), 18.52 and 17.05 hours. Results revealed that different sunflower varieties have different cardinal temperatures. Therefore, if we are planning to use these coefficients to quantify responses of sunflower to temperature and prediction of germination occurrence time, variety-specific coefficients should be determined and used.

Nowadays medicinal plants are considered as economically important plants throughout the world، while basic information on these plants is scarce. This study was aimed to quantify germination rate response of annual savory (Satureja hortensis L.) to temperature and salinity stress. For this purpose، seeds were exposed to different temperature (12، 15، 20، 25، 30، and 35 ͦ C) and salinity levels (0، 25، 50، 75، 100، 125 and 150 m M) treatments in Seed Research Lab.، Gorgan University of Agricultural Sciences and Natural Resources in 2013. Results indicated that temperature and salinity stress simple and interacted effects had significant effect on maximum germination percentage (MGR)، germination rate (reciprocal time to 50% germination)، and time elapsed to reach 10، 50 and 90% germination. Along with salinity levels increment، both germination percentage and rate decreased. With temperature increasing to optimum temperature، both germination percentage and rate increased، while it decreased from optimum temperature onward. Assessment of three nonlinear regression models including segmented، dent-like and beta models revealed that the last one was the superior model. Base on the superior model (Beta)، base، the optimum and ceiling temperatures were estimated as 8، 24. 77 and 41 ͦ C، respectively. Biological hours for control treatment (zero salinity level) were calculated as 83. 68 hours. Optimum and ceiling temperatures were not affected by salinity stress، but base temperature and biological hours for germination was delayed as 1. 35 ͦC decrement and 1. 65 hours increment per each 25 m molar salinity levels.

Almolookhiyeh (Corchorus olitorius L.) known in the world as a valuable medicinal plant that was produced for the first time in Iran in 2011. This study was aimed to quantify germination response of Almolookhiyeh to temperature. For this purpose، seeds were exposed to different constant temperatures (10، 15، 20، 25، 30، 35، 40، 45 and 50°C) in Seed Research Lab، Gorgan University of Agricultural Sciences and Natural Resources in 2011. Results showed that the effect of temperature on the maximum germination percentage (MGP)، germination rate (R50)، germination uniformity (GU)، and time to 10، 50 and 90 percent germination as (D10)، (D50) and (D90)، the percentage of normal seedlings (NS%) and seedling length (LS) was highly significant. Assessment of three nonlinear regression models including segmented، dent-like and beta models based on 10، 50 and 90 percent germination revealed that beta model was superior to other models. Based on the superior model (Beta)، base، optimum and ceiling temperatures were estimated as 10. 18، 37. 31 and 50°C، respectively. Biological hours also were calculated as 13. 56 hours. Using beta model to regress seedling length against temperature and normal seedling percentage versus temperature showed that seedling emergence، the maximum seedling length and the highest normal seedling percentage were occurred at 11 to 44، 35. 34 and 31°C، respectively.

This study was conducted to quantify germination response of annual savory (Satureja hortensis L.) to temperature and water potential. For this purpose، seeds were exposed to different temperature (12، 15، 20، 25، 30، 35، 37 and 40°C) and water potential (zero، -0. 1، -0. 3، -0. 5 and -0. 7 MPa) treatments in Seed Research Lab.، Gorgan University of Agricultural Sciences and Natural Resources in 2013. Results indicated that temperature and water potential and interacted effects had significant effect on maximum germination percentage، germination rate (reciprocal time to 50 percent germination)، and time to 10، 50 and 90 percent germination. Along with water potential decrement، both germination percentage and rate decreased. With temperature increasing to optimum temperature، both germination percentage and rate increased، while it decreased from optimum temperature onward. Assessment of three nonlinear regression models including segmented، dent-like and beta models revealed that the last one was selected as the superior model. Based on the superior model (Beta)، base، optimum and ceiling temperatures were estimated as 7. 56، 23. 98 and 40°C، respectively. Biological hours for control treatment (zero potential water) was calculated as 91. 17 hours. Cardinal temperatures were not affected by water potential، but biological hours for germination was delayed as 17. 64 hours per each unit water potential increment.

The main objective of this study was to describe emergence rate response to temperature and estimate cardinal temperatures (base, optimum and ceiling temperatures) and biological days requirement for safflower emergence. To do this, four safflower cultivars (Esfahan, Goldasht, Padideh and Sofeh) were sown at 12 sowing dates (every month) and the emergence rate (inverse of time to 50% emerged seeds) was calculated for each sowing date. The segmented, dent-like and beta functions were used to describe the relationship between emergence rate and temperature. Root mean square of deviation (RMSD), coefficient of variation (CV), correlation coefficient (r) and linear regression coefficients (a, b) between predicted and observed days to emergence were used to select the superior function. Results indicated that the compared to the dent-like and beta functions, the segmented function described well the response of safflower emergence to temperature due to the higher r (0.90-0.97), and lower RMSD (2.17- 4.06) and CV (12.3-22.4). Fit of the segmented function on data of emergence rate to temperature showed cardinal temperatures (base, optimum and ceiling temperatures) among cultivars ranged from 2.30-3.44, 20.56-23.28 and 35oC, respectively. There was no significant difference among the cultivars in terms of cardinal temperatures. The biological days requirement for emergence among cultivars ranged from 8.05 to 9.78 which were not different significantly. The quantitative information provided by this study can be used in the crop models to predict the emergence time courses under diverse temperature conditions.