جستجوی مقالات مرتبط با کلیدواژه « survival percentage » در نشریات گروه « زراعت »

Chickpea is an important source of energy and protein of the Iranian people’s diet. Iran is one of the main centers of genetic diversity of this crop. The cultivation of chickpea nowadays is practiced using irrigation or supplemented irrigation in many parts of Iran, as more challenging by climate change, precipitation decline, and salinization of underground water resources. On the other side, there is no enough fresh water to meet the full water requirement of chickpea. Although chickpea consider as a salt sensitive crop but there are some reports that show some variable reaction to salinity amongst different chickpea genotypes. A collection of cold and drought stress tolerant chickpea genotypes are maintained in Mashhad Chickpea Collection (MCC) in the Plant Science Research Center of Ferdowsi University of Mashhad. Therefore, testing the tolerance of different genotypes and landraces of this crop to salinity stress is of important, and this experiment is arranged to test salinity tolerance of chickpea genotypes in this collection.
 

In order to identify and assess of chickpea genotypes salinity tolerant, seeds of 206 Mashhad Chickpea Collection genotypes were kindly prepared by Plant Science Research Center of Ferdowsi University of Mashhad (FUM). The experiment was carried out in the research green house of Faculty of Agriculture of FUM at the spring of 2021 which light was normal, and temperature and humidity were controlled. A randomized complete block design was used with three replications and each treatment consist of 10 plants for each genotype. Seeds were sown in the shallow trays in the lab at 25 degrees centigrade and emerged seedling were transplanted in the sand culture medium. Saline water prepared by adding NaCl to tap water till its EC reached to 12 dS.m-1. Salinity imposed after a week of transplanting through the Hoagland nutrient solution and continued for four weeks. Nutrient solution was renewed each week and 12 dS.m-1 NaCl dissolved in that solution. Measured traits included the height difference at the beginning of the imposing of salt stress and for weeks later, number of branch per plant, survival percentage, and biomass accumulation. Sodium and potassium content of shoots. Data were analyzed using Minitab for windows 17 and standard error and cluster analysis arranged using JMP4 software.
 

 The results showed that 31 genotypes have a survival rate of 76-100% which 10 genotypes showed survival rate of 100%. Plant height, biomass, and number of lateral branches per plant decreased as survival rate decreased. Significant increase in shoot Na+ concentration was only found in survival range of 0-25% while the shoot sodium content was the lowest in in group of 57-100% survival compared to the other three groups. Biomass accumulation also reduced more rapidly in low survival group (0-25%) compare with 76-100% survival group by 66%. The correlation analysis showed that survival rate, plant height and number of lateral branches per plant, biomass, plant height difference and shoot K+ concentration showed significantly positive correlation. Based on factor analysis, three factors were selected that in total 79% of the total variation was explained. The first and second factors were explained high percent of variation that include survival rate and plant height and number of lateral branches per plant, biomass, plant height difference and Na+ concentration. Genotypes MCC1782, MCC197 ,MCC1703 ,MCC1568, MCC1573, MCC1737, MCC1209, MCC1516, MCC1493, MCC1832, MCC1957, MCC1721, MCC2016, MCC1704, MCC1641, MCC1815, MCC1775, MCC178, MCC1754, MCC1627, MCC1716, MCC1918, MCC1827 ,were selected as the superior genotype under salinity stress of 12 dS.m-1  for four weeks. According to the result of cluster analysis, the genotypes were classified in four clusters. The genotypes of the third and fourth clusters had a high average salinity tolerance compared to other clusters with the investigated traits.
 

While chickpea is not traditionally considered a salt-tolerant crop, the observed variations among genotypes suggest that further efforts are required to screen and identify salt-tolerant genotypes and landraces for potential inclusion in breeding programs. It's important to note that the current study was conducted in a controlled environment, with only a few weeks of exposure to salinity treatment. Consequently, we propose a more extensive experiment that includes those genotypes exhibiting superior performance in terms of survival rate, biomass accumulation, low shoot sodium content, and high potassium content.

One of the major reasons behind the unstable yield of chickpea, is the simultaneity of the reproductive stage with drought and late-season heat. Autumn sowing of chickpea is among the suitable approaches to improve chickpea yield. On the other hand, freezing stress is a limiting factor in the autumn sowing of chickpea. Recently, seed priming has been developed as an essential method to induce plant tolerance to environmental stress. The priming will result in a rapid response of the plant to stress. Freezing, as an environmental stress, limits the growth and development of many plants in different parts of the world. Studies show that in addition to acclimation, short-term biotic and abiotic stresses as pretreatment could also increase the plant's tolerance to cold stress. This process alters the freezing response positively.

This experiment was conducted as a factorial in a completely randomized design with three replicates at the greenhouse of the Research Center for Plant Sciences of Ferdowsi University, Mashhad Iran, in 2018. The experimental factors consisted of various temperatures (0, -12, -15, and -17 °C), seed priming at 10 levels (control (without priming), hydropriming, priming with sodium chloride, salicylic acid, sodium nitroprusside, phosphate solubilizing bacteria and potassium solubilizing bacteria, amino acids, potassium nitrate, and zinc sulfate) and different chickpea genotypes (MCC505, ILC8617, MCC495, and Saral cultivar). In this experiment, the measured parameters included survival percentage, electrolyte leakage percentage, and lethal temperature resulting in 50% mortality according to the electrolyte leakage and survival percentage.

The results showed that the application of hydropriming, priming with sodium nitroprusside and zinc sulfate had favorable effects on the survival rate and electrolyte leakage. Among these, priming with sodium nitroprusside increased the survival percentage compared to the control (23%) at the -15 and -17 °C in the Saral cultivar, at -15 °C in the ILC8617 genotype, and at -12 and -15 °C in the MCC495 genotype treatment to 68, 58, 85 and 55 percent, respectively. In addition, this treatment reduced the electrolyte leakage by 13% at -15 °C in the ILC8617 genotype compared to the control treatment. Further, the mentioned treatment resulted in a 40% reduction in lethal temperature resulting in 50% mortality according to the survival percentage. In the MCC495 genotype compared to the control treatment.

Overall, the cold stress in the chickpea plants resulted in an increase in electrolyte leakage and a decrease in the survival percentage. Application of sodium nitroprusside priming by improving cold stress tolerance resulted in a reduction of lethal temperature resulting in 50% mortality based on electrolyte leakage and survival percentage results. Additionally, the applied priming in improving the cold stress tolerance mainly improved the survival percentage compared to the improvement in the electrolyte leakage.

The effect of different primings on the freezing tolerance of chickpeas was investigated and determined.
The freezing tolerance threshold of chickpea seedlings was determined at the laboratory under different primings.
The respondents of genotypes to priming and the behavior of genotypes towards each other were investigated.

The experiment was conducted as a factorial base on completely randomized design with three replications under controlled conditions at Ferdowsi University of Mashhad in 2018. 20 lentil genotypes, three freezing temperatures (0, -18 and -20°C) and six time point (before stress, 12, 24, 48, 72 and 96 hours after stress) were investigated. Decrease the temperature from 0 to -18 and -20°C reduced the maximum efficiency of PSII photochemistry in the light (F'v/F'm). The lowest values of F'v/F'm were observed at -18 and -20°C, 12 and 24 hours after stress, respectively. Then F′v/F′m gradually increased over time. However, at -20°C, the F′v/F′m did not reach the initial value before stress. PSII operating efficiency in the light adapted leaf (F′q/F′m) was reduced by decreased temperature in all genotypes and all time point. Despite the initial decrease in F′q/F′m, most of the studied genotypes, had a good ability to recover at temperatures of 0 and -18°C. The results of cluster analysis and principal component analysis (PCA) showed that the second component include survival percentage, dry weight, F'v, F′q/F′m and F′v/F′m explains 20.76%. Most genotypes belonging to the second group including MLC11, MLC286, MLC407 and MLC469 are in this component. Due to the 100% survival of these genotypes at -18°C and their suitable potential for recovery of chlorophyll fluorescence components and regrowth, their use is recommended for additional studies for autumn cultivation in cold regions.

Autumn sowing leads to production improvement and yield stability of Plantago major due to the longer growing season, avoid late summer heat stress, and effective use of rainfall. However, in order to succeed in autumn sowing, cold tolerance is essential. It is crucial to carry out plant selection to evaluate and identify top traits for adaptation to environmental factors and ultimately higher production of valuable plants such as broadleaf plantain. Therefore, evaluation of the characteristics of important plants such as broadleaf plantain plays a fundamental role in the selection of top ecotypes for different purposes of selection and increase of yield in different climatic conditions of each region.

This experiment was conducted as split-plot based on randomized complete block design with three replications at Research Farm of Agriculture Faculty of Ferdowsi University of Mashhad (36°15’ N, 56°28’ E, 985 m altitude) during the growing season 2013-14. The experimental factors included six ecotypes of Plantago major (Bojnord, Kalat, Mashhad, Ghaen, Torbat Heydarieh, and Birjand) and four sowing dates (late September, late October, late March, and late April). Irrigation was done immediately after planting and during the growing season according to the need of the farm by furrow method. Survival percentage, spike length, peduncle length, number of capsules, seed in capsule, 1000 grain weight, grain yield, biomass, and harvest index were evaluated. Data analysis was performed in SAS v9.4, and the means were compared by Duncan test at a 95% confidence interval.

The results showed that delay in autumn sowing from September to October reduced the survival percentage in all ecotypes. While, the delay in spring sowing from March to April improved the survival percentage in Birjand, Ghaen, Mashhad and Kalat ecotypes by 12, 8.9, 7.3 and 5%, respectively. The highest percentage of survival in April sowing belonged to Mashhad, Birjand, Ghaen, and Kalat ecotypes and in March sowing belonged to Bojnord ecotype. The highest grain yield (796.9 g m-2) was observed in Ghaen ecotype and the lowest was obtained in Torbat Heydariyeh, Mashhad, and Kalat ecotypes. So that grain yield in Ghaen ecotype was 48, 46, and 59% higher than the mentioned ecotypes, respectively. The highest biomass was observed in September sowing in Bojnord ecotype (2768 g m-2) and the lowest was obtained in April sowing in Kalat ecotype (622 g m-2). Ghaen ecotype had the highest harvest index in all sowing dates. Autumn planting of Plantago major L. leads to reduce in survival percentage compared with the survival percentage of spring planting. Lack of significant difference in grain yield of Plantago major ecotypes in autumn and spring sowing dates indicates the high flexibility of this plant to the date of sowing.

Despite the effectiveness of other factors in the improvement of a plant’s growth, it could be predicted that the Plantago major L. ecotypes that have the ability for establishment in cold conditions are more likely to be in a better position than other ecotypes at other stages of development. Due to the occurrence of heat and drought stresses during the spring growing season and production of suitable biomass for most ecotypes in autumn sowing, the continuation of field and controlled experiments is necessary to evaluate the success of autumn sowing of this plant seems necessary.

In order to investigate the effect of salicylic acid application on reducing the effects of cold stress due to delayed planting in rapeseed genotypes, this experiment was conducted as a factorial-split plot during the 2014 and 2015 growing seasons in the Faculty of Agriculture, University of Zanjan, Iran. Interaction of the sowing date (11th September and 7th October) and salicylic acid (control (spray with distilled water), 250 µM and 500 µM) were as the main-plot and rapeseed genotypes (Karaj-3, L14, Okapi, Zarfam) were assigned to subplots. The effect of planting date* salicylic acid* genotype on winter survival percentage, grain yield and its components, harvest index, and biomass was significant. Delayed planting reduced survival percentage of all rapeseed genotypes; but the severity of reduction varied depending on the genotype. It was also found that the decrease in survival percentage due to delay in planting can be partially compensated for by the use of salicylic acid, which varied depending on the salicylic acid concentration and genotype. Delayed planting date reduced grain yield in all genotypes and salicylic acid application had the opposite effect and increased grain yield. Karaj-3 had the highest grain yield on 7th October planting date and 500 µM salicylic acid, while Zarfam had the lowest grain yield on 11 September and 0 µM salicylic acid. Application of salicylic acid compensated for part of the reduction in yield due to delay in planting, so that the lack of application of salicylic acid and the use of 250 and 500 μM salicylic acid in planting on 7 October caused grain yield reduction in Karaj-3 genotype by 36, 31 and 18% respectively, compared to 11 September, while grain yield in L14 genotype showed 26, 21 and 8% reduction respectively, compared to 11 September planting date. The grain yield of Zarfam genotype at delayed planting date decreased by 9% and 5% and increased by 13%, respectively, in conditions of non-application and application of 250 and 500 μM salicylic acid compared to the 11 September planting date. There was a positive significant correlation between grain yield components and winter survival percentage. Although delayed planting reduced grain yield, yeld components, harvest index, and biomass in all genotypes, the severity of the decrease varied among the genotypes. Consumption of salicylic acid moderated the effect of delay in planting and this modulatory effect was higher in the application of salicylic acid with a concentration of 500 μM than 250 μM. In general, the results showed that in both planting dates, the Karaj-3 genotype had the highest grain yield in all salicylic acid levels, so it is recommended for planting in areas with similar conditions.

To study freezing tolerance (-13, -15 and -18°C) of 40 lentil (Lens culinaris Medik.) genotypes, a factorial experiment in completely randomized design was carried out at the Research Center of Plant Science, Ferdowsi University of Mashhad, Mashhad, Iran, in 2017-2018. Significant differences observed between genotypes for survival percentage after freezing stress and chlorophyll a, carotenoids, anthocyanins, soluble carbohydrates, proline, malondialdehyde (MDA), phenol, protein, DPPH, ascorbate peroxidase and peroxidase before freezing stress. Stepwise regression analysis showed that chlorophyll b had the most positive effect and protein, and MDA had the most negative effect on survival percentage. Cluster analysis grouped genotypes into five clusters. For most of the studied traits, genotypes in clusters 4 and 5 were greater than average of all genotypes as well as genotypes in other clusters. In clusters 4, anthocyanins, protein, MDA, phenol, proline, ascorbate peroxidase and peroxidase contents were higher than other clusters. Survival percentage, chlorophyll b, carotenoids, total pigments, and DPPH of cluster 5 were higher than the other clusters. Principal component analysis showed that MLC469, MLC458, MLC409, MLC74, MLC84, MLC169, MLC394, MLC95, MLC17, MLC163 and MLC303 for antioxidant capacity and metabolites, and MLC70, MLC410, MLC47, MLC31, MLC91, MLC8, MLC286, MLC407, MLC472, MLC61, MLC83 and MLC334 for photosynthetic pigment capacity were more suitable than the other genotypes. It can be concluded that these attributes are very important in predicting, before cold stress, the effect of cold stress on survival percentage of lentil genotypes.

Low yield and instability, is one of the most important issues in chickpea cultivation. In most regions of Iran, chickpea is mainly planted in spring. Consequently, the plant will be exposed to abiotic stresses such as heat and drought during growth season, especially during the final stages of growth. To increase the chickpea yield, Autumn planting can be used, but low tolerance of common chickpea genotypes to freezing stress is a problem. Therefore, according to the benefits of autumn planting of chickpea, identification of freezing tolerant genotypes of chickpea along with suitable yield is a necessity. In this way, the present study was conducted as a field experiment to assess winter tolerance of 29 deci- type chickpea genotype in Mashhad conditions.

Experiment was conducted as Complete Randomized Block Design with three replications and 29 deci-type chickpea genotypes in research station of Faculty of Agriculture, Ferdowsi University of Mashhad in 2016-2017. Genotypes were supplied from seed bank of Research Center for Plant Sciences, Ferdowsi University of Mashhad and seeds were planted in November 1st. The lowest minimum daily temperature during the growing season was -13ºC. To calculate survival percentage, number of plants werfor each genotype was recorded 30 days after emergence and on March 15th. At the end of the growth season, plant height, number of main and secondary branches, pod number per plant, 100-seed weight, seed weight per plant, seed yield per square meter, biomass, biological yield and harvest index were measured.

significant differences were found among genotypes according to all the studied traits. While only one genotype was entirely killed as a result of freezing stress, survival range differed between 8-100% for the other genotypes. Among all 29 deci chickpea genotypes, 11 genotypes were tolerant (76-100% survival) and five were relatively tolerant (51-75% survival). MCC890, MCC349 and MCC873 had the highest winter survival with 98.1, 95.7 and 95.2%, respectively. In total, 9 genotypes including MCC373, MCC884, MCC869, MCC916, MCC349, MCC386, MCC870, MCC291 and MCC876 produced high yield of 154g.m-2 (equivalent to 1540 kg.ha-1) and all of these genotypes had higher survival percentage than 66.7%, except MCC916. Significant positive correlation were found between seed yield and survival percentage (r=0.76**), number of secondary branches (r=0.23**), pod number per plant (r=0.52**), 100-seed weight (r=0.38**), biological yield (r=0.59**) and harvest index (r=0.58**).

According to the results of the present study, it seems possible to achieve cold tolerant deci chickpea genotypes for cultivation in cold regions. Based on cluster analysis, two groups of genotypes including 1) MCC10, MCC49, MCC207, MCC890 and 2) MCC868, MCC918, MCC884, MCC386, MCC291, MCC349, MCC916, MCC373 can be used in breeding programs due to their superior attributes such as early- season cold tolerance.

Knowledge of freezing stress tolerance in wild barley and feral rye as the most important weeds in wheat fields can be used to predict their geographical distribution and management plannings. To this end, an experiment was conducted in Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran, in autumn 2017. Two wheat genotypes (cultivar Pishgam and Iranian landrace Ghezel Khoushe) and two weeds (wild barley and feral rye) were grown up to two to four true leaves stage under natural conditions and then exposed to a temperature range of +4 to -20 °C (+4 oC as control and 0, -4, -8, -12, -16 and -20 oC as freezing temperatures). The results showed that reducing temperature from -8 to -12 °C led to a 36% decrease in survival of wild barley, while the survival of wheat (Pishgam and Ghezel Khoushe) and feral rye was 100%. Wild barley had the highest lethal temperature reducing 50% of survival (LT50su = -12.8 °C) and temperature rducing 50% of leaf area (RLAT50 = -11.2 °C). Among the studied plant species, wheat (landrace Ghezel Khoushe) and feral rye with -11.8 °C and -11.6 °C, respectively, had the lowest temperature rducing 50% of shoot dry weight (RSDWT50), while the wild barley with -8.1 °C had the highest RSDWT50. The highest and lowest chlorophyll content (SPAD) among the living plants were observed at +4 and -12 °C, respectively, and  feral rye with 19.5 and wild barley with 10.3 SPAD unit showed the highest and lowest chlorophyll content, respectively. The results of this study showed that high tolerance of feral rye to freezing stress is probably one of the main reasons for its widespread distribution in winter wheat fields. Therefore, it is necessary to predict dispersion and possible invasion and consequently appropriate strategies to manage this weed in areas with cold climates.

Plants grow well only within a specific temperature range. Getting out of this range is regarded as a stress. Low temperature is regarded as one of the important abiotic stress among the main factors threatening the growth of plants in temperate regions that causes disorder in the growth, development and operation of the plant by affecting some of vital processes of the plant. Environmental stresses especially cold stress affects the morphological and physiological features of the plant. Among these effects are damage to the cell membrane and change in its properties, reduction in photosynthesis and carbon dioxide efficiency, change in chlorophyll fluorescence characteristics, synthesis of chlorophyll and reducing the relative amount of water content. Since rapid and effective assessment of plant cold tolerance is important for researchers and also field trials have no regular process and have high error, different kinds of artificial freeze tests such as survival percentage test and regrowth after using stress has been developed.
In order to investigate the cold tolerance of Fenugreek, an investigation was done in factorial arrangement and in a completely random design in three replications in 2013-2014, in College of Agriculture in Ferdowsi University of Mashhad. The investigated factors include sowing date in four levels ( September 13, October 14, March 5, and April 3), ecotype in 10 levels (Azari, Ardestan, Tall, Dwarf, Shiraz, Shirvan, Mashhad, Neishabur, Hamedan and Hendi) and freezing temperature in seven levels ( control, 0, -3, -6, -9, -12, -15 °C). The plants grew in pots and cold acclimation in outside conditions then the plants which were planted in September and October as well as March and April. The pots were transferred to the freezer thermo gradient to apply the cold temperature in the middle of January and in the middle of May, respectively. Four weeks after applying the stress, survival percentage, Lethal Temperature 50% of Plant according to the Survival Percentage (LT50su), height, leaf area, Reduced Leaf Area Temperature (RLAT50), dry weight and Reduced Dry Matter Temperature 50 (RDMT50) were measured.
All ecotypes (except for Azari and Ardestan ecotypes) in the third sowing date could tolerate lowering temperature to -9 °C in every four sowing date. Lowering temperature to -12 °C also led to the death of all ecotypes in March and April sowing dates, while in September sowing date despite the death of most Fenugreek ecotypes, both Neyshabur and Mashhad ecotypes could tolerate this temperature. Also, in October 14 sowing date, in Neyshabur, Mashhad and Shirvan ecotypes the survival percentage was high, but the survival percentage of Azari, Ardestan and Tall compared with the control treatment decreased 61, 50 and 39, respectively, and the other ecotypes were destroyed completely. Ecotypes of Mashhad and Neyshabur had the lowest LT50su in the first and second sowing dates but in the third and fourth sowing date no significant differences was seen in this respect. In March 5 sowing date, after lowering temperature to -9 °C, the maximum percentage of decrease in height compared with control was in Dwarf ecotype (71 percent) and the minimum was seen in Shiraz (33 percent). In spite of this, Dwarf ecotype in the other sowing dates assigned to itself the lowest decrease percentage of height (respectively 35, 24 and 33 percent) and had a better ability to recovery. In every four sowing date lowering the temperature to -12 °C caused the total mortality of Hamedan, Hendi and Shiraz and they didnt have any leaf surface, but the response of the other ecotypes in October 14 sowing date was different. Two ecotypes Tall and Neyshabur having the highest (92 percent) and the lowest (66 percent) decrease in leaf surface compared with the control temperature were known as the most sensitive and the most tolerant ecotypes in this sowing date. In October 14 sowing date the response of the ecotypes to -6 °C compared with the other sowing date was better and the highest dry weight was associated with this date by lowering the temperature to -9 °C two ecotypes of Shirvan and Azari had the highest and the lowest decrease in dry weight (respectively 33 and 14 percent) in the second sowing date.
Lowering the temperature to less than -9 °C causes a decrease in the plant survival percentage and recovering in most of the ecotypes of Fenugreek. In spite of this, percentage of the plant survival depending on the sowing date, so that in the second sowing date the percentage of survival was more than the other sowing dates and except for Shiraz, Hamedan and Hendi ecotypes, the other ecotypes were able to tolerate -12 °C. Ecotypes of Shirvan, Mashhad, Neyshabur and Dwarf under both of spring and fall sowing dates had a better regrowth than the other ecotypes, while Azari and Ardestan ecotypes under the fall sowing showed a better regrowth than spring sowing date. There was a significant correlation between RLAT50 and RDMT50 with LT50su (r =0.53** and r = 0.64**, respectively), probably this subject shows the efficiency and the possibility of replacing each of these indexes in the investigation of the cold tolerance in Fenugreek. To sum up, the ecotypes of Mashhad, Neyshabur, Shirvan and Dwarf showed a better tolerance to freezing than the other ecotypes.

IntroductionChlorophyll fluorescence measuring is a quick and undestructive method, which is used as an important index to identify stress tolerant varieties for environmental stresses such as freezing. Rye planting is less prevalent comparing to other cool season cereals, but more investigations are needed because of suitable potentials in this crop for growing in cold area of Iran. In addition, low temperatures decrease physiological functions of plants and results in irreversible damages and disorders in physiological process of plants.
Material and MethodsIn order to study the possibility of using the chlorophyll fluorescence parameters for evaluation of freezing tolerance in perennial rye ecotypes, an experiment was performed using a factorial experiment based on completely randomized design with three replications at Agricultural Faculty of Ferdowsi University of Mashhad. Ten rye ecotypes (264, 941, 8425, 15771, 1587, 14947, 591, 1275, 3857 and 12460) were exposed to nine freezing temperatures (0 (control), -3, -6, -9, -12, -15, -18, -21 and -24◦C) and maximum efficiency of photosystem II (ME of PII) were measured four times (12, 24, 48 and 96 hours) after freezing. Correlation between ME of PII with Electrolyte Leakage percentage (EL %) and survival percentage (SU %) were tested.
Results and DiscussionThe results indicated that there was a significant difference among rye ecotypes for ME of PII, while ecotype 12640 had the highest ME of PII and the lowest efficiency was observed in ecotype 264. There was no difference in ME of PII among rye ecotypes until to -18 oC, but ME of PII decreased in -21oC and -24oC after 12 to 24 hours recovery period. This efficiency was zero in -24°C during 48 and 96 hours after recovery, while ME of PII did not get to zero in this temperature during 12 and 24 hours after stress. ME of PII impairment by freezing temperatures was similar in 48 and 96 hours and it seems that no changes happened in the efficiency after 48 hours. There was a rapid reduction in slope of efficiency from -15oC to -24oC in 264 and 941 ecotypes than the other ecotypes, while ecotype 12640 had the highest ME of PII than the other ecotypes in mentioned temperature range. In the four measuring times, ME of PII was not reduced until -18°C, but it was severely decreased by temperature reductions to -21oC and -24°C, as ME of PII decreased to the lowest value after 48 hours. Decreasing the ME of PII in rye ecotypes was different due to the ectypes in the times after freezing stress, the most reduction was observed in 264 and 941ecotypes and ecotype 12640 had less decrease in the slope of ME of PII. There were differences among rye ecotypes in reduction temperature for 50% of ME of PII; while ecotype 12640 get reduction temperature for 50% of ME of PSII in -24.8oC 12 hours after freezing stress; and ecotypes 264 and 941 had the highest reduction temperature of 50% ME of PII in -20.2 oC and -20 oC, respectively. Reduction temperature for 50% of ME of PII decreases in 24 hours after freezing stress; at this time, 12640 and 3857 ecotypes showed the lowest reduction temperature for 50% of ME of PII by -22.6°C and -22.2°C, respectively, and 264 ecotype had the highest reduction temperature for 50% of ME of PII by -19.2°C. There were significant correlations between ME of PII, EL% and SU%. Since EL test was conducted 24 hours after freezing stress, it seems that measuring ME of PII in 12 hours after freezing stress increases quickness in test and determining the stress effects rapidly. Higher correlations between plants survival percentage with ME of PII 12 hours after freezing stress, indicate that ME of PII is a non-destructive factor for estimating long term effects of freezing stress on rye plants. In conclusion, the mentioned factors can be used as a quick procedure to identify cold tolerant plants.

In tolerance to coldness researches, scholars are looking for exams which in addition to having easiness, velocity and enough validity, be repetitive as well and mean while the feasibility of controlling the thermal conditions be in it. Using different kinds of freezing exams in controlled and artificial conditions have been suggested. Hence, damage evaluation via measuring the electrolyte leakage and determining the Lethal Temperature 50 According to the Electrolyte Leakage percentage (LT50el) is considered as a suitable and direct method for evaluating the amount of coldness damages by the researchers.
In order to evaluate freezing tolerance of fenugreek a factorial experiment in 2013-2014 year based on completely randomized design with three replications was conducted under controlled conditions in faculty of agriculture, Ferdowsi University of Mashhad. The investigated factors include sowing date in four levels (September 13, October 14, March 5, and April 3), ecotype in 10 levels (Azari, Ardestan, Long foot, Short foot, Shiraz, Shirvan, Mashhad, Neyshabur, Hamedan and Hendi) and freezing temperature in seven levels (control, 0, -3, -6, -9, -12, -15 0C). The potted plants grew and cold acclimation in outside conditions then the plants which were implanted in September and October, and the plants which were implanted in March and April , were transferred to the freezer thermo gradient to apply the cold temperature in the middle of December and in the middle of May respectively. After freezing, Percentage Electrolyte leakage (%EL) and Lethal Temperature 50 According to the Electrolyte Leakage percentage (LT50el) was determined. Survival percentage of them after freezing and 28 days growth was measured in the greenhouse.
Although in the all sowing dates the electrolyte leakage was constant up to the temperature of -6 0C and by more reduction in temperature, it had an increasing trend, but the leakage increase velocity in the sowing dates in the first decade of March war more than other dates. As in this sowing date by reducing the temperature from zero to -15 0C, the percentages of electrolyte leakage increased about 71 percent. In some ecotypes such as Shiraz and Hamedan by causing delay in sowing date from July to April the percentage of electrolyte leakage was increased. Although the electrolyte leakage percentage in all ecotypes in the second sowing date of fall and spring was reduced in compare to the first sowing date, the lowest and the highest reduction resulted from delay in sowing date belonged to Hamedan and Ardestan respectively. Although by temperature reduction the percentage of electrolyte leakage was increased in the all ecotypes, but this increase was more intense in the Hendi ecotype than other ones. In this ecotype by reducing the temperature from zero to -15 0C, the electrolyte leakage percentage increased 73 percent whereas in Neyshabur ecotype this increase was 53 percent. The percentage of electrolyte leakage from the Trigonella foenum-graecum ecotypes in each sowing date increased by temperature reduction. In the majority of ecotypes this increasing trend was witnessed from the -6 0C. In the all ecotypes, the October 14 sowing date in the majority of the studied temperatures had lower leakage percentage than other sowing date. According to the LT50el index, the sowing date of the first decade of October in ecotypes was lower in compare to other dates. In other words, earlier sowing date of ecotypes probably leads to increase in plants sensitivity to coldness. The highest and lowest tolerance to freezing, according to this index, belonged to Neyshabur and Azeri ecotypes respectively. Between Lethal Temperature 50 According to the Electrolyte Leakage percentage (LT50el) and survival (r=-0.536*) negative and significant correlation was witnessed which indicates that using this index in evaluating the damage of freezing tolerance in Trigonella foenum-graecum is possible.
Generally in this study in all of the ecotypes, reducing the temperature led to increase in the percentage of electrolyte leakage. This leakage increase slope in the majority of ecotypes began from -6 0C and in -15 0C was maximized. Delay in autumnal and spring sowing dates by affecting the plant growth stage cause increase in plants tolerance to freezing. In other words, the plants which were in advanced vegetative level in the exerting time of freezing temperatures had lower tolerance to freezing. Among the studied ecotypes, however, the Neyshabur and Azeri ecotypes had the highest and the lowest tolerance to freezing respectively considering the leakage amount and LT50el. Therefore, it seems that the sowing date of October is suitable for sowing Neyshabur, Mashhad, Shirvan and Short foot ecotypes which had lower leakage percentage and more suitable LT50el in compare with other ecotypes. However, more researches in evaluating the plant’s tolerance to freezing in real winter conditions and determining correlation relationships between the results in controlled situations and farm will be useful.

IntroductionFlixweed is an annual dicotyledonous winter herb from Cruciferae (Brassicaceae) family which grows in many countries of the world. In Iran it is seen in many of wheat and canola producing regions. Flixweed is used for healing a variety of diseases such as measles and smallpox, cough, asthma, edema and tumor. It also has diuretic, anticancer, antipyretic, antioxidant, anthelmintic, analgesic and tonic activities [2]. In temperate and cold regions of Iran, winter cold is one of the most important environmental stresses which affect growth, development and yield of plants. So determination and improvement of freeze tolerance of winter plants such as Flixweed might promote their cultivation and utilization in cold regions. At present measuring the survival after a recovery period which is followed by a freezing test in controlled conditions is a common method for determining the level of plants freeze tolerance. Calculation of LT50 point or critical temperature based on survival percentage of plant is considered as a quantitative and simple method for evaluating the cold tolerance [1]. But sometimes this criterion is not enough alone and other indices (for example dry weight and Reduced dry matter temperature 50% of plants (RDMT50)) are used to achieve a more accurate estimation of cold tolerance level [3]. In spite of numerous medicinal and industrial properties of Flixweed, there is not a lot of information about freeze tolerance of this plant, so the objective of this study was evaluating the freeze tolerance of Flixweed by survival % and some of growth traits after recovery period.
Materials and methodsIn order to evaluate freeze tolerance in some of Flixweed, a factorial experiment was conducted based on completely randomized design with three replications in faculty of agriculture, Ferdowsi University of Mashhad in autumn of 2009. Experimental factors include five ecotypes of Flixweed (Eghlid, Sabzewar, Hamedan, Torbat-e-Jam and Neyshabour) and 10 freezing temperature levels (from zero to -18 with 2 °C intervals). For this aim, Flixweed seeds were cultivated in pot in autumn and they were grown in natural weather until 5-7 leaf stage. Afterward for applying freezing temperatures, plants were transferred to a thermo gradient freezer. The initial temperature of programmable freezer was 5°C; but gradually decreased in a rate of 2°C.h-1 until reached to desired temperatures. When the freezer temperature reached to -2°C, the plants were treated by the Ice Nucleation Active Bacteria (INAB) to help the formation of ice nuclei in them, also to prevent from super-cooling of samples and to ensure that the mechanism of freeze resistance is tolerance not avoidance. After artificial freezing stress applying (which lasted up to two hours for each freezing temperature); Flixweed seedlings were transferred to greenhouse for recovery. Three weeks after freezing stress, survival percentage (SU %), Lethal temperature for 50% of plants according to the survival% (LT50su), number of leaf and reduced number of leaf temperature 50% (RNLT50), number of node and reduced number of node temperature 50% (RNNT50), dry weight and reduced dry matter temperature 50% (RDMT50) were evaluated. Analysis of variance was performed by MSTAT-C software and correlations between data were carried out by MINITAB 16 program. Mean separation was conducted by least significant difference (LSD) test at 1% probability level.
Results and DiscussionResults showed that Hamedan ecotype had the highest SU% and Neyshabour ecotype had the lowest SU%. In Eghlid and Neyshabour ecotypes, decline of SU% begun from higher temperarures (-8 °C) compared with other ecotypes (-10 °C). This trend was seen for dry weight and number of leaf too. At -12 °C, number of node in Hamedan ecotype decreased 30% approximately than control, while in Eghlid and Neyshabour ecotypes, this reduction was much higher. In this experiment LT50su ranged between -10.2 to -12.1 °C depending on the ecotypes. Ranking of Flixweed ecotypes according to the LT50su, RNLT50, RNNT50 and RDMT50 indices showed that the Neyshabour and Hamedan ecotypes were the most sensitive and tolerant Flixweed ecotypes to freezing stress respectively. In this survey, there was high and positive correlation between survival percentage and dry weight (r=0.69***), in addition there was negative and significant relationship between SU%, LT50su and RNNT50 (r=-0.67*** and r=-0.82*** respectively).
ConclusionAccording to these results, it seems that temperature threshold for winter injury happening in Flixweed is -12 °C. Despite this for better understanding of cold tolerance of Flixweed, further researches are required under controlled and field conditions.

Garlic is a plant with a relatively high tolerance to cold winter but extreme autumn and winter in cold regions are among the factors that affect the growth and survival of plants. So it seems that one of the critical success factors for fall planting is identification of cold tolerant plants in these areas. To evaluate and recognition tolerant plants to cold stress and to avoid some inevitable limitations in field evaluation, different types of artificial freezing tests have been developed. Electrolyte leakage test is one of this methods that is simple, repeatable and cheap and relatively fast which determines the degree of damage to cell membranes caused by the stress. When the plant tissues damage by cold, membrane activity decreases and electrolytes inside the cell leaks to the outside its. It has been reported by many researcher that cold stress increases electrolyte leakage and this trait can be used as a criterion for evaluation of freezing tolerance. Also the freezing temperature in which 50% of ions are leaked from the cells has been proposed to be used as the 50% threshold of damage of freezing stress.
In order to evaluate freezing tolerance of garlic a factorial experiment was conducted in 2012 year based on completely randomized design with four replications under controlled conditions in faculty of agriculture, Ferdowsi University of Mashhad. Experimental factors consisted of two planting dates (19 September and 22 October) and four ecotypes of garlic (Bojnurd, Torbat- Heydarye, Neyshabur and Khaf). Plant after growth and hardening under natural environment exposed to eight freezing temperatures (0, -3, -6, -9, -12, -15, -18 and -21 degree ºC). After freezing, electrolyte leakagepercentage and lethal temperature for %50 of plants according to electrolyte leakage percentage (LT50el) were determined. After 21 days survival percentage was measured in the greenhouse.
Electrolyte leakage percentage decreased in four ecotypes of garlic in the second compared to the first planting, but the greatest reduction (11.3%) was observed in the Khaf ecotype, while this reduction was 1.1% in the Torbat-Heydariye. In both planting dates electrolyte leakage was roughly stable until -15 degree ºC and it was increased at lower temperatures but increasing in the first was more than the second planting, So that by reducing the temperature from -15 °C to -21 °C electrolyte leakage increased in first and second planting by about 34 and 24 percent, respectively. Also, lethal temperature 50% of plants according to the electrolyte leakage percentage in the second planting date was about 1° C lower than the first planting. At the time of freezing stress, most plants were planted in September were at four-leaf stage and the plants were cultivated in October at the two-leaf stage and although the first planting plants were more time under normal conditions and thus acclimation, But electrolyte leakage was more in them. This case may be due to more food reserve in second planting plants. In the both planting date in the Bojnurd and Torbat-Heydariye ecotypes electrolyte leakage percentage was stable until -15oC and then increased with decreasing of temperatue, While in Neyshabur and Khaf ecotypes in the first planting the temperature reduction from –6 and -12 oC was increased electrolyte leakage. However, in the last two ecotypes (Khaf and Neyshabur) in the second planting date electrolyte leakage was relatively stable up to temperatures of -15 oC and at lower temperatures electrolyte leakage increased. It seems that more plant growth and development toward the higher growth leads to less tolerance in the first planting of plants. Lower values of lethal temperature 50% are indicating greater tolerance to cold and amount of this index was lower in October planting, so it can be said that early planting garlic (28 September) is likely leads to increase plant sensitivity to cold. There was high and negative correlation between electrolyte leakage% and survival percentage (r=-0.70*) in this survey. In other words, by increasing the survival percentage electrolyte leakage decreased.
In the first planting electrolyte leakage from Khaf and Neyshabur ecotypes increased with exposure to temperatures of -6 and -9 ° C, while in two other ecotypes this situation stared from -15° C temperature. While the in second planting in four ecotypes began the process of temperature -15 ° C. Different reactions of ecotypes to freezing stress, especially in the first planting is probably due to genetic characteristics geographical origin. Also, growth stage of plants were effective in the cold tolerance of them, So that Khaf and Neyshabur ecotypes in lower growth stages (second planting plants) compared to the advanced growth stages showed more freezing tolerance and it seems that the two listed ecotypes in the later planting have freezing tolerance more than the first planting. Torbat- Heydariye and Bojnurd ecotypes had more membrane stability and they showed better reaction in both fall planting under cold stress, despite the continuation of these studies under controlled and field conditions will provide more information about cold tolerance mechanism of this plant in real winter conditions.

Flixweed (Descurainia sophia L.) is a medicinal plant from Brassicaceae family which also known as a weed for winter cereals and oil seed rape. Low temperatures are one of the most important abiotic stresses that threat Flixweed growth and productivity. Therefore it is important to recognize the freeze tolerance of Flixweed for successful planting and utilization in cold regions such as Mashhad in Khorasan Razavi Province (Iran’s north. east). Among many laboratory methods which have been developed to estimate and to evaluate plants response or their tolerance to freez¬ing temperatures, electrolyte leakage (EL) test is widely used. This test is based on this principle that damage to the cell membranes results in enhanced leakage of solutes into the apoplastic water, hence recording the amount of leakage after stress treatments provides an estimation of tissue injury. Indeed continuing integration of plasma membrane is one important factor for survival of plants under freezing stress and any disturbance in membrane structure can lead to damage and death. So determination of LT50 point or critical temperature for electrolytes leakage and survival of plant is the most reliable, quantitative and simple methods for evaluating the cold tolerance of plants. The aim of this trial was to determine the LT50 according to the EL and SU% for Flixweed ecotypes.
In order to evaluate freeze tolerance in Flixweed, a factorial experiment based on completely randomized design with three replications was carried out in college of agriculture, Ferdowsi University of Mashhad. Experimental factors included five ecotypes of Flixweed (Eghlid, Sabzewar, Hamedan, Torbat-e-Jam and Neyshabour) and 10 freezing temperature levels (0, -2,-4, -6, -8,-10,-12,-14,-16 and -18°C). Flixweed seeds were cultivated in pots in autumn of 2008 and were grown until 5-7 leaf stage under natural weather conditions for acclimation. Then to apply freezing temperatures, they were transferred to a thermo gradient freezer. The initial temperature of programmable freezer was 5°C; but gradually decreased in a rate of 2°C.h-1 until reached to desired temperatures. When the temperature reached to -2°C, the plants were sprayed with the Ice Nucleation Active Bacteria (INAB) to help the formation of ice nucleus in them. As well this spraying was conducted to prevent from super-cooling of samples and to ensure that mechanism of freeze resistance is tolerance not avoidance as well. After reaching a desired freezing temperature happened, the samples were removed from the freezer and then were thawed slowly during 24 hours in a refrigerator at 5±1°C. Cytoplasmic membrane stability was evaluated by electrolyte leakage (EL) test, afterward lethal temperature was calculated for 50% of plants according to the electrolyte leakage % (LT50el). In order to evaluate correlation between EL% with survival percentage (SU%), remained plants were transferred to greenhouse and after 21 days recovery, SU% and then lethal temperature was determined for 50% of plants according to the SU% (LT50su). Analysis of variance performed by MSTAT-C software and correlation between data carried out by MINITAB 16 program. LT50el was determined by Slide write software. Mean separation was conducted by least significant difference (LSD) test at 1% probability level.
Results showed that the reduction of temperature to less than -8°C, led to increment of electrolyte leakage % and decline of survival %. Interaction effect of ecotype and temperature on electrolyte leakage and survival percentage was significant at 1% probability level. Enhancement of electrolyte leakage % for Neyshabour ecotype started from -8°C, while the others were affected from lower temperatures. In addition in Eghlid and Neyshabour ecotypes, decline of survival % begun from higher temperatures (-8 °C) compared with the other ecotypes (-10 °C). Cold hardiness is often reported as LT50el, means the temperature at which 50% of the electrolytes leaked from the cells. LT50el often is simply equaled to 50% sample mortality or LT50su. According to the LT50el and LT50su indices, Hamedan, Sabzewar and Torbat-e-Jam ecotypes had better freeze tolerance than Neyshabour and Eghlid ecotypes and according to the LT50su, Hamedan ecotype had potential to freezing tolerance up to -12°C.
In this survey, there was strong and negative correlation between EL% and SU% (r= -0.72***). Furthermore, there was high and positive correlation between LT50el and LT50su (r= 0.53*). These results indicate efficiency and alternative likelihood of each index in assessment of Flixweed freeze tolerance. Regarding to more rapid rate of EL method compared to SU evaluation, it seems better to utilize of this index.

Water is the most important factor for production of agricultural crops. Adequate water supply is necessary to obtaining maximum productivity of horticultural crops (Jones and Tardieu, 1998). According to Global Circulation Models precipitation scarcity might become worse in the near future over the world. Severe drought periods might decline yield and quality of crops (Delfine et al., 2005). Unfortunately, water deficiency is increasingly becoming a serious problem in agriculture in Iran whereas the national average annual precipitation is less than 249 mm (Baghalian et al., 2011). Therefore in our country, production of agricultural crops always accost many problems because of water scarcity (Hassani et al., 2009). Thus it is important to understand to what extent water stress impairs plant growth and yield in alternative crops (Delfine et al., 2005).
Plants respond quickly to water stress in order to prevent the photosynthesis. Stomata closure in response to water deficit stress primarily results in decline in the rate of photosynthesis.
Photosynthesis limitation causes growth and yield decreasing (Alaei et al, 2013).
Shortage of water in arid and semiarid regions of the world can reduce growth and production of medicinal and aromatic plants, especially Mentha species. Frequent irrigation is necessary during mint plant growth, as mentha species need moist soil conditions in the 100 centimeters of soil where rhizomes are located. This layer of soil has the greatest root density and always must be kept moist (Mitchell and Yang, 1998). But excessive irrigation may decrease mints yield because of limitation of oxygen for plant roots, promoting root diseases, leaching of plant nutrients especially nitrogen and losing more leaves than normal (Mitchell, 1997). According to the results of statistical analysis of Alaei et al (2013), irrigation treatments had significant effects on growth and yield of Dracocephalum moldavica. In this experiment as the amount of irrigation water declined, the plant height, leaf area, leaf number, fresh and dry weight of root and shoot, root length, branch number, and yield per pot decreased. This was while root to shoot ratio, and days to first bloom, first flower and first fruit increased. Study on effects of water deficit stress on Balm (Mellisa officinalis L.) showed that the effect of this stress on shoot yield, leaf and stem yield, stem height was significant at 1% probability level. This was while the number of lateral stem was not significant (Ardakani, 2007). Petropoulos et al., (2007) showed that parsley growth (foliage weight, root weight and leaf number) was significantly reduced by water stress, even at 30-45% water deficit levels. Water deficit has been revealed as effective on growth parameters, yield and biomass. Water stress has decreased plant height, number of secondary branches, dry and fresh weight of shoot, root mass, dry and fresh weight of root and length root (Babaee, 2010). The study on the effect of different levels of water stress on moldavian balm demonstrated that there was not a significant effect of water stress on leaf area and number of leaves, but it was significant on fresh and dry herb (Gholizadeh, 2007).
Material and In order to evaluate response of three Mentha species to water deficit stress, an experiment was carried out in a factorial-randomized design with five replications in controlled conditions and Mentha longifolia (wildmint), Mentha spicata (spearmint) and Mentha piperita (peppermint) species were subjected to four soil moisture regimes (100 (control), 80, 60, 40 of field capacity (FC)) and studied characteristics were included percent of survival, number of branches and stolon, number of leaves, length of branches and relative chlorophyll content were measured every ten days Besides all characteristics that were mentioned before, total dry weights were determined after both harvest.
The results showed that soil moisture treatments had significant effect on survival of three mint species. Trends of branch’s number and length and number of leaves indicate that adequate soil water could achieved better growth in wildmint than two other species in control and 80% of FC, but number and length of stolon in peppermint were significantly excel as compare as two other species in all treatments. However reduction of soil moisture to the 60% of FC severely decreased number and length of branches, number of leaves and number and length of stolon in all species, but spearmint had better growth in this treatment. There were low differences among SPAD of these species in control treatment, though spearmint’s SPAD was higher than two other species in 60 percent of FC in whole growing season. Total dry weight of spearmint in 80% of FC was 31 percent lower than control treatment, while in peppermint and wildmint 40 and 61 percent reduction were observed, respectively. In 60% of FC leaf dry weight of peppermint and wildmint were 92 and 96 percent lower than control, but in spearmint the mentioned parameter in this treatment was 66 percent lower than control treatment.
Water deficit stress reduced growth characteristics of all three species, but growth of spearmint in 20 and 40% deficiency of soil water (as compare with control) was better than two other species. Although spearmint was more tolerant than two other species to water deficit stress, but more study must be achieved for better understanding of mint responses to water deficit stress.
Our results regarding the effect of water stress on dry weight were in coincidence with those reported by Simon et al., (1992) in basil; Ardakani (2007) in balm; Johnson (1995) in Spanish thyme and Safikhani (2007) in moldavian balm who confirmed that water deficit could affect yield by decreasing growth.

Saffron (Crosus sativus L.) is a perennial and herbs plant, belongs to the Iridaceae family and reproduces via corms (Behnia, 1991). Saffron is native to the mediterranean floristic region, extending eastward into the Iran-Turanian region and lie within the longitude 10°W to 80°E and latitude 30°N to 50°N. These areas are characterized by cool to cold winters and warm summers with very little rainfall. Iran is the most important saffron producers and exporters in the world market (Kafi et al, 2002). Saffron is cultivated in northeast of Iran which are characterized by cold winters and warm summers. The main part of the Saffron’s growing season is exposed to cold and winter frost, and low temperatures limits its production. Therefore, it is likely that a cold weather or frost during winter waste the saffron, so that it is necessary to identify cold tolerant ecotypes of saffron and determine the range of low temperatures that saffron may withst and without any considerable damage.
The objective of this experiment was to evaluate and compare the response of saffron ecotypes to freezing temperatures under controlled conditions.
In order to evaluate the effect of freezing stress on three saffron ecotypes (Ghaen, Kashmar and Torbat heydarieh) a factorial experiment based on completely randomized block design with three replications was carried out under the controlled conditions in the Faculty of Agriculture, Ferdowsi University of Mashhad, Iran. Three native saffron ecotypes (Ghaen, Kashmar, and Torbate Heydarieh) were subjected to six different temperatures (0, -4, -8, -12, -16 and -20 oC). Two saffron’s corms were sown in plastic pots with 25 cm diameter and 23 cm hight to a depth of 8 cm. The pots were primarily filled with an equivalent ratio of sand, compost and soil. For cold acclimation, plants were grown in natural conditions and after that, transferred to the thermogradiant freezer with the six freezing temperatures. The seedlings were sprayed with the Ice Nucleation Active Bacteria (INAB) to help the formation of ice nuclei in the seedlings. Plants were kept at the nominated freezing temperature for 1 h. Following the freezing treatments, all samples were kept at 5±2°C for 24 h to decrease the rate of thawing. Leaf and corm cell membrane integrity were measured via electrolyte leakage percentage (%EL) index and lethal temperature 50 according to %EL (LT50el) was determined. Three weeks after plants growth in cold frame, survival percentage of each saffron ecotype was measured by counting the plants and determining their proportional with the number of plants before freezing.
Results showed that %EL was significantly affected by experimental treatments. The highest and the lowest electrolyte leakage values were observed in the Kashmar and Torbat heydarieh ecotypes at -20 ºC, respectively. Rezvan beydokhti et al (2011) showed that there were significant different amoung Persian shallot ecotypes for electrolyte leakage percentage. The EL increased markedly as temperatures decreased and the peak of EL% obtained at 20 ºC. The EL% of Organs (Leaf and corm) in response to the freezing temperature was different. It seems that the cell memberace of saffron’ leaf is more sensitive than corms to freezing stress. Interaction between temperature and organs showed that the highest and lowest %EL was observed in the leaf and corm at -20ºC and 0ºC, respectively. The temperature resulting in 50% leakage has been known as LT50el i.e. freezing temperature that causes 50% mortality (Cardona et al., 1997). There was significant difference (P ≤0.01) among saffron ecotypes in terms of LT50el. The lowest and highest LT50el was observed in Torbat heydarieh, Ghaen and Kashmar, respectively. Shashikumar and Nus (1993) reported that Bermuda grass cultivars were different in LT50el. The more tolerance cultivars showed the lower LT50el. There were significant correlation (r=0.82**) between %EL and corm’s LT50el where by reducing %EL, ecotypes’ LT50el decreased.
There were significant differences (P≤0.01) among freezing temperatures for the survival percentage. Survival percentage of all ecotypes did not affected up to -12°C, however, it is reduced by decreasing temperature, and the lowest survival percentage was obtained in -20°C.
Survival percentage varied among saffron ecotypes. Torbat heydarieh ecotype showed the highest (96.1%) and Kashmar ecotype had the lowest (94.4%) survived seedling.
The results of correlation analysis demonstrated a negative, significant correlation between leaf and crom’s EL% and survival percentage (r = -0.98**). Such results showed in other studies for different plants (Rife and Zeinali, 2003).
The results of this experiment showed significant effect of freezing temperatures on EL% where EL% increased as temperature decreased. Amoung ecotypes Torbat heydarieh ecotype showed the lowest %EL, lowest LT50el and the most tolerant to the freezing stress. The saffron’s corm was more tolerant than leaf in freezing temperatures. Therefore, the EL method could be used as a fast and efficient method in evaluating the cold tolerance of saffron ecotypes.
Acknowledgements: This study has been supported by the grant approval of the Ferdowsi University of Mashhad, Iran and the authors would like to appreciate it.

In order to evaluate yield and yield components properties of cold-tolerant chickpea under winter sowing and complementary irrigation conditions، two experiments in the context of partial balanced block design with 81 chickpea genotypes and three replications were carried out. Complementary irrigation was performed during growing season including irrigation immediately after sowing، 20 days after the first irrigation and at early phase of flowering. After winter cold، survival percentage of the chickpea genotypes was calculated and total precipitation rate from sowing to harvesting was 267 mm. Moreover، properties of grain yield components (survival percentage، pod number per plant، the number of grains per pod and weight of 1000 grains)، grain yield، biological yield and harvest indices of the genotypes were measured and recorded. Based on the results، the difference between the genotypes was significant for all the measured properties. Under complementary irrigation، 40 percent of the genotypes showed winter survival rate higher than 76 percent and grain yield in 52 percent of the genotypes was higher than 100gr/m2. Under winter sowing condition، grain yield in 32 percent of the samples was higher than 40gr/m2. Finally، under winter sowing and complementary irrigation regime، the genotypes ‘MCC333’، ‘MCC186’، ‘MCC803’ and ‘MCC743’ possessing yield over 600 kg/ha were determined as the superior genotypes.

To evaluate the freezing tolerance in sugar beet (Beta vulgaris L.), seven cultivars (Suprema, Jolge, Monotunno, Giada, PP8, SBSI1, Palma) were exposed to the 10 temperatures (0, -2, -4, 6, -8, -10, -12, -14, -16 and -18°C). The study carried out as a factorial arrangement of treatments based on randomized completely design with three replications at College of Agriculture, Ferdowsi University of Mashhad in 2009. Plants were kept until 4-5 leaf stage in natural environment at early autumn, then transferred to the thermogradient freezer. No. of leaf, leaf area, leaf dry weight, survival percentage, lethal temperature 50 according to the survival percentage (LT50su) and reduced dry matter temperature 50 (RDMT50) were determined after 21 days (end of recovery duration). Results showed that by reduction of temperature No. of leaf, leaf area and its dry weight significantly decreased. Amounts of LT50su between the cultivars were significantly different. Monotunno with LT50su -16.9°C was more cold hardly than others and PP8 and SBSI1 with LT50su -15.2 C were susceptible to the freezing temperatures. Decreasing temperature below -14°C reduced survival percentage in all cultivars. PP8 and SBSI1 cultivars perished completely at -16°C while others like Suprema and Monotunno had high survival percentage, but all of them killed at -18°C.Correlation between RDMT50 and LT50su was high but not significant. However there was a strong and significant correlation (r = 0.99**) between LT50su and survival percentage.

Ajowan is one of the endemic plants in Khorasan province، and there is a little information on its tolerance to cold stress. In order to study freezing tolerance of ajowan، an experiment was conducted in faculty of agriculture، Ferdowsi University of Mashhad، based on factorial-completely randomized design with three replications and three ecotypes of ajowan (Neishabour، Birjand and Torbat-e-Heidarieh) were imposed on eight freezing temperatures (0 (control)، -1. 5، -3، -4. 5، -6،-7. 5، -9 and -10. 5 °C). Plants were grown in natural environment till 4-5 leaf stage، then for freezing treatments transferred to thermo-gradient freezer. The cell membrane stability was evaluated by electrolyte leakage index (EL) and temperature for killing 50% of samples according to the electrolyte leakage (LT50el) was determined. Furthermore، survival percentage، leaf number and dry weight، temperature for killing 50% of samples according to survival (LT50su) and reduced dry matter temperature 50 (RDMT50) were determined after three weeks recovery in the glasshouse. Response of ajowan ecotypes for electrolyte leakage was different and birjand ecotype had the lowest %EL، whereas the slope of %EL in mentioned ecotype was lower than two other ecotypes. However there were no significant differences among ajowan ecotypes on LT50su. Decreasing temperature to -7. 5 °C reduced survival percentage of Neishabour and Torbat-e-Heidarieh ecotypes to lower than 20 percent، whiles in this temperature Birjand’s survival percentage was about 60 percent. It seems that Birjand ecotype with the lowest electrolyte leakage، the highest survival and dry matter and the lowest LT50su was more tolerant than two other ecotypes.

Freezing stress affected some vital processes of plant, and causing disturbance on the plant growth. In order to study the effect of low temperatures on freezing tolerance of chickpea (Cicer arietinum L.) a factorial experiment with 4 replications carried out using 3 chickpea genotypes (MCC496، MCC763 and MCC798) and 7 freezing temperatures (-4, -6, -8, -10, -12, -14 and -160C). Explants were cultured on MS medium with 2mg. l-1 BAP and 0. 125 mg. l-1 IBA. For acclimation, explants were transfered to 4ºC for 12 days. Then explants were freezed in thermo- gradient freezer. The percentage of survival and injury were determined after 3 weeks. Result showed that the effect of different freezing temperatures were significant on survival and injury percentage (P≤0. 05). By temperature decreasing, survival percentage decreased, wherease injury percentage increased but between 3 genotype differences were not significant. LT50 (injury percentage) in genotypes MCC763 and MCC798 were -15 ºC and in genotype MCC496 was -15/5 ºC. Also, LT50 (survival percentage) in 3 genotypes MCC496, MCC763 and MCC798, were -13, -12 and -12/5 ºC. This study suggests that in vitro screening of chickpea genotypes for cold tolerance is satisfactory and can be replaced by selection in the field, mainly due to its high repeatability.