نشریه پژوهش های بذر ایران
سال ششم شماره 1 (پیاپی 11، بهار و تابستان 1398)

Strangle wort (Cynanchum acutum) is a perennial weed that could be propagated by seeds and vegetative organs. This brings about harvesting problems for some crops such as cotton, sugar beet, wheat and maize. In recent years, this weed has caused huge losses in sugar cane fields. The role of environmental conditions in weed management is highly important. Given this, the present study seeks to investigate the effects of environmental conditions (salinity and drought stress) on germination characteristics of strangle wort weed.

In order to investe the effect of different salinity and drought levels on strangle wort (Cynanchum acutum), two seperate experiments were conducted at Hakim Farabi Khuzestan Sugar Cane Research Institute in 2014-2015. The experimental design was completely randomized, with four replications. The treatments were different salinity levels at 8 levels (0, 2.5, 4.5, 6.5, 8.5, 12.5, 16.5 and 20.5ds/m) and the second experiment involved different drought stresses (osmotic potential) at 7 levels (0, -1, -3, -6, -9, -12 and -15 bar).

The results of salinity stress experiment showed that with increases in salinity levels from 0 to 20.5 ds/m, germination, radicle length, plumule length and seedling weight decreased by 61, 80, 91 and 99%, respectively. The results of drought stress experiment showed that with increases in salinity levels from 0 to -15 bar, all studied traits, i.e., germination, radicle length, plumule length and seedling weight all decreased by 100%. The analysis of variance results showed that in all the traits, there were significant differences between salinity and drought stress in 1% probability level. In this research, in the salinity experiment, in most of traits, especially radicle length quickly decreased after 8.5 ds/m salinity to higher levels and in drought stress experiment, after -3 bar to higher levels.

On the whole, it seems that sufficient information about this weed is vital for the adoption of the best control method, and gaining insights into how strangle wort responds to environmental stress, especially salinity stress, could help us to come up with new control approaches for this invasive weed. This can present a proper ecological approach that could be adopted in sustainable agriculture programs, which is environmentally sound as it decreases the use of chemical inputs. In addition, in order to lower the tolerance of this weed to salinity and especially drought stress, it is suggested that it be used for weed management programs. According to the results of this study, soil salinity higher than 8.5 ds/m and drought tension above than -3 bar can cause sizeable reduction in most traits (growth parameters) especially in root length. In most of the traits scrutinized, the tolerance of the weed to salinity and drought stress was 12.5 ds/m and -6 bar, respectively.

Evaluation of germination characteristics of strangles wort under salinity and drought stress conditions. Determination of tolerance threshold of strangles wort germination seed to salinity and drought stress.

Guar (Cyamopsis tetragonolob) which belongs to fabaceae and leguminosae families is self-pollinating and is indigenous to India and Pakistan. This plant is suitable for growth in dry, damp and sandy soils, and can tolerate saline and relatively alkaline soils. Determining the best time for harvesting seeds and its timing with maximum quality is one of the important issues in the field of seed production management. The changes in the physiological quality of seeds occur during development until seed treatment. The use of high-quality seeds plays an important role in the final yield of crops. The purpose of this study was to determine the most suitable time for harvesting seeds because seed moisture content at harvest time is one of the most important factors affecting seed quality.

This research was carried out in July 2013 at Iraqi Research Station in Gorgan, Golestan, Iran in a split-plot design with four replications. The treatments consisted of the time of harvesting the seeds from the mother's base in six stages (with different moisture content) and harvesting places (upper, middle, and bottom pods) so that, starting from the podding, every 7 days, the seeds were removed from the base. The mother was harvested and such traits as germination rate, germination percentage, seedling vigor, seed moisture content, and alpha-amylase activity were calculated. In this research, a logistic model was used to study the changes in germination percentage, germination rate, seedling vigor index and straw index during seed dressing on Guar.

The results of this study showed that the hypothesis that seed reaches its maximum quality at the end of the period of seed filling is confirmed, suggesting that with a moisture content of 30 and 14% in late seed filling period, Guar seeds have the highest quality. In general, the results of the present study confirm that the stages of development and management of Guar seeds on maternal basis have an impact on its quality. In the early stages of growth (humidity 85, 80 and 62 percent), due to prematurity and lack of essential seed structures, the qualitative traits of germination percentage, germination rate, seedling vigor, and strawberry index were low, and with the evolution of essential structures and reduced seed moisture content (58, 30 and 14%), the quality traits increased.

In general, it can be concluded that the best timing for harvesting Guar seeds with the highest quality in Golestan province is when seed moisture reaches 14% or 100 days after planting, and the pods formed at the bottom are the ones with the highest quality.

To investigate the qualitative indices of Guar seed on the mother plant during seed filling period .To determine the best harvest time and its adaptation with the highest quality of Guar seed

In addition to dormancy, seeds of Allium hirtifolium have a weak emergence in the field. Among methods for improving the efficiency and emergence of seeds, nutritional priming can be considered for its performance on weak seeds. The presence of micronutrients is one of the factors that may affect the efficiency of the seeds. Therefore, the aim of this study was to investigate the effect of priming with nutrients on optimization of dormancy status, germination, and enhancement of shallot seeds for its conservational, restoration and domestication programs.

In order to study effects of nutrients on germination and emergence of Allium hirtifolium, a CRD factorial experiment was conducted with four replications at Seed Science and Technology Lab of Shahrekord University in 2015. Two dormancy breaking treatments (sulfuric acid and sulfuric acid + gibberellic acid) as the first factor and nine nutrition treatments including four levels of ZnSO4 (5, 10, 50 and 100 mM) and four levels of FeSO4 (0.5, 1, 1.5 and 2%) versus control were compared on shallot seeds.

The results showed that dormancy breaking treatments, nutrient pretreatment of seeds and their interaction had significant effects on germination percentage, germination rate, time to reach l0% and 50% germination, germination uniformity, seedling length and vigor index I at 1% probability level. Sulfuric acid and FeSO41% increased germination versus control. Application of gibberellic acid affected the behavior of iron but did not indicate significant effects for zinc. The concentration of 5 mM ZnSO4 increased the rate of germination, compared with the control but decreased with higher concentrations. The gibberellic acid did not show any sharp effects on germination rate. Time to reach 50% germination was also affected by FeSO4 0.5% and 1% and lower levels of zinc. Application of gibberellic acid did not show any significant impact on the germination time reduction, compared with control and increased T50 in higher concentrations. Although germination traits were rarely affected by gibberellic acid, seedling length and vigor index were positively influenced with GA, and the highest seedling length was achieved at 0.5 and 1% of iron and gibberellic acid.

Seed priming with nutrients can improve germination and plant vigur indices. Different concentrations of iron and zinc showed different impacts on the seeds, which showed interaction with dormancy breaking methods. Although application of gibberellic acid did not have an effective role in increasing germination rate and reducing the time to reach 10% and 50% of germination, it enhanced seedling length and vigor index I, especially for iron.

Addition of iron and zinc sulfate to shallot seeds whose dormancy was broken with sulfuric acid caused higher germination rate of  25.54%, compared with the control. Gibberellin compensated for zinc effect in germination and was able to replace it, but had a slight synergic effect with iron sulfate. Although gibberellin application did not affect germination traits, the seedling length and vigor index showed a positive response to it.

Pulses are a group of crops which are important in human nutrition and also sustainability of agronomical systems and economic advantage. Regarding optimum planting density of mung beans (40 plant m-2), more than 700 tons of certified seeds of mung bean seeds are needed all over the country, confirming the importance of the production of high quality seeds. Seed quality may be affected by different environmental conditions such as water deficit. Since intercropping can alleviate the negative effects of drought on crop growth, the hypothesis that crops can benefit from intercropping has been formulated in previous studies. Since there is no sufficient information on germination performance and seed weight of mung bean during seed growth and development in response to partial root zone irrigation and intercropping, the current experiment was aimed to evaluate the effect of partial root zone irrigation and intercropping on some quality traits of mung bean and to determine the best time of harvesting to produce high quality seeds in mung bean.

The experiment was conducted as factorial (3× 2× 5) based on RCBD with three replications. The first factor was planting pattern (including sole mung bean, inter-row maize-mung bean intercropping and within-row maize-mung bean intercropping). The second factor was irrigation method (partial root zone irrigation and conventional irrigation) and the third factor was harvest time (5-day intervals in 5 stages). Germination percentage, 1000-grain weight, root length, shoot length and seedling dry weight were determined for evaluation of seed quality.

The results indicated that the interaction of cropping pattern× harvest time and cropping pattern× irrigation× harvest time had no significant effect on traits. However, the interaction of irrigation× harvest time on germination percentage, root length and seedling dry weight was significant (P≤0.01). With increasing growth and maturation of seed, germination percentage increased in both irrigation methods. Germination percentage of mung bean was reduced by partial root zone irrigation. The effect of partial root zone irrigation on germination percentage was higher at the end of seed filling period. Partial root zone irrigation resulted in the reduction of root length. The differences between conventional and partial root zone irrigation for root length at different harvest times were 4, 9, 9, 18 and 15 percent, respectively. In both irrigation methods (i.e., conventional and partial root zone irrigation) seedling dry weight increased with increasing the seed growth and maturation. However, deficit of irrigation had negative effects on seedling dry weight of mung bean. With reduced water availability, 1000-grain weight and shoot length were also reduced. 1000-grain and shoot length of mung bean in conventional irrigation were 11 and 10 percent higher than those of partial root zone irrigation, respectively.

Intercropping had no significant effect on seed quality of mung bean. However, deficit of irrigation reduced its seed quality. For harvesting high quality seeds in mung bean, there is a need for plants that experience no drought stress. That the time of reaching the maximum seed quality coincided with the ending of the seed filling period confirms the Harington’s hypothesis.

Seed quality of mung bean during seed growth and development was evaluated. Effect of deficient irrigation induced by partial root zone irrigation on seed quality of mung bean was determined. The effect of planting pattern of mother plants on seed quality was investigated.

Understanding the complex characteristics that control the life span of the seed has ecological, agricultural and economic importance. Inappropriate storage conditions after harvesting destroy a large part of annual yield partly due to microbial activity in the storage. Damage from storage fungi varies based on the climatic conditions, crops and storage facilities. This study was carried out to investigate the effect of storage conditions and initial seed moisture content on the growth of storage fungi and also the relationship between the degree of contamination with fungi and the quality and biochemical changes of the seeds.

The present study was carried out as a factorial experiment based on a completely randomized design to assess the impact of storage fungi on soybean seed deterioration at different storage conditions. The treatment included three degrees of initial seed moisture content including low moisture content (10%), medium moisture content (12%) and high moisture content (14%) as the first factor. Moreover, two storage conditions including the seed storage in Moghan and controlled seed storage in Seed and Plant Certification and Registration Institute were considered as the second factor. Soybean seeds of Williams's cultivar were investigated for the infection of Aspergillus flavus, Aspergillus niger, Fusarium and Penicillium fungi and also related biochemical traits and seed quality such as germination percent, seedling vigor index, soluble sugar and total protein.

The results of this experiment showed that the increase of the seed moisture content by 14% can significantly decrease the seed quality. Therefore, the seed moisture content of 14% was identified as unsuitable moisture for the storage of soybean seeds. In addition, the infection with storage fungi has a direct relationship with the degree of seed moisture and seeds with high moisture content are rapidly attacked by the storage fungi which can decrease seed quality and viability. Moreover, the Aspergillus niger infection increased from 27.5 to 43.75 and the germination percent decreased from 52.5 to 23 percent in seeds with a moisture content of 14% in Moghan storage, as compared with the controlled storage. Furthermore, this study showed that when the percentage of storage fungi increases, the soybean seed deterioration increases. Studying the biochemical changes of deteriorated seeds during the storage showed that as the aging of the seeds increases, soluble sugars and protein percentage decrease. The amounts of soluble sugars and total protein of the seed were significantly lower in seeds maintained under unsuitable conditions. Furthermore, the content of soluble sugars and total protein decreased significantly by the increase of the seed moisture, which resulted in the increase in seed deterioration.

Based on the obtained results, initial seed moisture and storage conditions are two important determinants of fungi infestation during storage, which can affect the content of soluble sugars and total protein causing seed deterioration, seed vigor and viability. It can be concluded that the soybean seed moisture content of 12%, which is the standard moisture content of soybean seed production in Iran, is regarded as suitable moisture for seed storage.

Introduction of proper storage conditions and initial seed moisture in order to decrease fungal damage and soybean seed deterioration. Determination of different fungal damages during the storage of soybean seeds. Determination of relationship between the degree of soybean seed infection of storage fungi and the seed’s quality, its amount of protein and soluble sugars.

Iran is located in the arid and semi-arid regions of the world with an average rainfall of 240 mm per year, which requires rethinking of the adoption of methods. One of the alternative ways is to use organic and biological fertilizers. Biological fertilizers are considered as the main and the most important factor in the integrated management of plant foods for sustainable agriculture as they play an important role in product improvement and efficiency. Therefore, this research was carried out with the aim of investigating the effect of seed pre-treatment with some organic and biological fertilizers in rainfed wheat.

A factorial experiment with three replications was conducted at the Laboratory of Seed and Plant Certification and Registration of the Center of Agriculture and Natural Resources Research located in Hamedan. Seed inoculation was considered in 5 levels (Seafull, Disper Root Gs., Bio-Health, Trichodermin and control) on 8 different rainfed wheat cultivars (Azar-2, Hashtrood, Baran, Rasad, Owhadi, Sardari, Takab and Homa). First, the seeds were disinfected with sodium hypochlorite, and were then cultured in special containers and were placed in the germinator at 20 ° C. After 4 and 8 days, the number of germinated seeds was counted. Germination seeds were counted in each treatment and germination indices such as germination rate, average daily germination, coefficient germination rate, longitudinal vigor index, weight vigor index, seedling fresh weight, root length/shoot ratio, shoot fresh weight, root fresh weight, seed reserve utilization rate, seed reserve utilization efficiency, fraction utilization seed reserve, seed dry weight were calculated.

With application of different levels of fertilizer, the rate of germination treatment Homa×Bio-Health (155%), average daily germination treatment Hashtrood×Bio-Health (69%), coefficient germination rate treatment Owhadi×Disper Root Gs (60%), longitudinal vigor index treatment Owhadi×Bio-Health (108%), weight vigor index treatment Homa×Bio-Health (64%), root fresh weight treatment Hashtrood×Disper Root Gs (106%), shoot fresh weight treatment Hashtrood×Seafull (23%), seedling fresh weight treatment Homa×Bio-Health (42%), root length/shoot ratio treatment Owhadi×Trichodermin (75%), seed reserve utilization rate treatment Homa×Bio-Health (118%), and fraction utilization seed reserve treatment Homa×Bio-Health (119%) increased, compared with the control. In addition, the application of Bio-Health fertilizer and Hashtrood cultivar had the highest amount in almost all the mentioned attributes

Investigation of the different levels of fertilization showed that in most of the indices related to germination and heterotrophic growth of seedling, pretreatment with Bio-Health biofertilizer had a significant difference with other fertilizer levels.

Evaluation of germination indices for recent cultivars of rainfed wheat, released by rainfed Research Institute of Iran. Investigating and comparing fertilizers with various multifactorial compounds (fungi and bacteria) and with each other. Conducting research on commercial compounds and comparison of live biochemical and non-organic matters in a single experiment.

White Astragalus (Astragalus gossypinus Fisherr.) is one of the valuable plants for producing gum, which is of critical importance in soil conservation and the economy of the country. This plant is propagated by seed; its seeds are in the natural state of dormancy. Therefore, recognizing the factors affecting dormancy and creating optimal conditions for seed germination of this plant is necessary for the cultivation and reclamation of rangelands. This study was conducted with the aim of finding the best treatment for breaking the dormancy and improving seed germination under various chemical and physical treatments.

The experiment was carried out as a factorial based on a completely randomized design with four replications at the gene bank of cereal and legume Lab of Ilam University, 2017. The factors included two levels of scarification chemical (with and without sulfuric acid (H2SO4) for 10 minutes), three levels of stratification (control, moist chilling at +4 °C and dry chilling -20 °C), potassium nitrate in two levels (zero and 1% KNO3) and gibberellic acid in two levels (zero and 5 ppm GA3). Germination indices including germination percentage, germination rate, seedling and radicle length, seedling fresh weight and vigor index were measured.

Initial assessment of vital indices in seed such as germination and primary growth showed that the simultaneous application of scarification by sulfuric acid and moist chilling at +4 °C has the most impact on removing dormancy and increasing germination percentage. The highest germination rate was observed in moist chilling at +4 °C, which was 32.19 percent more than that of the control treatment. Scarification by sulfuric acid reduced the mean germination time in moist chilling at +4 °C. Scarification by sulfuric acid increased the fresh weight of the seedling by 55.25 percent, compared with the control. Pre-treatments with potassium nitrate undre control conditions, moist chilling at +4 °C and dry chilling at -20 °C increased the fresh weight of seedlings, at 52.66, 30.94 and 17.18 percent, respectively. Application of potassium nitrate increased root length by about 60.7 percent, compared with control. The highest radicle length (78.71 mm) was obtained when the seed was treated with sulphuric acid with wet chilling at 4 ° C for two weeks, which was 30 percent higher than control. The highest seedling length (84.88 mm) was obtained in scarification with sulfuric acid, wet chilling, and potassium nitrate and gibberellic acid. The highest seed vigor index (61.85 %) was observed in the treatment of scarification with sulfuric acid under moist chilling, and pre-treatments of gibberellic acid and potassium nitrate.

In general, it can be concluded that seed dormancy of Astraglus gossypinus involves both physical and physiological dormancy. The best treatment for removing the dormancy of this species seems to be scarification with sulfuric acid for 10 minutes puls concentrated stratification in moist chilling at +4 °C for two weeks.

Determination of the optimal seed dormancy techniques of white Astragalus for the purpose of increasing seed germination percentage.. Comparison of the efficiency of different dormancy breaking techniques.. The combined effect of sulfuric acid, chilling and priming with gibberellic acid and potassium nitrate on germination indices.

In recent years, Japanese morning glory has been recognized as a new weed in some soybean cultivation areas in the Province of Golestan. Japanese morning glory, an annual herbaceous plant, belongs to Convolvulaceae family. Germination is the first step in the competitiveness of a weed in an ecological niche. Among the factors influencing seed germination, temperature and light are the most important environmental factors. The relationship between temperature and germination rate is mainly determined by nonlinear regression, and various models such as dent-like, segmented, beta, and second-order major models are used for this purpose. In this study, we examined the aspects of germination biology of this weed under the influence of temperature and light.

In order to investigate the effect of temperature and light on germination of Japanese morning glory, two separate experiments were conducted. Treatments included constant temperature at 7 levels (10, 15, 20, 25, 30, 35, 40) in the first experiment and alternating temperature at 6 levels (30/25, 10/15, 30/20, 35/25, 40/30, 45/35) and light conditions (14 hours of brightness 250 μmoles/m-2-sec-1) and darkness in the second experiment based on a completely randomized design with four replications. The number of germinated seeds was taken up to 4 days after stopping germination every day. Percentage and speed of germination and time reaching 50% germination were calculated. Three models of dent-like, segmented lines and beta were used to determine the cardinal temperature between the temperature and germination rate.

The results showed that temperature had a significant effect on percentage, speed and time taken to reach 50% (D50) of germination of Japanese morning glory. The highest percentage of germination (95%) and germination rate (19.80 seeds per day) were observed in the alternating temperature of 20/30 ° C treatment, respectively. The lowest percentage of germination (83.33%) was observed at alternating temperatures 25/35 °C, and the lowest germination rate (15.10 seeds per day) was observed at 10-20 °C. The segmented lines, dent-like and beta were best fit based on the highest R2adj 0.95, 0.96 and 0.95, respectively. Light had no significant effect on germination, so that germination occurred under both light and dark conditions. According to the results, Japanese morning glory is able to germinate at a wide range of constant and alternating temperatures, although germination is faster at warmer temperatures. On the other hand, the lack of light for germination is another advantage that increases germination, competition, and expansion in agronomic environments.

The findings of the present study suggest that the highest percentage of germination and rate of germination were observed in alternating temperatures of 20/30 °C respectively. Among the nonlinear regression models, the dent-like model represented the best model for describing the germination rate against the temperature in Japanese morning glory. It seems that this weed has better germination at warmer temperatures. Probably from mid-spring following warmer weather, and upon the availability of water, this weed is in a good situation to germinate and compete. It was also found that light had no significant effect on the germination of this weed.

Non-photoblastic seeds. Superiority of dent-like model for predicting germination of Japanese morning glory

Interference includes competition for environmental potentials and allelopathy. By releasing chemical compounds, usually of secondary metabolites, in various ways such as root exudation, decomposition, leaching and volatilization, allelopathic weeds may have positive, negative or even neutral effects on crops. Therefore, the purpose of this experiment was to evaluate the hetrotoxic potential of Sorghum halepense, Portulaca oleracea and Centurea depressa in characteristics of germination, chlorophyll content and carotenoid pigments of cress under laboratory conditions.

For bioassay experiments, various concentrations of 0, 20, 40, 60, 80 and 100% of the weeds such as S. halepense, P. oleracea and C. depressa were prepared with the help of distilled water and were subsequently separately applied on 50 certified seeds of cress. In this experiment, characteristics such as rate and germination percentage, content of chlorophyll a, b, total chlorophyll content and carotenoids were measured based on the chilled acetone method.

Regression model showed that rate and germination percentage of cress significantly decreased at concentrations higher than 80% of S.halepense only. For every unit increase in the concentration, radicle length, seed vigor, content of total chlorophyll and carotenoids of cress decreased about 0.08 cm, 8.68, 0.007 mg/g and 0.007 mg/g, respectively. According to the results, there was an exponential relationship between different concentrations of the P. leracea extract with germination characteristics and photosynthesis pigments of cress so that in most cases, these characteristics up to concentration of 40% had moderate decline, but beyond this concentration, they showed a steep decline. In case of C. depressa, rate and germination percentage, as well as the shoot length of cress decreased about 14.67, 14.67 and 29.81% respectively, using only a concentration of 100%. However, radicle length and seed vigor of cress decreased with increased concentrations of aqueous extract of C. depressa. The most reductive effects were obtained in the treatment of 100%, which were about 52.38 and 55.44% respectively. Amount of total chlorophyll of cress decreased about 14.37, 27.59 and 25.29% respectively in concentrations of 60, 80 and 100% of C. depressa extract, as compared with the control. On the other hand, concentrations of 20 and 40% of C. depressa had no significant effect on the pigment studied. The result of carotenoids content was the same as total chlorophyll.

Based on the results, the weeds studied, especially P. oleracea, with high concentrations, had strong hetrotoxic effect on germination characteristics and photosynthesis pigments. This requires further investigation in a natural environment where targeted plants grow in close proximity.

Hetrotoxic compounds of Portulaca oleracea, especially in high concentrations significantly decrease seed germination and photosynthetic pigments of cress as compared with Sorghum halepense and Centurea depressa. Given the evidence for the hetrotoxic effect of aqueous extract of the weeds studied, they could be introduced as candidates for production of bio-herbicides.

Agriculture has been influenced by different abiotic stresses such as temperature, drought and salinity, which reduces roughly half of the yield of crops. In many forage plants, germination and early seedling growth are the most sensitive stages of their growth in the face of environmental stresses. Current research was conducted to study the effects of drought and salinity iso-osmosis stresses on germination indices and growth parameters of three clover species, including Trifolium resupinatum, T. alexandrinum and T. incarnatum.

Two separate experiments (drought and salinity) were conducted as a factorial experiment based on a completely randomized design with three replications. The test factors included clover species with three levels, including T. resupinatum, T. alexandrinum and T. incarnatum and different levels of drought and salinity potentials (0, -2, -4, -6, -8, -10 and -12 bar) due to polyethylene glycol 6000 (PEG 6000) and sodium chloride (NaCl), respectively. Sterile disposable petri dishes with a diameter of 10 cm were used, in each of which, 27 seeds were placed on filter paper and then 5 ml of the desired treatment solution was added to each. Petri dishes were then placed in a germinator at 20°C and relative humidity of 75%. After the end of the desired time germination (About 14 days), from each petri, germination percentage and rate, number of secondary roots, time to get 50% germination (D50), root to shoot ratio and the number of abnormal seedlings were recorded.

Inhibitory effects of salinity and drought stresses affected all germination indices. Germination percentage, rate of germination, root and shoot length all decreased with increasing stress levels, while time to get 50% germination (D50) increased with the increase in stress levels. Under both drought and salinity, all growth parameters of Trifolium resupinatum were higher than the other two species. Germination percentage of T. incarnatum was 0% at -12 bar of drought, but germination of T. resupinatum and T. alexandrinum was 70.33% and 7.33% at -12 bar of these stresses, respectively. Under salinity conditions, all the seeds of the three species germinated at -12 bar. Root to shoot ratio increased with increasing stress levels and at high stress levels, it decreased. The decreases were 41.39% and 0% in drought and salinity, respectively. The number of secondary roots increased with increasing stress levels and the maximum number was observed in Trifolium alexandrinum which was 5.42 and 1 in drought and salinity, respectively. The number of abnormal seedling increased with increasing salinity levels, while under drought conditions there was no abnormal seedling.

Comparison of the effects of sodium chloride and polyethylene glycol showed that sodium chloride reduced germination index due to toxic effects or osmotic effects more than polyethylene glycol solution. It seems that Trifolium resupinatum has the best yield in both drought and salinity stresses, and that in drought condition, Trifolium alexandrinum, and in salinity stress, Trifolium incarnatum have the best performance.                                                                                                                       

Introduction of clover species with more tolerance to drought and salinity in germination stage. Evaluation of germination indices of clover species under drought and salinity iso-osmotic conditions.

In order to take more advantage of the spring growing season, the mechanisms of germination of spring plants are of great importance at temperatures lower than the optimum temperature. Since one of the ways to reduce damage due to low temperature is enhancing the seedling antioxidant system, in this study the effects of salicylic acid and gibberellin on germination and antioxidant system of pumpkin (Cucurbita pepo) seeds were investigated under low temperatures.

A factorial experiment including four concentrations of gibberellin (0, 250, 350 and 450 mg/L), four concentrations of salicylic acid (0, 0.5, 1 and 1.5 mM) and three temperature levels (8, 11 and 14 °C) was performed with a completely randomized design within controlled conditions and six replications at Shahrekord University in 2017. The seeds were immersed in containers containing solutions of 0, 250, 350 and 450 mg/L of gibberellin and solutions with 0, 0.5, 1, and 1.5 mM salicylic acid, were placed in a growth chamber for 24 h under dark conditions at 15 °C. Then the seeds were washed at the desired temperatures, and the germination was recorded every 24 hours based on the 2 mm of radicle length. At the end of the eighth day, after the separation of normal and abnormal seedlings, 20 normal seedlings were selected from each petri dish. Following that, the germination rate, germination percentage, soluble protein, malondialdehyde, superoxide dismutase, guiacol peroxide enzyme, and catalase enzyme were measured. Comparison of means was conducted by the least significant difference test at the 0.05 probability level.

The results showed that none of the treatments used at 8 °C helped germination of the plant and, therefore, 8 °C treatment was removed from the experiment. At the temperature of 11 ° C, the use of salicylic acid 1 mM and at 14 °C, the use of gibberellin 350 mg/L showed the maximum germination rate and germination percentage, compared with the control. At 11 °C, the activity of antioxidant enzymes was more affected by gibberellin hormone so that the highest activity of superoxide dismutase enzyme was observed in 350 mg/L and the highest activity of catalase and guaiacol peroxidase enzymes and the lowest amount of soluble protein were observed in gibberellin 250 mg/L. The salicylic acid hormone was more successful at 14 ° C. The salicylic acid 1.5 mM increased the activity of superoxide dismutase enzyme; and salicylic acid 0.5 mM increased the activity of catalase and salicylic acid 1 mM improved the activity of guiacol peroxidase. This hormone also succeeded in reducing the amount of soluble protein.

In this experiment, seedling tolerance at low temperatures was confirmed by gibberellin and salicylic acid treatments. It is generally concluded that the use of gibberellin and salicylic acid increases the activity of antioxidant enzymes and, as a result, makes pumpkin (Cucurbita pepo) seedlings tolerant to low-temperature stress, and thus, can ameliorate the effect of possible chilling on growth of this crop at the beginning of the season.

Gibberellin and salicylic acid treatments make pumpkin seedling tolerant to low temperatures. Application of gibberellin and salicylic acid increases the activity of antioxidant enzymes. By using gibberellin and salicylic acid, the effect of possible chilling can be reduced at the beginning of the growing season.

Production of nanoparticles and their use are on the rise in different areas of plant science. However, in spite of their increasing production, there is limited information about their effects on plant biology. In the current study, the potential of TiO2 nanoparticles was investigated for the purpose of improving seed germination of Sorbus luristanica and then subsequent effects of nanoparticles on the growth and biomass of the plants were determined.

Seeds of S. luristanica were collected from its natural stands. The seeds were primed with different concentrations of 0, 75, 150, 250, 350 and 500 TiO2 nanoparticles miligeram per liter for 24 h. The treated seeds were placed in wet sand at room temperature for 2 weeks and then in cold for 3 months. The expriment was set as a completely randimized design with 4 replications. Aftre 3 months of stratification in moistened sand, the stratified seeds were put in the germinator and with the appearance of seed germination signs, germination data were recorded daily during 22 days. At the end of the seed germination experiment, some germination parameters such as seed germination percentage, seed vigority and mean time to germination were calculated. Moreover, some growth and biomass parameters including leaf number, plant height and dry and fresh biomass of leaf, stem as well as roots were measured. In addition, scaning electron microscopic (SEM) was used for observation of presence and adhesiveness of TiO2 nanoparticles on the seed coat.

Based on the results, all the germination parametres including seed germination percentage, seed vigoroty and mean germination time were improved by the TiO2 nanoparticles treatments. In addition, 500 mg.L-1 treatment considerably improved seed germination characteristics. The peresence of TiO2 nanoparticles on the treated seeds and lack of the nanomatreials on the conrtol seeds were obsereved by scaning electron microscopic pictures. The One-way ANOVA showed that 75 mg.L-1 treatment was more succesful for improving the grwoth (such as shoot length) and biomass production (fresh and dry biomass of leaf, stem and root and total biomass as well).  

It can be concluded that priming of the seeds of this species with different concentrations of TiO2 nanoparticles leads to improvement of seed germination and growth and biomass parameters. However, the patterns of effects were different in each phase. Therefore, the objectives should be formulated first and then the best concentration should be chosen. It seems that with appropriate concentrations, nanoparticles can be useful for breaking seed dormancy and production of the species. Given the promising resutls of 150 mg.L-1 treatment, it can represent a successful treatment for breaking seed dormancy and seedling production of S. luristanica.
Highlights

1- Study of seed germination of Sorbus luristanica for the first time 2- Using Nano-materials and their potentials in breaking seed dormancy and improving the species germination 3- Using SEM in order to study presence and adhesiveness of nanoparticles on the seed coat