نشریه پژوهش های بذر ایران
سال هفتم شماره 1 (پیاپی 13، بهار و تابستان 1399)

 Sweet corn (Zea mays var. saccharata) is a corn variety that is distinguished from other varieties due to the presence of genes that affect starch production in the endosperm. Given that the most of plants including sweet corn face with problems such as non- uniform germination and poor seed emergence in the early stages of germination. Thus, the use of organic stimulants is one of the ways to reduce the harmful effects of non-biological stresses, increase seed germination, uniform appearance and increase their yield and quality. The present study was carried out to investigate the effect of different concentrations of chitosan on seed germination and some biochemical traits of sweet corn under osmotic potential conditions.

 To investigate the effect of chitosan and osmotic stress on germination and biochemical parameters of sweet corn, a factorial experiment was conducted in a completely randomized design with four replications at the Seed Technology Laboratory, Faculty of Agriculture, Yasouj University in 2017. The first factor was osmotic stress at 0, -3, -6, and -9 bar osmotic potentials and the second factor was pre-treatment at five levels of chitosan zero, 0.25%, 0.5%, 0.75% and 1% and one level of distilled water. The seeds were immersed in the desired solutions of chitosan for 3 hours at 25 °C and under dark conditions, and then the pre-treated seeds were germinated under standard germination condition. In each petri dish, 25 seeds were placed on a filter paper and osmotic potential was applied using polyethylene glycol 6000. Seed germination was carried out in the germinator at 25 ± 1 ° C for 7 days under dark conditions. The germination traits and biochemical traits were measured according to standard methods.

 Osmotic stress reduced germination percentage and germination rate, seedling vigour length index, germination uniformity coefficient, allometric coefficient, and soluble protein content and also increased the mean germination time, proline, soluble sugar content and hydrogen peroxide. Pre-treatment of seeds with a concentration of 0.5% chitosan increased protein, proline, and soluble sugars content at all osmotic stress levels. At the osmotic stress levels, the highest and lowest levels of hydrogen peroxide respectively were observed in 0.5% chitosan treatment and distilled water treatment. The results showed that pre-treatment with 0.5% chitosan increased germination percentage and rate and seedling vigour length index, and also reduced the mean germination time and malondialdehyde. Pre-treatment of seed with zero and 1% chitosan led to reduction in some of the germination and biochemical traits in comparison with 0.25, 0.5, and 0.75% chitosan.

 The results showed that seed treatment with 0.5% chitosan could reduce the harmful effects of osmotic potential on some germination and biochemical traits in sweet corn seedlings and improve seedling growth.

1-Chitosan increases the germination percentage and germination rate.
2-Chitosan increases soluble sugars, proline, and soluble protein.
3-Chitosan reduces the amount of malondialdehyde and hydrogen peroxide.

Plants release much of bioactive chemicals from different parts such as leaves, stems and roots through different mechanisms to their surrounding environement. These biologically active chemicals are often referred to as "allelochemicals". Allelopathic compounds play a major role in reducing germination and the growth of crops.

In this study, the effect of leaching on the reduction of phytotoxicity effect of soybean, black cumin, dragonhead and dill was investigated on the emergence and early growth of canola (Brassica napus L.). The experiment was conducted as factorial based on a completely randomized design with four replications in 2016. Treatments included four previous crop residue (soybean, black cumin, dragonhead, and dill), and three levels of leaching (without leaching, one-time leaching, and two-times leaching). The leaching-free treatment (control) was sub-irrigated to maintain the uniformity of environment moisture. Five days after the first leaching, the two leaching treatment was irrigated again. Five days after the second leaching, when the soil moisture was suitable for seed planting, 10 seeds of canola were cultivated in each pot at a depth of 3 cm of soil. After three weeks seedlings of canola were removed from the pot and the traits were measured.

The results showed that the growth characteristics of canola, except root length, were affected by the residues of the previous crop. In non-leaching conditions, the residue of the four plants reduced the rate and amount of canola emergence, and the greatest reduction in canola emergence was recorded for the application of black cumin residue (7.5%). In the leaching conditions, the length of canola leaves increased, which was higher in the twice leaching treatment. This trend shows that as the amount of leaching frequency increased, it is highly likely that more inhibitiing materials leave the soil and conditions become suitable for canola germination and growth.. The highest dry weight of canola root was observed in one-time leaching treatment. The dry weight of canola leaf grown in dill and soybean residues was increased as a result of one-time leaching, whereas the dry weight of canola grown in black cumin and dragonhead residues showed a higher increase in two-times leaching. Results show that four studied plants have canola growth inhibiting compounds and leaching can ameliorate this effect. The response of canola in the soil containing black cumin and dragonhead residues is higher in two-times leaching, and in the soil containing plant residues dill, one-time leaching is sufficient. In soils containing soybean residue, the response index was almost similar in case of one and two-times leaching.

Generally, the results showed that the application of leaching before planting canola reduced the inhibitory effects of plant residue on germination and growth of canola. Therefore, it is suggested that in the agricultural ecosystems in which canola is present in crop rotation, cultivation of canola must be avoided in presence of soybean, black cumin, dragonhead, and dill residue to eliminate their inhibitory effects on canola growth. In areas with water restriction, autumn rainfall can act as leaching and reduce the effect of allelopathic compounds. In case leaching is not possible, cultivation of canola inside the residue of these plants must be avoided.

1-Leaching can reduce the effect of allelopathic compounds. 2- Allelopathic compounds of some plants such as black cumin showed better response to two-times leaching.

Seeds, like other materials, are hygroscopic and exchange moisture with their surroundings. The changes in the moisture of seeds during storage depend on their hygroscopic nature and this feature plays an important role in determining the seed quality and longevity. Furthermore, studying the hygroscopic characteristics if seeds can be useful in seed storage studies as well as in commercial applications such as drying and seeds processing. Therefore, in this study, the relationship between seed moisture content and relative humidity in seed of rapeseed cultivars was studied.

In this study, the relationship between the ambient relative humidity and seed moisture content of three rapeseed cultivars at 10, 20 and 30 °C was investigated using hygroscopic equilibrium curves. Therefore, water desorption and absorption curves were studied separately. Water absorption and desorption curves were obtained by drying the seeds at 1% relative humidity and seed hydration at 100% relative humidity, respectively, followed by transferring the seeds to different relative humidities at different temperatures and finally determining the equilibrium moisture content of the seeds. It should be noted that glycerol and sulfuric acid solutions were used to creation different relative humidity. Finally, the relationship between seeds moisture content against the relative humidity was quantified by fitting the D’Arcy-Watt equation.

The results indicated that the seeds moisture content varied in cultivars and temperatures at different relative humidities. Also, there was a difference between water desorption and absorption curves in all cultivars and temperatures; desorption curves were generally higher than water absorption curves. The greatest difference among the cultivars regarding seed moisture content was observed at 100% relative humidity, and this difference was less severe at lower relative humidities. Also, the highest seed moisture content of rapeseed cultivars was observed at 20 °C and 100% relative humidity, and the lowest seed moisture content was recorded at 30 °C and 1% relative humidity.

According to the results, it was found that the relationship between seed moisture content and relative humidity followed a sigmoidal function, and this relationship would also vary depending on cultivar and temperature. There was also a difference between the adsorption and desorption curves, which is called "hysteresis", and showed that the seed moisture content at a constant relative humidity was generally higher in the state of dehydration compared with that in the state of hydration. Due to this event, desorption curve is situated higher than the absorption curve.

Response to hygroscopic equilibrium curves in seeds of different rapeseed cultivars was compared. Sulfuric acid and glycerol solutions were used to create different relative humidity.

 London rocket is an important winter annual weed of the mustard family (Brassicaceae), which is propagated by seed. Germination of a seed population in response to water potential reduction is modeled using the concept of hydro time. This model has outputs that are physiologically and ecologically meaningful. One of the presumptions of the Hydro time model is the normal distribution of the base water potential among the seed population.

 In order to quantify the germination characteristics and determine the cardinal temperature of germination of London rocket (Sisymbrium irio L.), an experiment was done in 2018 at Science Research Branch, Islamic Azad University, Tehran, Iran. The seeds were placed at constant temperatures (5, 10, 15, 20, 25, 30, 35, 40 and 45 °C). Germination percentage, germination rate, root length, shoot length, seedling length and seedling fresh weight were evaluated. Intersected-lines, dent-like and quadratic polynomial models were used to determine cardinal temperatures. London rocket seed germination was tested across a range of water potential (0, -0.2, -0.4, -0.6 and -0.8 MPa) at the optimal temperature of 22.80 °C. The hydro time model, based on the normal distributions was fitted to data.

 Results showed that seed of London rocket did not germinate at temperatures of 5, 35, 40 and 45° C, and 25° C was the best temperature for seed germination (48%). The longest root length (4.49 mm) was observed at 20°C, which did not have significant differences with temperatures of 15 and 25 °C. The longest shoot length (10.19 mm) was obtained at 25 °C and there were not any significant differences among this temperature and temperatures of 15 and 20 °C. Similar trend with the trait of root length was observed for the trait of seedling length. The best model for estimating the cardinal temperatures in London rocket was intersected-line model with respect to coefficient of determination and mean square error. According to the intersected-lines model in London rocket, the minimum, optimum and maximum temperatures were calculated 5.83, 22.80 and 37.91°C. According to the hydro-time model based on normal distribution, the hydro-time constant and the base-water potential (which is a threshold for germination beginning) of London rocket degree were 284.28 (MPa/h) and -1.18 (MPa) at 22.80 °C, respectively.

 Knowledge of germination and emergence of weeds also helps to predict the potential distribution to new habitats. The obtained coefficient of determination (0.94) between observed germination and predicted germination showed that the hydro time model based on normal distribution fitted well to germination percentage of London rocket seed. Due to the low hydrotime coefficient of this weed and the drought problem that most provinces face, it is expected that this weed will become more problematic in most provinces of Iran in the future.

1- The best temperature for germination of London rocket seed is 25 °C.
2- The best model for estimating the cardinal temperatures in London rocket is intersected-line model
3- The hydro-time constant and the base-water potential of London rocket degree based on normal distribution are 284.28 (MPa/h) and -1.18 (MPa) at 22.80 °C, respectively.

Without a doubt, plant hetrotoxicity is one of the important factors in determining the distribution and abundance of some species in plant communities. Thus, the purpose of this experiment was to evaluate the effect of phenolic composition obtained from the methanol extract of Echinochola crus-galli on germination traits and cytogenetic behavior of rice.

This experiment was done to assess hetrotoxic potential of various concentrations (0, 0.024, 0.048, 0.076 and 0.1 mM) of the phenolic composition obtained from the methanol extract of whole-organ of E. crus-galli on germination traits of rice as well as mitosis division of meristematic cells of radicle in a completely randomized design. To extract thephenolic composition, warm extraction method using a methanol solvent was used. For studying mitosis division, first rice seeds were germinated. Then, each of the steps such as fixation, hydrolysis, staining, squashing and microscopic studies were done on the end of the radicle. Mitosis indices and percentage of mitosis inhibition were calculated and also percentage of each of chromosomal abnormalities at four stages of prophase, metaphase, anaphase and telophase as compared to total cells was calculated.

The lowest percentage and rate of germination and relative germination were found in two concentrations of the 0.076 and 0.1 mM of phenolic composition of E. crus-galli, so that no germination was observed in these treatments. In this study, mitosis division was normal in control samples, so that the rice plant included 12 chromosomes in the metaphase stage. Also the chromosomes were normal in the telophase stage and chromosomal abnormalities were not observed in meristem cells of radicle tip of the control. The lowest value of mitosis indices and the number of dividing cells were related to the concentration of 0.048 mM wuth 30.19 and 385 cells, respectively. In the present study, chromosomal abnormalities in the stages of metaphase, anaphase and telophase were increased with increasing concentration of phenolic composition, and were 28.85 and 16.95% in 0.048 mM concentration of phenolic composition, respectively. The most chromosomal abnormalities were of sticky and laggard type, which were related to the concentration of 0.048 mM of phenolic composition with 39.83 and 32.25%, respectively. The highest number of chromosomal bridges and clumping were obtained in 0.024 mM of phenolic composition with about 19.27 and 29.83%, respectively.

In this study, phenolic composition obtained from the methanol extract of E. crus-galli had asignificant inhibitory effect on germination traits and mitosis division in root tip cells of rice. Thus, the amount of E. crus-galli residues in the field should be considered in direct and indirect cultivation of rice. Highlights: 1-Difference in impact of the phenolic composition obtained from the methanol extract of Echinochola crus-galli on germination and reduced cytogenetic behavior of rice is related to their threshold concentration. 2- It is advised to cultivate varieties of rice resistant to the remnants of harmful compounds of E. crus-galli as direct cultivation or under nursery condition.

Legumes are the most important source of plant protein and Mung bean has a high nutritional value for humans, as it produces seeds containing high protein percentage. The major problem of salinity in seed germination of higher plants is due to excessive amounts of sodium chloride, osmotic pressure, disruption of nutrient uptake and transport, and direct effects of ionic toxicity on the membrane and enzymatic systems that in turn reduce germination. External use of methyl jasmonate can modulate the effects of various stresses, such as salinity and drought, by increasing the antioxidant activity of the seed. Therefore, the purpose of this research was to evaluate the effect of methyl jasmonate and salinity stress on germination and enzymatic properties of Mung bean.

This study was conducted as factorial based on a completely randomized design with three replications during 2015-16 at the laboratory of Department of Agronomy, Tarbiat Modares University. The experimental treatments included four methyl jasmonate solution (0, 50, 100 and 150 mM) and four salinity stress levels (0, 2, 4 and 6 dS/m salinity from NaCl). Petri dishes were placed in a germinator at 25 ° C and in full darkness for 14 days. In this experiment, germination rate and percentage, time to reach 50% germination, alpha and beta amylase, catalase and peroxidase were measured.

The results of the experiment showed that the lowest rate of slope and final germination percentage were obtained in 50 and 100 mM solutions of methyl jasmonate. In terms of T50, an increase of 4.7 days was observed per one dS/m increase in salinity stress and the lowest T50 was estimated at a methyl jasmonate solution concentration of 78.68 mM. In terms of the activity of germination enzymes, reduction of 0.031 μmol/ml/min per 1 dS.m increase in salinity stress and the highest amount of α-amylase were estimated 72.6 μmol/ml/min at a methyl jasmonate solution concentration of 73.33 mM. Also, the lowest activity of β-amylase enzyme was 0.79 μmol/ml/min at a concentration of 5.6 dS/m salinity stress and the highest activity of β-amylase enzyme was estimated to be 1.7 μmol/ml/min at a methyl jasmonate solution concentration of 86.67 mM. The highest activity of catalase (25.7 ∆A/mg protein/min) was observed at 14.72 dS/m salinity stress and the lowest activity of catalase enzyme (8.9 ∆A/mg protein/min) was estimated at 5.88 mM methyl jasmonate solution. The highest activity of peroxidase enzyme (22.06 ∆A/mg protein/min) was at 24.3 dS/m salinity stress and the lowest activity of the enzyme peroxidase (2.5 ∆A/ mg protein/min) was determined at a methyl jasmonate solution concentration of 266.66 mM.

In general, pre-treatment of methyl jasmonate can reduce the germination time, increase the rate of germination and reduce the oxidative stress in salt stress conditions by improving the activity of germination enzymes, increasing the activity of enzymes, increasing the activity of hydrolyzing enzymes and increasing the easy availability of seedlings to nutrients during germination. Highlights: 1- Germination rate and percentage and morpho-physiological changes of Mung bean seed as affected by methyl jasmonate were investigated. 2- The role of alpha and beta amylase germination enzymes in accelerating the production of Mungbean seedlings under saline conditions were estimated. 3- Methyl jasmonate- induced catalase and peroxidase enzymes activity in resistance to salinity stress were estimated.

Soybean is a plant that has a moderate tolerance to drought stress. Drought stress is one of the most important abiotic stresses affecting soybean production by about 40%. In addition, drought stress reduces seed vigor as a result of stress conditions. Positive effects of mycorrhizal fungi on the increment of dry matter and plant biomass, especially in low-irrigated conditions and in dry areas have been proven. The reason for the increase in crop yield in mycorrhizal inoculated plants is their water balance in water deficit stress conditions and as a result, absorption of water and mineral elements. Rhizobium bacteria, carbohydrates, and other foods are catched from the phloem vessels and the received energy is used to convert nitrogen to ammonium ion and eventually amino acids. Japonicum rhizobium bacterium is not naturally found in soils of Iran and the bacteria should be added to the soil along with seeds.

This experiment was carried out to determine the germination characteristics, seed vigor and its related traits in soybean Kosar cultivar grown under drought stress conditions and inoculation with mycorrhiza and bacteria with three replications during 2018. In the field experiment, drought stress included optimal irrigation (irrigation after 70 mm evaporation), moderate stress (irrigation after 110 mm evaporation) and severe drought stress (irrigation after 150 mm evaporation from class A evaporation pan), mycorrhizal fungus in three levels, mycorrhiza-free, and inoculation with glomus mosseae, Glomus intraradices and Rhizobium bacterium in two levels, including no inoculation and inoculation with Rhizobium japonicum.

The mean comparison showed that the seeds obtained under normal irrigation, inoculation with mycorrhiza and bacteria had the highest dry weight of radicle, plumule and seedling, percentage and germination rate. The lowest electrical conductivity of the seeds and the mean time of germination were obtained under these condition. Severe and moderate drought stress reduced stress tolerance index, root tolerance index and stem tolerance index, seedling vigor index and seed vigor index compared to optimum irrigation about 42-23, 38-18, 30-18, 50-26 and 41-21) percent, respectively. Inoculation with Glomus mosseae and Glomus intraradices increased the seed vigor index, radicle lentgh, plumule lentgh and seedling length compared to non-inoculation with mycorhizal fungi by 48-42, 27-26, 41-37 and 35-33 percent, respectively. Inoculation with Rhizobium japonicum increased radicle lentgh, plumule lentgh and seedling lentgh compared to non-inoculation with bacterium by 21%, 16% and 18%, respectively. The highest water percentage in seedling tissue was obtained under optimum irrigation conditions, inoculation with mycorrhizal fungi and inoculation with rhizobium bacteria.

According to the results of this study, in all three different irrigation conditions to improve germination and increase seed vigor, the use of mycorrhiza fungi is effective especially glomus mosseae and inoculation with Rhizobium bacteria.

Germination characteristics, germination rate and duration of soybean Kosar cultivar on seeds obtained under different irrigation conditions were investigated. The effect of mycorrhiza and bacteria on seed vigor and related traits were evaluated under different levels of drought stress. The damage done to the seed membranes due to the interaction of irrigation and inoculation with mycorrhiza and bacterium was investigated.

Germination and seedling establishment are the primary stages of crop growth that are highly sensitive to salinity and drought stresses. On the other hand, seed hardness affects the quality of plant germination. Therefore, the aim of this study was to analyze the effect of seed pre-treatment on germination characteristics of Medicago scutellata var Rabinson.

In the present study, the effects of pre-treatment methods of scarification (sand paper, knife and sand), stratification (0, -5, -10, and -15 °C), ultrasonic waves (3, 6, 9, 12, and 15 min), and magnetic field (two intensities of 125 and 250 mT in 4 times exposure by 6, 12, 18, and 24 h) on seed germination of annual medic germination affected by salinity and drought stresses (0, -3, -6, -9, and -12 bar) were investigated with three replications. Twenty seeds per Petri dish were used for each treatment. Seedlings were incubated in the dark at 20/18±0.3°C in a growth chamber. After ten days, the dry weight of the seedling was obtained after oven drying at 70°C. Root length, shoot length, seed germination percentage, seedling growth rate (SLGR), the weight of mobilized seed reserve (WMSR), seed reserve depletion (SRDP), and seed reserve utilization efficiency (SRUE) were measured.

Based on the preliminary results using Taguchi method, the -15 °C stratification treatments under salinity and drought, 6 and 9 min of exposure to ultrasonic waves under salinity and drought, and magnetic field intensity of 250 mT for 6 and 9 h were chosen for the experiment of salinity and drought, respectively. In salinity experiment, the maximum root length (23.47 mm), shoot length (15.76 mm), weight of mobilized seed reserve (0.119 mg per seed), and seed reserve depletion percentage (58.9 %) was in scarification treatment; the maximum seed germination (47.2 %) was observed in control treatment; the maximum seedling dry weight (0.195 mg) was identified in magnetic field treatment; and the maximum seed reserves utilization efficiency (0.665 mg.mg.seed-1) was obtained in ultrasonic waves treatments. In drought experiment, the maximum root length (22.84 mm), shoot length (8.09 mm), seed germination (49.93 %), the weight of mobilized seed reserve (0.096 mg per seed), and seed reserve depletion percentage (43.1 %) was measured in ultrasonic treatment; the maximum seedling dry weight (0.09 mg) was found in magnetic field treatment; and the maximum SRUE (0.516 mg.mg.seed-1) was observed in control treatment.

According to the results, there is a direct relationship between the decline in seedling dry weight and the decline in the weight of mobilized seed reserve. However, the scarification and ultrasonic waveschr('39') treatments had significant effects on seedlings resistance to salinity and drought, respectively. Furthermore, the use of ultrasonic waves and scarification produced higher germination percentage and more vigorous seedlings under drought and saline conditions. In terms of germination and seedling growth, the differences among the treatments increased by the increase in stress intensity. This advantage led to greater seed reserve utilization. Moreover, pre-treatment methods resulted in longer cotyledon length and improvement in vigorous seedlings. Future studies should focus on the study of enzymes activity and/or hormones affecting seed reserve utilization rate in response to drought and salinity stress. 

Highlights

1- The most sensitive growth stage of annual medic (seedling production stage) to salinity and drought stress was evaluated. 2- Various pre-treatments to improve the germination of annual medic to enter crop rotation in arid and semi-arid regions due to self-seeding and short growing period were investigated.

One of approaches to reach sustainable agriculture is to exploit crop diversity, especially in legume species. Since Melilotus spp. (sweet clover) is a forage crop with a suitable yield especially in the marginal lands; therefore collection and characterization of this germplasm is the first effective step for its conservation and utilization in the country. Few accessions of Melilotus genetic resources had been collected in the National Plant Gene Bank of Iran, before this study.

Sweet clover genetic resources were collected all over the country using standard descriptors during two years. Twenty-six characteristics of collection sites were recorded and their descriptive statistics were estimated. The collected materials were planted in an experimental field to identify their life cycle. The seeds of collected germplasms were conserved in mid (2-4 °C)- and long (-20 °C)-terms conditions for further using.

A total of 258 accessions were collected. The geographical altitude of plant origin differed from -11 m in Babolsar to 3090 m in Noor Abad in Lorestan. The materials were mostly collected from non-saline habitats. However, eight accessions were collected from mid to high salinity locations. Taxonomically, M. albus, M. officinalis, and M. indicus were identified with a number of 21, 201 and 36 accessions, respectively. M. dentatus and M. sulcatus, which have been mentioned in the former researches in Iran, were not collected in the recent study.

The collected germplasms from marginal lands (saline, low drainage and low fertility lands) may be tolerant to such marginal lands, therefore they can be exploited for the future research. All M. indicus species were annual; whereas there were annual as well as facultative and obligate biennial accessions in the two other species. Lack of access to M. dentatus and M. sulcatus may be an alarm that they may be threatened species in the country. Collected materials in this study along with the former collection in the Iranian National Plant Gene Bank (80 accessions) have provided high potentials of Melilotus genetic resources for exploitation in the further. Highlights: 1- The three-fold increase in the Melilotus germplasms in the ex-situ conservation system. 2- Alarm for M. dentatus and M. sulcatus which may be threatened with extinction in the country.

Seed deterioration is a physiological phenomenon that affects all germination, biochemical, cytological, and growth characteristics of plants. So it is necessary to use seed vigor enhancement methods to resolve these problems. One of these methods is the application of seed priming techniques to reduce deterioration effects. Therefore, the present study aimed to investigate the effect of different pre-treatments by using Nano-zinc, ascorbic acid, humic acid, gibberellin and KNO3 on germination indices and chromosomal aberration of aged onion seeds.

This experiment was performed as factorial based on a completely randomized design with 3 replications (100 seeds per replicate) in the faculty of agriculture at Urmia University. The first factor was the level of aging at 4 levels (control, 12h, 24h, and 48h) and the second factor was seed pre-treatments at 6 levels (control, Nano-zinc (30 mg), ascorbic acid (100 mg), humic acid (150 mg), gibberellin (200 mg/l) and KNO3 (0.1%). Given that the germination was not similar at different levels of aging, the seeds were germinated at control and 12h of aging after 6 days, at 24 and 48h of aging after 8 and 9 days, respectively. Hence, germination percentage, germination rate, normal seedling, mean germination time, and seed vigor were evaluated after the mentioned times. Chromosomal aberrations were also examined.

The results showed that the interaction effect of aging and seed pre-treatments on germination indices were significant at %1 probability level. By increasing the period of aging, all germination characters decreased significantly. The highest germination percentage (80%, 70%, 50%) and germination rate (5.350, 3. 316, 1.525 seed/day) were obtained by using Nano-zinc At 12h, 24h and 48h ageing levels. Nano-zinc and gibberellin had the highest effect on seedling vigor and normal seedlings. Seedling vigor increased significantly by using Nano-zinc and gibberellin at 12h (1133, 933.9), 24h (742.9, 692), and 48h (369.9, 323.3). The chromosomal aberration was reduced by using pre-treatment.

In this study, the most effective pre-treatments to improve germination characteristics and reduce chromosomal aberrations were gibberellin (200 mg/l) and Nano-zinc (30 mg). Therefore, it can be stated that the use of Nano-zinc and gibberellin as seed pre-treatments can significantly reduce the effects of deterioration on onion seeds.

1- Nano-Zinc and gibberellin were the most effective priming treatments on seed germination and growth characteristics of the aged onion seeds. 2- Priming treatment reduced the percentage of chromosomal aberration in the onion and the highest effect was obtained using Nano-zinc and gibberellin.

Seed germination is a complex and dynamic stage of plant growth, and seed priming is a technique by which the seeds obtain germination potential physiologically and biochemically before being placed on growth media and facing the ecological conditions of the environment. Seed priming increases yield and antioxidant enzymes in plants by increasing germination and seed vigor and as a result, increases percentage of germination. Several studies have investigated the effect of seed priming with organic materials including salicylic acid on improving seed germination in various plant species. Research results have shown that salicylic acid can be used as a growth regulator to increase the germination of plants. Tomato, with scientific name of Lycopersicon esculentum (Mill), belongs to the Solanaceae family and is widely adapted to different climatic and soil conditions. The aim of this study was to evaluate the effect of different concentrations of Salicylic acid on seed germination and some factors of morphophysiologic and biochemical traits of tomato seedlings.

This research was conducted as factorial in a completely randomized design, including priming treatment in 3 time frames (12, 18 and 24 hours) with three replications. Priming treatments consisted of salicylic acid (2, 2.5 and 3 mg/l) and distilled water. The measured traits were germination parameters including percentage, time, rate, and uniformity of germination and morphological traits including transplant height, crown diameter, root length, leaf number, and leaf area, shoot and root fresh and dry weight and biochemical traits including chlorophyll, peroxidase enzyme, proline, total nitrogen, potassium, calcium, phosphorus, and sodium.

The favorable effect of salicylic acid was obtained at the concentration of 3 mg/l on mean germination time compared to the distilled water. The positive effect of salicylic acid was observed on transplant height and leaf area (at the concentration of 3 mg/l at 18 and 24 hours’ time frame), shoot and root fresh and dry weight (at 24 hours) compared to the control. Immersion in distilled water for a period of 12 and 24 hours resulted in the highest root length, while salicylic acid treatment reduced root length significantly. The highest transplant height (14.3 cm), leaf number (34), chlorophyll index (59), peroxidase enzyme (10873 unit/g.min-1), total nitrogen (2.89%), potassium (9.81%), and proline content (14.80 µM/g fresh weight) were observed in 24 hours treatment with concentration of 3 mg / l salicylic acid.

According to the results of this study, salicylic acid at certain concentration improves seeds germination of tomato plants through the regulation of physiologic and biochemical processes. It seems that salicylic acid led to increase in plant growth and improvement of seed germination and morphophysiological parameters of the tomato via affecting cell growth and division. Seed priming with salicylic acid at the concentration of 3 mg/l and in longer time frames had positive effect on most traits, whereas the results for each trait were different in relation to priming time.

1-Priming of tomato seed in distilled water for 18 hours reduces the time of seed germination. 2-Salicylic acid can be used as an appropriate pretreatment for producing seedlings with better quantitative and qualitative characteristics by affecting the morpho-physiologic and biochemical properties of tomato seedlings.

Camelthorn (Alhagi maurorum) has a high tolerance to salt and water stresses, and its forage quality is greater than cereal straw and is equal to alfalfa. Seeds of camelthorn do not germinate easily due to the hard seed coat. Therefore, camelthorn cultivation as an agricultural crop needs more research, especially on breaking seed dormancy and increasing germination. Despite numerous studies about camelthorn as a weed, there are few studies on evaluating agronomic factors of camelthorn as a field crop. Hence, in this study, some aspects of germination and salinity tolerance of camelthorn were examined.

In this research, different aspects of camelthorn germination were examined at the National Salinity Research Center in 2018. In the first experiment, different pretreatments including control, sandpaper, hydro-priming, hot water, and sulphuric acid were assessed. With the selection of sulphuric acid as the best treatment, varying durations (0, 5, 10, 15, 20, and 25 min) and concentrations (98% and 75%) of sulphuric acid priming were compared in the second and third experiments. In the fourth experiment, the seeds collected in 2018 were compared with the seeds collected in 2017 and 2016. The effect of different salt stress levels (0, 6, 12, 18, 24, 30, and 36 dS m-1) was evaluated on camelthorn germination and early growth in the fifth experiment. In the sixth experiment, lighting regimes including continuous dark, continuous light, and an alternative period of dark- light were examined and in the seventh experiment sibling factors (together and individual seeds) were evaluated. Seed germination and seedling length were calculated and salinity tolerance threshold levels and 50% reduction threshold were estimated.

The results of the first experiment showed that the highest germination percentage was obtained in sulphuric acid priming (56.6%), which was six folds greater than the control. In the second experiment, it was shown that the highest germination percentage (81.1%) and seedling growth (5.7 cm) was observed in sulphuric acid priming 98% for 25 min. Important note was that these results were related to domestically produced sulphuric acid, and the highest germination and seedling growth were observed in 75% concentration for the imported sulphuric acid. In the fourth experiment, it was found that at least 3 years of seed longevity had no significant effect on seed germination. Considerable losses in germination and growth were observed from 30 dS m-1 salinity level; however, germination did not completely stop even at 36 dS m-1 salinity. In the sixth and the seventh experiments, it was found that there were no significant differences between seeds germination in the continuous dark, continuous light, and an alternative period of dark- light as well as between individual and together seeds. So, camelthorn seed is not photoblastic and had no negative sibling factor.

Generally, it was concluded that the best method for improving germination is priming with sulphuric acid 98% (internal) or 75% (imported) for 25 min. According to achievement of high germination in sulphuric acid pre-treatments (chemical scarification), it seems that seed dormancy in camelthorn is presumably physical. Furthermore, although the salinity tolerance threshold of this plant is estimated 14.2 dS m-1, it can germinate minimally even in very higher salinity. Light salt stress not only decreases the germination of this plant but also is necessary for growth promoting. Based on the high salinity tolerance of camelthorn in the germination stage, its cultivation in haloculture systems is recommended for more investigation.

1- Sulphuric acid 98% priming for 25 min led to breaking seed dormancy and acceptable camelthorn germination. 2- In moderate salinity, germination was not significantly changed and seedling growth was promoted compared with the non-stress conditions. 3- Salinity tolerance threshold level of camelthorn was estimated 14.2 dS m-1.