جستجوی مقالات مرتبط با کلیدواژه « سرعت جوانه زنی » در نشریات گروه « زراعت »

AbstractAtriplex patula is a wild plant from the Chenopodiaceae family that has medicinal, nutritional, fodder and dedesertification applications. In order to determine the type of seed dormancy and characteristics of germination and the method of breaking dormancy and determining the cardinal temperatures of germination in this species, two experiments were conducted separately. In the first experiment, the first factor, potassium nitrate was evaluated at 4 levels and cold stratification as the second factor at 3 levels. The percentage and rate of seed germination were calculated. The second experiment was conducted to determine the germination cardinal temperatures, by 9 temperature levels (0, 5, 10, 15, 20, 25, 30, 35 and 40℃) and by determining the germination rate and fitting the most suitable regression model between temperature and germination rate. In both experiments, each treatment had 4 replications of 25 seeds and the percentage and germination rate were calculated. The results showed that potassium nitrate with a concentration of 250 mg/liter along with cold stratification at 3°C for one week had the most positive effect on the breaking of seed dormancy and the germination percentage and germination rate. the rate and percentage of germination reached 8.16 and 90%, respectively. In the second experiment, the cardinal germination temperatures, including the minimum, optimum and maximum temperatures, were obtained as 1.86°C, 22.5°C and 38.89°C, respectively, and the toothed regression model showed the best fit. According to these findings, seed dormancy in Atriplex patula was determined to be of non-deep physiological type.IntroductionWild grassland plants are among the sources that have been considered for new food sources with the rapid increase of the world population and can be used as agricultural plants in the future. Atriplex patula is a herb of the Chenopodiaceae family, which has been reported for its medicinal, nutritional, fodder and dedesertification uses. Atriplex species are halophytes that are distributed in a variety of saline habitats, including the margins of wetlands, coastal areas, hills, and deserts (Bueno et al., 2017). These plants are suitable for dry and semi-arid degraded pastures in terms of compatibility with the environment, being evergreen and growing in poor and salty lands. Domestication of wild plants has obstacles, one of which is the existence of seed dormancy and, as a result, the problem of germination, so in order to improve seed germination, it is necessary to apply treatments to remove the obstacles to germination. According to the type and depth of seed dormancy, various treatments have been proposed to break dormancy and stimulate plant seed germination, which also depends on the genotype of the plant species. In order to determine the type of dormancy and characteristics of germination and a method for breaking dormancy and determining germination cardinal temperatures in this species, two experiments were conducted separately.Materials and MethodsThe first experiment was conducted as a factorial in a completely randomized design with two factors. The first factor was potassium nitrate at 4 levels (0, 250, 500 and 750 mg.L-1) and the second factor was cold stratification at 3 levels (without cold stratification and cold stratification at +3℃ and +6℃). The number of treatments was 12 and 25 seeds were used in 4 repetitions. The rate and percentage of seed germination were calculated. In order to determine the germination cardinal temperatures, an experiment was conducted in a completely random design by 9 temperature levels (0, 5, 10, 15, 20, 25, 30, 35 and 40℃). Each treatment had 4 replications of 25 seeds. this experiment was done by determining the germination rate and fitting the most suitable regression model between temperature and germination rate.Results and DisscussionThe results of variance analysis of the effect of treatments used to break seed dormancy in this research, showed that the germination percentage of Atriplex patula seeds and their germination rate were significantly affected by the application of potassium nitrate, and cold stratification, and the interaction of these two treatments with a probability level of 99% (P<0.01). Based on the results, potassium nitrate (250 mg.L-1) along with cold stratification at 3°C for one week had the most positive effect on seed dormancy breaking and increasing the germination percentage and rate. The rate and percentage germination reached 8.16 and 90% respectively by this treatment. The lowest germination percentage was related to the control treatment (0 mg.L-1 potassium nitrate × without cold stratification), and the highest germination percentage was 90.00%, related to the interaction of two factors of potassium nitrate 250 mg.liter-1 × cold stratification at 3℃. Cold stratification treatment had a greater effect on seed dormancybreaking than potassium nitrate treatment. The lack of cold stratification, in different concentrations of potassium nitrate, decreased the germination percentage of seeds, although the treatment of seeds with different concentrations of potassium nitrate had a significant difference with the control treatment, but without the wet cooling treatment, the germination percentage decreased. In the second experiment, the germination cardinal temperature, including the minimum, optimal, and maximum temperatures, were obtained as 1.86, 22.51, and 38.89℃, respectively, and the best model was chosen to be the cardinal temperatures of the tooth-like model. The lowest germination rate (0.4) was observed at 5°C. With the increase in temperature from 5°C to above, the germination rate increased and at 25°C, the highest germination rate was achieved. From the temperature of 25°C and above, the germination rate decreased with a significant difference. Different temperatures with their effect on germination may be useful for evaluating the characteristics of germination and establishment potential of plant species. The issue that should be noted is that the germination rate is more important than the germination percentage in the discussion of plant establishment, because the faster the germination, the more likely the roots will come out of the soil and absorb soil moisture and result better establishment of the seedling (Hashemi et al., 2017).ConclusionAccording to the results of the present research, it was found that seed dormancy in Atriplex patula is of non-deep physiological type. Cold stratification at 3°C is more effective than potassium nitrate in breaking seed dormancy of this plant.

In a laboratory study, the effect of seed nutritional pretreatment on germination and seedling growth traits of lentil (Lens culinaris Med.) in the form of two separate experiments in the form of a completely randomized design with three replications for two pretreatment materials [prime with iron sulfate (FeSO4) and zinc sulfate (ZnSO4) ] were investigated. In each experiment and for each prime material, five levels of prime material concentration (30, 60, 90, 120 and 150 mM) were considered. The measured traits were germination percentage and speed, length of root and shoot, wet and dry weight of seedling, and longitudinal root index of seedling. The results of the data showed that in terms of the type of pretreatment, iron sulfate was superior to zinc sulfate and caused the major improvement of the germination indicators, except for the germination speed. Also, by increasing the concentration from 30 to 60 mM, the highest indicators of germination and seedling growth were obtained. However, with a further increase in the concentration of the pre-treatment material, a decreasing trend was observed in all the measured traits, which could possibly be due to the toxicity in the seeds under high concentrations of metals. In general, according to the obtained results, it seems that the use of these two substances, especially iron sulfate, with a maximum concentration of 60 mM, is beneficial for improving the germination and nutritional characteristics of seeds.

Several studies reported that drought stress in the soil, by reducing the germination indicators, causes a decrease in onion growth and yield. Ascophyum nodosum seaweed extract contains plant growth regulators such as auxin and cytokinin, high and low consumption nutrients, vitamins and antioxidants and can reduce various stresses on plants. For this purpose, different levels of seaweed extract and drought stress were investigated on the germination and growth indices of onion (Behbahan native cultivar). A factorial experiment was performed based on completely randomized design with 3 replications. The investigated factors include: algae extract at 4 levels (0, 3, 6, and 9 percent by volume) and drought stress at four levels non-stress, mild stress, moderate stress, and severe stress (including 0, -0.3, and 0.6 and -0.9 MPa). Drought stress was applied by PEG. The results of this research showed that in conditions non-drought stress, mild stress and moderate stress, the use of Ascophyllum nodosum algae extract (levels of 3% and 6%) caused a significant increase in traits such as germination percentage, germination vigor, seed vigor index, seedling length, plumule length and radicle length. In severe stress conditions, no significant difference was observed between the control levels, 3% and 6%. Considering the development of onion cultivation in Behbahan and the report of negative effects caused by drought stress on onion seeds (Behbahan native cultivar), the use of Ascophyllum nodosum seaweed extract in the soil is recommended to reduce the negative effects caused by drought stress. Algae extract improved the germination indicators, growth characteristics and proper establishment of seedlings , which can increase the yield of this plant.

This study aims to investigate the effect of priming treatments (control without priming, hydropriming, priming with 0.25% potassium nitrate and priming with 0.5% potassium nitrate) on the germination characteristics of sugar beet cultivars and growth characteristics under five levels of salinity (0, 4, 8, 12, and 16 dS/m) on germination and seedling growth in four replicates in a petri dish in laboratory conditions as a factorial experiment based on a completely randomized design. The results showed that the effect of seed priming and salinity stress on the average germination time, germination speed coefficient, germination variance, germination uniformity, root length, stem length, stem and root dry weight, water content relatively, chlorophyll a, chlorophyll b and carotenoids were significant. The results showed that in all three genotypes, the number of germinated seeds decreased with the increase in salinity level, and in the control levels and the use of water as a priming factor, this decrease was moderated. With the increase of salt concentration up to 12 ds level, the relative water content increased sigmoidally and showed a relatively stable trend at two levels of 12 and 16 ds. In most of the investigated traits, Shokofa variety has shown less reaction than other genotypes. In the investigation of the reaction process of genotypes to the speed, variance and homogeneity of germination in prime and salinity levels, it has shown a decrease with increasing salinity concentration.

This research was carried out to estimate the cardinal temperatures of Ambrosia psilostachya seed germination and evaluation of some nonlinear regression models. The experiment was performed at Tehran University Weed laboratory in 2022. In this experiment, the seeds were exposed to 8 temperature treatments (5, 10, 15, 20, 25, 30, 35, and 40ºC) with 3 replications in a completely randomized design. The germination rate, seed germination percentage and mean germination time of seeds were measured. Cardinal temperatures of seed germination were estimated using four regression models including segmented, dent-like and beta (four and five parameters) models. The performance of models and statistical indices was compared by RMSE (root mean squared of error), R2 (coefficient of determination) and AICc (corrected Akaike Information Criterion). Highest germination percentage was obtained at 15, 20 and 25°C (60.3%, 63.7% and 63%, respectively). The Highest germination rate (0.13d-1) and the lowest mean germination time (7.48d) were obtained at 25°C. Due to lower AICc and RMSE, the beta model (five parameters) was the best model for predicting the response of germination percentage to temperature in A psilostachya. Generally, base, optimal and ceiling temperatures were estimated 5, 25.5 and 42.13°C respectively by beta five-parameter model.

The germination process is one of the most critical stages of a plant's growth and determines the success of the emergence of a weed in an agroecosystem because it is the first stage in which the weed competes for a niche. Various environmental factors, including temperature and moisture, affect the germination of weed seeds. Modeling techniques are capable of predicting germination, seedling emergence, and establishment of weed species. The ability to predict weed germination in response to environmental conditions is very effective for the development of control programs. The experiment was conducted to determine the cardinal temperature and evaluate the best model for quantifying the response of the germination rate of Western ragweed weed seeds under different water stress conditions.

A factorial experiment was conducted in the form of a completely randomized design in three replications. The investigated factors include temperature with eight levels (5, 10, 15, 20, 25, 30, 35, and 40 C˚) and water potential with six levels (0, -0.3, -0.6, -0.9, -1.2, and -1.5 MPa) on the germination of Western ragweed. In order to quantify the response of Western ragweed germination rate to temperature, three non-linear Dent-like, Beta, and Segmented regression models were used.

The results showed that the effect of temperature, water potential, and their interactions on maximum germination, germination rate, and time required to reach 10, 50, and 90 percent germination were significant. Also, the results showed that by increasing the temperature from 10 to 25 C˚, the percentage and rate of germination increased whereas by increasing water potential, the percentage and rate of germination decreased. In comparing the models, based on RMSE, R2, CV, and coefficients a and b parameters, the Beta model was the most suitable for estimating the temperatures of cardinal Western ragweed. The base, optimum, and ceiling temperatures using the Beta model were 3.88, 25, and 40 C˚, respectively.

The use of the Beta model to quantify the germination response of Western ragweed seeds to different levels of water potential at different temperatures had acceptable results. Therefore, by using the output of these models at different temperatures, it is possible to predict the germination rate at different potentials.

With regard to the ever-growing water deficit in the world, the adoption of the direct-seeded rice cultivation system has been suggested as an alternative to the transplanting method. One of the disadvantages of the direct-seeded method is low and non-uniform germination and emergence due to low seed vigor in rice. Priming is a technique which improves the rate and uniformity of seed germination under these conditions. Thus, this study aimed to investigate the effects of priming treatments on seed germination of different rice cultivars under different temperature conditions using the thermal time model.

This study was conducted in 2019 at the seed research laboratory of Gorgan University of Agricultural Sciences and Natural Resources. In this experiment, germination of primed and non-primed seeds in three rice cultivars (Nada, Anam, and Tolo) was investigated under different temperatures (15, 20, 25, 30, and 35°C). The priming treatments which consisted of control, hydropriming, and osmopriming with different chemicals (potassium chloride 2%, potassium nitrate 1%, calcium chloride 4%, glycine betaine 10 ppm, salicylic acid 10 ppm, and ascorbic acid 10 ppm) were investigated under different temperatures.

The results showed that priming treatments had no significant effect on the seed germination percentage of rice cultivars at different temperatures. The thermal time model based on binomial distribution fitted well to cumulative germination percentages in all priming treatments. Among the parameters of the thermal time model, the greatest priming effect was on the reduction of the thermal coefficient, followed by the reduction of the sigma coefficient, which resulted in the increased rate and uniformity of germination. Priming treatments had no significant effect on base temperature. Also, the responses of rice cultivars to seed priming treatments varied so that in Anam and Neda, priming with calcium chloride but in Tolo, hydropriming was more effective on the model parameters, especially thermal time to 50% of germination.

In general, priming treatments did not affect the base temperature of germination in rice cultivars, but they significantly affected the rate and uniformity of seed germination. As the latter issue is one of the main problems in the direct-seeded rice system, suitable priming treatments for each cultivar can be adopted to increase the rate and uniformity of seed germination and emergence in this system.

Stevia is an important natural sweetener in the world, which this issue has led to more demand for stevia production. In order to investigate various breaking dormancy treatments on stevia seeds this study was conducted as a factorial experiment based on the completely randomized design with three replications and two factors in the research laboratory of Shahid Bahonar University of Kerman in 2021. The factors were included gibberellic acid in three levels (0, 0.5 and 1 mM) and temperature treatment (control, warm water, liquid nitrogen, wet cooling treatment for seven days, wet cooling treatment for 14 days, dry cooling treatment for seven days and dry cooling treatment for 14 days). The results showed that the effect of temperature and gibberellic acid treatments on germination characteristics of stevia was significant at the probability level of 1%. Among the studied treatments, the interaction of dry cooling and 1% gibberellic acid was the most effective treatment, and the highest germination percentage (74.01%) and germination speed (14.15 seed day-1) belonged to the mentioned treatment. The results of mean comparisons showed that the effect of gibberellic acid application led to a significant increase in hydrogen peroxide, alpha-amylase, protease and dehydrogenase traits compared to the control. Therefore, it can be stated that dry cooling treatment with 1% gibberellic acid can be effective in improving germination characteristics in stevia plant.

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

Corn is one of the most important crops in the cereal family, and after wheat, it has the largest cultivated area in the world. Among the types of corn, sweet corn seeds are sensitive to storage conditions due to their low starch content and poor seed vigor. Therefore, it is essential to understand their physiological and biochemical behavior during storage to prolong their longevity and prevent the loss of vigor. On the other hand, seed deterioration is a natural phenomenon, resulting in seeds losing their viability and quality even under optimal storage conditions. This undesirable phenomenon causes more damage, especially in sensitive seeds such as sweet corn. Part of this damage is related to the decrease in the speed and percentage of seed germination, which leads to a decrease in plant density and failure to achieve the desired density in the field, resulting in decreased crop yield. This experiment evaluated and tested the ability of seed priming with ascorbic acid to improve damage caused by sweet corn seed deterioration.

This experiment was carried out in the Laboratory of Seed Science and Technology, Faculty of Agriculture, Bu-Ali Sina University, as a factorial in a completely randomized design with four replications. The seed used for the experiment was Chase variety. Wheat seeds deteriorated by accelerated aging method for 72 hours at 43 °C. Then, the deteriorated seeds were primed at 25°C with 1, 1.5 ml of ascorbic acid and distilled water for 18 hours. The studied traits included germination percentage, mean germination time, germination rate, vigor index, malondialdehyde content, soluble sugars, soluble proteins, and superoxide dismutase enzyme activity.

The results showed that vitamin priming of seeds with ascorbic acid improved the germination percentage, germination rate, vigor index, soluble sugars, soluble proteins, and activity of the antioxidant enzyme superoxide dismutase in deteriorated seeds. Among the examined traits, the mean germination time and malondialdehyde content of primed seeds decreased compared to non-primed ones. The concentrations of ascorbic acid used in mean germination time, germination rate, vigor index, and soluble sugars were not significantly different. However, it had a more favorable effect than hydropriming in improving the studied parameters of sweet corn seeds. While seed priming with a concentration of 1.5 mM ascorbic acid had the most significant effect on germination percentage, soluble proteins, malondialdehyde content, superoxide dismutase activity, and its difference with other priming treatments was significant. Even though seed priming with a concentration of 1.5 mM ascorbic acid had the greatest effect on the germination percentage, soluble proteins, malondialdehyde content, superoxide dismutase activity. However, its difference was significant from other priming treatments. It increased the percentage of germination, soluble proteins, and superoxide dismutase activity by 71, 85, and 44%, respectively, and decreased the content of malondialdehyde by 52.9%.

Based on the results from this experiment, it can be concluded that applying ascorbic acid, especially the concentration of 1.5 mM, as the best priming treatment is recommended to recover the lost quality of deteriorated sweet corn seeds and improve their germination characteristics.

In order to study the effect of salicylic acid priming on seed germination indices and seedling growth of triticale under salt stress, a research was carried out as a factorial experiment in a completely randomized design with four replications in seed science and technology laboratory of plant production and genetics department of Agriculture Sciences and Natural Resources University of Khuzestan in 2018. Experimental factors were salicylic acid priming (control (no priming), 0.5 mM salicylic acid in 3 hours, 1 mM salicylic acid in 3 hours, 1.5 mM salicylic acid in 3 hours, 2 mM salicylic acid in 3 hours, 0.5 mM salicylic acid in 6 hours, 1 mM salicylic acid in 6 hours, 1.5 mM salicylic acid in 6 hours, 2 mM salicylic acid in 6 hours) and different salinity levels (include 0, 4, 8, 12, 16 and 20 dS/m). The analysis of variance showed that the effect of priming, salinity stress and the interactive effects were significant on all measured traits (except germination percetage) at 1 percent probability level. The comparison of means showed that salinity stress decreased germination traits but salicylic acid priming reduced the negative impact of salinity stress and improved different germination indices. The best concentration for salicylic acid priming was at 0.5 mM for 6 hours. Generally, the results showed that under salinity stress conditions, seed priming with salicylic acid can be used to reduce the negative impact of salinity stress on seed germination and triticale seedling growth.

In order to evaluate rice cultivars under salinity stress at germination stage, a factorial experiment was conducted in a completely randomized design with three replications in the laboratory of seed and seedling sciences and research of Gilan. Five rice cultivars (Anam, Khazar, Gilaneh, Kian and Hashemi) were studied at four salinity levels (zero, 50, 100 and 150 mM NaCl). The results of analysis of variance showed significant effects of salinity, genotype and interaction effect for all measured traits at one percent level. Also, according to the results of mean comparison, salinity except for allometric coefficient and germination percentage (at salinity level with concentration of 50 mM NaCl), caused a decrease in all studied traits including stem and root length, fresh and dry weight of stem and root, average daily germination and plantlet vigor index. The Kian cultivar had the highest percentage of germination (salinity level 50 mM equal to 98.66 %) at all levels. Finally, under the experimental conditions of this research, according to the results Hashemi and Gilaneh cultivars were found to be the most tolerant and sensitive cultivars, respectively.

Weeds are one of the most important problems in agriculture and cause a lot of damage to crops. Overconsumption of herbicides in recent decades has led to harmful impacts on the environment and living organisms, including humans. In order to deal with these problems today, efforts are being made to reduce reliance on artificial herbicides and change direction towards sustainable agriculture as a part of integrated weed management. Among natural compounds, essential oils, which are components of aromatic and medicinal plants, were investigated to discover new herbicides.

In order to investigate the effects of yarrow essential oil (Achillea wilhelmsii C. Koch) on the germination and growth of purslane (Portulaca oleracea L.) and rye (Secale cereale L.) seedlings, two factorial experiments were conducted in the form of a completely randomized design in three replicates at Islamic Azad University, Science and Research Branch. The first factor was the type of essential oil in two levels (normal and nanoemulsion) and the second factor was the concentration of essential oil in six levels (0, 100, 200, 400, 800, and 1000 µl L-1).

Scanning electron microscopy images showed the particles were relatively sperhical and their size varied from 1 to 100 nm. The zeta potential of the nanoparticles was -13.8 mV, indicating particle stability. Both type of essential oils reduced germination percentage, germination rate, plumule length, radicel length and seedling dry weight of both weeds and germination percentage decreased significantly with increasing concentration. At a concentration of 200 µl L-1, purslane treated with essential oil germinated 55.25%, but at the same concentration, the germination percentage of seeds treated with nanoemulsion of essential oil was 30.50%. Nanoemulsion of essential oil at concentration of 800 µl L-1 was able to completely prevent the germination and growth of purslane seedlings. Nanoemulsion of essential oil at a concentration of 1000 µl L-1 completely prevented rye seed germination. Germination rate decreased under treatment of yarrow essential oil and there was no difference between two types of essential oils at concentration of 200 µl L-1, but at a concentration of 800 µl, the germination rate of rye seeds treated with nanoemulsion of essential oil and ordinary essential oil reached to 1.40 and 0.32, respectively which was a significant difference.

The inhibition percentage of the studied traits in both weed species showed that the essential oil nanoemulsion was more effective than the normal essential oil. Yarrow essential oil was more effective on purslane weed compared to rye. Essential oils do not have similar effects on weeds and their inhibitory effects will be different depending on the concentration and species of weeds, and the selectivity of these compounds should be investigated. The production of nano essential oil of yarrow as a natural herbicide is a solution. It offers to control weeds in organic farming systems.

Highlights:

1- Nanoemulsion particles were produced from Yarrow essential oil
 2- Nanoemulsion particles had more inhibitory effects on the investigated weeds than the normal essential oil.

The selection of optimum planting date for every climate and mother bulb size are important factors affecting the quantity and quality of seed production in different cultivars. This study was performed in Isfahan province, Frieden, during two growing years 2016-2017 to determine the effect of planting time and mother bulb size on the quantity and quality of short-day onion seed varieties Texas Early Grano 502

A split-plot experiment was performed in a randomized complete block design with four replications. The main factor was cultivation dates at four levels: the end of August, the first of September, the end of September and the first of October and mother bulb size at three levels with 3.55, 5.5-7, and 7.5-9cm diameters were assigned as sub-plots. The measured traits were number of umbel per unit area, the number of fertilized capsules in umbel, the number of seeds per capsule, 1000 seed weight, seed yield and germination rate.

The results of combined analysis of variance showed that effect of year was only significant on the number of capsules per umbel at p<0.01. The interactions of year× mother bulb diameter and year× planting date× mother bulb diameter were not significant for any of the traits. The traits were not affected by the year. The results showed that the planting date had a significant effect on all traits except for 1000 seed weight, and the first planting date (the end of August) had the highest values in all traits. The highest germination percentage (89.83%) and the highest germination rate (12.8) were obtained on the first planting date, which showed a statistically significant difference with the subsequent planting dates. However, these two traits were not affected by mother bulb diameter treatment. The highest seed yield for onion diameter factor (505.65 kg h-1in the first year and 465.78 kg h-1 in the second year) was associated with mother bulb size of 7.5-9 cm.

The overall result showed that to obtain the highest and most desirable quality of onion seeds of Texas Early Grano 502 cultivar in Friedan of Isfahan, the planting date of the first of September and the size of the mother bulb “between” 7 to 9 cm is recommended.

Highlights:

1- Early planting time (the first of September) increased germination rate.
2- Increasing the mother bulb size increased the onion yield.

Linseed (Linum usitatissimum L.) is a multipurpose crop and is cultivated to obtain oil, fiber, and seeds. Under optimal moisture conditions, the temperature is considered an environmental factor affecting the germination of this crop. Hence, knowing the cardinal temperatures can help farmers to predict the successful germination, emergence, and even yield of linseed and help scientists to develop new cultivars that are more tolerant to high temperatures. Therefore, this study was performed to determine the temperature range and the cardinal temperatures of germination in two linseed genotypes.

The germination response of two linseed genotypes (Golchin genotype and Line 286) to nine temperatures (3, 5, 10, 15, 20, 25, 30, 35, and 40 Celsius degrees) was quantified in a CRD based split-plot experiment with four replications. For this purpose, three nonlinear regression models (beta, segmented, and dent-like) were used to fit to the data and select the superior model. The superior model was selected using the Akaike information index (AIC), the modified Akaike index (AICc), and ∆i.

Findings showed that the beta model had the best performance in estimating the line 286 cardinal temperatures according to its lower AIC (-3.96), AICc (-89.61), and ∆i (0). Accordingly, the base, optimum, and maximum temperature as well as the number of biological hours estimated by this model for Line 286 were 7.18, 24.22, 40.16 Celsius degrees, and 19.25 hours, respectively. In the Golchin genotype, the beta model with the lowest AIC=-3.89 and AICc= -89.083 fitted better compared with the other models. Nonetheless, considering ∆i for beta which was respectively 0, 1.61, and 4.49 for beta, segmented, and dent-like models, Beta and segmented models had a similar accuracy in estimation of cardinal temperatures for Golchin genotype. These findings represent that the suitable temperature range for germination of the Golchin genotype is 3.8- 23.85 Celsius degrees and the range of biological hours to 50% of germination varied from 16.42 to 19.77 hours.

Overall, according to the results of this study, it is possible to predict the time to germination under optimal moisture conditions using the beta model for Line 286 and one of the two beta and segmented models for the Golchin genotype.

Highlights:

1. A suitable model was developed for a suitable prediction of the seed germination percentage of two linseed genotypes (Golchin genotype and Line 286).
2. The cardinal temperatures for two linseed genotypes (Golchin genotype and Line 286) were determined.

Purple nutsedge (Cyperus rotundus L.) is a problematic weed in tropical regions particularly in Jiroft, Kahnooj and Birjand, so that farmers annually suffer severe damage to their vegetable and cucurbit crops. Currently, very little research on the biological basis of this noxious weed has been don.This study was conducted to evaluate the effect of burial depth on tubes germination and emergence of different purple nutsedge ecotypes. Purple nutsedge tubers were collected from birjand, kahnooj and jiroft regions. A factorial experiment was conducted based on randomized complete block design in University of Birjand with three replications. To investigate the viability of tubers before being used for bioassays, their germination potentials were examined in a growth chamber set at 25/15°C. Then, ten tubers of each ecotype with almost equal weight (3.6gr) and size were planted in polyethylene tubes with 25 cm in diameter and 50 cm in height. Ten tubers of each purple nutsedge ecotype were sown at 8 different depths, including 0, 2.5, 5, 10, 20, 30, 40 and 50 cm. At the termination of experiment, number of tubers and pre tubers, underground tuber dry weight, shoot number and above ground dry weight were recorded. Results showed that purple nutsedge tubers were able to emerge from very deep burial depths (up to a depth of 50 cm), and in this regard, there were some differences among the three ecotypes. Generally, as depth increases, the number and weight of tubers, and shoots decreased; whereas the burial depth showed no effect on the shoot height and pre-tuber production. Therefore, in addition to deep plowing, other control methods such as cultural control and chemical methods should be used in an integrated management.

This research was carried out in 2022 in order to study the effect of the aqueous extract of different parts of Zygophyllum eurypterum L. on seed germination and seedling growth of wheat and Convolvulus arvensis L. in two separate experiments including the laboratory and the greenhouse conditions, respectively. The experiments were exerted based on a completely randomized design with three replications and randomized complete block design with 4 four replications, respectively. The experimental treatments included water extracts of Zygophyllum eurypterum L in concentrations of 5, 10 and 15% of roots, 5, 10 and 15% of aerial organs (stem and leaves) and control (distilled water). The results showed that with the increase in the concentration of the extracts, the germination and growth traits as well as the total chlorophyll of both plants decreased significantly. In such a way that the highest amount of inhibition was related to 15% arial parts (stem and leaf) extract. Meanwhile, the antioxidant activity of wheat and weed C. arvensis L. increased by increasing the level of Zygophyllum eurypterum extracts. The level of 15% Zygophyllum eurypterum stem and leaf extract in wheat decreased the germination percentage by 63.7% and in C. arvensis L. by 89.2% compared to the control.  Increasing of extract concentration from zero to 15% of arial parts decreased root length decreased by 72.8% in C. arvensis L., and 52.9% in wheat compared to the control. The highest level of antioxidant activity of the weed C. arvensis L. was observed at the levels of 10 and 15% of arial parts extract which were 64 and 73%, respectively. Most of the studied traits of the weed C. arvensis L., such as germination percentage and speed and root length, were more sensitive to the effects of Zygophyllum eurypterum extract than wheat. Examining the results showed that arial parts of Zygophyllum eurypterum were more capable of dealing with germination and seedling growth than the root. Therefore, 15% aqueous extract of Zygophyllum eurypterum stems and leaves can be suggested to reduce the growth and weakening of the weed C. arvensis L.

Nowadays, due to land use change and destruction of natural resources induced by human activities, attention to desertification has immensely become widespread. One of the most important species for biological rehabilitation of desert areas on a large scale is the hawthorn plant. Hawthorn is a plant belonging to the family Amaranthaceae, the two species of which are called white saxaul (Haloxylon persicum Bunge ex Boissier & Buhse) and black saxaul (Haloxylon aphyllum (Minkw.) Iljin) are more notorious and widespread in Iran. These plants own extensive root systems and stabilize running sands. The aim of this study was to investigate the effect of mesoporous titanium dioxide nanoparticles on germination traits of black saxaul seeds under drought stress, as an important species in desert areas.

The experiment was performed as a factorial experiment in a completely randomized design with 3 replications. Experimental treatments included five titanium nano dioxides with concentrations of 0, 25, 50, 100 and 200 mg / l and six drought stress levels including 0, -4, -8, -12, -16 and -20 bar. After nanopriming, black saxaul seeds were subjected to drought stress for 15 days in a germinator at a temperature of 20 °C with four replications. After germination, in each of the treatments, germination percentage (GP), germination rate (GS), mean germination time (MGT) and seed vigor index (VI) were calculated.

The results of two-way ANOVA and mean comparison of germination indices showed that the highest germination percentage (74%) belonged to the zero level of stress treatment with a concentration of 200 mg/l and the lowest one (3%) belonged to -20 bar treatment with 25 and 200 mg/l nano-titanium dioxide. With increasing drought stress intensity from zero to -20 bar level, germination rate decreased from 7.01 to 0.43 seeds per day. The highest amount of seed vigor index at zero drought level belonged to the treatment of 200 mg/l concentration of nano-titanium, with a rate of 325.77.

The results showed that germination indices and initial growth of black saxaul seeds decreased in all primed and unprimed treatments with increasing drought stress, and nanopriming with titanium dioxide had a positive effect on seed germination traits.

Reports indicate the invasion of two species of Ivy-leaved morning-glory (Ipomoea hederaceae Jacq) and Asian spider flower (Cleome viscosa L.) to summer crops fields such as soybeans in Golestan province. Considering the importance of knowing the cardinal temperatures of germination in the models for predicting the presence of weeds and consequently designing correct management strategies on these plants, this experiment was conducted to study the germination behavior and to compare the cardinal temperatures of germination for two species of Ivy-leaved morning-glory and Asian spider flower under two conditions of constant and alternating temperatures.

In order to study the effects of constant and alternating temperature on the percent, rate and estimating cardinal temperature of germination for Ivy-leaved morning glory and Asian spider flower, two separate experiments as a Completely Randomized Design with four replications were carried out at the seed laboratory of Gorgan University of Agricultural Sciences and Natural Resources. Studied temperature treatments on Ivy-leaved morning glory included the constant temperatures of 10,15,17,20,25,30,35 and 40 oC and alternating temperatures of 12.5:7.5,10:15, 12.5:20, 15:25, 20:30, 25:37.5, 30:42.5 and 35:45 oC. Temperature treatments on Asian spider flower included the constant temperatures of 15, 20, 23, 25, 28, 30, 35, 40, 45 and 50 o C and alternating temperatures of 15:20, 20:25, 20:30, 25:30, 25:35, 30:40, 30:45, 30:50 and 40:50 oC.

Results indicated that alternating temperatures had a positive effect on the germination of Ivy-leaved morning glory, which increased from 78% at constant temperatures to 94% at alternative temperatures. However, the maximum germination percentage of Asian spiderflower at the alternative temperature of 20:30 was 79%, which had no significant difference with a constant temperature of 30 with 84% germination. The base temperature for seed germination of Ivy-leaved morning glory at alternating temperatures (10.09 oC) was a little lower than that of constant temperatures (11.25 oC). But in Asian spider flower, the base temperature at alternating temperatures (17.57 oC) was more than that of constant temperatures (15.43 o C).

The most important factor in the occurrence of such different responses to constant and alternating temperatures in Ivy-leaved morning glory and Asian spider flower is their adaptation to environmental conditions and their survival in highly degraded agricultural environments. These two weeds are warm-season plants and their seeds enter the soil seed bank in autumn. The presence of dormancy (regardless of its type) in the seeds of these two plants prevents the germination of their seeds in winter; and the experience of alternating temperatures at this time prepares the seeds for germination in the spring. The base temperature of Ivy-leaved morning glory was not much different under the constant and alternating temperature conditions. But the base temperature of Asian spider flower was higher under alternating temperatures compared with constant temperatures.

This study was done to investigate the germination response of goji berry to salinity, drought and salinity-drought stress. For this purpose, a factorial experiment based on completely randomized design in the research laboratory of Bradsir Agricultural Excellence Training Center in 2021 was conducted. In this research, goji berry responses were examined to four levels of polyethylene glycol 6000 to create drought stress (0, -2, -4 and -8 bar) and four levels of sodium chloride to create salinity stress (0, -2, -4 and -8 bar) in the germination stage. The results showed that with decreasing osmotic potential in drought and salinity stresses, germination percentage and germination rate, seedling dry weight and relative water content decreased but relative electrolyte leakage and proline content increased. In general, goji berry seeds withstood drought stress conditions better than salinity stress in terms of germination components, so that in the osmotic potential of -8 bar salinity stress, goji berry seeds were not able to germinate and did not produce any shoots and roots. In osmotic potential of -2 bar, germination rate and relative water content in drought stress decreased by 4.56% and 0.47%, respectively, and in salinity stress decreased by 30.18% and 18.24%, respectively, but relative electrolyte leakage increased in drought and salinity stress by 0.57% and 10.89%, respectively.