جستجوی مقالات مرتبط با کلیدواژه "dormancy" در نشریات گروه "زراعت"

Seed germination studies are considered key tools for conservation programs. Since the propagation of verbascum in natural areas is done mostly through seeds, it is necessary to investigate the appropriate methods to eliminate the stagnation of the seeds of this plant. Therefore, the present study investigates the breaking of seed dormancy of V. thapsus and V. kochiiforme species in the form of a completely randomized design with 4 replications. The treatments used included hot water, thermal treatment, physical and chemical scraping, wet cooling and combined treatment of wet cooling and physical scraping. Variance analysis of data and comparison of averages were done using LSD test at the five percent level. The results showed that chilling increased the germination of V. thapsus seeds. Also, the seeds of V. kochiiforme with 1-month chilling along with scratching had better germination than other treatments, and further chilling did not have a significant effect on increasing the germination of this species, but in some cases it led to the activity of fungi, which affected the germination and caused a decrease it became Therefore, according to the increase in germination after chilling V. thapsus, it can be concluded that it has physiological sleep and V. kochiiforme can have physical sleep in addition to physiological sleep due to its hard seed coat. Also, the boiling water treatment not only did not cause the germination of marigold, but also prevented the germination of this plant as an inhibitory factor.

Almonds are high in antioxidants, vitamin E, protein, and fiber. This nutrient-rich nut is an excellent addition to any diet since it is a versatile ingredient linked to several health benefits. The development of communications have led to a wider cultivation of temperate fruits, cultivars being selected and grown in different environmental conditions. This situation has increased the risks derived from the incomplete breaking of dormancy, and encouraged studies concerning the chilling and heat requirements of fruit cultivars for breaking dormancy and flowering. Estimating chilling and heat requirements of flower buds in fruit trees is important due to predicting flowering time for appropriate site selection to escape spring frost damage.

In order to investigate the chill and heat requirements of commercial almond cultivars, a factorial experiment was planned and implemented in a completely randomized design with 3 replications in Shahrekord university lab (in 2017). The first factor included commercial almond cultivars in five levels (Mamaei, Rabi, Sefid, Shahroud 7, and Shahroud 12) and the second factor included chilling in seven levels (100, 200, 300, 400, 500, 600, and 700 hours at 4-7 °C). As soon as dormancy was induced in the buds of each cultivar, 75 branches were prepared and transferred to a refrigerator with a temperature of 4 to 7 ° C to determine the chilling requirement. The samples were taken out of the refrigerator and placed in water and sucrose solution in the greenhouse environment, and the flowering status of flower buds was examined.

The results illustrated that the chill and heat requirements of Sefid and Mamaei cultivars were lower than average requirements of all cultivars in this respect. Furthermore, these two cultivars had the lower chill and heat requirements than other cultivars. Also, Sefid cultivar needed 170 hours of chill requirements and 5886 growing degree hours’ heat and Mamaei cultivar needed 170 hours of chill and 7707 growing degree hours’ heat. Rabi cultivar had lower chill and heat requirements than the average of all cultivars, but in Shahroud 7 cultivar both of chill and heat requirements were high. Shahroud 7 cultivar needed to 220.5 hours of chill and 10958 of heat growth degree hours for blooming. On the other hand, Shahroud 12 cultivar was identified as a cultivar with high chilling requirements and low heat requirements.

The minus effects of the lack of chilling for breaking dormancy in temperate fruits, both in vegetative growth, and fruit-bearing have been proved. Chilling requirements of temperate fruit cultivars have to be fully satisfied, if dormancy breaking is to result in the desired vegetative growth, and if the fruit-bearing capacity is to be fulfilled. On the other hand, in case of low chilling requirements blooming happens too early and cold temperatures produce an important loss of yield by frost.

Butomus is an aquatic weed belonging to the butomaceae family, which has invaded the paddy field ecosystem in recent years. This study was carried out in order to investigate some eco-physiological aspects and chemical management of butomus in paddy field. In the field studies; the emergence time, height, tillering, flowering, and life cycle of butomus in the paddy field ecosystem and the germination rate of bulblets in the laboratory and the effectiveness of pre-emergence and post-emergence soil-applied herbicides in pot experiments, and also foliar-applied herbicides were investigated. The results revealed that waterlogged lands are the main habitat of butomus, and the bulblets are the main reproductive organs of this weed. While puddling, about 100% bulblets are separated from the rhizomes which floated on the water and dispersed. Both rhizomes and bulblets of butomus were submergence tolerant and germinated from 15 cm or more of submergence. Flowering of butomus preceded about one week the initiation of rice panicle. Each plant produced dozens of flowering tillers taller than rice stalk, hundreds of spindle-shaped bulblets up to 25 mm long, with more than 95% emergence rate. In pre-emergence application, soil-applied herbicides including clomazone+pendimethalin, oxadiargyl, pretilachlor, pendimethalin, and thiobencarb, controlled butomus less than 65% and sulfonylureas herbicides; pyrazosulfuron, metazosulfuron, flucetosulfuron, and bensulfuron methyl provided more than 85% control of butomus. The effectiveness of sulfonylureas in the post-emergence application was around 10% lower compared with pre-emergence application. Foliar applied herbicides; penoxsulam and propanil controlled butomus 62% and 70% and its control by bispyribac sodium, penoxsulam+cyhalofop-butyl, bentazon+MCPA, and pyribenzoxim were 80, 86, 89, and 99%, respectively. Therefore, it is recommended to apply a soil-applied sulfonylurea or a foliar-applied herbicide in the paddy fields infested with butomus in addition to the specific herbicide for barnyardgrass control.

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.

Myrtus is a tree that has been widely used in land space in recent decades, as well as this medicinal property. The seed of this plant has dormancy and its dormancy should be broken by various treatments to provide germination. In order to investigate seed dormancy breaking treatments, the study was conducted in a complete randomized design with 4 replications in 2015 in the Horticulture Physiology Laboratory of Agricultural Sciences and Natural Resource University of Khuzestan. Treatments included: control, scarification with sandpaper for 2 minutes, soaking in water 4, 25, 50°C by 30, 60 and 90 minutes, application of potassium nitrate in concentration 100, 500, 1000 ppm with immersion time for 24 hours, use 50% sulfuric acid for 5, 10, 20, 40 minutes and then wash 3 times with distilled water, stratification at 4 °C with times of 10, 20, 40 days. The results of comparing the means showed that by applying 50% sulfuric acid treatment for 20 minutes, the highest germination rate was 64.25% and the highest germination rate was 12.8 units per day and the highest seed vigor (22.29 units). Was obtained. After this treatment, sanding was almost in the second place. The results also showed that some treatments such as 50% sulfuric acid for 40 minutes, potassium nitrate at a concentration of 1000 ppm and soaking in water at 50 °C for 90 minutes caused seed damage and reduced germination indices. In general, it was found that the main obstacle to seed germination was the seed coat.

There are some reports on seed development in medicinal plants, but no information has been reported in seed development of Nigella sativa. The purpose of this study was to investigate seed quality traits including time to maturity and physiological maturity, germination and dormancy changes in 14 different ecotypes of black cumin.

A randomized complete block design was conducted at the Aburaihan Campus of University of Tehran in 3 replications and 7 harvest times during two years of 2018 and 2019. Treatments were 14 native black cumin ecotypes (across Iran), germination temperature and post-flowering time during seed development on the mother plants. The studied traits included seed weight and moisture content and seed germination percentage during seed development. For germination test, a factorial experiment was conducted based on completely randomized design in three replicates which treatments consisted of different incubation temperatures and 14 ecotypes of N. sativa.

The results showed that the moisture content during development on the mother plants had a decreasing trend. In the first sampling, the highest percentage of moisture was observed in Arak ecotype and had a decreasing trend until harvest. At full maturity, seed moisture content in all ecotypes were less than 18%. Ecotypes of Zabol1, Bajestan, Sarayan, and Ashkedaz required the lowest time after flowering to reach their maximum seed weight, thus there was recommended for regions with short growing season. The Khaf ecotype with 2.3 mg seed weight had the highest weight and the Hamadan ecotype with 0.072 mg/day had the highest seed filling rate. In the ecotypes of Tafresh, Zabol2, Eghlid, Semirom, Arak, Hamadan, Razan, and Gerdmiran germination started 20 days after flowering and had an increasing trend until physiological maturity. In ecotypes such as Isfahan, Eshkezar, Zabol1, Sarayan, and Khaf germination started from 20 days after flowering and up to 30 days after flowering there was an increase in germination percentage, but after this time the percentage of germination decreased and reached zero until the full maturity, which in fact primary dormancy induced to the seeds.

Therefore, if the planting of seeds is done immediately after harvest, ecotypes of Tafresh, Zabol2, Eghlid, Semirom, Arak, Hamadan, Razan, Gerdmiran are suitable. Incubation temperature also showed that the highest germination percentage for all ecotypes was observed at 10 °C and decreased with increasing temperature and reached zero at 30 °C. Ecotypes of Hamadan, Semirom, Zabol1, Tafresh, and Gerdmiran had the highest germination percentage at 10 °C among the studied ecotypes. Therefore, dormancy in black cumin is probably Type 1 of nondeep physiological dormancy.

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

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

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

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

Optimal seed germination guarantees the plant durability, establishment and yield. Uniform and rapid germination and emergence of seeds under various environmental conditions play a significant role in achieving suitable yield. Nowadays, there are several ways to improve seed characteristics, and one of the most commonly used ones is seed priming. Priming can increase the percentage, rate and uniformity of seed germination and emergence. These in turn results in the establishment of strong plant especially under environmental stresses and lead to success in production. In addition, knowledge on the physiological responses of primed seeds to different environmental conditions, including temperature stress, can increase the effectiveness of this technique. Therefore in this study, the reaction of primed seeds from canola cultivars to temperature was investigated. The canola cultivars used in this study included DK-xpower, Traper and Hayola50. Hydroperiming and osmopriming were used as the priming treatments. Germination tests in primed and non-primed seeds were carried out at 5, 10, 15, 20, 25, 30, 35, 37 and 40 °C. Then the response of germination rate and germination percentage to temperature were investigated. The seed germination percentages of canola cultivars were different in response to temperature and priming treatments, and each cultivar had a distinct behavior. The effects of priming on germination percentage at low temperatures were significant in Hayola50 and Traper cultivars. Also, priming in all the studied cultivars could increase significantly the germination percentages at high temperatures. Germination rates were also affected by priming treatments and temperature. At each temperature, the germination rates of primed seeds were higher than non-primed ones. In all three canola cultivars, priming reduced the base temperature (from 0.4 to 1.5 °C). The optimum temperature was also strongly affected by priming treatments, especially in the Traper and Hayola50 cultivars. Also, ceiling temperatures in primed seeds increased with respect to control seeds (by about 1 to 5°C). In addition, under various temperatures, hydroperiming was more effective than osmopriming.Finally, priming could reduce the temperature sensitivity of seed germination and increase its tolerance to high temperatures. In general, priming treatments were able to improve seed germination of canola cultivars at different temperatures. Also, priming by either removing the secondary dormancy at low temperatures and /or improved germination under high temperatures was able to improve germination indices at examined temperatures. Finally, priming could reduce the temperature sensitivity of seed germination and increase its tolerance to high temperatures.

Seed of wild oats can persist in the soil for a long time due to its dormancy. Studing the different factors affecting germination behaviors of this weed seeds will result in a properly control program. To quantify the rate of wild oat population's germination response to light and darkness, two experiments were performed in laboratory. The experimental design was a completely randomized design with three replications. Experimental treatments were temperature (10/5, 3, 5, 10 and 15 ◦c), seed coat (with and without), and populations (Ahvaz, Kordestan and Shiraz). The results showed that germination responses to temperature changed based on seed coating. Seeds of wild oat populations were not germinated at constant temperatures of 3 and 5°C and also at fluctuating temperatures and Non-treated seeds germinated at 10 and 15°C. In the other words, increasing temperatures impact the germination velocity. The highest germination percentage (%87) occurred in the 10/5 C, in Shiraz population. Among populations, Ahvaz needed maximum growing degree days to reach 50% germination. Coated seed did not germinate at light or darkness in the 10/5 °C and 3 and 5°C. Significant difference were evident in germination percentage of coated and without coat seeds of wild oat population. This indicates the role of genetic factors and environmental conditions during plant growth and the germination behavior of seeds. Precise and accurate prediction of the time of seed germination and emergence based on feedback of environmental conditions should be considered to performe the effective control method or methods in integrated weed management.

Secondary seed dormancy is announced as the major reason for seed persistence of canola (Brassica napus L). Volunteer’s rapeseeds emerging from the soil seed bank can lead to unwanted gene dispersal to other plants after breaking secondary seed dormancy. In this study, with using poly ethylene glycol 6000, secondary dormancy was induced in 41 lines and 5 cultivars of canola under laboratory condition during 14 days and secondary seed dormancy recorded. This study was conducted in a randomized complete design. High germination percentage was shown in all lines and cultivars (higher than 94 percent), although categorized on five group included very low, low, medium, high and very high after secondary dormancy with using cluster analysis. Among different lines, five and two genotypes were placed in very low and very high groups, respectively. Most of lines were placed in average and low groups. It was observed that 5 varieties (RGS003, Zarfam, Hyola401, Hyola308 and Hyola50) had average secondary dormancy (40-60 percentage) that was related to breeding ignorance about secondary dormancy during seed production process. Lines classification based on different levels of secondary dormancy helps seed producers to select lines with low levels of it along with seed yield and other characteristics in order to deal with problems in seed producing process.

Germination is the first stage of plant growth affected by environmental conditions. So the plant’s allelopathic effects on germination of seeds needs to be investigated. In order to evaluate the allelopathic effects of Haloxylon ammodendron shoot extract on seed germination of (Nitraria schoberi L.) a factorial experiment was conducted in a completely randomized design. In this study, aqueous extracts of the aerial parts of Haloxylon ammodendron concentrations in zero, 1.25, 2.5, 5, 10 and 15 grams per liter were investigated on seed germination on (Nitraria schoberi L). The results showed that germination under different concentrations of aqueous extracts of the aerial parts of Haloxylon ammodendron had significant differences. So that by increasing extracts concentration, germination percentage, germination rate, seed vigor, seedling root length and shoot decreased. Different treatments of aerial part of Haloxylon ammodendron had different inhibitory effect on seed germination of (Nitraria schoberi L.), and decreased it. The highest inhibition was observed at concentrations of 10 and 15 grams per liter of aqueous extract. However, the inhibition was higher in 15 grams per liter of aqueous extract treatment than other treatments and stopped growth. As, the number of germinated seeds and seedlings length was superior compared to control. In summary, the results showed a direct correlation between the number of normal seedlings of (Nitraria schoberi L.) and concentration of aerial part of Haloxylon ammodendron.

To study themechanism of seed dormancy and increasing seed germination percentage and rate in galbanum, embryo, seeds with removed seed coat and intact seeds of this plant were firstly cultivated on MS medium. In the second experiment, the effect of some environmental factors (light and darkness, different temperatures including 8°C, 20°C and alternative temperature of 8°C and 20°C), GA3 and removed seed coat were studied on seed germination of galbanum. In the third experiment the effect of aqueous extract of galbanum seed were studied on seed germination and growth of Amaranth and Wild barley. On the basis of results, 95% of galbanum embryos were grown on MS medium normally. Low temperature (8°C) and removing seed coat had significant effects on seed germination percentage and seed germination rate of galbanum, so that seeds with removed seed coat were germinated 77% at 8°C temperature. Pretreatment of seeds with GA3 had no significant effect on seed germination percentage but increased seed germination rate. Also, darkness treatment had no effect on seed germination of galbanum. All different concentrations (2.5%, 5% and 10%) of galbanum seed aqueous extract had significant inhibitor effect on the seed germination and growth of amaranth and wild barley. Results showed that galbanum seed dormancy could be studied in two plant, physiological dormancy that can be removed by low temperature and chemical dormancy which can be overcomed by removing seeds coat.

Due to the importance of production and propagation of virus-free potato plants، some of the factors involved in the propagation of potato (plantlet production and virus-free in vitro microtuberization) has been studied. In most reports، adding a mixture of amino acids play an important role in plant tissue culture and development of the explants in many cases increase. This experiment was conducted in a completely randomized design with three replications to investigate the effects of glutamine، arginine، asparagine، cysteine and their combinations on microtuberization of potatoes. Lateral buds from in vitro shoots were cultured on MS medium under sterile conditions. Cultures were kept in constant darkness and temperatures of 17 ± 2°C in a germinator. During the first month of culture microtuberization rate and after two months other microtuberization traits such as microtubers weight was measured. Analysis of variance showed that all traits except microtuber without rest were significantly affected by four amino acids. In this study، arginine in combination with asparagine had a positive role in improving the most important characteristics such as weight and microtuberization rate.

Grapes are one of the temperate fruit crops most frequently damaged by freezing temperatures. An investigation was carried out to evaluate the effect of freezing temperatures during the dormant season on four commercial grape cultivars. Factorial experiment was conducted using a completely randomized design with three assemblage dates (end of autumn, middle of winter and end of winter), temperature treatments (25, -10, -12, -14, -16, -18, -20 and -220C) and cultivars (Kolahdary, Red rasin, Yaghoti and White rasin) with three replications in Horticultural Sciences Laboratory of Ferdowsi University Mashhad in the year 2010. It was concluded that in -220C, electrolyte leakage of cultivar Kolahdary at the end of autumn and Yaghoti at the end of winter with 60 and 62 % showed highest the value, respectively. Cultivar Red rasin in the middle of winter with %39 had lowest value. Also, cultivar Kolahdary at the end of autumn and cultivar Yaghoti at the end of winter by 24.13 and 27 mg/l and cultivar Red rasin at the middle of winter by 37.33 mg/l had lowest and highest carbohydrate values respectively. The lowest and highest value of re-growth were gained in cultivar Yaghoti and Red raisin by 12 and 45 % respectively. Therefore, due to high carbohydrate content and low electrolyte, leakage Red raisin was selected as freezing tolerance cultivars.

Hirschfeldia incana is one of the dominant and invasive weeds in canola fields of Fars province. The successful management of the weed is dependent in understanding of biology. In this study seed production potential, optimum conditions for germinating, seed viability and dormancy were investigated. The effect of osmotic potentials of water and seed burial depth were studied on seed germination and seedling emergence. The seed production was estimated more than 27000 grain/plant with 95% viability. Results showed that the cold ecotype had less primary dormancy than the warm ecotype. The seed germination occurred between 5 to 40°C and the most germination occurred at 30°C with continuous light. Most of the seedlings were appeared from the seeds at 2.5 cm depth. There was not any germination at 7cm depth or more. Seed germination was sensitive to osmotic potential of water in both of the ecotypes. The highest germination occurred at the zero MPa osmotic potential. By reducing the osmotic potential, seed germination was also decreased, and at to -0.2MPa no seed germination was observed.