جستجوی مقالات مرتبط با کلیدواژه « stress » در نشریات گروه « منابع طبیعی »

Seed germination is one of the most important and basic stages of plant growth and development so it has great importance and effect on other stages of its growth. Cassia is a plant from the legume family and has many medicinal properties. Cassia propagation is done by seeds, but no study and report on the tolerance of these seeds to salinity stress in the country have been presented yet. Two factorial experiments were performed in a completely randomized design at the Seed Technology Laboratory of Agricultural Sciences and Natural Resources University of Khuzestan. In the first experiment, the effect of hormone priming treatment with gibberellin, halopriming with potassium nitrate, and hydro priming on Cassia seed germination was investigated. The results of this experiment showed that the highest seed vigor was obtained in the treatment of 50 mg/l gibberellin for 12 hours of priming. After selecting the best treatment (gibberellin 50 mg/l for 12 hours), germination characteristics of primed seeds compared with no primed seeds under salinity stress (0, 4, 8, 14, 16, and 20 dS/m). The results showed that seed tolerance to salinity stress at the germination stage increased significantly with seed priming. The highest seed vigor was observed in priming treatment at no salinity stress condition (339.89) while the lowest seed vigor of primed treatment was observed in 20 dS/m. Unprimed seeds could not withstand salinity stress beyond 4 dS/m.

In order to investigate the combined effects of temperature and salinity stress on seed germination properties of ziziphus (Ramlik), a factorial experiment conducted at seed technology laboratory of Agricultural Sciences and Natural Resources University of Khuzestan in 2019. The experiment was arranged as complete block design with three raplications. First factor was salinity (0, 50, 100, 150, 200, 250 and 300 mM) and second factor was temperature (5, 10, 15, 20, 25, 30, 35 and 40 oC). Results of the experiment revealed that there was no seed germination in 5 oC, 10 oC at all salinity treatments. Seed germination and seedling growth were declined at all temperature treatments bythe increase in salinity concentrations. Salinity tolerance threshold of Ramlik at 25 OC was 173 mM but as temperature increased to 35 oC, it declined to 150 mM. The highest seed germination properties of Ramlik were observed at 25 oC. An increase in salinity led to a lower seed germination rate. As Ramlik seeds were capable to complete their germination at

Milk thistle contains flavonolignan silymarin in its fruits, making it one of the most important medicinal plants for protecting the liver and treating a variety of liver diseases, such as hepatitis and liver diseases containing toxins. The drought resistance mechanisms of medicinal plants, such as milk thistle, are of critical importance. The investigation of the effect of drought stress on the activity of antioxidant enzymes will aid in the identification of these mechanisms. Water stress modifies plant behavior via its effect on plant metabolism and consequently has a substantial effect on plant production. The biosynthesis pathway of secondary metabolites is altered by environmental stresses, altering the production and concentration of active substances in plants. In addition to playing a crucial role in defense mechanisms, secondary metabolites are an important source of bioactive compounds. However, flavonoids not only have antioxidant activity via the release of free radicals, but they also regulate cellular pathways in the defense of plants against environmental stresses, alter plant metabolism, and have a significant impact on plant production. In order to determine the effect of drought stress on the physiological and biochemical characteristics of milk thistle, treatments of 100%, 75%, 50%, and 25% water requirement were applied in a greenhouse in the village of Shandel, city of Hirmand. There were multiple harvesting stages, including 6 and 13 weeks after planting. Measurements included dry weight, fresh weight, chlorophyll a, chlorophyll b, carotenoids, proteins, proline levels, and antioxidant enzyme activity. First, the data were examined for normality in Minitab software version 18, using the Smearnof Columnograph method to determine data normality, and then the errors were examined for normality to confirm data normality. Then, analysis of variance of all traits and comparison test of Duncan were performed at 5% level with SAS software version 9.2 (SAS 2010).  The analysis of variance revealed significant differences in harvest time, irrigation level, and the interaction between harvest time and irrigation level. In both harvest stages, the concentration of carotenoids began to decrease as the level of stress increased. The amount of chlorophyll a at the stage 6 weeks after planting was less than at the stage 13 weeks after planting, but its amount decreased with increasing stress at both stages. The levels of protein and proline also increased as the level of stress increased. The activity of antioxidant enzymes also increased as the intensity of stress increased, to the point where 100% of water requirements reached the minimum value and 25% reached the maximum value. Due to the fact that most oxidative enzymes in this study increased in response to stress, it can be concluded that catalase, superoxide dismutase, guaiacol peroxidase, polyphenol oxidase, and ascorbate peroxidase can eliminate ROS in this plant. Therefore, milk thistle has a good adaptation to drought stress, which is likely due to the reduction of oxidative damage caused by the activation of the antioxidant system and the accumulation of osmolytes such as proline and protein. These modifications are a form of adaptation to stress conditions. The majority of traits were affected by growth stage and stress level. The levels of protein and proline increased with increasing stress intensity. Most antioxidant enzymes, including catalase, ascorbate peroxidase, and superoxide dismutase, increased in activity under the influence of stress. According to these findings, milk thistle responds to drought stress by increasing proteins and amino acids, decreasing photosynthetic pigments, and increasing the activity of antioxidant enzymes, among other mechanisms. Also, because the amount of metabolites in this plant increases with increasing drought stress, it is possible to determine the stress tolerance threshold of this plant, cultivate it on a large scale, and apply stress to increase secondary metabolites.

In order to investigate the effect of priming on different aspects of germination of aged pumpkin seeds under drought stress, a factorial experiment was conducted based on a completely randomized design with four replications in the laboratory. Treatments included different levels of aging (control, 85% and 75% of control germination), salt stress (0, 75 and 150 Mmol) and priming (control, hydro, gibberellin, GR24, benzyl aminopurine and spermidine). The seeds reached the desired vigor level by accelerated ageing test. Morphological traits were also studied using seedling growth test. Mobility of seed lipid reserves, carbohydrate, number of photosynthetic pigments, photosynthesis, α-amylase and the amount of sodium ions were measured. In the study of germination traits, motility of lipid reserves, carbohydrates, chlorophyll a, photosynthesis and sodium content, salinity stress, seed deterioration and priming led to a significant change in them compared to the control seed. While in the case of shoot and root dry weight, chlorophyll b, and chlorophyll a / b ratio under salinity, seed deterioration and priming, no statistically significant change were compared to the control seed, the greatest effect of gibberellin-related seed priming was observed on germination traits and spermidine on physiological traits.

To investigate of tolerance levels and screening of different thyme species to the temperature stresses, a factorial experiment was conducted in a completely randomized design with three replications in the vitro condition. The experiment was conducted using six Thymus species (Th. fallax, Th. fedtschenkoi, Th. pubescens,Th. vulgaris, Th. daenensis and Th. kotschyanus), at two moisture levels (dry and wet) and at 15 temperature levels (from -8 ° C to 48 ° C with an increase of 4 ° C). Measured characteristics included germination percentage and mean germination time. According to the results, the highest germination percentage belonged to Th. pubescens (70.83%) and Th.daenensis (70.44%) and the lowest germination percentage belonged to Th. vulgaris (53.04%). The average percentage of germination of seeds in dry condition (74.66%) was significantly higher than wet condition (56.12%). The highest germination percentage was observed at -4 (79.44%), zero (78.33%) and 4 (79.72%) Celsius that had significant differences with others. Interactions of species with moisture conditions showed, the highest germination percentage related to Th. kotschyanus (79.40%), Th. pubescens (78.95%), Th. daenensis (78.08%) and Th. falax (77.53%) in dry conditions and the lowest germination percentage belonged to Th. vulgaris (45.46%) in wet conditions.Using the results, different species of Thymus can be screened for temperature tolerance in dry and humid conditions and recommended for cultivation in different regions. In this experiment, native species were more resistant to temperature stresses.

The present study was carried out in the form of split plots in a RCBD with three replications. Experimental treatments include drought stress at three levels of irrigation at moisture of field capacity, irrigation at 80% of field capacity and irrigation at 60% of field capacity as the main factor; And application of iron nano-chelate fertilizer at four levels of 0, 3.5, 7 and 10 kg.ha-1 as a sub-factor. The results showed that irrigation at field capacity and consumption of 10 kg.ha-1 resulted in the highest amounts of plant height, number of fruits per plant, fresh and dry fruit yield, biological yield, and mucilage and okra oil yield., no statistically significant difference was observed between the 10 and 7 kg.ha-1 fertilizer for the above traits., in stress conditions (moisture 80 and 60% of field capacity), the use of nano-fertilizers in comparison with the non-use of fertilizers led to the moderation of the effects of stress on the mentioned traits. So that only for the yield of fresh fruit, in treatment of moisture 80% of soil field capacity consuming 10 kg per hectare of fertilizer caused a 20.05% increase in yield compared to not using fertilizer. And this amount was 19.29% for moisture in 60% of soil field capacity. Also in the present study it was observed that the highest percentage of fruit mucilage was obtained from moisture treatment in 60% of field capacity and the highest percentage of fruit oil was obtained from irrigation treatment in soil field capacity moisture

In order to study the effect of salinity and nitrogen on the competition between coriander and Torilis arvensis, a factorial experiment with three factors of competition (The absence and the presence of Torilis arvensis), nitrogen fertilizer (0, 30, 60 and 90 kg Ha-1) salinity stress (0, 50, 75 and 100 mM NaCl) was carried out in a completely randomized design with three replications in the research greenhouse of Faculty of Agriculture, Razi University in 2018. Nitrogen and salinity affected on coriander growth characteristics. With the increasing salinity level, plant height, leaf number, fresh and dry weight of plant and leaf, yield and leaf area decreased. But nitrogen had a positive effect on morphological characteristics studied. The interaction between salinity and nitrogen showed that in all three levels of salinity with increasing nitrogen concentration increased coriander growth characteristics. So that the highest plant height, fresh and dry weight of the plant and leaf dry weight were observed in treatment 0 mM NaCl with 60 and 90 kg Ha-1 nitrogen levels. The highest number of leaf (13.99) was in treatment 0 mM NaCl with 60 kg Ha-1 nitrogen. Under salinity stress conditions, application of nitrogen 90 kg Ha-1 could reduce the negative effects of salinity stress by increasing growth and finally improving the morphological characteristics of the plant, which can affect the competition between coriander and Torilis arvensis.

Aging and salinity stress are main challenges towards of producing a healthy seedling. This research was conducted to investigate the effects of seed aging on the seed germination properties of Wild mustard under salinity stress condition. Experimental treatments were five levels of seed aging 0, 24, 48, 72 and 96 h and different levels of salinity stress 0, 100, 200, 300, 400 and 500 mmol. Seed germination, germination rate and seed vigor were declined at high salinity concentrations. Catalase activity and total seed protein content were decrease due to the aging. Seed protein content (1.4 mg/g fw) declined about 92% and reach to 0.1 mg/g fw after 96h of aging. Catalase activity was decrease due to aging while in contrast, peroxidase activity was higher from 0.04 to 0.11 u/ mg protein after 96 h of aging. It was observed that all fatty acids of wild mustard seed oil were changed at higher aging durations. Behenic acid (C22:0) and Erusic acid (C22:1) were 0.656 and 38.543% in noaged seeds and they increased to 0.751 and 40.186%, respectively.

In order to investigate the effects of seed inoculation with arbuscular mycorrhizal fungi on some chemical characteristics and seed germination of corn (Zea mays L.) under drought stress conditoins, a factorial experiment based on randomized complete design with three replications was conducted at the physiology laboratory of Islamic Azad University Branch Ardabili, during 2015. Studied factors were: drought stress in four levels (Zero, -4, -8 and -12 bar) and seed inoculation with mycorrhizal fungus in four levels (no inoculation, seed inoculation with Funneliformis mosseae, Rhizoglomus fasciculatum and Claroideoglomu etanicatum. The results showed that the effect of drought stress and seeds inoculation with mycorrhizal fungi on germination components, seed protein content and antioxidant enzymes was significant at 1% probability Level. Seed inoculation with Rhizoglomus fasciculatum showed higher antioxidant enzymes activity and higher seed protein content compared with inoculation with Funneliformis mosseae, Claroideoglomus etanicatum and no inoculation. In drought stress conditions, plants will reduce oxidative stress leads to increased activity of antioxidant enzymes has been. The results of the mean comparison of data showed that with increasing drought stress germigation percen and germination rate index decreased and the means of germination time, increased. With respect to the results of this study, it seems that mycorrhiza fangi by an improvement in water and nutrient absorption, improve plant growth in drought stress condition. Thus, in order to increasing of germination components and chemical characteristics, it can be suggested that seeds inoculation of corn was applied with Rhizoglomus fasciculatum

It seems mucilaginous seed coat is an aspect of plants evolutionary adaptation to desert environments. Because of mucilage production, seed coat of Balangu Shirazi (Lallemantia royleana) absorbs water multiple times more than of its initial weight. To determine the possible role of mucilaginous seed coat, two mucilaginous (M) and demucilaged (DM) seeds were examined in two separate experiments of drought with six levels (0 as control, -0.1, -0.2, -0.3, -0.4,and -0.5 MPa) and salinity with six levels (0 as control, 2, 4, 6, 8, and 10 ds.m-1) through factorial experiment as completely randomized design with three replications of 25 seeds. Germination of demucilaged seeds significantly was higher than mucilaginous seed in drought trial; though in salinity stress, there was no significant difference between germination of mucilaginous and demucilaged seeds. Mean germination time (MGT) in mucilaginous seeds was higher than the demucilaged seeds in both salinity and drought stresses. In salinity experiment, length of root, stem and stem/root length ratio in mucilaginous seed was higher than the demucilaged seed significantly; while there was no any differences in drought stress. Interaction of seed with drought was not significant but there was significant interaction between seed and salinity.

In this study, distribution and tension concentration are analyzed in dowel joint. In current research, the effect of screw diameter are 4, 5 mm and type of woods are fugues oriental is, Alnus subcordata and white spruce on tension resistance and bending moment were tested. The dimensions for malting T- form joints were 5×5×2/5 wooden dowel used in this research was carpinus betulus which is the common dowel in malted. Also, Poly-vinyl acetate was used in Joints. The combination of above said factors in dowel joint 6 male totally 24 T sample by 4 repetitions and tension resistance and bending moment were measured by mechanical test machine. For exertion strength in order to analyze the aforementioned resistance, loading speed equal to 1.25 mm/min was used. Also, for analyzing the way of distribution and tension concentration in joint and changing process of tension base on changing the variables in this research finite element method and ANSYS Software were used. Based on the findings, the German modeling of joint which endures the maximum tension is equal to the type being used in real joints. Distribution of tension in the middle of the bending moment depths is maximum and tension in screw joints is consent Reid in failure Points.