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

Dracocephalum moldavica L. is a herbaceous, annual plant from the Lamiaceae family that is native to Central Asia and domesticated in Central and Eastern Europe. Essential oil of this plant has antimicrobial and bacterial properties and has many uses in the pharmaceutical, cosmetic, food and perfumery industries. Lead stress in plants causes disturbances in mitosis, leaf chlorosis, decreasing of the vegetative and productive growth stages and reduces photosynthesis and enzyme activities. One of the effects of lead toxicity is due to the similarity of the structure of calcium ions and lead, and for this reason, lead ions disrupt many mechanisms related to calcium ions and prevent the activity of key enzymes.Photosynthesis is one of the most sensitive metabolic processes to lead toxicity, and several studies have reported the inhibition of photosynthesis under lead stress in various plants. Lead prevents the absorption of elements such as magnesium and iron. These elements play a role in the structure of chlorophyll and the oxygen-releasing complex in photosystem II. Heavy metals such as lead inhibit chlorophyll biosynthesis by inhibiting the enzymes gamma-aminolevalonic acid dehydrogenase and protochlorophyll reductase. Also the availability of different nutrients in the soil changes significantly under the influence of environmental stress so that using of vermicompost can be useful in stress condition as well as Jasmonate. Jasmonate is the final oxidation product of unsaturated fatty acids such as linolenic acid, that is effective in increasing the activity of plant defense systems under environmental stress conditions such as lead stress. In order to study the effect of pb (0, 100, 200, 300, 400 mg kg-1 soil) and jasmonate (0, 50, 100, 150 mmol l-1) on Dracocephalum moldavica L. under controlled conditions in soil enriched with vermicompost and without vermicompost an experiment designed and it was done under greenhouse conditions.

This test was done in a random factorial design with 4 repeats and indices including CO2 assimilation rate, transpiration rate, stomatal conductance, water use efficiency(WUE), PSɪɪ photochemical efficiency (Fv/Fm), photosynthesis quantum performance, electron transfer rate (ETR), were measured in vegetative and reproductive growth stages.

In the conducted study, it was found that CO2 assimilation rate, water use efficienty, stomatal conductance and Fv/Fm were significantly decreased as lead concentration was increased. Also jasmonate treatment significantly increased CO2 assimilation rate, water use efficienty, stomatal conductance and Fv/Fm in lead stress condition. So that plant treated with 400 mg kg-1 soil pb and 0 mmol l-1 jasmonate showed the lowest CO2 assimilation rate, water use efficienty, stomatal conductance and Fv/Fm while plant treated with 0 mg kg-1 soil pb and 150 mmol l-1 jasmonate showed the highest CO2 assimilation rate, water use efficienty, stomatal conductance and Fv/Fm. transpiration rate was significantly increased as well as increasing pb concentration so that plant treated with 400 mg kg-1 soil pb showed the highest transpiration rate. Also jasmonate treatment significantly decreased transpiration rate in lead stress condition. Vermicompost increased CO2 assimilation rate, water use efficienty, electron transfer rate (ETR) and significantly decreased transpiration rate in lead stress condition.Jasmonate reduces the destructive effects caused by stress on photosynthetic indicators such as the amount of chlorophyll and carotenoids and also increases the performance of photosystem II and consequently increases plant photosynthesis under stress conditions. It has been reported that methyl jasmonate can maintain the concentration of chlorophyll in the reaction center, thereby improving the speed of electron transfer and increasing the efficiency of photosystem II. In addition, jasmonate can prevent the severe reduction of stomatal conductance under stress conditions and increase the quantum efficiency of photosynthesis.In the response of plants to stress, jasmonates act as genes encoding inhibitory proteins such as theonine, hydroxyproline and proline, and in general, by activating defense mechanisms, they help the plant in reducing the absorption and accumulation of heavy metals. Organic fertilizers can also improve plant performance under environmental stress conditions. Vermicompost fertilizer increases porosity, increases absorption and retention of nutrients, improves ventilation, drainage and microbial activity in the soil.

Having nutritious mineral elements and plant growth hormones can improve plant growth in the presence of environmental pollutants such as heavy metals by influencing the physiological characteristics. It can be said based on the results obtained lead stress decreased photosynthesis index through effect on electron transport chain and photosynthetic pigments while jasmonate treatment and Soil enriched with vermicompost can reduce the destructive effects of lead stress. So that using of jasmonate and vermicompost in lead stress condition Recommended.

In this research, the efficiency of melatonin for reducing the adverse effects of drought stress on two commercial pear rootstocks (Dergzi seedling and Pyrodwarf clonal rootstocks) was evaluated as factorial experiment in randomized complete block design with three replications for one year in the research greenhouse of Tarbiat Modares University, Tehran, Iran. For this purpose, 10 days before the application of drought stress, melatonin with a concentration of 100 μM was applied in the root environment of plants. Experimental factors included: rootstock at two levels (Dargazi seedling and Pysodwarf clonal rootstocks), melatonin at two levels (without melatonin and 100 μM melatonin), drought stress (irrigation in 10 days interval and withholding water for 40 days) and duration (time) of dorugh stress at four levels (10, 20, 30 and 40 days after drought stress application). The results for chlorophyll content and maximum quantum efficiency of photosystem II showed that melatonin had significant effect on reducing the adverse effect of drought stress in both rootstocks. As the duration of drought stress increased, the rate of leaf chlorophyll degradation was less in the rootstocks treated with melatonin. The interaction effects of time × drought stress, drought stress × melatonin and melatonin × time on all studied traits were significant at the 5% and 1% probability levels. Melatonin pretreatment significantly prevented ion leakage and increased cell membrane stability index in both Dergzi and Pyrodwarf rootstocks. Also, melatonin pretreatment increased total phenol in the two rootstocks and improved plant tolerance to drought stress. The total phenol in plants under severe drought stress increased by 123 and 100 percent in comparison with Daragazi seedling and Pyrodwarf rootstock, respectively. Application of melatonin also contributed to higher absorbtion of nutrient elements of sodium, potassium and phosphorus under drought stress conditions.

To study the effect of slow release hydrogel-urea complex (SRHUC) on chlorophyll fluorescence and morphological parameters of barley under drought stress, an experiment was performed in 2017-2018 as factorial in Randomized Complete Block Design (RCBD) with three replications in the greenhouse of Aburaihan campus of University of Tehran. The combination of factorial levels were as fertilization factor containing nitrogen (N) from urea source in five levels of no N application, equivalent 125 and 65 kg.ha-1 N without and with SRHUC as CU-N125, CU-N65, SRHUC-N125 and SRHUC-N65, respectivly and drought stress in three levels of 70, 50 and 30% FC. Drought stress decreased flag leaf area and the lowest value (13.12 cm2) belonged to 30% FC. Furthermoreit decreased flag leaf dry weight, total number of tiller and SPAD index. SRHUC-N125, SRHUC-N65 and CU-N125 have showed the highest values of maximum (Fm) and variable (Fv) fluorescences. In 50% FC, N-containing treatmenats had the highest Fv/Fo and SRHUC treatments showed the highest performance index based on absorption (PIABS) that were equal to 1.66 and 1.60. In 30% FC, the lowest value (10913) of minimum fluorescence (Fo) was related to SRHUC-N125. SRHUC-N125 caused the highest flag leaf area (16.8cm2), stem diameter (4.2 mm) and SPAD index (43.6). It can be concluded that better N availability in Goharan cultivar, had favorable effects on chlorophyll fluorescence and growth parameters, especially in drought stress, and SRHUC application might result in more appropriate chlorophyll fluorescence and growth characteristics.

Excessive salinity of the soil reduces the production of agricultural products, including vegetable crops, Which especially are sensitive in the vegetative parts. The salinity threshold of most vegetable crops is low (between 1 and 2.5 ds.m-1) and the salinity tolerance of vegetables decreases when saline water is used for irrigation. Choosing the right cultivar for areas with high salinity is the first management strategies for the production of high quality products. Spinach is in the group of moderately sensitive plants to salinity stress, although there are differences between various cultivars. Therefore, the present study was designed and conducted to evaluate the growth and photosynthetic characteristics of two spinach cultivars, under salinity stress and to determine the most tolerant cultivar to salinity and suitable for cultivation in saline areas.

This research was carried out factorial with two factors including three levels of stress in a completely randomized design with four replications at research farm of Vali-e-Asr University of Rafsanjan in 2018. The factors included salinity stress (at four levels 0, 10, 20, 30 mM NaCl) and cultivar (‘Barg-Pahn-e-Varamin’ and ‘NARITA’ F1 hybrid). After 45 days from the beginning of salinity treatments, plants were harvested and the parameters were measured. Characteristics such as fresh and dry weight of shoot and root, leaf area, leaf number, photosynthetic pigments (chlorophyll a, b, carotenoid), total chlorophyll, SPAD index, photosynthesis rate, transpiration rate, stomatal conductance, chlorophyll fluorescence index (Fv/Fm ratio) and photosynthesis efficiency index (PI).

The results of this study showed that the growth characteristics of both spinach cultivars such as leaf number, leaf area, fresh and dry root weights, fresh and dry shoot weight, decreased under salinity stress conditions. With increasing salinity levels, leaf area of both cultivars decreased but the leaf area of Iranian cultivar was higher than the hybrid cultivar. The results also showed that the amount of photosynthetic pigments in the Iranian cultivar was higher than the hybrid cultivar in salinity conditions. In general, total chlorophyll content decreased under salinity stress, but the amount of chlorophyll a and total chlorophyll content were higher in the Iranian cultivar. Photosynthetic indices such as photosynthesis rate (Pn), stomatal conductance (gs), transpiration rate (Tr) and chlorophyll fluorescence index (Fv/Fm ratio) decreased under salinity stress, which was different in both Iranian and hybrid cultivars. Further reduction of these parameters in stress conditions in Iranian cultivar was less than the hybrid cultivar.

Growth characteristics such as leaf area, leaf number, fresh and dry root weight, fresh and dry shoot weight of two spinach cultivars decreased in salinity conditions. The amount of photosynthetic pigments in the Iranian cultivar was higher than in the hybrid cultivar and decreased in both cultivars under salinity stress. Photosynthetic indices also decreased under salinity stress, although changes in photosynthetic indices in both cultivars were approximately the same, but the value of these parameters were higher in Iranian cultivar. In general, salinity stress reduced the growth and photosynthetic parameters of both Iranian and spinach hybrids, but the reduction in growth characteristics in the "bargpah-e Varamin" cultivar was lower than the hybrid cultivar. Therefore, it seems that the Iranian cultivar is more tolerant to salinity stress than the hybrid cultivar, and this difference in cultivars to salinity stress can be attributed to their genetic diferences.

  Measuring of chlorophyll fluorescence is a nondestructive and sensitive way to give important information about photosynthesis apparatus. Fluorescence spectrum is different from the absorbed one by chlorophyll and it has higher wave length so the fluorescence yield could be measured by exposing a leaf with a defined wave length of light and then quantifying the higher reflected wave. The purpose of this experiment was to make comparison among chlorophyll fluorescence important parameters for early prediction of destructive effects of mesosulfuron methyl + iodosulfuron methyl before revealing the symptoms of Phalaris minor. A greenhouse experiment with five replications and six treatment based on completely randomized design was conducted to evaluate the chlorophyll fluorescence parameters of Phalaris minor sprayed by mesosulfuron methyl + iodosulfuron methyl up to seven days after spraying.Herbicide doses were 18, 12, 8, 5.3 and 3.5 g a. i./ha with an untreated treatment as control. Herbicide was applied at three leaf stage of Phalaris minor with MATABI elegance plus sprayer equipped by tee-jet 8001 nozzle at 300 kpa pressure. Fluorescence measurements were conducted by Handy PEA fluorimeter that flashes a wave length of 650 nm at 300 μ mol/m2.s intensity during 10 seconds on dark adapted leaf one day after spraying at 10 a.m. every day until seven days after spraying. The results indicated that Fv/Fm and Area parameters showed slow response to mesosulfuron methyl + iodosulfuron methyl application whereas Fvj and PI showed a fast reaction. Approximately from the first day after spraying the two mentioned parameters drastic reduction happened which was more intense but with bigger standard errors in PI compared to Fvj. with an increase in mesosulfuron methyl + iodosulfuron methyl dose both PI and Fvj parameters were decreased. It could be concluded that these two parameters show special sensitivity to the mesosulfuron methyl + iodosulfuron methyl application and before the symptoms of the herbicide appears, they give a picture of physiological destructive effects of the herbicide.Whereas the Fvj parameters during all seven days after spraying shows a steady reduction with low standard errors, PI index shows reduction with higher standard errors which make the Fvj parameters more reliable. The two Fv/Fm and Area which were repeatedly reported as a sensitive factor to the stresses at this experiment were not appropriate indices. The common dose response methods of herbicide can be replaced by chlorophyll fluorescence measurements and it can offer fast, accurate, and an important information about herbicide efficiency very fast and accurate

Drought stress is one of the most important and effective factors in agricultural practices in arid and semi-arid regions of the world. The arid and semi-arid regions comprise more than 70% of the total area of Iran. Reduction in chlorophyll concentrations has been attributed to the increase in chlorophyll degradation in water deficit conditions and impairment in the enzymes activity responsible for the synthesis of photosynthetic pigments. Under drought stress, maintenance of photosynthetic capacities and leaf chlorophyll are physiological parameters which influence drought stress tolerant of crop. Phosphorus is one the most essential elements for plant growth after nitrogen. However, the availability of this nutrient for plants is limited by different chemical reactions especially in arid and semi-arid soils. Plant growth-promoting bacteria (PGPB) are soil and rhizosphere bacteria that can benefit plant growth by different mechanisms. Given the negative environmental impact of chemical fertilizers and their increasing costs, the use of PGPB as natural fertilizers is advantageous for the development of sustainable agriculture. Inoculation of plants with native beneficial microorganisms may increase drought tolerance of plants growing in arid or semi-arid areas.
In order to study the effect of biologic and chemical phosphorous fertilizer on photosynthetic pigments of safflower cultivar (IL111), under water deficit condition, an experiment was conducted in 2012 at the Research Field of the Faculty of Agriculture, Shahed University. The experimental design was split-factorial arrangement in randomized complete block design with three replicates. The main factors were the three levels of irrigation treatment: full irrigation (irrigation up to 50% soil moisture depletion relative to field capacity), water stress in the vegetative and flowering stages (irrigation up to 75% soil moisture depletion relative to field capacity). The sub-factors were the six treatments resulting from three levels of phosphate chemical fertilizer (0, 50, and 100 kg ha-1 Triple Super Phosphate), each at two levels of Barvar-2 bio-fertilizer (with and without inoculation with Barvar-2). The applied biological fertilizer was in the type of the bacteria which release the phosphorus from soil components and neutralize the soil pH. The commercial name of the biologic fertilizer is Barvar-2. The effective gradients of the biological phosphorus fertilizer is comprised of two bacteria strains of p5 (Bacillus lentus) and p13 (Pseudomonas potida) with 108 cfu (colony forming units) which have been screened from soil bacteria populations. The bacteria strain p5 (Bacillus lentus) dissolves P from soil mineral compounds while p13 (Pseudomonas potida) separates P from soil organic compounds by exerting a variety of phosphatase enzymes.
The results showed that the highest amount of chlorophyll a, b and total chlorophyll obtained with application of chemical phosphorus by 100 kg ha-1 Triple Super Phosphate followed by inoculation with Barvar-2 under water deficit condition at vegetation and flowering stages. At drought stress in flowering stage, use of high level of phosphorus without inoculation with Barvar-2, had highest effect in terms of increasing amount of chlorophyll a/b ratio, but at treatment of inoculation with Barvar-2, the highest amount of chlorophyll a/ b ratio obtained with low level of chemical phosphorus by 50 kg ha-1 Triple Super Phosphate. The means comparison showed that highest amount of carotenoids, fv/fm, anthocyanin, flavonoids and soluble sugars obtained with application of chemical phosphorus by 50 kg ha-1 Triple Super Phosphate without Barvar-2 under water stress condition at vegetation and flowering stages. The inoculation with Barvar-2 followed by chemical phosphorus by 50 kg ha-1 Triple Super Phosphate significantly increased the amount of anthocyanin and soluble sugars of leaf under drought stress at flowering stage, while the amount of carotenoids and flavonoids, increased with Barvar-2 without using of chemical phosphorus.
Our experiment showed that application of chemical phosphorus fertilizer followed by inoculation with Barvar-2 had huge effect on chlorophyll a, chlorophyll b, total chlorophyll, chlorophyll a/ b, carotenoids, fv/fm, anthocyanin, flavonoids and soluble sugars under water stress condition at vegetation and flowering stages. The highest amount of photosynthetic pigment such as anthocyanin, flavonoids, carotenoids and soluble sugars could increases stress tolerance of safflower under water deficit condition. In general, the results of this experiment showed that application of Barvar-2 followed by chemical phosphorus had effective role in improve of qualitative traits of safflower under drought stress condition.

Sugarcane (Saccharum officinarum L.) is from poaceae trible and perennial native plant of asia continent warm areas. Ratio Fv/Fm estimates the maximum quantum yield of photosystem II. Under conditions of stress Fv/Fm decreased, this decreasing is due to low activity of reaction of photosynthesis centers and reducing of proteins that are responsible for water electron transport to chlorophyll a. Dust closed the pore openings and increased leaf temperature, lack of heat exchange, lack of transpiraition and loss of the entry of CO2 to leaves, on other hand dust accumulation on plant also creates a shadow on plant and decreases leaf photosynthesis. Since the maximum area under cultivation of sugarcane in the region, so studying the effects of dust on this growing phenomenon in the region seems to be necessary. This study aimed to examine the effects of dust, in a controlled environment greenhouse Development Research Institute of Sugarcane in the 2013-2014. In this experiment, dust courses and various concentrations of artificially applied. The experimental design was a randomized complete block design with 4 replications and 4 treatments. Treatments were: control (without dust), once a month, twice week, weekly dust apply. To isolate and correct actions dust on each treatment, the stool is made of metal with a half-inch galvanized pipe to a height of 2 meters, 3 meters in length and a width of one meter, was used. The stool was covered by a thin translucent plastic all interior and on both sides of it. The planting of cuttings CP69-1062 was used. Values of Fv/Fm (maximum quantum yield), NPQ (non photochemical quenching), qP (photochemical quenching), ΦPSII (efficiency of Photosystem two), SPAD number, photosynthesis rate, transpiration, leaf temperature, under stomatal CO2 concentration, electrolyte leakage, ascorbate levels, PAR and sugar content were measured. The results showed that the dust, decreases the values of Fv/Fm, qP, ΦPSII, photosynthesis rate, transpiration flux, under stomatal CO2 concentration, PAR and sugar content but increases the amount of NPQ, SPAD number and leaf temperature. A significant positive correlation between stomatal conductivity with photosynthesis, transpiration and CO2 under stomata were observed that showed restrictions on the entry of gases into the cell. sugar production showed a significant decline. qP had highly correlated with Fv/Fm, and qP reducing, cause to reduce of Fv/Fm. The result of dust stress and reducing of QA capacity, electron transfer into photosystem one reduced and causes a loss of light energy absorbed in the form of chlorophyll fluorescence excitation. In fact, during the excitation of chlorophyll, NPQ prevailed qP, and therefore, the quantum yield of photosynthesis reduced and the temperature of leaf increased because of stomatal closure and reduction stomatal conductivity and losses of energy in the form of light and heat grew. Sugar decreases because many enzymes involved in the sugars revival of the Calvin cycle are activated only with appropriate light intensity. Since the Fv/Fm component showed the highest correlation with most of the measured characters, so it can be use as a criteria along to the qP and NPQ for sugarcane studies under dust stress.

Salinity is one of the greatest factors that limit the producion of horticultural crops in many parts of the world, especially in arid and semi-arid areas. Tomato (Lycopersicon esculentum L.) is an annual herbacious plant whose annual global production is over 80 million tons. In areas with warm and dry climate which are suitable for the production of tomatoes, salt is considered a major problem. This research was done in order to study the salinity effects on growth and physiological characteristics of tomato plant cultivars Super strain–B and Red clud. Firstly, seeds were planted in metal trays filled with sand in the greenhouse environment with sufficient moisture, and then seedlings in two leaf stages were transplanted to hydroponics’ medium with a Johnson nutritional solution. After establishment, the five levels of salinity treatments including, zero (control), 40, 80, 120 and 160 mM of Nacl were applied in three replications. The results showed that salt stress significantly reduces shoot and root dry weight, number of leaves, leaf area, leaf chlorophyll content, and stress index (Fv/Fm) of both cultivars. Specific leaf area (SLA) in both cultivars decreased due to salinity treatment; however, this reduction was not significant in Red clud cultivar. Salinity also significantly increased the amount of proline in shoots in both cultivars. The results were suggestive of the relative resistance of tomato plant cultivar Red clud in comparison with Super strain-B to salinity conditions.

In order to evaluate of morphological، physiological and biochemical traits، related to drought tolerance، an experiment was carried out in field condition. In this study two commercial cultivars (MCC361، MCC358)، three Kabuli and three Deci type of tolerant genotypes (MCC392، MCC537، MCC696، MCC873، MCC870، MCC10،) and three Kabuli and three Deci type of susceptible genotypes (MCC759، MCC588، MCC774، MCC45، MCC39، MCC101) were grown in Ferdowsi University of Mashhad research field. These genotypes were compared in shoot length، dry weight، leaf area، Fv/Fm، leaf water potential، prolin and protein content and catalase activity in the flowering stage. There was a significant positive correlation between prolin and protein content. Catalase activity also had significant positive correlation with dry weight and leaf area. Susceptible genotypes had lower Fv/Fm، leaf water potential، prolin content and catalase activity than tolerant genotypes. Accordingly، Fv/Fm، leaf water potential، prolin content and catalase activity were introduced as suitable markers for identification of drought tolerant genotypes. Commercial cultivar (MCC358) was introduced as a tolerant genotype because of higher Fv/Fm، leaf water potential، prolin content and catalase activity as compared to susceptible genotypes under drought stress.