جستجوی مقالات مرتبط با کلیدواژه "cold stress" در نشریات گروه "زیست شناسی"

Recently, melatonin was proved to be a candidate hormone that could increase the cold and heat stress of the plant. Cold stress is important abiotic stress for plants in nature. In this study, in order to investigate the effect of exogenous application of melatonin on some physiological traits related to cold stress on the strawberry cultivar ‘Paros’ a pot experiment with three replications was performed in a completely randomized design. Strawberry plants pre-treated with 100 μM melatonin were subjected to freezing stress treatment (-9◦C for 3 h without cold acclimation) after two weeks some physiological traits (proline, carbohydrate, total flavonoid, chlorophyll content, ion leakage, hydrogen peroxide, content of water, malondialdehyde, and total phenol) related to cold stress in plant leaves were measured. The results showed that melatonin treatment has a significant effect on some physiological traits (proline, carbohydrate, total flavonoid, chlorophyll content, ion leakage, and hydrogen peroxide) in the strawberry plant under freezing stress. Proline, carbohydrate, total flavonoid, and chlorophyll content were significantly enhanced, and a significant reduction was observed in ion leakage and hydrogen peroxide in melatonin-pre-treated plants. In this experiment, melatonin treatment had no significant effect on the relative water content, malondialdehyde, and total phenol. According to the results of our study, exogenous application of melatonin may be effective to improve freezing tolerance in strawberry plants after two weeks of application.

Freezing is one of the abiotic stresses that has harmful effects on plant growth and productivity. This study was performed to investigate some physiological and biochemical responses of two ornamental and cold-resistant plants, including the viola (Viola × wittrockiana) and snapdragon (Antirrhinum majus) under freezing stress.

To apply different temperature treatments on 70-day-old plants, the minimum temperature in January was used in three different places, including the greenhouse, the city of Isfahan and Fereydunshahr (temperatures of 20, 3- and -11 ° C, respectively) for 15 days.

Changes in the chlorophyll a/b ratio were differences in the two plants with increasing freezing stress, but shoot length gradually decreased and at the lowest temperature in viola and snapdragon plants were 63 and 50% of their controls (20 °C), respectively. The content of phenolic compounds, soluble carbohydrates and hydrogen peroxide also increased. In addition, a significant increase in catalase activity was observed in both plants under freezing temperatures, while the increase in ascorbate peroxidase activity was significant only in snapdragon at -11 °C. However, no significant change in the activity of guaiacol peroxidase was found in two plants under freezing temperatures.

Therefore, it seems that snapdragon and violet plants can withstand freezing stress by using osmotic regulation mechanisms as well as different abilities of antioxidant enzymes, which indicate different resistance strategies depending on their genotype.

Carrageenan and salicylic acid are bio stimulants that are involved in stress resistance by affecting the physiological and biochemical processes of the plant. In this study, carrageenan in two concentrations of 0.5 and 1 g / l and salicylic acid in 0.5 and 1mM concentrations were used for foliar application. This study was performed by factorial experiment in a completely randomized design with three replications. The pretreatments were applied in 6-leaf stage and the solutions were sprayed on the plant five times in the early morning in 10 days. One day after the last pretreatment, a number of pots were transferred to the refrigerator for 24 hours at a temperature of 5 °C for chilling stress, then the pots were returned to the greenhouse and after one day, samples of plant were collected from control and cold tressed pots. In this study, it was observed that pretreatment of plants with carrageenan and salicylic acid increased all growth parameters, osmolytes (include soluble sugars and proline), antioxidant enzymes include catalase, ascorbate peroxidase and guaiacol peroxidase activity, but reduced the oxidative stress index such as ion leakage, malondaldehyde and hydrogen peroxide content. The best results were obtained with the use of carrageenan 1 g / l and 0.5 mM salicylic acid. These results indicate that carrageenan and salicylic acid increased the resistance to cold stress in Impatiens flowers by increasing the protective parameters of the plant.It seems that these compounds as bio stimulants can be suitable for managing cold stress in other ornamental plants and can be used to reduce the chilling stress of autumn and winter in plants.

Accumulation of fructan in different organs of wheat plants is important physiological factor to cope with different environmental stresses. Fructans are fructose based oligo- and polysaccharides derived from sucrose. Depend on the linkage among frucosyle residues, different types of fructan molecules could be found in the plant species. In wheat stem, levan-type (containing β-(2,1) linkage) and graminan-type fructan (containing β-(2,1) and β-(2,6) linkages) are accumulated. Three different enzymes of 1-SST, 6-SFT, and 1-FFT are believed to be involved in wheat fructan biosynthesis. Since the fructan synthesis in wheat is complex, therefore various type and amount of fructan are found among wheat cultivars. Hydrolysis of fructans are catalyzed by 1-FEH and 6-FEH preferentially degrading β-(2,1) and β-(2,6) linked fructan, respectively. Wheat cultivar with greater fructan accumulation and mobilization in the stem are resistance to terminal heat and drought stresses. Fructans increases tolerance to salt stress by cell membrane stabilization, osmotic adjustment and preservation of current photosynthesis. During cold hardening, wheat seedling accumulates water soluble carbohydrates as well as fructan in their leaves and crown

Sugarcane is cultivated in different parts of the world up to a latitude of about 32 degrees north and south. The resistance of this plant to cold is low. Considering the sensitivity of sugarcane to cold, in order to identify the pathways and genes by differential expression in sugarcane cultivars during cold stress and employ them in sugarcane plant breeding programs, 454 sugarcanes were investigated using morphological and biochemical indices, in the Research Farm of Khuzestan Sugarcane Research Institute following the incidence of -1.2 ℃ temperature in the region in December 2015. In the first stage, the cold-tolerant or sensitive cultivars were selected using morphological indices. In the second stage, biochemical indices such as proline and malondialdehyde were measured in the tolerant cultivars (selected at the first stage) after a cold stress period in 2016, which showed increases in comparison with susceptible cultivars. According to the data obtained at the two stages, two cultivars, namely BR00-01 and TUC66-107, were identified as the most tolerant and sensitive to cold, respectively. Based on the results of morphological studies, the cultivars with a higher tolerance to cold stress were also hose with higher proline and MDA levels in the biochemical study stage compared with the sensitive cultivars. There was also a high correlation between morphological traits and biochemical indicators in terms of cold resistance. Therefore, by measuring morphological and biochemical indices, it is possible to determine to a large extent the type of reaction of a sugarcane cultivar to cold stress before doing molecular analysis and spending huge sums of money, and to select superior clones when sifting sugarcane clones at different breeding stages.

Environmental stresses are among the main factors limiting growth and reproduction of the plants. Cold stress is one of the most important environmental stresses which incurs serious losses to different plant products and is considered as a threat to sustainable plant production. A set of morphological, physiological, biochemical, and molecular changes that occur during the autumn acclimates plant species to the low winter temperatures. Investigation of cold tolerance mechanisms at the cellular levels is a vital step in genetic manipulations for the purpose of improving plants’ resistance against cold. The occurrence of sudden low temperatures either in early autumns or late springs incurs various damages to plants. Cold acclimation during the autumn is necessary for plants to tolerate the low temperatures in winter. Although the overall adaptive process through which plants become tolerant to the low temperature is similar, this phenomenon varies slightly according to the plant species and climate condition. Moreover, when experiencing cold stress, different plant organs show various degrees of injuries, which can be minimized following proper agricultural practices through plant reinforcement. In fact, in time strengthening of the plant and avoiding any stress source can minimize the cold stress damages to the plant. An overview of the causes of cold stress injuries and plant response mechanisms can be helpful in reducing a part of low temperature detrimental effects.

The aim of this study was to investigate the importance of some physiological and biochemical properties related to cold adaptation mechanisms.We aimed to adopt properand efficient indices for identification of winter cold tolerance and susceptibilityin two strawberry cultivars. Differentphysiological and biochemical traits were studied under different cold treatments on the leaf and crown tissues of two strawberry cultivars of Selva and Queen Elisa. Plants prepared from new runners after being planted in the pot and grown until late November. Potted plantswere kept in out doorcondition to gradually adapt to low temperature. After plant adaptation, coldtreatments were artificially applied with adjustable chilling apparatus. The samples were kept under the final cold treatment for three hours and then removed from the apparatus and transferred to the laboratory for measurement of different traits. Factorial experiment was conducted in a completely randomized design. The results showed that the levels of oxidative enzymes including superoxide dismutase, guaiacol peroxidase and catalase were significantly affected by cultivar, texture and temperature changes. Also, with decrease in temperature, the ion leakage rate, proline, protein, hydrogen peroxide, membrane lipid and carbohydrate peroxidation increased and these values were generally higher in Queen Elisa cultivar than in Selva. Increasing levels of these factors were more evident in the process of lowering temperature in the crown tissue. The leaf relative water content also decreased with decreasing temperature, which overall confirms the tolerance to cold Queen Elisa cultivar.

In order to investigate the effects of foliar application of calcium (Ca), potassium (K) and Volck oil separately or in combination on budburst and cold tolerance related physiological indices in Bidaneh-Sefid grapevine, a randomized complete block design with four replications was conducted in 2017 in a commercial vineyard located in Abasobad of Khondab town of Markazi province. The treatments included control, Volck oil, Volck oil + Ca, Volck oil + K, K, Ca, Ca + K and Volck oil + Ca + K. the vines sprayed with Volck (1%) of calcium (2%) and potassium (3%) in two stages in mid April at the wooly stage and one week later. The traits included days to budburst, ion leakage, peroxidation of membrane lipids, chlorophyll a and b, relative water content, soluble carbohydrates, proline, soluble proteins and phenol. The combined treatment of Volch + Ca + K resulted in 5 day retardant in budburst compared to control vines. The highest concentrations of carbohydrate, phenol and protein were obtained with Ca + K combined treatment, and the lowest ones were observed in both control and Volck oil- treated vines. The highest amounts of chlorophyll a, b, carotenoids and total chlorophyll were obtained from Ca and K treatment and the lowest was observed in Volck oil treatment. The highest concentrations of proline, carbohydrate, and soluble protein were related to Ca + K treatment, and the lowest ones were obtained for control treatment. The highest relative water content, ion leakage and membrane lipid peroxidation were detected in control vines. Therefore, in order to avoid late spring frost in vineyards, the combination of Volck oil + Ca + K was found to be appropriate in vineyards.

High light (HL) can limit plant photosynthetic activity, growth and productivity. The HL effect was more pronounced in plants grown at low temperature. In order to determine the effects of chilling stress (4 0C) and light intensities (450 and 850 µmol m-2 s-1) on antioxidant defense system and  phenolic metabolism of Aloe vera L., an experiment was  conducted in a randomized complete block design with four replications in a research greenhouse. The results indicated that the Aloe vera has a stronger HL tolerance. Increased tolerance in HL-treated plants was related to screening of photoradiation by phenolic compounds (but not the mechanism of ROS scavenging). Although total phenolics and flavonoids concentration as well as phenylalanine ammonia-lyase (PAL) and catalase (CAT) activity responded positively to the chilling treatment, but cold stress considerably increased the rise in malondialdehyde (MDA) content (as a marker of lipid peroxidation), suggesting that Aloe vera is sensitive to chilling treatment. Additionally, chilling raised free radical scavenging activities of Aloe vera leaf gel using DPPH radical-scavenging because of an enhancement of total phenolic, and may be recommended for increasing leaf gel quality.

High light damages photosynthetic machinery, primarily photosystem II (PSII), and causes photoinhibition that can limit plant photosynthetic activity, growth and productivity. To address this issue, we investigated the basic photoprotection mechanisms including ROS scavenging activity and phenolic compounds production in wheat (Triticum aestivum L.), as a C3 plant, after treatment with low temperature (4°C) and high irradiance (450 and 850 μmol m-2 s-1). Results indicated that wheat plants showed more tolerance to low temperature. Increased tolerance in cold-treated plants was achieved through enhancement in antioxidant system activity. Plants treated with light intensity at 850 μmol m-2 s-1 showed the highest level of stress leading to lower maximal quantum yield of photosystem II (PSII) (Fv/Fm) values. In contrast, the light intensity at 450 μmol m-2 s-1 did not reduce significantly the maximal quantum yield of PSII. This may be attributed to the enhancement of catalase (CAT) activity and anthocyanin synthesis (screening of photoradiation in epidermis cells), and consequently further protection of PSII from photodamage.

In order to assessment of the relation among low temperature with (Fv/Fm, leaf chloropyll and caratenoied contents) of clover spp, an experiment was arranged as split plot in RCBD with four replications include plant date as main plot ( 15 and 29 Sep.) and clover spp as sub plot ( Persian spp with 7 cultivars, Berseem , Red and Crimson clover with 1 cultivar) at Seed and Plant Improvement Institute of Karaj in during 2010-2011. The measurement of physiological traits in clover spp recorded at rosset growth stage in days with temperature under zero centigrad. The results showed that low temperature stress cuased significant decrease clover spp that the decrease rate could be because of low temperature stress at field. At among clover spp, Red clover cv. Nassim had the least less chlorophyll content. The results also showed that chlorophyll (a) is more affected to low temperature than (a/b), (a/b) and (b). During stress ( S1, S2 and S3), Fv/Fm of clover cultivars was 0.734, 0.788 and 0.555 respectively, that represent the effect low temperature stress to Fv/Fm in all treatments especially S3. In addition, the results showed that in low temperature stress, Red clover cv Nassim had less yield Fv/Fm than to other cultivars. In general the using of Fv/Fm, chloropyll content and caratenoied leaf parameters is recommended for screening and evaluating of clover cultivars in under low temperature stress conditions at fields.

In order to evaluate the physiological and morphological traits and Photochemical efficiency of photosystem II of Salvia leriifolia under freezing stress in controlled condition, an experiment was carried out as a factorial experiment based on completely randomized design with three replications in Ferdowsi University of Mashhad. The plants exposed to twelve freezing temperatures (0, -2, -4, -6, -8,-10, -12, -14, -16, -18, -20 and -22˚C) in seedling stage. Leaf area and dry weight, root length and dry weight, Electrolyte Leakage (EL), survival percentage after three weeks and chlorophyll fluorescence parameters in recovery periods (0, 6, 12, 24 and 72 hr. after stress) were studied. Results showed that effect of freezing temperatures on all traits were significant (P≤ 0.001). EL increased significantly with decreasing temperature and reached to maximum 83% at -20 ˚C. Although plant survival percentage did not affect until -14 ˚C, all seedlings were died in -220C. Lethal temperature based on survival (LT50su) and electrolyte leakage (LT50el) were -17.0 and -11.8. Results also indicated that Reduced Dry Matter Temperature 50% (RDMT50) was -16.5 °C. Photochemical efficiency of photosystem II (F′v /F′m) was not affected up to -6˚C, but it decreased by 70% with decreasing temperature to -22 ˚C. F′v /F′m decreased by 40% during 24 hours after recovery compared to control, but it increased when recovery continued to 72 hr. Results also indicated that EL had negative correlation with survival percent (r= -0.82***) and F′v /F′m (-0.95***).

Tea was planted in Lahijan by Kashefalsataneh in 1930. The main concern about important commercial plants such as tea is the formation of ice crystals in low temperatures. This can damage the live cells leading to lowering the quality of the plant and eventually its death. Formation of reactive oxygen species (ROS) and oxidative stress is the result of various environmental stresses leading to freezing. Investigating the variations in any of these factors could help to understand the mechanism of freeze resistance in ever-green plants. The aim of the present research was to investigate lipid peroxidation, the presence of antifreeze protein and variations in the activity of some antioxidant enzymes, including superoxide dismutase (SOD), ascorbate peroxidize (APX) and catalyse (CAT) in tea leaves subjected to 20, 0, -2, -5 and -8°C in tea leaves from the north of Iran. The results showed formation of an antifreeze protein with MW of about 20 KD in response to cold stress. It was also found that the activity of SOD, APX and CAT increased in tea leaves due to cold stress. The activity of SOD increased down to -8°C. APX and CAT increased their activity down to -5°C. On the other hand, the lipid per oxidation factor, MDA, was also elevated in response to the cold stress.

In order to evaluate the effects of both cold and light stresses on chlorophyll fluorescence and feasibility of using chlorophyll florescence technique to evaluate effect of light intensity on cold tolerance in soybean، an experiment was done in a factorial arrangement based on a completely randomized design with three replicates. Two soybean cultivars consisted of 032 and BP grown under greenhouse conditions. After three weeks، plants were kept in either 5 or 28 °C and either 2000 or 8000 lux of light intensity then chlorophyll fluorescence parameters was measured. Results showed that cold stress in both light intensities significantly decreased variable fluorescence (Fv)، maximum photochemical quantum yield of photosystem II (Fv/Fm) and effective photochemical quantum yield of photosystem II [Y (II)] while increased quantum yield of regulated non-photochemical [Y (NPQ)]، quantum yield of non-regulated non-photochemical [Y (NO)] and non-photochemical quenching (NPQ). These parameters، however، generally more changed in 8000 than in 2000 lux. Under cold stress، reducing in Fv/Fm and increasing in NPQ was greater in 032 than BP cultivar. Also، in 032 cultivar، greater ratio of reduced Y (II) replaced by Y (NPQ) to avoid greater increase in Y (NO). Cold stress in two light intensities (2000 and 8000 lux) could damage to photochemical and photosynthetic systems in soybean plants، however، damage rate increased when light intensity increased from 2000 to 8000 lux. In cold stress conditions، cultivar 032 showed more tolerance than BP since it could dissipate more excessive energy through non-photochemical quenching and xanthophylls. Therefore، 032 cultivar showed more tolerance to cold stress and could be recommended particularly for regions with cold temperature along with higher light intensity.

The paclobutrazol is one of plant growth regulators from triazoles group that is able to protect plants against environmental stress conditions. This experiment was carried out to investigate paclobutrazol (0، 25 and 50 mg/L) effects on reduction of injuries caused by low temperature (5±1ºC) stress in two cultivars of Phaseolus vulgaris [Daneshkadeh cv. (white bean) and Sayyad cv. (red bean)]. The results showed that low temperature stress، reduced fresh weight and dry matter and also reduced length of shoots and roots and leaf chlorophyll contents but increased electrolyte leakage percentage. Paclobutrazol treatment reduced fresh weight and dry matter and length of shoots but increased root dry weight and root development. Moreover، paclobutrazol-treated plants، when exposed to the cold stress condition، showed electrolyte leakage percentage less than control plants. Treatment of seedlings with paclobutrazol led to an increase in chlorophyll contents، either in stress or non stress conditions. White bean was more sensitive to cold than red bean and paclobutrazol affected white bean more than red bean. Therefore، it could be concluded that paclobutrazol treatment improved ability of plant responses to the cold stress and this effect was more remarkable in cold sensitive cultivars.

The rape (Brassica napus) is an economically valuable plant shose tolerance to stresses has always drown concern. It is well known that، the cold (0-20 °C) and freezing (<0 °C) stresses can influence growth and productivity of the farm plants and the degree of impressionability is dependent on the type of stresses، genetics of the plants and the resistance mechanisms. In this investigation، the varieties of SLMO46 and Quantum were evaluated as resistant and sensitive varieties، respectively، against low temperature stresses. One of the effective factors in plant resistance to the stresses is quantity of the ascorbate peroxidase (APX) and the metallothionein (MTL) in the plant tissues. The ascorbate peroxidase activity in the SLMO46 tissues was more than Quantum and the activity was increased about two times during the cold stress. Quantitave analysis of Apx2 and Mtl genes expression according to 2-ΔΔCt showed that the quantities were 2. 1 and 9. 1 in the SLMO46 and 1. 8 and 5. 2 in the Quantum، respectively. The data indicated that under normal condition، the enzyme activity in the resistant plants was more than the sensitive one and the stress can induce about 60% increment in the enzyme activity.