جستجوی مقالات مرتبط با کلیدواژه « تریازول ها » در نشریات گروه « زراعت »

To study the different irrigation treatments on agronomic characteristics of soybean with and without use of triazoles and calcium silicate, an experiment was conducted as split-plot factorial in a randomized complete block design with three replications at the Research Field of Faculty of Agriculture, Tarbiat Modares University. The results showed that three-way interaction among experimental factors significantly influenced all traits, except plant height. Under non-stressed conditions for L17 and under moderate stress for Williams, hexaconazole spraying caused maximum and minimum protein yield with more than fourflods differences between them. Calcium silicate spraying on Williams under non- and moderate- stressed conditions, with 0.23 difference, showed most and least values of harvest index, respectively. Biological and seed yield under stress conditions decreased 9519 and 3328 kg/ha, respectively. According to the findings of these research, water deficit stress can cause reductions in values for quantitative traits and yield components of soybean, and under stress conditions, spraying admendatory materials can mitigate the harm of stress and increase the crop tolerance. Considering different response of soybean cultivars tested in terms of oil yield to spraying under varios conditions, it can be noted that penconazole and calcium silicate spraying on Williams under non-stressed conditions, and penconazole and hexaconazole spraying on L17 under moderate- and severe stressed conditions, exhibited higher efficiency in increasing oil yield.

Cold and freezing are the most important limiting factors on development of sensitive plants. When the ambient temperature deviates from optimal, physiological, and biochemical, metabolic and molecular changes will occur within plants. This is an effort of plants to maximize growth and developmental processes and to maintain cellular homeostasis during such adverse conditions. At the extremes of the natural temperature range of plant, the degree of physiological, cellular, metabolic and molecular dysfunction becomes so severe that it leads to death. Triazoles are the most potent groups of growth retardants with multiple effects. Plant growing with paclobutrazol generally has little effect on rates of net photosynthetic rate. However, because the compound reduces leaf area, net photosynthesis on a per plant basis is probably reduced. They have exhibited growth regulating, fungicidal, herbicidal, apicidal and antibacterial activities. More recently, it was found that triazole compounds are able to increase tolerance of plants to cold and freezing stress. Kochia (Kochia scoparia (L.) Schrad.), an out crossing species whose pollen move between plants in windy areas, has recently been considered as a forage or fodder crop in marginal lands. Steppuhn and Wall (1993) claimed that Kochia offers great potential as a crop that can be grown on saline soils, yielding fodder in quantities approaching that produced by alfalfa (Medicago sativa L.). Shamsutdinov et al. (1996) also reported more than 15 Mg ha-1 dry-matter production for Kochia under saline conditions and concluded that it is a good candidate for forage hay. Thus, the aim of the present study was to determine whether the triazole compounds could increase tolerance of kochia against freezing stress.
An experiment was carried out with hexaconazole and penconazole in 0, 10 and 20 mg.L-1 and freezing temperatures 0, -2, -4, -6 and -8 degree centigrade in factorial based on CRBD with three replications at research greenhouse of college of agriculture, Ferdowsi University of Mashhad in 2009. Plants were kept in natural condition until three weeks after planting, which in this stage they had three leaves, and then treated with fungicide. After 24 hours plants were frozen in thermo gradient freezer, in the dark. At first, the temperature of thermo gradient freezer was five degrees centigrade, and then temperature decreased two degree centigrade per hour. In order to make ice nucleation in plant at -3-degree centigrade ice nucleation active bacteria was sprayed. Plants were keeping an hour in each temperature treatment. In order to balance the ambient temperature, the plants are kept at the desired temperature for one hour and then the pots transport in a cold chamber at a temperature of 5 ± 2°C for 24 hours. The cell membrane stability was measured through electrolyte leakage (EL) and the lethal temperature 50 (LT50el) (according to El) also were determined in the youngest developed leaf from each plant. The electrolyte leakage in the solution was measured after 24 h of floating at room temperature using a conductivity meter. Total conductivity was obtained after keeping the flasks in an oven (75°C) for 90 minutes. Results were expressed as percentage of total conductivity. Survival percentage, plant height, dry weight and (LT50su) (according to survival) were determined after three weeks recovery in the natural condition. The data were analyzed statistically using a two-way ANOVA, applied to the various measured and calculated parameters, followed by a Duncan test for mean comparison between treatments at a 95 % confidence level by MSTAT-C program.
The results showed that increase of fungicide concentration by 10 and 20 mg.L-1 higher than control decreased electrolyte leakage but, electrolyte leakage build-up with decrease freezing temperature. Fungicide application increased -2 °C freezing tolerance in kochia. Increasing fungicide concentration in 10 and 20 mg.L-1 than control causes decreased LT50el from -5.9 to -7.2. Application of triazoles responsible of reduced electrolyte leakage but they did not effect on survival. The use of different concentrations of fungicides hexaconazole and penconazole of photosynthetic pigments in Kochia showed no significant effect. However, the concentration of chlorophyll a and b in the use of fungicides hexaconazole was more than penconazole.
Triazole application initially had a positive effect on the reduction of electrolyte leakage, but survival and re-growth did not affect. Generally, the use of Triazoles compounds prior to stresses such as cold, could expect the plants can tolerate oxidative stress, which usually occurs after cold stress.

Applications of chemical substances such as triazoles can alleviate the environmental stresses like cold stress. Therefore, a factorial experimental based on completely randomized design was conducted. Different concentrations of paclobutrazol (0, 10, 20 mg per liter) were applied on seedling roots environment before freezing stress and after that plants were exposed to freezing temperatures (0, -3, -6, -9, -12 and -16°C) under controlled conditions. Before applying freezing temperatures, soluble sugar, proline, total phenol, photosynthetic pigments and DPPH radical scavenging activity were measured. Following exposure to freezing temperatures, cell membrane stability and a temperature lethal to 50% of samples based on electrolyte leakage (LT50el) were determined. Survival and regrowth of plants were determined at three weeks after seedlings recovery under natural conditions. Results showed that the electrolyte leakage remained constant where the temperature was reduced to -9°C, and reducing the temperature to -12° C caused a sharp increase in electrolyte leakage. Moreover, plants survival was not influenced up to -9 ° C, but reducing the temperature to -12°C caused a significant reduction in plant survival. Paclobutrazol application increased chlorophyll a, b, DPPH radical scavenging activity and survival in kochia, whereas decreased proline, soluble carbohydrates, total phenol concentration and electrolyte leakage. Influence of Interaction between temperature and population on total pigments indicated an increase in pigment content in Broojerd population at 20 milligrams per liter of paclobutrazol, and proline and carbohydrates contents were significantly greater in Sabzevar population where no paclobutrazol was applied. Generally, application of 10 and 20 milligrams per liter of paclobutrazol prevented a severe reduction of kochia plants survival under freezing stress.