جستجوی مقالات مرتبط با کلیدواژه « drought » در نشریات گروه « گیاهپزشکی »

The control of rice striped stem borer in paddy fields requires the use of all components of integrated pest management. The implementation of these methods is effective if the rice field is in natural conditions in terms of water resources, but in case of drought stress, which one of the methods will be more effective for pest control? In order to answer this question, the present research was carried out in the Rice Research Institute of Iran (Rasht) in 2019 and 2020. In this research, different irrigation methods as the main factor include permanent flooding (every day) and irrigation with intervals of 5, 10 and 15 days and the secondary factor is different control methods including granule application with G10% diazinon insecticide, spraying with fipronil SC5% insecticide, biological control (release of Trichogramma wasp + use of commercial formulation of Bacillus thuringiensis subsp. kurstaki), a combination of methods (chemical control and biological control) and control (only water spraying) were used. The results of this research showed that the least damage by the rice striped stem pest in the vegetative and reproductive stages of rice plants was in the daily and five-day irrigation treatments with the combined use of methods as well as the granule spraying method in the experimental field. Also, the results of the investigations during the two years of the experiment showed that the highest yield was related to irrigation every day and five days, related to two methods, a combination of methods and a granulation method. In 10- and 15-days’ irrigation, the highest yield was observed in foliar spraying and biological control treatments. Therefore, according to the obtained results, it is recommended to use biological control and foliar spraying with one of the confirmed liquid insecticides to control the rice striped stem borer pest in water stress conditions

Drought stress is one of the main environmental factors affecting the growth and productivity of plants around the world. Periods of severe drought are predicted to increase significantly in the near future, particularly as a result of extreme heat waves. Salinity is also one of the most important challenges facing the food supply for the world's population in the future, and the degree and time of exposure to stress can make this challenge stronger or weaker.Environmental limitations affecting plant growth, development and performance of physiological processes during plant response to stress provide important information about the plant mechanism, which is useful for eliminating or reducing the harmful effects of stress in plant tissues. The negative effects of climate change (such as drought, sea level rise, and global warming), as well as the salinization of agricultural land, and have been cited as one of the most important problems of the World Agriculture Organization (FAO).Understanding the relationship between changes in environmental conditions and climate change and Arundo donax with regard to the growth of coastal native species and also understanding the water wastage by this plant compared to coastal native plants is vital to remove this plant in the current situation where there is drought in most areas.In this situation, it is necessary to know how different environmental factors such as salinity levels, dryness, temperature, nutrients, light and fire affect the growth and invasion of Arundo donax for long-term and large-scale control. The purpose of this research is to obtain valuable information about the growth and development of existing ecotypes of the Arundo donax plant in Iran and the effect of various environmental factors on the germination, growth and fertility of this plant in order to plan for the long-term restoration of river ecosystems and how to control and The fight or its optimal use should be determined.

In order to investigate the effect of drought and salinity treatment on the growth and establishment of the rhizome of Arundo donax, an experiment was conducted in 2021 using rhizomes collected from the ecotype of Gorgan city and factorially in the form of a randomized complete block design in 3 replications in the research farm of Ferdowsi University of Mashhad. The experimental treatments included different levels of drought stress {100%, 75% and 50% of crop capacity} and different levels of salinity stress {0 (distilled water), 4, 8 and 12 dS/m}.

The general results of the experiment showed that the presence of salinity and drought stresses both decrease the growth and development indicators of this plant, and the presence of these two environmental stresses can increase the indicators of biomass of aerial organs, biomass of underground organs, plant height, and stem diameter. The effect of salinity stress on the reduction of the measured indices was less than that of drought stress, so that the difference between the levels of salinity stress at different levels of drought stress in all the measured indices, except the shoot biomass, had insignificant differences with each other, but in the comparison of the effect of drought stress at different levels of the surface together we come to the conclusion that drought stress alone leads to a significant decrease in growth indicators compared to the control treatment. The maximum amount of shoot biomass in non-stress conditions (control) was 2840 (gr), and with the increase of salinity and drought stress levels, this value decreases, so that the lowest amount of biomass in drought stress and maximum salinity conditions was 988 (gr). The biomass of the shoots of Arundo donax increased over time in different levels of salinity and drought stress, and its value was from less than 300 grams at the beginning of the growing season in all stress levels to more than 1000 to 2500 (gr) at the end of the growing season in different stress levels. 

The parameters obtained from the effect of salinity and drought stress on the stem diameter, plant height and leaf surface of Arundo donax showed that this plant showed some resistance under minor drought stress and these indicators decrease less in it, but in severe drought stress this amount decreased sharply. The results of analysis of variance of this experiment also showed that salinity and drought treatment and their interaction led to a significant difference with the control treatment. The simple effect of salinity treatment showed a significant difference in other indices compared to the control treatment, except for the index of leaf area and stem diameter, however, the simple effect of drought treatment showed significance in all the measured indices.

Weeds are among the worst limiting factors of the crop yield potential. I. purpurea belongs to Convolvulaceae family and is an annual broadleaf vine and a problem weed in many annual and perennial crops. This weed is becoming an increasing problem in soybean fields of Mazandaran province, Iran. Seed germination is one of the most important processes for weed success in agricultural ecosystems; because the first step is for a weed to compete in an ecological nich. Understanding the biology and germination pattern and emergence of common weeds in crops is an undeniable necessity in effective weed management systems. This process is regulated by several environmental factors such as light, salinity, pH and soil moisture. Among the factors affecting germination, temperature and light are the most important regulatory environmental factors. Temperature has significant effects on germination characteristics such as onset, rate and rate of germination, therefore it is the most critical factor that determines the success and failure of plant establishment. Salinity and drought are one of the most important environmental stresses that affect germination. Weed phenology is determined by the interaction between plant internal factors and external environmental signals such as temperature, day length and drought; phenological stages and their characteristics are very important for the design and implementation of weed management methods. A better understanding of the germination biology of I. purpurea would facilitate the development of better control strategies for this weed. Also, predict the weed phenological developments are useful research tools for advancing our knowledge of population dynamics or crop and weed competition; in this way, the study of phenology allows accurate estimation of weed competition time and its effect on crop yield. The aim of this study was to investigate the effect of temperature, salinity, and drought and to investigate the phenology of this weed based on the growing degree-day.

 These experiments were conducted in the weed science laboratory of Sari Agricultural Sciences and Natural Resources University. The treatments were carried out in a completely randomized design with four replications. The treatments including constant temperature with 8 levels: 5, 10, 15, 20, 25, 30, 35, and 40 °C; salinity stress in 9 levels of control, 0.92, 1.84, 3.68, 7.36, 14.75, 29.5, 35 and 40 (dS m-1 chloride sodium), drought stress in 6 levels of control, -0.2, -0.4, -0.6, -0.8 and -1 MPa. To study the phenology of I. purpurea, a field experiment was accomplished in a randomized complete block design.

The results showed that I. purpurea seeds started to germinate at 10 °C and the germination percentage increased with increasing temperature. No germination occurred at 40 oC. To determine the cardinal temperatures beta, segmented and dent-like models were used. The dent-like model was the best model to predict the germination rate. Based on the dent-like model outputs, base, lower limit optimum, upper limit optimum and maximum temperatures of I. purpurea seed germination were 7.39, 23.54, 29.54, and 39.54 °C, respectively. Also, the salinity level of 31.33 dS m-1 causes a 50% reduction in germination percentage. In drought stress, the highest germination percentage (100%) was observed in the control treatment and the lowest germination percentage (97.5%) was observed in -0.4 MPa. In general, six phenological stages were recorded, including emergence, stem elongation, budding, flowering, fruiting, and seed maturation. The results showed that the shortest and longest growth stages of this weed in terms of time are emergence and stem elongation, respectively. It was observed that the I. purpurea is a weed that completes its phenological stages in 168 days by achieving 2378.01 growing degree-day. These results revealed that the best time to control of this weed is before the flowering stage.

Seed germination of this weed is in the temperature range of 10 to 35 °C and it seems that this weed germinates better at warmer temperatures. Chemical methods are among the most common methods in controlling weeds and other invasive species in the country, so the spread of these species in addition to direct effects can increase the use of chemical pesticides on farms and double the negative consequences of these species. Therefore, with full knowledge of the different stages of I. purpurea phenology, it is possible to plan for proper management. From a managerial point of view, the best time to use the herbicide is in the 3-4 leaf stage; however, in case of negligence at this stage, they should be checked before bud production so that its seeds do not enter the seed bank; because the seeds of this plant are considered as causes of pollution in the field.

Increasing need for wood and on the other hand declining wood resources have caused desire for afforestation with fast–growing species such as poplars, but poplar species usually are susceptible to drought. Ectomycorrhizal fungi can improve the water status of host plants and increase plant survival and growth under drought conditions. The precise mechanism of this function is still not clear, but amino acid metabolism has been reported to play an important role in plant tolerance to drought stress. In this study seedlings of Populus caspica were propagated through tissue culture and their symbiosis with Pisolithus arhizus was carried out to evaluate the plantlets resistance to drought in acclimatization process. It was found that establishment of this symbiosis enhanced seedling height, biomass of root, shoot and leaves, photosynthesis, transpiration, stomatal conductance and leaf chlorophyll. Determination of amino acids in ectomycorrhizal and non–ectomycorrhizal roots of P. caspica plantlets (in both drought and irrigation conditions) showed that generally, the concentration of most amino acids increased in ectomycorrhizal root systems, which proved amino acids are the most important assimilation and nitrogen transfer forms in ectomycorrhizal tissue. Significant accumulation of many amino acids such as asparagine, glutamine, glutamic acid, histidine, tyrosine, threonine, alanine and methionine in ectomycorrhizal roots under stress conditions (compared to the ectomycorrhizal roots under irrigation and the control roots) was found, thus it can conclude that tolerance of ectomycorrhizal roots to drought stress is closely associated with their accumulation of free amino acids. Arginine, citrulline and aspartic acid accumulated in non–inoculated P. caspica root systems under irrigation conditions (compared to the mycorrhizal root systems), which confirmed the use of these amino acids in some metabolic pathways in the mycorrhizal root systems. Implications of these changes in the functioning of the ectomycorrhizal symbiosis are discussed.

Abiotic stresses are major environmental factors that affect agricultural productivity worldwide. Depending on the crop, the yield losses associated with abiotic stresses can reach 50 to 82 percent. Extreme temperatures, drought, salinity, flooding, freezing, ultraviolet light, heavy metals, nutrient deficiency, unsuitable pH, air pollutants and mechanical damage are the most basic stressors. Because biotic stresses cause metabolic toxicity, membrane degradation, reduction of photosynthesis, decrease of nutrient uptake, changes in levels of phytohormones and ultimately affect the plant growth and its productivity, therefore reducing the effect of these stresses, is essential. Plant growth promoting rhizobacteria play an important role in plant disease management and have a high potential in alleviation the abiotic stresses.