فهرست مطالب shahrzad karami

Spirulinacyanobacterium (Arthrospira platensis) has a vast range of nutritional organic and inorganic substances and can be used as new material for organic cultivation of plants. In order to evaluate the effect of non-living powder of Spirulinacyanobacterium on spinach (Spinasia olerace L.) yield and nutrient uptake and comparing the results with some organic and chemical fertilizers, a greenhouse experiment was carried out in a completely randomized design with three replications. Treatments including of control, four non-living spirulina levels (500, 1000, 2500, 5000 mg kg-1), vermicompost (10000 mg kg-1), cattle manure and sheep manure (20000 mg kg-1), chemical fertilizers: (1) 80 mg N kg-1 and 10 mg P kg-1, (2): 150 mg N kg-1 and 20 mg P kg-1 as urea and monocalcium phosphate, respectively. Results showed that the highest and lowest dry weights were obtained in 500 mg non-living Spirulina kg-1 and sheep manure respectively. The total content of nitrogen (N), phosphorus (P), potassium (K), zinc (Zn), iron (Fe), manganese (Mn) and copper (Cu) in spinach was significantly increased with application of 500 mg non-living Spirulina kg-1as compared to control. Application of higher levels of cyanobacterium (more than 1000 mg kg-1 soil) had not significantly effect on spinach yield and some nutrient uptake. Results showed that the effect of fertilizers on some studied characteristics such as dry weight, N, P, K and micronutrient uptake was as following order: Spirulina cyanobacterium > cattle manure> vermicompost> chemical fertilizer (N and P)> control= sheep manure.

Cadmium is one of the most important heavy metals in soil that it is important in terms of environmental and human health. The main purpose of this study was to evaluate the effect of Spirulina algae and incubation time on chemical forms of cadmium in a calcareous soil. The experiment was conducted in a factorial (2 × 3 × 3) arranged in a completely randomized design with three replications. Treatments consisted of three Spirulina levels (0, 500 and 1000 mg kg-1 soil), cadmium levels (5, 20 and 40 mg kg-1 soil as cadmium sulfate (CaSO4.6H2O) and incubation times (1 and 2 months). Results showed that addition of 500 and 1000 mg Spirulina kg-1 soil in all of the cadmium levels in the first month decreased exchangeable fraction and increased the organic and carbonate fraction and cadmium that bound to iron and manganese oxides. Over the incubation time (in the second month), due to decomposition of algae, the organic fraction of cadmium decreased and soluble fraction of cadmium increased. In general, at first application of Spirulina decrease the bioavailability of metals and increase the organic and less soluble fraction of them, but over the time, it can increase the bioavailability of metal and therefore might be increase the uptake of Cd for plants. Therefore before application of Spirulina as an organic fertilizer, in cadmium polluted soils, it should be applied with caution. Further investigation using Spirulina at more incubation time and on a larger number of soils is recommended.

Heavy metals such as cadmium (Cd) are found naturally in soils, but their amount can be changed by human activities. The study of the uptake and accumulation of heavy metals by plants is done in order to prevent their threats on human and animal’s health.Cadmium is a toxic element for living organisms. Cadmium competes with many of nutrients to be absorbed by the plant and interferes with their biological roles. Water stress affects the cell structure and the food is diverted from its normal metabolic pathway. It also reduces the availability and uptake of nutrients by the plant. One reason for the reduction of plant growth under drought stress is the accumulation of ethylene in plants. There are ways to mitigate the negative effects of drought stress that one of which is the use of Plant Growth Promoting Rhizobacteria(PGPRs) to increasing the availability of nutrients. Soil beneficial bacteria play an important role in the biological cycles and have been used to increase plant health and soil fertility over the past few decades.The aim of this study was to investigate theeffect of PGPRson the concentration and uptake of macro nutrients by corn in a Cd-contaminated calcareous soil under drought stress.
A greenhouse factorial experiment was conducted in a completely randomized design with three replications. The treatments were two levels of bacteria (with and without bacteria), four levels of Cd (5, 10, 20, and 40 mg kg-1), and three levels of drought stress (without stress, 80, and 65% of field capacity). The pots were filled with 3 kg of treated soil. Cd was treated as its sulfate salt in amounts of 5, 10, 20, and 40 mg kg-1. The soil was mixed uniformly with 150 mg N kg-1 as urea, 20 mg P kg-1 as Ca (H2PO4)2, 5 mg Fe kg-1 as Fe-EDDHA and 10, 10 and 2.5 mg Zn, Mn and Cu kg-1, respectively as their sulfate salt in order to meet plant needs for these nutrients. Six seeds of Zea mays (var. HIDO) were planted at each pot. Each seed of maize was inoculated with 2 mL (1×108 colony-forming units (cfu) mL-1) of Micrococcus yunnanensis (a gram positive bacterium with the ability of production of sidrophore and phosphate dissolving characteristic). Each pot was irrigated daily with distilled water to near field capacity by weight, until 15 days after corn planting. Then corn was thinned to 3 plants per pot and irrigation was started with different levels of drought stress (without stress (F.C), 80, and 65% of field capacity) by weight. At harvest (8 weeks after planting), the aerial parts of the plants was cut at the soil surface. The harvested plants were washed with distilled water, dried to a constant weight at 65C. Representative samples were dry-ashed and analyzed for macro nutrients.
The results indicated that the inoculation of bacteria increased shoot dry weight (DW) and total uptake of nitrogen (N), phosphorus (P), and potassium (K). Drought stress decreased DW, total uptake of N, P, and K, concentrations of N and K in corn shoots, and concentration of K in the soil. The application of biological fertilizers, such as plant growth promoting rhizobacteria, increase plant growth through increasing microorganism’s activities and population in the soil and so increase macro nutrients uptake by the plant. Phosphate solubilizing rhizobacteria increase plant growth and phosphate availability with production of organic acids and secretion of phosphatase enzymes or protons and conversion of non-soluble phosphates (either organic or inorganic phosphates) to the forms that are more available for the plants and improve their nutrition and increase their growth. Drought stress decreases Dry Matter Weight(DMW) through decreasing relative humidity of the air of plant growth environment and increases evaporation, transpiration, plant temperature and light intensity of the sun. It prevents normal development of roots, water uptake, and plant growth by reducing the moisture content of the soil. It also decreases uptake and availability of Phosphorus in arid soils because plant growth and root activity in arid soils are lower from those of wetlands and as phosphorus is immobile in the soil, its uptake by the plant will decrease. N concentration of plants will increase drought stress conditions through rapid accumulation of amino acids that had not been converted into protein. The combined effects of drought stress and inoculation of bacteria on decomposition of silicates, cause the release of nutrients such as potassium. Increasing levels of cadmium in both cases, with and without bacterial inoculation, decreased DW, N and K uptake by corn because of its toxicity and its competition and interactions with these nutrients.
The inoculation of bacteria mitigated the negative effects of drought stress and cadmium contamination by increasing dry weight of corn and increasing uptake of macronutrients by aerial parts. Drought stress in both cases (with and without bacterial inoculation) reduced shoot dry weight, total uptake of macro nutrients, N and K concentrations in corn shoots and post-harvest potassium concentration in the soil. Cadmium levels decreased shoot dry matter and N and K uptake by the plant. The use of bacteria was more effective at low cadmium and drought stress levels.