Mohammadsadegh Sadeghi; Seyyed Jalal Tabatabaie; Hassan Bayat
Abstract
Introduction: Spinach is a leafy vegetable which is rich source of vitamins, antioxidant compounds (e.g. flavonoids, acid ascorbic) and essential elements (e.g. Fe, and Se). Spinach is capable of accumulating large amounts of nitrogen in the form of nitrate in shoot tissues which is undesirablein the ...
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Introduction: Spinach is a leafy vegetable which is rich source of vitamins, antioxidant compounds (e.g. flavonoids, acid ascorbic) and essential elements (e.g. Fe, and Se). Spinach is capable of accumulating large amounts of nitrogen in the form of nitrate in shoot tissues which is undesirablein the human diet. The concentration of nitrate in plants is affected by species, fertilizer use, and growing conditions. Green leafy vegetables such as spinach, generally contain higher levels of nitrate than other foods. Nitrate ofplant tissueslevels are clearly related to both form and concentration of N fertilizers applied. Nitrogen fertilizers have been known as the major factors that influence nitrate content in vegetables. Ideally, the N fertility level must be managed to produce optimum crop yield without leading to excessive accumulation of nitrate in the harvested tissues.Usinghigh amounts ofN fertilizer produced higher yield with higher nitrate inleaves but the highest amount of nitrate was accumulated in the petioles.There are several plant species that may accumulate nitrate, including the Brassica plants, green cereal grains (barley, wheat, rye and maize), sorghum and Sudan grasses, corn, beets, rape, docks, sweet clover and nightshades. The presence of nitrate in vegetables, as in water and generally in other foods, is a serious threat to man’s health. Nitrate is relatively non-toxic, but approximately 5% of all ingested nitrate is converted in saliva and the gastrointestinal tract to the more toxic nitrite. This study was aimed to investigate theeffects of nitrogen and nutrient removal on nitrate accumulation and growth characteristics of spinach (Spinacia oleraceae L.).
Materials and Methods: A pot hydroponic experiment was carried out to evaluate the effect of different levels of nitrogen and nutrient removal (one week before harvest) on nitrate accumulation and growth characters. A factorial experiment based on completely randomized design was conducted with twolevels of removal (removal of nutrient one week before harvest) or not to remove and fourlevels of nitrogen (25, 50, 100 and 200 mg/l) with sixreplications. During the growing season in the greenhouse, temperature was fixed between 24-27 °C and photoperiod of 16 hours of light and 8 hours of darkness. The measured traits were root fresh and dry weight, shoot fresh and dry weight, Fv/Fm ratio, and chlorophyll index, number of leaf per plant, leaf area, nitrate and total nitrogen.
Results and Discussion: The results of this experiment showed that increasingnitrogen concentration from 25 to 200 mg/l increased shoot dry weight, number of leaves and leaf area, by 22.00, 7.26, 4.79 and 14.00 fold, respectively. Nitrogen also increased Fv/Fm and chlorophyll index. Nutrient removal in a week before harvest had no significant effect on fresh and dry weight of shoots and roots, number of leaves,leaf area, chlorophyll index and Fv/Fm. Increasing concentrations of nitrogen increased nitrate and total nitrogen in petiole while removing the nutrient solution in a week before harvest significantly decreased amounts of the above-mentioned traits. Nutrient solution removal is an appropriate strategy to reduce nitrate accumulation in spinach that has no effect on yield loss.
Conclusions: The results showed that increasing the concentration of nitrogen increased plant growth indicators such as shoot fresh and dry weight, root fresh and dry weight, leaf area and number of leaf per plants, so that the greatest increase was obtained from concentration of 200 mg/lit. Increasing the concentration of nitrogen enhanced nitrate and total nitrogen of petiole so that the highest concentration of nitrate and total nitrogen was observed in200 mg/lit nitrogen. Nutrient solution removal in a week before the harvest had a significant effect in reducing all traits but it decreased nitrate accumulation and total nitrogen of petiole significantly. At the end of the experiment, it was found that increasing the concentration of nitrogen increased nitrate concentrations and total nitrogen in the petioles while nutrient removal in a week before harvest reducedthe amount of leaf nitrate. Thereforethe removal ofnutrient solution is one of the strategies to reduce nitrate accumulation that had no effect on yield loss of crop. Based on the results from this research, nitrogen at a concentration of 200 mg/lit, with the removal of nutrient solution a week before harvest is recommended for growing in hydroponic culture of spinach.
Rozita Khademi Astaneh; Seyyed Jalal Tabatabaie; Sahebali Bolandnazar
Abstract
Introduction: Selenium is a non-metallic, rare chemical element and essential for many organisms but this element is not mentioned as an essential element for plants. Due to its presence in antioxidant defense systems and hormonal balance, selenium is known to be necessary in human and animal health ...
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Introduction: Selenium is a non-metallic, rare chemical element and essential for many organisms but this element is not mentioned as an essential element for plants. Due to its presence in antioxidant defense systems and hormonal balance, selenium is known to be necessary in human and animal health Plants exhibit a variety of physiological responses to selenium.Some species accumulate large amount of selenium, while many plant species are sensitive to presence of large amounts of selenium in soil and water. The mean, the maximum and tolerance level of selenium required for humans is 45, 55 and 400 micrograms, respectively (Dietary Reference). but acute toxicity level in animals are found with a concentration of 1000 ppm. Plants absorb and storage selenium in chemical form and concentration depends on pH, salinity and calcium carbonate content. High contents of selenium reduce plant growth and plant dryness, however in some plants low selenium concentrations improved growth and increase stress resistance by maintenance of chloroplast enzymes. Positive response to the use of selenium were mentioned in lettuce, potato, mustard, crap, darnel, soybean (Glycinemax L), potatoes and green tea leaves. Research has shown that there is a positive relationship between selenium concentration and glutathione peroxidase activity, which is a reason to delay aging and increase growth of aging plants. The results of this study had shown that the application of selenium treatments increased leaf area of plants and, consequently, the higher availability of asmilates, can increase plant growth. The results of the studies also indicated that all vegetative characteristics of plants are increased due to the concentration of selenium and the accumulation capacity of plants affected by selenium application. Since there is no research on the effect of selenium on cabbage, it seems that the use of this element can affect the growth and development of this plant.
Materials and Methods: This experiment was tested in a controlled condition hydroponic greenhouse of Horticulture Department, College of Agriculture, University of Tabriz, The greenhouse was covered with polyethylene monolayer and equipped with a cooling and fogging systems to control the temperature in the warm months and humidity, respectively. Daily temperatures were setted3 ± 20 3 ± 16. Seeds of Gemmifera varieties brussels cabbage weregerminated in petri dishes. Seedlings were transferred to the plastic cups (to the floating system) with perlite in four leaf stage. . Plants root system were floated in solution. Modified Hoagland nutrient solution (Table 1) was prepared (12 liters per container with 40 and 32 cm height and diameter, respectively.
Results and Discussion: Results of vegetative Brussels sprouts button showed that selenium significantly increased leaf, stem and root dry weight, leaf number and leaf area. Leaf area, leaves, stems and roots fresh and dry weight increased with increasing selenium up to 8 mg L- but then decreased due to a high concentration of selenium toxicity. There were no significant difference in the treatments on stem length, stem diameter. Number of buds was significantly (P≤0.05) affected by selenium treatments and the highest number of sprouts were in two levels of 8 and 16 mg selenium per liter, respectively. Yield and shoot dry weight showed a significant increase (at 1 percent) with increasing levels of selenium,.Conclusions Plants yield significantly (P≤0.01) affected by selenium treatments, so that selenium concentration in the nutrient solution increased from 0 to 8 mg L-1increased yield and reduced afterward. The maximum yield was observed at a concentration of 8 mg L-compared with control. Based on the findings of this study, selenium concentration can be up to 8 mg L-1 in order to improve plant growth to nutrient solution.
Mohammad Hassan Bagheri; Hamid Reza Roosta
Abstract
In this study the effect of nitrogen form and different oxygen levels on growth and development and macronutrients concentrations in lettuce plants was investigated. This investigation showed that sole ammonium application caused fresh and dry weight reduction of shoot and root in lettuce plant. But ...
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In this study the effect of nitrogen form and different oxygen levels on growth and development and macronutrients concentrations in lettuce plants was investigated. This investigation showed that sole ammonium application caused fresh and dry weight reduction of shoot and root in lettuce plant. But different oxygen levels had no effect on them. Nitrogen concentration of shoot was higher in ammonium treatments compared to nitrate treatment and with increasing of oxygen levels in the presence of ammonium, nitrogen content also increased, although it was not the same in nitrate treatment. Phosphorous concentrations in shoot and root were not affected by any of treatments and their interaction. Ammonium also caused reduction of potassium concentration in shoots, but different oxygen levels and its interaction with nitrogen form had no significant effect on it. Magnesium content of shoot also decreased in the presence of ammonium, although it was not the same in root. With increase of dissolved oxygen level, magnesium content of shoot decreased in ammonium treatment, but in nitrate treatment the concentration of this element was not affected by oxygen levels. It is concluded that probably reduction of potassium and magnesium in ammonium-fed plants has a role in plant growth reduction, and it was also observed that in spite of increase in the concentration of shoot nitrogen and root magnesium with increase of dissolved oxygen level in ammonium treated plants, lettuce growth was not affected by oxygen levels.
Mahbobeh Rajabi; Hamid Reza Roosta; Hamid Reza Karimi; Hossein Hokmabadi
Abstract
Considering to high lime in pistachio orchards of Iran, choosing of tolerant rootstock and cultivars to high pH is important. In order to investigate the effect of sodium bicarbonate on pistachio rootstocks factorial trail with two factors of sodium bicarbonate at 3 levels (0, 50 and 100 mM) and pistachio ...
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Considering to high lime in pistachio orchards of Iran, choosing of tolerant rootstock and cultivars to high pH is important. In order to investigate the effect of sodium bicarbonate on pistachio rootstocks factorial trail with two factors of sodium bicarbonate at 3 levels (0, 50 and 100 mM) and pistachio rootstocks at 4 levels (Atlantica, Sarakhs, Badami-e-Riz Zarand and Qazvini) carried out in hydroponic system. Bicarbonate caused growth reduction in all rootstocks. As the highest reduction in plant fresh weight was observed in Atlantica (70.39%) and Srakhs (51.92%) at 100 mM, and the lowest reduction in Qazvini (31.54%) rootstock. Sodium bicarbonate treatments at 50 and 100 mM caused RWC reduction, proline increase and Cu and Mn reduction in shoots and roots. So that, the highest reduction of Mn and Cu concentrations was observed in Atlantica and the lowest reduction in Qazvini (31.54%) rootstock. The results of this study showed that Qazvini is a tolerant rootstock to sodium bicarbonate, Sarakhs and Badami semi-tolerant and Atlantica sensitive rootstocks.
