جستجوی مقالات مرتبط با کلیدواژه « Hydroponic » در نشریات گروه « آب و خاک »

One of the most important factors of soilless cultivation systems is the cultivation bed. Plants need adequate water and elements to grow and function well. But today, a mixture of cocopeat and perlite is used in some greenhouses, which gives better results and is suitable for the production of tomatoes outside the season. Currently, cocopeat is the main substrate used in most hydroponic systems for tomato production in the country, which is an expensive imported material. It is important to carry out new researches to investigate the effect of stress and the integration of cultivation media to produce as many black cherry tomatoes as possible. The effect of the type of cultivation medium on different plants is different. The purpose of this research is to investigate the effect of drought stress and the integration of organic and inorganic cultivation medium on the chemical characteristics of several raw materials that can be used as black tomato growing medium.

For this purpose, in order to investigate the possibility of reducing the effects of drought stress by combining cocopeat and perlite, a factorial research was conducted in the form of a completely randomized design with three replications in the research greenhouse of Islamic Azad University, Karaj branch. In this research, two factors of drought stress (Fc100%, Fc50%, Fc25%, Fc12.5%) and different percentages of the cultivation bed (Cocopeat 0% + Perlite 100%, Cocopeat 25% + Perlite 75%, Cocopeat 50% + Perlite 50%, Cocopeat 75% + Perlite 25%, Cocopeat 100% + Perlite 0%) were investigated. The studied traits included the number of fruits, fresh and dry weight of the shoot, root length, relative moisture content of the leaves, the amount of chlorophyll a and b, and total.

Based on the results of the treatment combinations, cocopeat 75-perlite 25 and cocopeat 100- zero perlite had the highest performance, especially under severe stress of dehydration, and the lowest efficiency in the treatment combinations Co0Pe100+FC12.5%, Co25Pe75+FC12.5%, and Co50Pe50+FC12. 5% and Co100Pe0+FC12.5% were obtained. Also, FC100% treatment with the highest amount of total chlorophyll (3.10 mg per gram of fresh tissue) in the statistically superior group and FC12.5% treatment with the lowest amount of total chlorophyll (2.22 mg per gram of fresh tissue) were included in the weakest statistical group. In other words, maintaining soil moisture at the level of agricultural capacity increased the amount of total chlorophyll by 39.63% compared to the decrease in moisture at the level of 12.5% of agricultural capacity.

Based on the results, the substrates containing richer foods provided better results. By adding cocopeat to the substrate, the negative effects of drought stress can be controlled. The reason for this superiority is the amount of nutrients in this substrate due to its ability to store more nutrients and water. The use of perlite in hydroponic culture beds is useful because it has large and small pores that improve the culture bed's ventilation. One of the negative effects of drought stress is the reduction of chlorophyll. As a result, the photosynthesis system of the plant will be damaged, and with the increase in the amount of proline, chlorophyll will decrease because the amounts of chlorophyll and proline have an inverse relationship with each other. Lack of water will cause a decrease in growth, leaf surface, wet and dry weight, destruction of cell membranes, destruction and reduction of proteins and enzymes, accumulation of amino acids, reduction of growth enhancers, damage to pigments and plastids, and reduction of root growth.

Urea is one of the nitrogen chemical fertilizers for vegetable production in soil. But it is seldom used in soilless cultures. Leafy vegetables such as Lettuce (Lactuca sativa L.) contain high levels of nitrate and attempts have been made to reduce the nitrate concentration in this crop for human consumption. Using reduced forms of nitrogen, i.e. urea, is one of the applied strategies for reducing nitrate accumulation in lettuce. Little information is available concerning urea as a source of nitrogen for production of leafy vegetables such as lettuce in soilless culture. This experiment was conducted to investigate the effect of different ratios of urea:nitrate in nutrient solution on the growth indices, yield and nitrate accumulation of red French lettuce (Lactuca sativa L. cv. Lolla Rossa) in soilless culture.

A hydroponic experiment using completely randomized design was carried out with seven ratios of urea:nitrate in nutrient solution and four replications in the research greenhouse of Shahrekord University. Urea:nitrate ratios in nutrient solution were: 0:100, 10:90, 20:80, 30:70, 40:60, 50:50 and 60:40. Lettuce seedlings were grown in 2 L plastic pots (one plant per pot) containing mixture of cocopeat + perlite at the ratio of 2:1 (v/v) and were manually fertigated with nutrient solutions on a daily basis. Four weeks after transplanting, lettuce plants were harvested and fresh weights of shoot and root were determined. Plant growth indices including of plant height, plant diameter, leaf length, leaf width, leaf number, leaf greenness index and leaf brix level were measured. After measuring the growth indices, the leaves were grouped separately according to leaf numbers 1-10=outer leaves, >11= inner leaves. The samples were dried in an oven at 60 °C and were ground. Nitrate concentrations in samples were determined calorimetrically using a spectrophotometer at a wavelength of 410 nm. Analysis of variance was performed using SAS software version 9.4. Means comparison was conducted using least significant difference test at 0.05 probability level.

The results indicated that application of different ratios of urea to nitrate in nutrient solution had not significant effect on the lettuce growth indices including of plant diameter, leaf length, leaf width, leaf number, leaf greenness index and leaf brix level in comparison with 0:100 of urea:nitrate ratio. Also, root and shoot fresh weights were not affected by urea:nitrate ratio in nutrient solution. The greatest quantity of shoot fresh weight (141 g per plant) was obtained with a 50:50 urea:nitrate ratio. However, this was not significantly different from the shoot fresh weight (125 g per plant) observed when urea was not included in the nutrient solution. Shoot nitrogen concentration (except for plants nourished with a 50:50 urea:nitrate ratio) was not affected by increasing the urea:nitrate ratio in the nutrient solution. The results revealed that application of urea in nutrient solution effectively provided the nitrogen requirement of lettuce. This indicates that lettuce plants can efficiently hydrolyze urea and use it efficiently as a nitrogen source. Application of urea in the nutrient solution led to significant decrease in the nitrate concentration of lettuce root (P< 0.05). Moreover, increasing urea:nitrate ratio in nutrient solution resulted in significant decrease of the nitrate concentration of outer leaves, inner leaves and all leaves of lettuce (P< 0.01). The highest and lowest nitrate concentration in inner, outer and all leaves of lettuce were obtained in plants nourished with 0:100 and 50:50 urea:nitrate ratio in nutrient solution, respectively. Application of urea:nitrate ratio of 50:50 led to the meaningful decrease of nitrate concentration in root (43%), outer leaves (41%), inner leaves (44%) and all leaves (43%) of lettuce in comparison with 0:100 of urea:nitrate ratio. Urea had a repressive effect on nitrate influx and decreased its uptake by plants. Also, after urea uptake by plant root, it is first degraded by cytosolic ureases and then ammonium is incorporated via the GS-GOGAT (Glutamine Synthetase- Glutamine α-OxoGlutarate Amino Transferaze) cycle. Therefore, application of urea in nutrient solution can lead to the reduction of nitrate accumulation in plants.

Based on the shoot fresh weight and nitrate concentration in lettuce leaves, replacing 50% of nitrate in nutrient solution with urea is recommended for red French lettuce production in hydroponic culture under the conditions of the present study. Compared to other nitrogen fertilizers, urea has a lower price and its application in nutrient solution is useful in reducing production costs.

High nitrate concentrations, especially in leafy vegetables, is a great threat to human health. Various factors play a role in reducing nitrate accumulation in vegetables, one of which is the availability of iron. The purpose of this study was to compare the effect of different sources of iron on the accumulation of nitrate in lettuce in hydroponic system. Therefore, the experiment was performed in a completely randomized design with 4 treatments and 5 replications. Treatments included different sources of iron including iron sulfate, iron chelate (Fe-EDTA) and iron amino chelate with the same iron concentration of 20 μM. An iron free solution was also considered as control. The results showed that iron amino chelate application increased root dry weight (138%), shoot dry weight (59%), stomatal conductance (80%), photosynthesis rate (107%), chlorophyll content (91%), Fv/Fm (60%) and iron concentration of shoots (113%) as compared to the control. Also, iron amino chelate increased the activity of nitrate reductase (168%), nitrite reductase (33%) and glutamine synthetase (67%) enzymes compared to the control. Application of iron amino chelate, iron chelate and iron sulfate reduced the nitrate concentration by 55%, 11% and 18% compared to control, respectively. Generally, the results showed that the application of iron amino chelate reduced nitrate accumulation by increasing the activity of enzymes involved in nitrate metabolism. According to the results, iron amino chelate can be used to reduce nitrate concentration and increase lettuce yield in hydroponic cultivation.

There is necessary to clean up the nitrate and phosphate from surface waters before effluence of them to environment and eutrophication formation because of water health importance and considering to nitrate and phosphate consequences. Nitrate and ammonium as the - forms of inorganic and nitrogen have been subjected to the center of issues related to environment pollutants and water resources in a long time. The nitrate is more important than other inorganic nitrogen forms such as ammonium because of various reasons such as high dynamics and causing diseases such as some of digestion system and lymph nodes cancers in adults and methemoglobinemia in infants. Therefore the maximum concentration of this ion in drinking water has been determined as 45 mg.Lit-1 by WHO. Regarding the importance of the water health and the complications due to existence of some compounds such as nitrate and phosphate, in this experiment, the possibility of elimination or decreasing excess nitrate and phosphate from water in hydroponic conditions using of two watercress and pennyroyal plants was evaluated. Watercress(Nasturtiumofficinale) and pennyroyal (Menthapulegium)were selected because of some properties such as adaptability with the most climates of Iranamd less requirements care.

Two RCD factorial experiments were carried out to evaluate the ability of watercress and pennyroyal to biosorption of nitrate and phosphate from polluted water in hydroponic conditions. First factor was plant species including watercress and pennyroyal. Second factor included nitrate (50, 100, 150 Mg/L) and phosphate (5, 10, 15 Mg/L) in first and second experiment respectively.The final concentrations of nitrate and phosphate in water was measured using spectrophotometer in wavelength of 410 nm and 690 nm by sulphatebrucine and chloride methods, respectively, which are mentioned in Standard Methods for the Examination of Water and Wastewater. At the end of the each experiment, watercress and pennyroyal plants were brought out from the pots carefully and their roots and shoots were separated. Roots and shoots were placed in aluminum foil separately and were dried by oven method (50°C and 48 h). The weights of dried samples were measured by a digital balance scale (0.001 gr accuracy). Three accumulation indices including Bio-concentration Factor, Translocation Factor and Tolerance Index were calculated by measuring of nitrate and phosphate accumulation in roots and shoots

According to the results, root phosphate accumulation in two plants was different significantly (p ≤ 0.05). Also, the level values of nitrate and phosphate were resulted to their root accumulation significantly. In this regard, the phosphate accumulation in watercress root changed to 10 mg. Lit-1 significantly and reached to 4.3 mg.Kg-1 dry weight in this concentration. While for pennyroyal, there was no significant increasing in roots phosphate accumulation when its concentration was increased in medium (p ≤ 0.05). Although phosphate accumulation was difference between the two plants in root and shoots, there was similar the alteration of phosphor bioconcentration trend. Because increasing of phosphate concentration resulted in significant decreasing of this index. Whilst both of watercress and pennyroyal accumulated high amount of nitrate and phosphate, quantity of accumulation in shoots was higher than of roots. Consequently, nitrate translocation factor was 1.3 in watercress and 1.07 in pennyroyal, and phosphor translocation factor was 1.07 and 0.94 in watercress and pennyroyal respectively.

Results indicated that two plants were pollutants purified of nitrate and phosphate (The nitrate translocation factors were 1.3 and 1.07 in watercress and pennyroyal and the phosphate translocation factors were 1.07 and 094 in watercress and pennyroyal, respectively). Generally, it was found that watercress and pennyroyal have extractive behavior completely about nitrate and phosphate. Because of the high ability of these plants in biosorption of phosphate and nitrate, with recovery of nitrogen and phosphorus cycle, they can be used as organic resources of nitrogen and phosphor supply in agricultural soil and prevent from entrancing them to seas. It is more important about phosphate, which has slowly cycle. Therefore two main roles for watercress and pennyroyal in aquatic ecosystems are expected. First, perform as bio-filter and returning the nitrogen and phosphor from surface water or wastewater for preventing the environmental pollution and second as secondary saleable or utilizable crop such as green manure and so on.

Pistachio (Pistacia vera L.) is an important economic crop, which is mostly planted in saline conditions in Iran. Verticillium wilt disease of pistachio caused by Verticillium dahliae is known as a serious disease for pistachio trees. The causal agent was recovered from shoot and soil samples collected from main pistachio growing areas in Kerman province. The present experiment was carried out to study the effect of salinity on disease using three common P. vera rootstocks including Sarakhs, Badami-e-Zarand and Qazvini and four levels of salinity (0, 1400, 2800 and 4200 mg NaCl per kg soil) in hydroponic culture (1/2 strength Hoagland,s solution). Salt stress was applied before inoculation on ten week old seedlings. The experiment was carried out as factorial in RCD with four replications. Two weeks after salt stress induction, four seedlings were transplanted into pots containing 5 kg sandy-clay virgin soil artificially infested with 40 microsclerotia per gram of soil with equal salinity. In NaCl treatments, Sarakhs showed lower shoot and root dry weight and higher concentration of Na, K and Cl than the other rootstocks. Based on the results, Sarakhs, Qazvini and Badami were found to be susceptible, tolerant and intermediate to NaCl, respectively. In the presence of V. dahliae, salt stress significantly reduced shoot and root dry weight and increased stem and root colonization by the pathogen and Na, K and Cl concentration compared to non-stressed inoculated plants. Sarakhs had higher percentage of colonization of stem and root by V. dahliae and concentration of Na, K and Cl than other cultivars. As a general conclusion, salt stress before inoculation by V. dahliae can increase the severity of Verticillium wilt of pistachio, especially in salt-sensitive rootstocks.