Growing vegetables
Parastoo Molaei; Fatemeh Nekounam; Mohammad BabaAkbari Sari
Abstract
Introduction Over time, water deficit and environmental pollution by traditional agriculture that forces the producer to contribute to competitive and sustainable agriculture. Leafy vegetables are beneficial to human health, therefore, to adapt an eco-friendly approach in some vegetables, the partial ...
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Introduction Over time, water deficit and environmental pollution by traditional agriculture that forces the producer to contribute to competitive and sustainable agriculture. Leafy vegetables are beneficial to human health, therefore, to adapt an eco-friendly approach in some vegetables, the partial substitution (25–50%) of mineral NPK by biofertilizers in lettuce improves the yield and agronomic features and produces healthy plants for human nutrition as well. Lettuce (Lactuca sativa L.) from Asteraceae family is considered as one of the most popular salad vegetables as a cool season crop. PGPB (Plant Growth-Promoting Bacteria) are rhizosphere bacteria that improve plant growth through a broad range of processes, i.e., phosphate solubilization, biological nitrogen fixation, siderophore manufacturing, phytohormone manufacturing, antifungal activity, systemic resistance induction and plant-microbe symbiosis promotion. The promoting of growth and yield of horticultural crops such as cucumber, potato, tomato and spinach by plant growth promoting bacteria inoculation at nutrient solutions under soilless systems have also been reported. Material and Methods In order to study the effect of growth-promoting bacteria on the yield, iron concentration and phenolic compounds of lettuce (Lactuca sativa cv. New Red Fire) under floating systems, the experiment was carried out in a completely randomized design with three replications in the Research greenhouse of University of Zanjan, during 2020. Experiment treatments consisted of five levels of PGPB (Pseudomonas vancouverensis, Pseudomonas koreensis, Pantoea agglomerans, Pseudomonas putida, and one level of combined bacteria (Pantoea agglomerans+ Pseudomonas koreensis + Pseudomonas putida+ Pseudomonas vancouverensis)) and control plant (without bacteria treated). Application of bacteria was done in two stages, one step before cultivation as seed inoculation and the next step as root inoculation. Lettuce plants grown in hydroculture condition with Hoagland nutrient solution. Growth conditions were environmentally controlled at a relative humidity of 60/70 % day/night and temperature was maintained between 20 and 17 °C. At 40 days after transplanting date, the lettuce head were harvested. The freshly harvested lettuce head were immediately weighed separately of each plant for fresh weight determination. Leaf samples were dried at 72 °C for 48 h in a drying oven and kept for further investigations. Also, leaf number per plant, chlorophyll and carotenoids contents, Fe concentration, total phenol, total flavonoids and anthocyanin contents were measured. ResultsThe obtained results in the current study indicated that the application of PGPB on lettuce caused significant increase in growth, photosynthetic pigments and iron concentration. The maximum growth rate and photosynthetic pigments content was observed in combined four bacteria treatment, so that, an increase of 388.2% chlorophyll a, 439.8% chlorophyll b, 398.3% total chlorophyll, 246.3% carotenoids contents, 42.6% plant fresh weight and 22.2% number of leaves was obtained compared to control plants. Plant Growth-Promoting Bacteria (PGPB) can enhance growth and development of plants. PGPB have direct and indirect influences on plant growth process. The immediate promotion of growth involves either supplying the plant with a compound produced by the bacteria, i.e., phytohormones, or promoting certain nutrient uptake from the setting. Whereas, the indirect plant growth promotion happens when PGPB decreases or prevents the deleterious impacts of one or more phytopathogenic species. Plants inoculated with PGPB showed higher leaf iron concentration compared to control plant. Thus inoculation with combined four bacteria induced a 26.2 % increase of lettuce leaves iron concentration. The obtained results in the current study revealed that the inoculation with PGPB significant decreased the total phenol, flavonoid and anthocyanin contents. The maximum content of phenol (483 µg g-1FW), flavonoid (188.1 µg g-1FW) and anthocyanin (27.5 µmol g-1FW) were observed in control plants compared to treated plants. Conclusion According to the results of this research, the use of PGPB in the hydroculture system, on the one hand, led to a significant increase in iron absorption, the synthesis of photosynthetic pigments, and subsequently promote growth and increases lettuce yield. On the other hand, due to facilitating the growth conditions and increasing the absorption of nutrients for the host plants as a result of inoculation with PGPB, led to a decreases of phenolic compounds including total phenol, total flavonoid and anthocyanin contents.
Pomology
Farhad Azarmi-Atajan; Mohammad Hossein Sayyari Zahan; Abdollah Mirzaei
Abstract
IntroductionPhosphorus (P) is one of the most important nutritional elements of plants and it is necessary for the development of plant roots. Due to the high cost of chemical fertilizers, it is important to use cheap sources such as rock phosphate (RP) to supply P needed by plants. The efficiency of ...
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IntroductionPhosphorus (P) is one of the most important nutritional elements of plants and it is necessary for the development of plant roots. Due to the high cost of chemical fertilizers, it is important to use cheap sources such as rock phosphate (RP) to supply P needed by plants. The efficiency of RP is low and its use alone cannot supply the P required by the plant. One of the ways to increase the efficiency of RP is to use phosphate solubilizing bacteria (PSB). Considering the salinity of soil and irrigation water in many pistachio-growing areas of Iran, the use of salt-resistant PSB can increase their resistance to salt stress in addition to supplying the P required by pistachios. Materials and MethodsIn order to investigate the role of PSB in supplying the required P of pistachio seedlings under saline conditions, a factorial experiment was conducted in the form of a completely randomized design with 3 replications in greenhouse conditions. The factors included PSB at three levels [control (PSB0), Pseudomonas sp. 1 (PSB1) and Pseudomonas sp. 2 (PSB2)], RP at two levels (0 and 30 mg P from rock RP) and irrigation water salinity at three levels (0, 5 and 10 dS/m). The bacteria used in this study were able to produce ACC-deaminase, indole acetic acid and dissolve tricalcium phosphate in vitro. For inoculation, inoculum containing each bacterium with a population of 108 cells/ml was prepared in the nutrient broth medium and each pistachio seed (P. vera L. cv. Badami) was inoculated with 500 µL of bacterial inoculum. The plants were irrigated with non-saline water for four weeks and then with saline water until harvesting based on experimental treatments. During the growth period, the soil moisture of the pots was kept at about 80% of the field capacity by weight method. Finally, shoot and root sampling was performed and various characteristics such as shoot and root dry weight, chlorophyll, carotenoids, proline, soluble sugars, RWC, MSI and phosphorus as well as sodium concentrations were measured. Analysis of variance of traits was performed using SAS software and the means were compared using the LSD method with a probability level of P≤0.05. Results and DiscussionThe results showed that water salinity decreased the dry weight of shoot and root, chlorophyll a, chlorophyll b, carotenoids, relative water content (RWC) and membrane stability index (MSI) of leaf and p concentration of shoot and root of pistachio seedlings. Auxin produced by bacteria can directly increase cell division and growth or indirectly increase ACC-deaminase production. On the other hand, proline, soluble sugars and sodium were accumulated in the leaves of seedlings with increasing water salinity. According to the results, although the use of RP alone did not show significant effect on the studied indicators, its simultaneous use with PSB had the greatest role in improving the growth of pistachio seedlings, especially in saline conditions. The highest amount of dry weight of shoot (1.89 g.plant) and root (1.59 g.plant), chlorophyll b (1.30 mg/g fresh weight), carotenoids (1.35 mg/g fresh weight), soluble sugars (59.1 mg/g fresh weight), proline (36.7 mg.g-1 fresh weight), leaf RWC (91 %), leaf MSI (84%) and the P concentration of shoot (0.39 %) and root (0.35 %) was obtained from the simultaneous application of RP and PSB (especially PSB2) in non-saline conditions. The PSB increase soil P availability by reducing of soil pH by release of protons and organic acids and mineralization by production of acid phosphatases. Bacteria, in addition to increasing soil P availability, improve phosphorus uptake and chlorophyll content in plants by affecting root morphology and its development in soil. On the other hand, inoculation with PSB (both separately and together with rock phosphate) reduced sodium accumulation in the aerial parts and roots of pistachio seedlings. ConclusionUnlike pistachio trees, the tolerance of pistachio seedlings to salt stress is low. According to the results, the salinity symptoms were visible in the pistachio seedling leaves at the water salinity level of 10 dS/m, which caused the drying of the lower leaves and the burning of the edges of the young leaves. On the other hand, although the application of RP alone did not have significant effect on increasing the tolerance of plants to salt stress, the simultaneous use of RP with PSB increased growth, the accumulation of proline and soluble sugars, the concentration of chlorophyll and carotenoids, the amount of RWC and MSI and P concentration of pistachio seedlings, especially in saline conditions. Therefore, the use of PSB can help the growth and establishment of pistachio seedlings under salinity stress conditions and increase the efficiency of RP and supply P needed by the seedlings.
Medicinal Plants
Samaneh Samavat; Mahdiyeh Salehi Vozhdehnazari; Mehdi Yahyazadeh Balalami; Mahshid Rahimifard
Abstract
Introduction
So far, more than 40 different types of alkaloids have been known in poppy (Papaver somniferum L.) as a valuable medicinal plant, the most important of which are morphine, codeine, thebaine, noscapine, and papaverine. The biosynthesis of these alkaloids may be strongly influenced by a variety ...
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Introduction
So far, more than 40 different types of alkaloids have been known in poppy (Papaver somniferum L.) as a valuable medicinal plant, the most important of which are morphine, codeine, thebaine, noscapine, and papaverine. The biosynthesis of these alkaloids may be strongly influenced by a variety of biotic and abiotic elicitors. In fact, microbes as biotic elicitors can affect the production of poppy alkaloids. Among them, plant growth promoting rhizobacteria (PGPR) can be noticed, which stimulate and improve plant growth through various mechanisms such as mineral phosphate solubilization, plant hormone production, siderophores secretion, nitrogen fixation, etc. The use of PGPR agents can not only lead to an increase in plant biomass, but simultaneously, due to their role as biotic elicitors, they cause to an increase in the biosynthesis of secondary metabolites in plants. These biotic elicitors target plants’ defense mechanisms and result in triggering a series of metabolic changes throughout the plant. The use of PGPR agents to stimulate the plant to produce secondary metabolites has several advantages: First, in some plants, defensive metabolites are active biological compounds that lead to the induction of food production with high added-value in the plants. Secondly, physiologically, with the increase in the synthesis of secondary metabolites, the resistance of the plant against pathogens also increases. Accordingly, the present study was performed with the aim of investigating the effects of bacterial strains with the ability to solubilize inorganic phosphate as biotic elicitors on the amount of morphine, papaverine, and noscapine alkaloids in P. somniferum.
Materials and Methods
In this research, the solubility of inorganic phosphate by four bacterial strains including Enterobacter xiangfangensis S2, Pantoea dispersa S7, Pantoea stewartii S25, and Pseudomonas canadensis S36 was evaluated quantitatively using Sperber broth medium. Under greenhouse conditions, the effect of foliar spraying of P. somniferum plants with a suspension of the bacterial strains (108 CFU.ml-1) on the amount of morphine, papaverine, and noscapine in the plants’ capsules, stems, and leaves was investigated. About three weeks after the appearance of capsules in poppy plants, the aerial parts of the plants (stems, leaves, and capsules) were sprayed with the bacterial suspensions. One week after foliar spraying, poppy plants were harvested in order to determine the amount of the desired alkaloids. Three pots were considered for each treatment and there were three poppy plants in each pot. Alkaloids were extracted based on an alcoholic method and detected using HPLC. Morphine and noscapine standards were prepared at a concentration of 1000 μg.ml-1 and papaverine standard at a concentration of 250 μg/ml. Then the mixture was prepared in proportions of 1, 1:50, 1:10, 1:50 and 1:100 and injected into the HPLC set to draw the calibration curve. All the experiments were conducted in a form of completely randomized design with three replications for each treatment (P<0.05).
Results and Discussion
The results showed that the highest (458.67 µg.ml-1) and the lowest (130.47 µg.ml-1) phosphate solubility were related to S2 and S36 strains, respectively. S7 and S25 strains were not statistically significantly different from each other and after S2 strain, they were placed in the second statistical position. In the bacterial strains’ treatments, the level of morphine in the stems and leaves as well as the capsules increased significantly in most cases compared to the control. The amount of papaverine in the stems and leaves decreased significantly, but it had no significant changes in the capsule. Also, noscapine showed a significant increase in the stems and leaves and reached from 0.8 mg.g-1 DW in the control to 8.12 in the S2 treatment. While, the amount of noscapine increased significantly in the capsules, only in the S2 and S36 treatments. Other strains did not show significant differences with the control for noscapine content in the capsules. The results showed that the interaction effects of the type of the alkaloids and the use of phosphate solubilizing bacterial strains on the concentration of the studied alkaloids in poppy stems, leaves and capsules are significant (P<0.01).
Conclusion
It can be concluded that there is no need to apply genetic engineering to increase the production of valuable secondary metabolites by medicinal plants. Rather, this goal can be achieved much cheaper by using bacterial elicitors. Accordingly, by selecting compatible and efficient bacterial strains with phosphate solubilizing activity, the amounts of morphine, papaverine, and noscapine alkaloids in the aerial parts of P. somniferum as a valuable medicinal plant can be noticeably increased.
