h.r. roosta

In order to investigate the effect of calcium-enriched sepiolite under stress conditions on the concentration of nutrients in cucumber, an experiment was conducted with two factors of stress (control, salinity stress: 70 mM sodium chloride, alkalinity stress: 70 mM sodium bicarbonate, and combined salinity and alkalinity stresses: 70 mM sodium chloride + 70 mM sodium bicarbonate) and the levels of sepiolite (0, 10 and 20% w/w) in a completely randomized design. The results showed that calcium-enriched sepiolite had favorable effects on the concentration of nutrients and the dry weights of plant root and shoot. For example, in non-stressed conditions, with the application of 10 %w/w sepiolite, in addition to a 94% increase in the dry weight of the shoot, the concentrations of Mg and Ca in the shoot increased by 15 and 45%, respectively. With the application of 20% w/w sepiolite, the dry weight of the shoot increased by 80% in the conditions of salinity stress. Additionally, this treatment resulted in significant increases in the concentration of Cu in the shoot, Ca in the root, Mg in the root and shoot, and Fe in the root, with increases of 89, 63, 230, 38, and 656%, respectively. Overall, the findings of this research showed that the use of sepiolite in stressful conditions can be beneficial in improving the concentration of nutrients, especially Fe, Mg and Ca, and reducing sodium accumulation in cucumber.

Previous studies have shown that salinity and alkalinity stresses caused a reduction in growth of plants (Roosta, 2011). Sepiolite mineral has been found in different regions of Iran and its agricultural and industrial uses have been started (Galan, 1996). Although some researches have been done on the environmental applications of this mineral as an adsorbent, there is very little information about the use of calcium-enriched sepiolite in the plant culture environment. Therefore, considering the role of salinity and alkalinity in reducing the production of products and the characteristics of sepiolite clay, this research was conducted to investigate the effect of calcium-enriched sepiolite as a soil conditioner to reduce the adverse effects of salinity and alkalinity stresses on cucumber.

The studied sepiolite was obtained from a mine in Fariman and after being grinding it was saturated with calcium chloride. This research was carried out in the greenhouse of Vali-e-Asr University of Rafsanjan as a hydroponic culture in a medium containing perlite and Ca-enriched sepiolite. The experiments included three levels of sepiolite (0, 10% and 20% w/w) and four levels of stress (no-stress conditions as control, salinity stress by 70 mM sodium chloride, alkalinity stress by 70 mM sodium bicarbonate, and combined salinity and alkalinity stresses by sodium chloride 70 mM and sodium bicarbonate 70 mM). The treatments were arranged in a factorial way in the form of a completely randomized design with three replications. At the end of experiment, the plants were completely removed from the pots and the aerial and root parts were separated, and after washing with distilled water, they were dried at 70 ºC for 48 hours and then powdered. The total concentrations of Ca, Mg, Na, Cl, Zn, Cu, Fe and Mn in plants shoot and root were determined according to standard methods.

The results showed that the use of Ca-enriched sepiolite reduced the adverse effects of stress on the concentration of nutrients. In non-stressed conditions, the concentrations of Mn and Mg in the root and shoot increased due to 10% sepiolite application. The concentration of Ca in the root and shoot increased in all sepiolite-treated pots, and Ca-enriched sepiolite decreased Na concentration in the root and shoot. Under salinity stress, the concentration of Cu in the shoot, Fe and Ca concentrations in the root and Mn concentration in the shoot and root increased, but the concentrations of Zn and Mn in the root and shoot decreased due to 20% sepiolite application. Under alkalinity stress, the concentration of Cu in the shoot, Mn and Ca concentrations in the root, and Mg and Fe concentrations in the root and shoot increased while the Na concentration in the root decreased. Under the combined salinity and alkalinity stresses, the concentrations of Cu and Mn in the shoot, and Fe and Mg concentrations in the shoot and root increased.

Based on the results of this research, calcium-enriched sepiolite had favorable effects on the concentration of nutrients such as calcium, magnesium, and iron in cucumber plants, and by removing sodium from the reach of the plant, it reduced the adverse effects of salinity and alkalinity stresses of the culture medium. Therefore, calcium-enriched sepiolite can be suggested as an amendment under salinity and alkalinity stress conditions.

Nutrient solutions used in the production of lettuce in soilless culture do not contain silicon (Si) as a beneficial element. Therefore, this experiment aimed to evaluate the role of Si in lettuce growing hydroponically. Results showed that the highest fresh weight, dry weight and total dry weight of lettuce were obtained in the control. The highest percentage of the edible part to root was observed in 0.5 mM silicon treatment. In the shelf life aspect, the lowest percentage of lettuce weight loss was recorded in 0.5 and 1.25 mM silicon concentrations and the best food quality was obtained in the treatment of 0.75 mM silicon. The highest stomatal conductance and transpiration rate were observed at the Si concentration of 0.25 mM and the highest antioxidant activity was observed at a concentration of 0.5 mM. The highest phenol and flavonoids were recorded in the treatments of 1.75 and 2 mM silicon, respectively. The highest leaf silicon concentration was found in the treatment of 1.75 mM silicon and the lowest amount of nitrate in lettuce was obtained in the concentrations of 0.25 and 0.5 mM silicon.

Today, soil salinization and alkalization have become an environmental problem that has limited agricultural production. The use of silicon and LED light can reduce the limitation of agricultural production in saline and alkaline conditions. For this purpose, a factorial experiment based on a completely randomized design in three replications was implemented to investigate the effect of sodium silicate and light sources in reducing salinity and alkalinity stress on Physalis angulate L. Treatments included sodium silicate at 0 and 75 mg L-1, four sources of natural light greenhouse (control), red light (100%), blue light (100%) and 70% red light + 30% blue light and NaHCO3 + NaCl at 0, 10 + 40 and 20 + 80 mM. The results showed that simultaneous use of silicon and LED light in all three conditions of non-stress, mild and severe stresses increased the leaf relative water content and water use efficiency, particularly in severe stress condition. The use of silicon increased the contents of phenol and proline in both non-stress and stress conditions, and the use of LED especially blue + red light, also increased these factors. Although the interactions of the studied factors were not significant on the amount of soluble sugars, glutamine synthetase enzyme of root and shoot, Mn and Zn and SPAD index, the application of silicon as well as LED light had an increasing effect on all these factors. Therefore, the use of silicon and LED light can improve the growth factors of Physalis angulata L. and increase the resistance of this plant to salinity-alkalinity stress.

In order to investigate the effect of nutrient solution type and concentration on physiological and morphological characteristics of strawberry cultivar ‘Parus’ in hydroponic culture (75% volumetric perlite + 25% volumetric cocopeat), an experiment using a completely randomized design with three replications was conducted. The growth media included Full-Strength Morgan (FSM), Double Strength Morgan (DSM), Half-Strength Morgan (HSM), Full-Strength Hoagland (FSH), and Half-Strength Hoagland (HSH). The results showed that nutrient solution type had significant effects on plant growth characteristics and quality of strawberry fruit, so that the highest number of leaves (7.16 per plant), shoot height (28.62 cm), fresh weight (11.70 g per plant) and dry weight (2.66 g per plant) of the shoot were related to the HSH treatment. But, the highest fresh weight (15.15 g per plant) and dry weight (1.40 g per plant) of roots were obtained in DSM and FSM treatments, respectively. Fruits of plants treated with FSM nutrient solution had the highest amount of vitamin C (83.4 mg/100 ml of extract) and total soluble solids (5.7%), while HSM produced the highest titrable acidity (0.17%). Nutrient solutions had no significant effect on crown diameter, and pH, firmness and color of the fruits. Therefore, HSH treatment is recommended for vegetative phase because it improves the growing conditions with less water and nutrients used. With FSM and HSM treatments, fruits with higher quality were obtained. Also because MFS nutrient solution produced more vitamin C (as a powerful antioxidant) and soluble solids (as a flavoring agent), this nutrient solution is recommended for the reproductive growth phase.

In order to compare the effect of three nutrient solution replacement methods in an NFT system and pruning on hot pepper, a factorial experiment was conducted. Factors included nutrient solution replacement method (complete nutrient replacement, partial nutrient replacement according to EC, and partial nutrient replacement according to plant requirements) and pruning (pruning and non-pruning). Results showed that the highest vegetative growth was recorded in plants fed by complete replacement of nutrient solution, while plant fed based on EC showed the lowest vegetative growth and nutrients concentration. Leaf Chlorophyll a (Chl a) and Total Chlorophyll (TChl) decreased in plants fed according to EC control and plant requirements compared to complete replacement of nutrient solution. All these traits were higher in non-pruned plants than in pruned plants. Fruit yield decreased in plants fed based on nutrient solution EC and plant requirements, and pruning treatment decreased these traits, but the highest single fruit weight belonged to pruned plants fed based on plant requirements. The highest fruit carotenoid content, Total Soluble Solids (TSS), and vitamin C were recorded in plants fed according to nutrient solution EC, and these traits were higher in the pruned plants compared to non-pruned ones. The results also showed that pruning caused a reduction in plant growth and fruit number, therefore, it is not recommended for hot pepper cv. Sentela.

This research carried out in the Rafsanjan pistachio orchard to investigate the effect of N form، manure، K and Fe on yield، nut quality and leaf mineral nutrients concentrations of Pistacia vera L. cv. Fandoghi grafted on Badami-Riz Zarand rootstock. The experiment was as factorial with four factors including; manure (without manure and 10 kg tree-1 sheep manure)، N form (ammonium sulfate and calcium nitrate)، K (without K and 600 kg K tree-1) and Fe (without Fe and 100 g Fe tree-1) and randomized complete blocks design with 6 replications. Fertilizers were added to the soil in holes with 40-60 cm depth on two sides of trees، and treatments effects was evaluated during two years. The results showed that ammonium application increased the nut yield compared to nitrate fertilizer، this increase in yield is may related to the higher N and Fe in plants and consequently leaf chlorosis alleviation due to the chlorophyll contents elevation by these elements. Combination of ammonium-N and Fe increased split pistachio nuts. In this research، ammonium application increased the concentration of Fe، Zn، N and K and reduced P، Ca and Mg concentrations in leaves. Therefore، it is suggested to use N fertilizer containing ammonium rather than nitrate in pistachio orchards with mainly high soil pH.

Regarding to this issue that nitrogen is one of the main essential elements for plant that growth and efficiency of plant is related to it, and on the other hand most of the water and soil resources in Iran are alkaline; in order to evaluation of the interactive effect of different concentrations of sodium bicarbonate and nitrogen form on snap bean in hydroponic system, this research was done in factorial design with two factors, sodium bicarbonate (0, 1, 5 and 15 mM) and nitrogen form (ammonium and nitrate). Results showed that ammonium decreased vegetative growth compared to nitrate, and on the other hand bicarbonate caused increase of the effect of ammonium toxicity and reduced the plant growth. Ammonium increased flower and pod production compared to nitrate. In the presence of nitrate in nutrient solution, addition of bicarbonate caused reduction in reproductive growth of snap bean plants that can be due to the cumulative effect of bicarbonate and nitrate on the pH increase in nutrient solution.