نشریه روابط خاک و گیاه
پیاپی 51 (پاییز 1401)

To investigate the effect of sodium selenate (Na2SeO4) and sodium selenite (Na2SeO3) on some morphological characteristics and nutrients concentration in peppermint, an experiment was conducted in a completely randomized design with four replications. Different levels of sodium selenate and sodium selenite (0, 4, 8, and 12 mg l-1) were applied in soilless cultivation in the research greenhouse of the Faculty of Agriculture, Ferdowsi University of Mashhad. Then morphological traits and the concentrations of nutrients in the leaf were measured in the flowering stage. The results showed that the application of two forms of selenium at a concentration of 4 mg l-1 increased the growth traits in peppermint. The highest concentration of both salts decreased the plant growth. The results also showed that with increasing the concentration of selenite and sodium selenate, the selenium concentration increased, but the use of sodium selenate caused higher concentration of this element in the leaf. At a concentration of 4 mg l-1 selenium, the concentrations of macronutrients including nitrogen, phosphorus, potassium, calcium, and magnesium in the leaf increased by 43.7, 11.1, 3.2, 11.6, and 9.2%, respectively, compared to the control but were not significant. The highest nitrogen concentration was observed at the concentration of 4 mg l-1 sodium selenite 43.7% greater than the control. With increasing the concentration of selenium, except for molybdenum and manganese, the concentration of zinc, iron, boron, and copper increased. The highest concentrations of iron and boron were obtained at 12 mg l-1 sodium selenate, 60.2 and 25.7% greater compared to the control, respectively. The highest concentrations of zinc and copper measured at 12 mg l-1 sodium selenite were 63.3 and 40.6% greater than the control, respectively. In general, it is concluded that 4 mg l-1 of sodium selenate can be applied to improve the growth and nutritional condition of the peppermint.

The aim of this study was to evaluate the effects of three citrus rootstocks on some rhizospheric features including biological and chemical properties in a calcareous soil without and with phosphorus (P) addition. For this purpose, a factorial experiment was conducted in a completely randomized design with three replications. Experimental factors included Thomson Navel orange (Citrus sinensis L. Osbeck.) grafted on Sour orange (SO), Swingle citrumelo (SC), or Troyer citrange (TC) rootstocks and two levels of P fertilizer application [with (100 mg-P kg-1 soil) and without P addition]. Eighteen months after planting seedlings in pots, plants were harvested and rhizosphere soils were separated and some biological properties including dissolved organic carbon (DOC), the population of fungi and bacteria, microbial biomass P (MBP), alkaline phosphatase (AlP) and acid phosphatase (AcP) activities and available P (Olsen-P), and P fractions (including the exchangeable; associated with Fe and Al oxides; associated with Ca compounds; and residual) were determined in the rhizosphere soils. In both P levels, DOC and population of fungi and bacteria were higher in Sour orange rhizosphere soil than other rootstocks (p<0.05). However, the lowest values of pH, AlP and MBP were found in Sour orange rhizosphere soil compared with other rootstocks (p<0.05). Olsen-P was lower in Sour orange rhizosphere soil than other rootstocks. Additionally, the results showed that the depletion or accumulation pattern of various fractions was under the rootstock and P-level control. The amounts of exchangeable P and P associated with Fe and Al oxides in the rhizosphere soils had been only influenced by the root activity of citrus rootstocks and P addition (p<0.05). However, citrus rootstocks did not have significant effect on P associated with Ca compounds and residual P and these two forms of P had been solely influenced by P addition. Based on the results, among the rootstock SO could improve P acquisition efficiency mainly by modifying biological conditions and chemical reactions in its root surroundings soil and altering P fractions in its rhizosphere soil.

This research was conducted to investigate the effect of potassium sulfate application on some physiological characteristics of tissue culture-derived date palm plants under water stress conditions. The study was conducted as factorial experiment based on a randomized complete block design with three replications. After complete establishment of plants, potassium sulfate at five levels (zero, foliar application of 2 and 4 g L-1, soil application of 50 and 100 g for each plant) and then water stress at three levels (100, 80 and 60% of cumulative evaporation from Class A evaporation pan) were applied. The results showed that with the application of potassium sulfate at high levels of water stress, the chlorophyll index increased and ion leakage percentage decreased. In the third level of water stress without application of potassium, the chlorophyll index was recorded at 42.61, but with the soil application of 100 g potassium sulfate, the chlorophyll index significantly increased to 58.78. The ion leakage of 34.75% was also observed at the third level of water stress without the application of potassium sulfate, while with the application of 100 g potassium sulfate, it reduced significantly to 25.42%. The potassium concentration in leaves in the treatment without potassium application was 1.61%, while in the treatment with soil application of 100 g of potassium sulfate, the value of 1.88% was recorded with a significant increase. Overall, soil application of 100 g of water-soluble potassium sulfate for each plant had the best results in terms of the physiological responses of date palm plant in dealing with water stress conditions.

Titanium dioxide nanoparticles (TiO2 NPs) are being used widely for different purposes such as plant science and environmental remediation. Soil remediation using TiO2 NPs with the aim of minimizing their toxicity in plants requires sufficient knowledge about the fate of these nanoparticles in the soil. Excessive amounts of nanomaterials may pose inhibitory effects on the growth of plants cultivated in TiO2 NPs-affected soils. The main aim of this study was to investigate the effect of different levels of TiO2 NPs in soil on sorghum (Sorghum bicolor) growth and the fate of these nanoparticles in plants. Sorghum seeds were sown in plastic pots containing different concentrations of TiO2 NPs. Sorghum was found to be a tolerant plant species in the presence of TiO2 NPs in soil; however, addition of higher doses of TiO2 NPs (i.e., 800 and 1000 mg kg-1 soil) adversely affected seed germination and plant growth. Results indicated that the total titanium (Ti) contents in sorghum treated with nanoparticles increased compared to the control. Significantly higher accumulation of Ti in the root compared to the shoot of sorghum was observed in all of the treatments. Results indicated that the total Ti contents in the plants treated with TiO2 NPs were higher than those in control, with the highest Ti accumulation capacity of 21.32 mg per pot obtained in the soil treated with 500 mg kg-1 TiO2 NPs. Toxicity of higher doses of TiO2 NPs to the plants was observed in this study. The results showed that sorghum has an acceptable tolerance in the low to moderate concentrations of TiO2 NPs, whereas the high concentrations of these nanoparticles have inhibitory effects on the sorghum growth. Selection and application of proper doses of nanomaterials may prevent their negative effects on affected plants, while promoting the plant phytoextraction ability.

A greenhouse research study was conducted at Golestan Agricultural Science and Natural Resources Research Center, Gorgan, in autumn and winter 2021, to investigate the effects of three different nutrient solutions on the yield and growth parameters of two local lettuce cultivars grown in solid growing media of hydroponic system. Two local lettuce cultivars (Var1 and Var2) were subjected to different nutrient solutions. Three nutrient solutions were different in nitrogen (N), potassium (K) and calcium (Ca) concentrations. The control nutrient solution consisted of concentrations 180, 210 and 190 mg L-1 for N, K and Ca. Corresponding concentrations were 140, 150 and 140 mg L-1, and 220, 270 and 220 mg L-1 for N2 and N3 nutrient solutions, respectively. The experiment was conducted as a factorial in completely randomized design with 3 replications and two factors of cultivar type (Var1 and Var2) and nutrient solution (control, N2 and N3). Based on the results, the fresh and dry weights were not significantly different between the two cultivars, but significant differences were observed for other traits. Among the nutrient solution treatments, the highest fresh weight was obtained in N3 nutrient solution (17.1 and 12.5% greater than N2 and control, respectively). Using N3 nutrient solution increased leaf dry weight (by 17.6 and 7.5%), leaf number (by 12.7 and 17.0%), leaf width (by 9.1 and 1.5%), leaf length [by 4.8 and -1.5% (not significant)], root fresh weight (by 85.4 and 58.9%), and root volume (by 264.7 and 186.5%) compared to N2 and control, respectively. Therefore, the N3 nutrient solution increased the shoot and root growth and can be suggested for maximum lettuce production in hydroponic culture.

Chromium (Cr+6) is one of the heavy metals that can disrupt various physiological processes in plants. One of the strategies to moderate the heavy metals stress is the symbiosis of plant roots with symbiotic fungi. Therefore, in order to investigate the effect of chromium and symbiotic fungus on the growth and physiological characteristics of red lettuce (Lactuca sativa L. cv. Little Gem), a factorial experiment was carried out as factorial based on completely randomized design in four replications as a hydroponic culture. The experimental treatments included chromium in three levels of 0 3 and 15 mg L-1, and symbiotic fungi in four levels of control, Rhizophagus irregularis, Serendipita indica and R. irregularis + S. indica. The results showed that by increasing the concentration of Cr in  the nutrient solution, leaf and root fresh weights, total chlorophyll, root length, nitrogen, phosphorus and potassium decreased significantly. But increasing the concentration of chromium in the nutrient solution increased the content of leaf Cr, anthocyanine, soluble carbohydrates and malondialdehyde increased. The symbiotic relation of S. indica and R. irregularis with Cr-stressed plants showed a significant increase in root colonization percentage, total chlorophyll content, nitrogen, phosphorus and potassium compared with the plants grown under Cr treatment alone and without symbiotic fungi. The findings showed that the symbiosis of S. indica and R. irregularis fungi with lettuce under the Cr stress conditions led to the improvement of growth and physiological traits, reduced the content of leaf chromium and moderated the chromium toxicity.