Contribution of Piriformospora indica on improving the nutritional quality of greenhouse tomato and its resistance against cu toxicity after humic acid addition to soil.

Protected cultivation has a significant contribution in vegetable production. We investigated whether humic acid addition to soil and Piriformospora indica can improve the nutritional quality of greenhouse tomato. We conducted a pot experiment, in which the effects of P. indica inoculation, humic acid addition, and Cu spiking to soil (0, 120, 240, and 500 ppm Cu) were tested. Humic acid addition to soil spiked with 500 ppm Cu decreased the Cu concentration in the fruits of plants inoculated with P. indica from 0.65 to 0.40 mg 100 g Fw-1, which is still above the maximum allowed limits of Cu in tomato by World Health Organization (WHO). The lycopene and ascorbic acid content of tomato fruits were consistently improved by humic acid addition and P. indica inoculation. The antioxidant enzymes' activity changed in response to humic acid addition, Cu spiking to soil, and P. indica inoculation. With increasing Cu level up to 240 ppm, the activity of superoxide dismutase (SOD) and peroxidase (POD) increased significantly. However, with spiking more Cu to soil, the activity of antioxidant enzymes reduced and the MDA content increased significantly. Addition of humic acid to soil and/or presence of P. indica increased the activity of antioxidant enzymes when the soil spiked with 500 ppm Cu. This study indicated that addition of P. indica and humic acid to the soil can enhance the nutritional quality of greenhouse tomato by reduction of Cu toxicity as a common pollutant in the greenhouse media and increasing the antioxidant content of fruits.

Soil-indigenous arbuscular mycorrhizal fungi and zeolite addition to soil synergistically increase grain yield and reduce cadmium uptake of bread wheat (through improved nitrogen and phosphorus nutrition and immobilization of Cd in roots).

Soil pollution with heavy metals is a major problem in industrial areas. Here, we explored whether zeolite addition to soil and indigenous arbuscular mycorrhizal fungi (AMF) can reduce cadmium (Cd) uptake from soil by bread wheat. We conducted a pot experiment, in which the effects of indigenous soil AMF, zeolite addition, and Cd spiking to soil [0, 5, 10, and 15 mg (kg soil)-1] were tested. Zeolite addition to soil spiked with 15 mg Cd kg-1 decreased the Cd uptake to grains from 11.8 to 8.3 mg kg-1 and 8.9 to 3.3 mg kg-1 in the absence and presence of indigenous AMF, respectively. Positive growth, nitrogen (N), and phosphorous (P) uptake responses to mycorrhization in Cd-spiked soils were consistently magnified by zeolite addition. Zeolite addition to soil stimulated AMF root colonization. The abundance of AMF taxa changed in response to zeolite addition to soil and soil Cd spiking as measured by quantitative polymerase chain reaction. With increasing Cd spiking, the abundance of Funneliformis increased. However, when less Cd was spiked to soil and/or when zeolite was added, the abundance of Claroideoglomus and Rhizophagus increased. This study showed that soil-indigenous AMF and addition of zeolite to soil can lower Cd uptake to the grains of bread wheat and thereby reduce Cd contamination of the globally most important staple food.

Health risk assessment of Pb and Cd in soil, wheat, and barley in Shazand County, central of Iran.

BACKGROUND: Heavy metal contamination via mining activity is a serious problem around the world. This study was conducted to evaluate the total non-cancer hazard quotient (THQ) and excess lifetime cancer risks of lead (Pb) and cadmium (Cd) to different population groups via soil, wheat and barley ingestion, soil-dermal contact, and inhalation soil particulates around Shahin mine located in Shazand County. METHODS: Soil and plants were sampled randomly from 60 agricultural fields around Shahin mine. The samples Pb and Cd concentrations were determined using atomic absorption spectroscopy (AAS). The THQ and the excess lifetime cancer risks of Pb and Cd were estimated using the formulas suggested by the U.S. Environmental Protection Agency (USEPA). The Pb non-cancer risk for children (<6 years old) was assessed using the integrated exposure uptake bio-kinetic (IEUBK) model. RESULTS: The mean contents of Pb (234.47 mg kg-1) and Cd (1.89 mg kg-1) in soil samples were higher than the background values. The mean Pb and Cd concentrations in wheat grains were 0.44 and 0.23 µg g-1 respectively, which were about 6.5 and 5.8 times higher than that was observed in barley grains, respectively. The THQ of Pb and Cd for all groups were greater than 1. The excess lifetime cancer risks of Pb via wheat and barley consumption for all receptor groups were greater than 1 × 10-6. CONCLUSIONS: Crop ingestion and soil inhalation had the greatest and lowest portions to increase the THQ and excess lifetime cancer risks of Pb and Cd in the study region, respectively.

Green manure addition to soil increases grain zinc concentration in bread wheat.

Zinc (Zn) deficiency is a major problem for many people living on wheat-based diets. Here, we explored whether addition of green manure of red clover and sunflower to a calcareous soil or inoculating a non-indigenous arbuscular mycorrhizal fungal (AMF) strain may increase grain Zn concentration in bread wheat. For this purpose we performed a multifactorial pot experiment, in which the effects of two green manures (red clover, sunflower), ZnSO4 application, soil γ-irradiation (elimination of naturally occurring AMF), and AMF inoculation were tested. Both green manures were labeled with 65Zn radiotracer to record the Zn recoveries in the aboveground plant biomass. Application of ZnSO4 fertilizer increased grain Zn concentration from 20 to 39 mg Zn kg-1 and sole addition of green manure of sunflower to soil raised grain Zn concentration to 31 mg Zn kg-1. Adding the two together to soil increased grain Zn concentration even further to 54 mg Zn kg-1. Mixing green manure of sunflower to soil mobilized additional 48 µg Zn (kg soil)-1 for transfer to the aboveground plant biomass, compared to the total of 132 µg Zn (kg soil)-1 taken up from plain soil when neither green manure nor ZnSO4 were applied. Green manure amendments to soil also raised the DTPA-extractable Zn in soil. Inoculating a non-indigenous AMF did not increase plant Zn uptake. The study thus showed that organic matter amendments to soil can contribute to a better utilization of naturally stocked soil micronutrients, and thereby reduce any need for major external inputs.

Daily intake of heavy metals and nitrate through greenhouse cucumber and bell pepper consumption and potential health risks for human.

Limited information is available on the health quality of greenhouse vegetables. Lead, cadmium, nickel, chromium, and nitrate (NO3-) concentrations in greenhouse cucumber (Cucumis sativa L.) and bell pepper (Capsicum annuum L.) and their dietary intakes were determined. The non-cancer risk for NO3- was determined using the non-cancer hazard quotient. Lead non-cancer risk in children was calculated using the Integrated Exposure-Uptake Biokinetic model. Higher concentrations of cadmium, lead, and chromium were found in bell pepper than cucumber. The mean NO3- concentration in the greenhouse cucumber was about 2.7 times higher than the World Health Organization standard limit. Cadmium, lead, nickel, and chromium daily intake for different populations groups through consumption of the vegetables were < 0.01-0.04, 0.35-1.00, 0.03-0.24, and 0.05-0.27 microg/g, respectively. The dietary intake of NO3- for adult was greater than children. Elevated lead and NO3- concentrations in the greenhouse vegetables are important concerns for consumers. Potential health quality problems in greenhouse products have to be considered.