Natural variation occurs in the uptake and distribution of essential and nonessential trace elements among crop species and among cultivars within species. Such variation can be responsible for trace ...element deficiencies and toxicities, which in turn can affect the quality of food. Plant breeding can be an important tool to both increase the concentration of desirable trace elements and reduce that of potentially harmful trace elements such as cadmium (Cd). Selection programs for a low-Cd content of various crops, including durum wheat, sunflower, rice and soybean have been established and low-Cd durum wheat cultivars and sunflower hybrids have been developed. In durum wheat (
Triticum turgidum L. var
durum), low-Cd concentration is controlled by a single dominant gene. The trait is highly heritable, and incorporation of the low-Cd allele can help to reduce the average grain Cd to levels below proposed international limits. The allele for low-Cd concentration does not appear to affect major economic traits and should not cause problems when incorporated into durum cultivars. The cost of Cd selection in a breeding program is initially large both in terms of Cd determination and reduced progress towards development of other economic traits, but declines as more breeding lines in the program carry the low-Cd trait and are utilized in new crosses. Production of low-Cd crop cultivars can be used as a tool to reduce the risk of movement of Cd into the human diet.
Trace element solubility and availability in land-applied residuals is governed by fundamental chemical reactions between metal constituents, soil, and residual components. Iron, aluminum, and ...manganese oxides; organic matter; and phosphates, carbonates, and sulfides are important sinks for trace elements in soil-residual systems. The pH of the soil-residual system is often the most important chemical property governing trace element sorption, precipitation, solubility, and availability. Trace element phytoavailability in residual-treated soils is often estimated using soil extraction methods. However, spectroscopic studies show that sequential extraction methods may not be accurate in perturbed soil-residual systems. Plant bioassay is the best method to measure the effect of residuals on phytoavailability. Key concepts used to describe phytoavailability are (i) the salt effect, (ii) the plateau effect, and (iii) the soil-plant barrier. Metal availability in soil from metal-salt addition is greater than availability in soil from addition of metal-containing residuals. Plant metal content displays plateaus at high residual loadings corresponding to the residual's metal concentration and sorption capacity. The soil-plant barrier limits transmission of many trace elements through the food chain, although Cd (an important human health concern) can bypass the soil-plant barrier. Results from many studies that support these key concepts provide a basis of our understanding of the relationship between trace element chemistry and phytoavailability in residual-treated soils. Research is needed to (i) determine mechanisms for trace element retention of soil-residual systems, (ii) determine the effect of residuals on ecological receptors and the ability of residuals to reduce ecotoxicity in metal-contaminated soil, and (iii) predict the long-term bioavailability of trace elements in soil-residual systems.
Metal hyperaccumulator plants like
Alyssum murale have a remarkable ability to hyperaccumulate Ni from soils containing mostly insoluble Ni. We have shown some rhizobacteria increase the ...phytoavailability of Ni in soils, thus enhancing Ni accumulation by
A. murale. Nine bacterial strains, originally isolated from the rhizosphere of
A. murale grown in serpentine Ni-rich soil, were examined for their ability to solubilize Ni in different soils and for their effect on Ni uptake into
Alyssum. Microbacterium oxydans AY509223;
Rhizobium galegae AY509213;
Microbacterium oxydans AY509219;
Clavibacter xyli AY509236;
Acidovorax avenae AY512827;
Microbacterium a
rabinogalactanolyticum AY509225;
M. oxydans AY509222;
M. arabinogalactanolyticum AY509226 and
M. oxydans AY509221 were added to low, moderate and high Ni-contaminated soils.
M. oxydans AY509223 significantly increased Ni extraction by 10
mM Sr(NO
3)
2 from the high and medium soils and had no effect on Ni extraction from the low Ni soils. The other eight bacterial isolates significantly increased Ni extraction from all soils. There were no significant effects of bacterial inoculation on fresh and dry weight of
A . murale shoots grown in the low and high Ni soils compared to an unamended control.
M. oxydans AY509223 significantly increased Ni uptake of
A. murale grown in the low, medium, and high soils by 36.1%, 39.3%, and 27.7%, respectively, compared with uninoculated seeds.
M. oxydans AY509223 increased foliar Ni from the same soils from 82.9, 261.3 and 2829.3
mg
kg
−1 to 129.7, 430.7, and 3914.3
mg
kg
−1, respectively, compared with uninoculated controls. These results show that bacteria are important for Ni hyperaccumulation and could potentially be developed as an inoculum for enhancing uptake during commercial phytoremediation or phytomining of Ni.
Cadmium (Cd) is toxic to animals and humans after it accumulates over decades in the kidney cortex. Food crops grown in Cd-contaminated soils are the primary sources of excessive Cd entry into ...humans. Although plant available Zn concentration in soil is an important factor which can greatly reduce Cd uptake by plant roots and its translocation into the edible parts, Cd:Zn ratio is suggested to be a more important factor in comparison with Zn concentration alone in determining Cd uptake by plants. In the present study, the physiological mechanisms of Cd absorption by roots and its translocation to leaves of lettuce (Lactuca sativa L.) at various Cd:Zn ratios in the rooting media were investigated. For this purpose, seedlings of hydroponically-grown lettuce were exposed to combinations of four Zn (0, 12.5, 50 and 100μM) and four Cd (0, 0.5, 1 and 10μM) concentrations providing different ratios of Cd:Zn. At each level of Cd, decreasing the Cd:Zn ratio by increasing Zn concentration in the nutrient solution caused significant reduction of root symplastic Cd and also reduced Cd loading into the xylem and Cd transport to and accumulation in leaves. The highest root symplastic Cd (1087mg/kg-1 Dry Weight DW) and shoot Cd concentrations (64mg/kg-1 DW) were observed at the highest Cd:Zn ratio of = 0.8 (Zn = 12.5, Cd = 10). At the Cd:Zn ratios of ≤ 0.01, shoot Cd concentration was less than the Detection Limit (< 0.02mg/kg DW). Decreasing Cd:Zn ratio in nutrient solution was accompanied with significant increase in root apoplastic Cd and decrease in the root symplastic Cd. According to the obtained results, at the Cd:Zn ratio equal to 0.01 and less, Cd concentration in lettuce shoots decreased to < 0.02mg/kg.
•Root Cd uptake and its translocation to lettuce leaves at various Cd:Zn ratios was investigated.•At each Cd level, decreasing Cd:Zn ratio by increasing Zn concentration reduced root symplastic Cd.•Reduced Cd:Zn ratio resulted a decrease of Cd loading into the xylem and its accumulation in leaves.•Increasing Cd in nutrient solution caused increasing root symplastic Zn and Zn loading to xylem.•At the Cd:Zn ratio of ≤ 0.01, Cd concentration in lettuce shoots decreased to < 0.02mg/kg.
High blood pressure (BP) is a known risk factor for mobility and cognitive impairment in older adults. This study tested the association of cumulative BP exposure from young adulthood to midlife with ...gait and cognitive function in midlife. Furthermore, we tested whether these associations were modified by cerebral white matter hyperintensity (WMH) burden.
We included 191 participants from the CARDIA study (Coronary Artery Risk Development in Young Adults), a community-based cohort of young individuals followed over 30 years. Cumulative BP was calculated as the area under the curve (mm Hg×years) from baseline up to year 30 examination. Gait and cognition were assessed at the year 30 examination. Cerebral WMH was available at year 30 in a subset of participants (n=144) who underwent magnetic resonance imaging. Multiple linear regression models were used to assess the association of cumulative BP exposure with gait and cognition. To test effect modification by WMH burden, participants were stratified at the median of WMH and tested for interaction.
Higher cumulative systolic and diastolic BPs were associated with slower walking speed (both
=0.010), smaller step length (
=0.011 and 0.005, respectively), and higher gait variability (
=0.018 and 0.001, respectively). Higher cumulative systolic BP was associated with lower cognitive performance in the executive (
=0.021), memory (
=0.015), and global domains (
=0.010), and higher cumulative diastolic BP was associated with lower cognitive performance in the memory domain (
=0.012). All associations were independent of socio-demographics and vascular risk factors (body mass index, smoking, diabetes mellitus and total cholesterol). The association between cumulative BP and gait was moderated by WMH burden (interaction
<0.05). However, the relation between cumulative BP and cognitive function was not different based on the WMH burden (interaction
>0.05).
Exposure to higher BP levels from young to midlife is associated with worse gait and cognitive performance in midlife. Furthermore, WMH moderates the association of cumulative BP exposure with gait, but not with cognitive function in midlife. The mechanisms underpinning the impact of BP exposure on brain structure and function must be investigated in longitudinal studies using a life course approach.
Rice (Oryza sativa L.) grown on cadmium (Cd)-contaminated soils has caused health problems in Asian subsistence rice farmers. For other crops, normal co-contaminant zinc (Zn) inhibits the increased ...uptake of Cd. We used a multi-chelator-buffered nutrient solution to characterize the interaction of Zn and Cd in uptake-translocation of Cd in "Lemont" rice. The activity of free Zn
2+
varied from 10
−7.6
to 10
−5.2
M, while free Cd
2+
held constant at 10
−10.7
M. Zinc activity 10
−5.6
M and higher was phytotoxic to rice, resulting in severe chlorosis, reduced growth, and increased Cd transport to shoots. In contrast to previous studies with wheat, lettuce, and spinach, free Zn
2+
maintained at adequate to sub-phytotoxic levels (10
−7.6
to 10
−6.1
) did not inhibit Cd uptake by rice. The inability of Zn to inhibit Cd uptake by rice is a key factor in Cd risk from zinc-lead mine waste contaminated soil compared with other crops.
To quantify the accuracy of and clinical events associated with a risk alert threshold for impending hypoglycemia during ICU admissions.
Retrospective electronic health record review of clinical ...events occurring greater than or equal to 1 and less than or equal to 12 hours after the hypoglycemia risk alert threshold was met.
Adult ICU admissions from June 2020 through April 2021 at the University of Virginia Medical Center.
Three hundred forty-two critically ill adults that were 63.5% male with median age 60.8 years, median weight 79.1 kg, and median body mass index of 27.5 kg/m2.
Real-world testing of our validated predictive model as a clinical decision support tool for ICU hypoglycemia.
We retrospectively reviewed 350 hypothetical alerts that met inclusion criteria for analysis. The alerts correctly predicted 48 cases of level 1 hypoglycemia that occurred greater than or equal to 1 and less than or equal to 12 hours after the alert threshold was met (positive predictive value = 13.7%). Twenty-one of these 48 cases (43.8%) involved level 2 hypoglycemia. Notably, three myocardial infarctions, one medical emergency team call, 19 deaths, and 20 arrhythmias occurred greater than or equal to 1 and less than or equal to 12 hours after an alert threshold was met.
Alerts generated by a validated ICU hypoglycemia prediction model had a positive predictive value of 13.7% for real-world hypoglycemia events. This proof-of-concept result suggests that the predictive model offers clinical value, but further prospective testing is needed to confirm this.
Historic emissions from two zinc smelters have injured the forest on Blue Mountain near Palmerton, Pennsylvania, USA. Seedlings of soybeans and five tree species were grown in a greenhouse in a ...series of mixtures of smelter-contaminated and reference soils and then phytotoxic thresholds were calculated. As little as 10% Palmerton soil mixed with reference soil killed or greatly stunted seedlings of most species. Zinc was the principal cause of the phytotoxicity to the tree seedlings, although Mn and Cd may also have been phytotoxic in the most contaminated soil mixtures. Calcium deficiency seemed to play a role in the observed phytotoxicity. Exposed soybeans showed symptoms of Mn toxicity. A test of the effect of liming on remediation of the Zn and Mn phytotoxicity caused a striking decrease in Sr-nitrate extractable metals in soils and demonstrated that liming was critical to remediation and restoration.
•Zinc in smelter-contaminated acid soil was highly toxic to tree seedlings.•Phytotoxic thresholds (Zn in soil, leaves and roots) were estimated.•Liming greatly ameliorated the phytotoxicity.•Calcium deficiency played a role in the phytotoxicity.•Soybeans showed symptoms of Mn toxicity.
This work estimates the phytotoxic thresholds of Zn to tree seedlings in smelter-contaminated soil and explains the interactions of Zn with Mn and Ca.
• Alyssum murale has a remarkable ability to hyperaccumulate Ni from soils containing mostly nonlabile Ni. Here, rhizobacteria are shown to play an important role in increasing the availability of Ni ...in soil, thus enhancing Ni accumulation by A. murale. • Three bacteria, originally isolated from the rhizosphere of A. murale, were examined for their ability to solubilize Ni in soil and for their effect on Ni uptake into Alyssum. Sphingomonas macrogoltabidus, Microbacterium liquefaciens, and Microbacterium arabinogalactanolyticum were added to both sterile and nonsterile Ni-rich Serpentine soil from OR, USA. • Sphingomonas macrogoltabidus significantly reduced Ni extraction by 10 mM Sr( NO3)2from soil, M. arabinogalactanolyticum significantly increased Ni extraction, whereas M. liquefaciens had no effect. Extractability of few other metals was affected by inoculation. When these bacteria were added to surface-sterilized seeds of A. murale grown in nonsterile soil, they increased Ni uptake into the shoot by 17% (S. macrogoltabidus), 24% (M. liquefaciens), and 32.4% (M. arabinogalactanolyticum), compared with uninoculated controls. • These results show that bacteria are important for Ni uptake, which from a commercial perspective, could significantly increase revenue generated during phytomining of Ni from soil.
The nickel (Ni) hyperaccumulator Alyssum murale has been developed as a commercial crop for phytoremediation/phytomining Ni from metal-enriched soils. Here, metal co-tolerance, accumulation and ...localization were investigated for A. murale exposed to metal co-contaminants. A. murale was irrigated with Ni-enriched nutrient solutions containing basal or elevated concentrations of cobalt (Co) or zinc (Zn). Metal localization and elemental associations were investigated in situ with synchrotron X-ray microfluorescence (SXRF) and computed-microtomography (CMT). A. murale hyperaccumulated Ni and Co (> 1000 μg g⁻¹ dry weight) from mixed-metal systems. Zinc was not hyperaccumulated. Elevated Co or Zn concentrations did not alter Ni accumulation or localization. SXRF images showed uniform Ni distribution in leaves and preferential localization of Co near leaf tips/margins. CMT images revealed that leaf epidermal tissue was enriched with Ni but devoid of Co, that Co was localized in the apoplasm of leaf ground tissue and that Co was sequestered on leaf surfaces near the tips/margins. Cobalt-rich mineral precipitate(s) form on leaves of Co-treated A. murale. Specialized biochemical processes linked with Ni (hyper)tolerance in A. murale do not confer (hyper)tolerance to Co. A. murale relies on a different metal storage mechanism for Co (exocellular sequestration) than for Ni (vacuolar sequestration).
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