Regulation of sulfate uptake and assimilation in barley (<i>Hordeum vulgare</i>) as affected by rhizospheric and atmospheric sulfur nutrition

To study the regulation of sulfate metabolism in barley (Hordeum vulgare), seedlings were exposed to atmospheric hydrogen sulfide (H2S) in the presence and absence of a sulfate supply. Sulfate deprivation reduced shoot and root biomass production by 60% and 70%, respectively, and it affected the plant’s mineral nutrient composition. It resulted in a 5.7- and 2.9-fold increased shoot and root molybdenum content, respectively, and a decreased content of several other mineral nutrients. Particularly, it decreased shoot and root total sulfur contents by 60% and 70%, respectively. These decreases could be ascribed to decreased sulfate contents. Sulfate deficiency was additionally characterized by significantly lowered cysteine, glutathione and soluble protein levels, enhanced dry matter, nitrate and free amino acid contents, an increased APS reductase (APR) activity and an increased expression and activity of the root sulfate uptake transporters. When sulfate-deprived barley was exposed to 0.6 µl l−1 atmospheric H2S, the decrease in biomass production and the development of other sulfur deficiency symptoms were alleviated. Clearly, barley could use H2S, absorbed by the foliage, as a sulfur source for growth. H2S fumigation of both sulfate-deprived and sulfate-sufficient plants downregulated APR activity as well as the expression and activity of the sulfate uptake transporters. Evidently, barley switched from rhizospheric sulfate to atmospheric H2S as sulfur source. Though this indicates that sulfate utilization in barley is controlled by signals originating in the shoot, the signal transduction pathway involved in the shoot-to-root regulation must be further elucidated

Nickel toxicity in Brassica rapa seedlings: Impact on sulfur metabolism and mineral nutrient content

Weltweit haben anthropogene Aktivitäten zu erhöhten Nickel­gehalten im Boden (Ni2+) geführt, was sich negativ auf die Pflanzenproduktivität auswirken kann. Der physiologische Hintergrund der Ni2+ Phytotoxizität ist noch weitgehend unklar. Eine zehntägige Exposition von Brassica rapa Sämlingen mit 1, 2 und 5 μM NiCl2 führte zu stark erhöhten Ni Gehalten im Gewebe, einer verringerten Biomasseproduktion und zu Blattchlorosen bei Konzentrationen von ≥ 2 μM Ni2+. Bei einer Konzentration von 5 μM Ni2+ war kein Pflanzenwachstum mehr zu beobachten. Eine Ni Toxizität trat auf, wenn der Ni Gehalt im Sprosses 1,0 μmol g–1 Trockengewicht und der in der Wurzel 23 μmol g–1 Trockengewicht überschritt. Eine Ni2+ Exposition von 2 μM beein­flusste den Mineralstoffgehalt in Spross und Wurzel nur geringfügig. Daher beeinflusste eine Ni2+ Exposition die Gehalte an Schwefelmetaboliten in der Pflanze kaum. Bei ≥ 1 μM Ni2+ war der Gesamtschwefelgehalt der Wurzel nur geringfügig erniedrigt, was vollständig auf einen verminderten Sulfatgehalt zurückzuführen war. Darüber hinaus war der Gehalt an wasserlöslichen Nicht-Protein-Thiolen sowohl im Spross als auch in der Wurzel nur bei 5 μM Ni2+ erhöht. Aus diesen Ergebnissen geht hervor, dass der Schwefelstoffwechsel wahrscheinlich nicht direkt an den Ni2+ Toleranzmechanismen von B. rapa beteiligt ist.Throughout the world anthropogenic activity has resulted in enhanced soil nickel (Ni2+) levels, which may negatively affect plant productivity. The physiological background of Ni2+ phytotoxicity is still largely unclear. Ten-day exposures of Brassica rapa seedlings to 1, 2 and 5 μM NiCl2 resulted in strongly enhanced tissue Ni levels, a decreased biomass production and leaf chlorosis at ≥ 2 μM Ni2+. At 5 μM Ni2+ plant growth was completely halted. Ni toxicity occurred when the content of the shoot exceeded 1.0 μmol g–1 dry weight and that of the root, 23 μmol g–1 dry weight. Ni2+ exposure at ≤ 2 μM only slightly affected the mineral nutrient content of both shoot and root. Hence, Ni2+ exposure hardly affected the sulfur metabolite content of the plant. At ≥ 1 μM Ni2+ the total sulfur content of the root was only slightly lowered, which could fully be ascribed to a decreased sulfate content. Moreover, the water-soluble non-protein thiol content of both shoot and root was only enhanced at 5 μM Ni2+. From these results it was clear that sulfur metabolism was unlikely to be directly involved in the Ni2+ tolerance mechanisms of B. rapa

Atmospheric H₂S exposure does not affect stomatal aperture in maize

Main conclusion: Stomatal aperture in maize is not affected by exposure to a subtoxic concentration of atmospheric H2S. At least in maize, H2S, thus, is not a gaseous signal molecule that controls stomatal aperture. Abstract: Sulfur is an indispensable element for the physiological functioning of plants with hydrogen sulfide (H2S) potentially acting as gasotransmitter in the regulation of stomatal aperture. It is often assumed that H2S is metabolized into cysteine to stimulate stomatal closure. To study the significance of H2S for the regulation of stomatal closure, maize was exposed to a subtoxic atmospheric H2S level in the presence or absence of a sulfate supply to the root. Similar to other plants, maize could use H2S as a sulfur source for growth. Whereas sulfate-deprived plants had a lower biomass than sulfate-sufficient plants, exposure to H2S alleviated this growth reduction. Shoot sulfate, glutathione, and cysteine levels were significantly higher in H2S-fumigated plants compared to non-fumigated plants. Nevertheless, this was not associated with changes in the leaf area, stomatal density, stomatal resistance, and transpiration rate of plants, meaning that H2S exposure did not affect the transpiration rate per stoma. Hence, it did not affect stomatal aperture, indicating that, at least in maize, H2S is not a gaseous signal molecule controlling this aperture

Are consumers satisfied with the use of prosthetic sports feet and the provision process?:A mixed-methods study

BACKGROUND: Special feet connected to a prosthesis, prosthetic sports feet, enable athletes with a lower limb amputation to run. The selection of a prosthetic sports feet is usually based on body weight and preferred sports performance. The selection of a prosthetic sport feet is also based on clinicians who likely have limited experience due to a small number of athletes with a lower limb amputation. HYPOTHESIS: Athletes with a lower limb amputation are not satisfied with the use and service associated with prosthetic sports feet due to a lack of prosthetic sports feet provision guidelines, poorer function of prosthetic sports feet compared to the anatomical foot and ankle, and limited experience of clinicians. EVALUATION OF HYPOTHESIS: A mixed-methods study in 16 athletes with a lower limb amputation using a prosthetic sport foot from Össur or Otto Bock, included semi-structured interviews and quantitative analysis. Three dimensions of prosthetic sports feet were investigated: 1) use, 2) provision process, and 3) cosmetics. Qualitative data were analyzed to identify factors influencing consumer satisfaction. Quantitative data were analyzed to investigate satisfaction and perceived relative importance of the dimensions. RESULTS: Participants were satisfied with the prosthetic sports feet use. However, they were not satisfied with the process prior to provision. The prosthetic sport feet use was perceived as the most important dimension. Sports performance was the critical element in the prosthetic sports feet use and was influenced by stability, confidence and fear, safety, focus, energy return, and comfort. Cosmetics were unimportant. Motivation to purchase the prosthetic sports feet was the key element for the prosthetic sports foot acquisition. Satisfaction about the process prior to provision was negatively influenced by poor support of professionals during rehabilitation, the complexity and duration of the purchase process, and lack of information and accessibility of prosthetic sports feet. CONCLUSION: The most important dimension of the prosthetic sports feet was its use, which was directly influenced by performance. To further increase the satisfaction with prosthetic sports feet, clinicians should establish how to meet the desired sports performance level of athletes with a lower limb amputation. Improving the process prior to the provision process may increase satisfaction. We suggest increasing the support of professionals during rehabilitation and training through cooperation between involved services, organizing prosthetic sports feet try-out sessions, and increase the accessibility of the prosthetic sports feet. In this way, individuals with a lower limb amputation may become and stay more physically active and participate in sports

Floral displays suffer from sulphur deprivation

Nutrient deficiency is known to constrain plant growth in numerous ways, but how it impacts floral displays and pollination success remains unclear. Here we investigate how insufficient availability of sulphur – a vital plant nutrient that is a limiting factor in natural and agricultural regions throughout the world – influences the production of floral displays in Brassica rapa, Physalis philadelphica and three Petunia species with differently coloured flowers. Sulphur deficiency led to a drastic reduction in the number of open flowers, an aberrant flower morphology and smaller pollen with an altered mineral nutrient content. Intriguingly, sulphur deprivation also led to a clear reduction in pigmentation of yellow flowers, but not in flowers with white, purple and red colours. The pale yellow flower colour was due to decreased amounts of violaxanthin, lutein and other carotenoids, suggesting that the carotenoid synthesis pathway is particularly susceptible to sulphur deficiency. Additional experiments with nitrogen and phosphorus depletion confirmed that observed colour and morphological changes were not a general nutrient limitation response, but could be ascribed to sulphur depletion specifically. Taken together, our results showed that (mild) sulphur deficiency deteriorates a suite of floral traits, and that the effects may cascade to pollinators and so have the potential to undermine (agro-)ecosystem functioning.<br/

Molybdate toxicity in Chinese cabbage is not the direct consequence of changes in sulphur metabolism

In polluted areas, plants may be exposed to supra-optimal levels of the micronutrient molybdenum. The physiological basis of molybdenum phytotoxicity is poorly understood. Plants take up molybdenum as molybdate, which is a structural analogue of sulphate. Therefore, it is presumed that elevated molybdate concentrations may hamper the uptake and subsequent metabolism of sulphate, which may induce sulphur deficiency. In the current research, Chinese cabbage (Brassica pekinensis) seedlings were exposed to 50, 100, 150 and 200 lM Na2MoO4 for 9 days. Leaf chlorosis and a decreased plant growth occurred at concentrations ≥100 lM. Root growth was more affected than shoot growth. At ≥100 lM Na2MoO4, the sulphate uptake rate and capacity were increased, although only when expressed on a root fresh weight basis. When expressed on a whole plant fresh weight basis, which corrects for the impact of molybdate on the shoot-to-root ratio, the sulphate uptake rate and capacity remained unaffected. Molybdate concentrations ≥100 lM altered the mineral nutrient composition of plant tissues, although the levels of sulphur metabolites (sulphate, water-soluble non-protein thiols and total sulphur) were not altered. Moreover, the levels of nitrogen metabolites (nitrate, amino acids, proteins and total nitrogen), which are generally strongly affected by sulphate deprivation, were not affected. The root water-soluble non-protein thiol content was increased, and the tissue nitrate levels decreased, only at 200 lM Na2MoO4. Evidently, molybdenum toxicity in Chinese cabbage was not due to the direct interference of molybdate with the uptake and subsequent metabolism of sulphate

Effect of the Implantable Atrial Defibrillator on the Natural History of Atrial Fibrillation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75480/1/j.1540-8167.1999.tb00296.x.pd