Effects of sulphur on yield and malting quality of barley

Regulation of Sulfate Uptake and Assimilation in Barley (Hordeum vulgare) 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.

Response of spring wheat to NPK and S fertilization. The content and uptake of macronutrients and the value of ionic ratios

The aim of the study was to evaluate the effect of nitrogen (N) and sulphur (S) fertilizers on the content and uptake of macronutrients by grain dry mass (DM) of spring wheat. A field experiment was conducted in southeastern Poland on Cambisols (WRB 2007), in conditions of low S content in the soil. The experiment included 2 factors: fertilization with N (0, 40, 80, 120 kg ha-1) and with S (0, 50 kg ha-1).

The experiment showed a positive response of spring wheat to N and S fertilization. The highest grain yield was found after application of 80 kg N ha-1 and addition of 50 kg S ha-1 (5.43 t ha-1). The described combination resulted in beneficial content of phosphorus (P), potassium (K), magnesium (Mg), calcium (Ca) (P –4.267, K–4.533, Mg–1.567, Ca–0.433 g kg-1) and uptake of macroelements by grain dry mass (DM) (P–20.48, K–21.79, Mg–7.52, Ca–2.08 kg ha-1). A generally positive correlation was found between content and uptake of macronutrients with exception of P content. Fertilization with N caused significantly narrowed mass ratios of K+: Ca2+, K+: Mg2+ and mass and mole ratio of K+:(Ca2++Mg2+) and increased mass ratio of Ca:P. While S application narrowed significantly, mass ratios of K+:Ca2+ and K+: (Ca2+ + Mg2+) and increased mass ratio of Ca:P.

Quantification of Hordeins by ELISA: the correct standard makes a magnitude of difference

BACKGROUND

Coeliacs require a life-long gluten-free diet supported by accurate measurement of gluten (hordein) in gluten-free food. The gluten-free food industry, with a value in excess of $6 billion in 2011, currently depends on two ELISA protocols calibrated against standards that may not be representative of the sample being assayed.

AIM

The factors affecting the accuracy of ELISA analysis of hordeins in beer were examined.

RESULTS

A simple alcohol-dithiothreitol extraction protocol successfully extracts the majority of hordeins from barley flour and malt. Primary hordein standards were purified by FPLC. ELISA detected different classes of purified hordeins with vastly different sensitivity. The dissociation constant (Kd) for a given ELISA reaction with different hordeins varied by three orders of magnitude. The Kd of the same hordein determined by ELISA using different antibodies varied by up to two orders of magnitude. The choice of either ELISA kit or hordein standard may bias the results and confound interpretation.

CONCLUSIONS

Accurate determination of hordein requires that the hordein standard used to calibrate the ELISA reaction be identical in composition to the hordeins present in the test substance. In practice it is not feasible to isolate a representative hordein standard from each test food. We suggest that mass spectrometry is more reliable than ELISA, as ELISA enumerates only the concentration of particular amino-acid epitopes which may vary between different hordeins and may not be related to the absolute hordein concentration. MS quantification is undertaken using peptides that are specific and unique enabling the quantification of individual hordein isoforms.

Changes in saccharide, amino acid and S-methylmethionine content during malting of barley grown with different nitrogen and sulfur status

BACKGROUND

Changes in saccharide, amino acid and S-methylmethionine (SMM) concentrations and enzyme activities during the malting of barley grown with different nitrogen (N) and sulfur (S) supplementation were investigated in order to clarify their relationship with N and S fertiliser levels.

RESULTS

Concentrations of N and S in barley grain were significantly increased by the addition of N to the culture soil. Application of N decreased the starch concentration in grain. On the other hand, higher N fertilisation increased the β-glucan concentration in grain and malt, thus decreasing the accessibility of β-glucanase to its substrates. Proteolytic enzyme activity was significantly higher in the absence (-N treatment) than in the presence (+N treatment) of N fertiliser, making the concentration of the majority of amino acids in malt slightly higher in the - N treatment. SMM was synthesised in grain after imbibition, and application of N increased the SMM content in malt.

CONCLUSION

Although SMM can be controlled to a certain extent during kilning, a balanced supply of N and S during cultivation can also be helpful for the production of malt with lower SMM concentration. Adequate soil management is desirable to maintain the balance between good agronomic performance and high malt quality.