Total hemicelluloses from wheat at different stages of growth

The changes in total hemicellulose composition of leaf and stem tissues of field-grown wheat plants have been examined. In each plant tissue the percentage of xylose in the total hemicellulose increases with increasing plant maturity, that of galactose varies little and those of L-arabinose, D-glucose, and uronic acid decrease. There is a markedly higher proportion of D-glucopyranuronosyl than of 4-O-methyl-D-glucopyranuronosyl residues in leaf and stem tissues at all stages of maturity. The ratio of β(1 → 3) to β(1 → 4) linkages in the β-glucans, and the DP of these β-glucans decrease concommitantly with tissue maturity.     

Metabolism of gramine in Hordeum vulgare plants: A time course study

Intact Hordeum vulgare plants quantitatively degrade [α-¹⁴C] gramine to ¹⁴CO₂.     

Xylans from the tropical grass Panicum maximum

Two xylans have been isolated from the mature tissues of the tropical grass Panicum maximum—an arabino(4-O-methylglucurono)xylan and an acidic galactoarabinoxylan. Both consist of a main chain of β(1 → 4) linked d-xylopyranosyl residues. The former has average of ca 46 such residues to which are attached ca 7 l-arabinofuranosyl and (ca 2 4-O-methyl-d-glucopyranuronosyl residues at C3 and C2 positions respectively. The acidic galactoarabinoxylan has a $\text{DP}$_n of ca 90 and contains arabinose, galactose, xylose and uronic acid residues in the molar ratio 10:5:22:4. Methylation analysis and periodate oxidation indicated the highly branched nature of this polysaccharide.     

Lysine-rich proteins in high-lysine Hordeum vulgare grain

The salt-soluble proteins in barley grain selected for high-lysine content (Hiproly, CI 7115 and the mutants 29 and 86) and of a control (Carlsberg II) with normal lysine content, contain identical major proteins as determined by MW and electrophoretic mobility. The concentration of a protein group with a high lysine content varies significantly among the barleys examined. One protein, present in large amounts in Hiproly, is assumed to be partially responsible for the high-lysine character of Hiproly, CI 7115 and the mutants 29 and 86.     

Sitosterol biosynthesis in Hordeum vulgare

Excised barley embryos cultured on a nutrient medium containing methionine-[CD₃] incorporated deuterium into the newly biosynthesized sterols. Two deuterium atoms were present in 24-methylenecycloartanol, 24-methylenelophenol and campesterol and a maximum of four deuterium atoms were incorporated into 24-ethylidenelophenol, stigmasterol and sitosterol. Mevalonic acid-[2-¹⁴C(4R)4-³H₁] was utilized by the barley embryos to give 28-isofucosterol with a ³H-¹⁴C atomic ratio of 3:5 and stigmasterol and sitosterol with a ³H-¹⁴C atomic ratio of 2:5. 24-Methylenelophenol and 24-ethylidenelophenol were isolated from barley seed and 24-ethylidenelophenol-[2,4-³H₃] was incorporated into sitosterol by barley seedlings. These results show that in the production of sitosterol a 24-ethylidenesterol intermediate is produced and it is suggested that this is isomerized to give a Δ^24,(25) sterol prior to reduction to the saturated C₂₉ sterol side chain.     

Polyamine oxidation by enzymes from Hordeum vulgare and Pisum sativum seedlings

The properties of the amine oxidases of barley leaves and pea seedling cotyledons have been compared using a colorimetric assay in which the hydrogen p     

Amine levels in mineral-deficient Hordeum vulgare leaves

In potassium-deficient barley leaves, on the basis of fresh weight, putrescine was 13·3-fold greater and in magnesium deficiency 3-8-fold greater than controls. Putrescine was found to be reduced in phosphorus (× 0·6), sulphur (× 0·5) and nitrogen (× 0·2) deficiencies and on substituting nitrate for ammonium (× 0·2). Calcium deficiency and high salt (KCl) increased putrescine by 1·5-fold. High KCl reduced spermidine levels (× 0·2) without a corresponding reduction in spermine levels. The agmatine content was enhanced in magnesium- (× 2·5) and potassium- (× 5) deficient plants, while the arginine was increased × 1·4 and × 2·0 respectively on a fresh weight basis. Compounds tentatively identified as diaminopropane and 1-(3-aminopropyl)pyrroline were increased significantly with high KCl and low calcium. No homospermidine or diaminodipropylamine could be detected in any of the extracts, but traces of cadaverine may be present.     

Degradation of [β-14C]hordenine in Hordeum vulgare plants

[β-¹⁴C]Hordenine is ultimately degraded by intact plants of Hordeum vulgare to C₆-C₁ intermediates that are incorporated into polymeric material.     

Stereochemistry of the reaction catalysed by glutamic acid decarboxylase from a higher plant (Hordeum vulgare)

The decarboxylation of (2S)-glutamic acid to yield γ-aminobutyric acid catalysed by L-glutamic acid decarboxylase (EC 4.1.1.15) from Hordeum vulgare proceeds with net retention. The result is interpreted in terms of a single progenitor hypothesis of the pyridoxal phosphate enzymes and confirms that not only bacteria and animals but also plant decarboxylases catalyse the biosynthesis of biogenic amines from amino acids with net retention.     

An arabinogalacto(4-O-methylglucurono)xylan from the leaves of Hordeum vulgare

An arabinogalacto(4-O-methylglucurono)xylan with a $\text{DP}$_n of ca. 96 has been isolated from the leaves of barley. Based on structural studies it is proposed that the hemicellulose consists of a main chain of β (1→4)-linked d-xylopyranosyl residues to which are attached an average of 8·1 l-arabinofuranosyl residues, 3·8 galactopyranosyl-(1→4)-d-xylopyranosyl-(1→2)-l-arabinofuranosyl residues and 4·4 4-O-methyl-d-glucopyranuronosyl residues.     

Hemicelluloses of Arundo donax at different stages of maturity

The hemicellulosic composition of the internodes of Arundo donax depends on the maturity of the tissue. The percentage of xylose in the total hemicellulose increases with increasing plant maturity. The main hemicellulose is an arabino-4-O-methyl glucurono xylan which is already present in the youngest tissues and has the same structural features regardless of the age of the tissues. The average D.P. of this polysaccharide increases from about 60 to 150 with maturation of the plant tissue.     

Uronic acid residues in the total hemicelluloses of oats

A new method for the estimation of uronic acid residues is described. The changes in total hemicellulose composition of the leaf and stem tissues of field-grown oat plants have been further examined. In any one such tissue, increased plant maturity is accompanied by an increase in the percentage of xylose residues and by decreases in the percentages of arabinosyl, glucosyl, and uronosyl residues. The ratio of 4-O-methyl-D-glucuronosyl to D-glucuronosyl residues increases with maturity.     

Generation of α-amylase in germinating Hordeum distichon

The scutellar tissue of germinating barley synthesises significant amounts of a-amylase. The endogenous level of sugars probably limits the initial formation of α-amylase mainly by repressing the supply of gibberellins to the aleurone layer.     

On the intracellular site of biosynthesis of α-tocopherol in Hordeum vulgare

When barley seedlings were exposed to ¹⁴CO₂ for 1–3 hr, ¹⁴C was preferentially incorporated into plastoquinone, but only in low amounts i     

Gibberellin estimation and biosynthesis in germinating Hordeum distichon

Gibberellic acid (GA₃) and 13-deoxy-gibberellic acid (GA₇) were identified in extracts of germinating barley as their ¹⁴C-methyl esters. The maximal level of GA₃ was estimated by an isotopic dilution procedure to be 1·5 ng per grain. Germinating barley incorporated 2-¹⁴C-mevalonic acid into several terpenes, whose specific radioactivities were measured, but incorporation into GA₃ could not be detected. Cell-free embryo extracts from germinating barley converted 2-¹⁴C-mevalonic acid into isopentenol, dimethylallyl alcohol, farnesol and squalene, while ¹⁴C-isopentenyl pyrophosphate was incorporated into geraniol, farnesol, geranylgeraniol and squalene. There was no detectable incorporation into the gibberellin intermediate ent-kaurene.     

Ent-kaurene,occurrence and metabolism in Hordeum distichon

Barley grains contain hydrocarbons, including a material indistinguishable from ent-kaurene by GLC, and which after appropriate chemical conversions contain material behaving like ent-kauran-16,17-diol, ent-kaurene norketone and ent-17-nor-kaurane on TLC and GLC. The presence of ent-kaurene was confirmed by conversion to ent-kauran-16-ol and, following formation of acetate-[³H], recrystallization to constant specific activity with unlabelled carrier. In the initial ca. 15 hr of germination, preceding the rise in endogenous gibberellins, the level of ent-kaurene falls. Exogenous ent-kaurene-[¹⁴C] was not metabolized by intact barley grains. ent-Kauran-16,17-epoxide was formed non-enzymically by boiled extracts. Unboiled homogenates also formed ent-kauran-17-ol and ent-kauran-16,17-diol. The diol appeared to be formed from the epoxide, but the ent-kauran-17-ol was not. No recognized gibberellin precursors were detected. Nevertheless, endogenous ent-kaurene may be the stored biosynthetic precursor of gibberellins in germinating barley grains.     

Extraction of Sorghum vulgare and hordeum vulgare α-glucosidase

Sorghum and barley grain α-glucosidase are both insoluble in water. They are, nevertheless, active in the insoluble state. Limited extraction of the     

Enzymes of carbohydrate metabolism in developing Hordeum distichum grain

Variations in activity of several enzymes associated with carbohydrate metabolism were recorded during the development of barley endosperm. The enzymes investigated were: sucrose-UDP (ADP) glucosyl transferase; invertase; UDPG (ADPG) pyrophosphorylase; hexokinase; glucose-6-phosphate ketoisomerase; phosphoglucomutase, and nucleosidediphosphokinase.     

Properties of three sets of isoenzymes of alcohol dehydrogenase isolated from barley (Hordeum vulgare)

Three sets of isoenzymes of alcohol dehydrogenase were separated from root and shoot tissue of Hordeum vulgare by DEAE-cellulose chromatography. Set I showed only one band of ADH activity after polyacrylamide gel electrophoresis; Set II—two and Set III—three, making a total of six discernable bands. Only one set (I) was detected in the dry seed and one set (III) in the M9 (Adh-1-null) mutant available in tissue culture. The sets were found to have identical molecular weights (90 000), were all located in the cytoplasm but showed small differences in pH optima and substrate specificity. The affinity for ethanol (K_m value, mM) varied between Set I (27.5), Set II (7.2) and Set III (3.5), whilst the affinity for NADH varied five-fold between the three sets. A dimeric quaternary structure was inferred from the random reassociation of enzyme subunits after dissociation in high ionic strength buffer.     

Biochemical changes during embryogeny in Hordeum distichum

Changes in fr. and dry wt, soluble reducing sugars, protein. total carbohydrate, DNA, RNA, sucrose synthetase activity and invertase activity were recorded for the developing embryo of Hordeum distichum var Julia over the period 18–60 days after anthesis. Fresh wt increased until 45 days whereupon rapid dehydration commenced. Reducing sugar concentration remained low throughout development but total carbohydrate and protein accumulated rapidly over the initial period to reach maximum values at around 50 days. DNA concentration remained relatively constant throughout the middle and later stages of development, but RNA, on the other hand, increased rapidly to reach a maximum value at maturity. Sucrose synthetase (assayed in the direction of sucrose cleavage) was considerably more active with UDP than ADP and reached a maximum value around 35 days after anthesis. When assayed in the direction of sucrose synthesis the peak of activity was slightly later in development and doubled in value. Invertase activity was appreciable and was still present at maturity.