Hordeum Distichum Research Articles

Accumulation of Free Proline at Low Temperatures

AbstractThe accumulation of free proline in the first leaves of barley, Hordeum distichum L., and wheat, Triticum aestivum L., in response to a range of low temperatures was examined with 10‐day‐old plants. In barley (cv. Prior) no proline accumulated at 8°C or above, but in wheat (cv. Gabo) proline accumulated at 12°C and lower temperatures. In barley, the first leaf survived for 29 days following transfer to 5°C and continued to accumulate proline throughout this period. In contrast, the first leaves of plants maintained at 20°C survived for 13 days only and accumulated no proline. Proline accumulation at low temperature was shown to be light‐dependent, both in intact plants and excised leaf sections, and the light requirement could not be replaced by supplying leaf segments with precursors of proline. Proline accumulation in response to water stress was not light‐dependent at 20°C but was at 5°C.Inter‐specific and intra‐specific variation in the extent of accumulation in response to low temperature was also examined. Considerable variation was encountered but there was no clear relationship with geographical distribution or chilling sensitivity for the species and no correlation with accumulation in response to water stress in the cultivars of barley examined.

Metabolism of Ammonium Ion and Glutamate in Relation to Nitrogen Supply and Utilization during Grain Development in Barley

Changes in the activity of a number of enzymes concerned with amino acid synthesis and metabolism were recorded for the endosperm, testa pericarp, and embryo of developing barley (Hordeum distichum L.) grains. Both glutamate-pyruvate transaminase and glutamate-oxaloacetate transaminase activities were present in all tissues and at all ages examined. Glutamate dehydrogenase activity was largely confined to endosperm while glutamine synthetase activity was mainly in the testa pericarp.Ammonium ion concentration was maximal in endosperm by 20 days after anthesis. Glutamate concentration varied in endosperm and was in the range of 3.5 to 8.5 mm between 20 and 45 days after anthesis. Significant levels of ammonium ion and glutamate were also present in the testa pericarp over the major part of the developmental period.

ECONOMIC SIGNIFICANCE OF BARLEY STRIPE MOSAIC VIRUS IN THE CANADIAN PRAIRIES

A method is described by which losses in seed yield due to barley stripe mosaic virus (BSMV) in commercially grown two-row barley (Hordeum distichum L. emend. Lam.) in the Canadian prairies were estimated. Commercial loss estimates were based on previously obtained survey data on the incidence of barley stripe mosaic (BSM) and experimentally determined yield losses for three cultivars of two-row barley inoculated with BSMV at the tillering stage. Based on studies conducted in several fields, a correction factor (1.5 × % plants with BSM symptoms) was used to account for probable symptomless infection by BSMV in surveyed fields examined at the tillering and jointing stages. Using this method, it was estimated that BSMV infection of two-row barley in southeastern Manitoba and southern Alberta accounted for combined yield losses of approximately 7,600 t (equivalent to about $0.8 million) in both 1974 and 1975. The possible nature of symptomless infection by BSMV is discussed.

Does abscisic acid influence proline accumulation in stressed leaves?

Root treatments of barley (Hordeum distichum L.) plants with 10(-7) to 10(-4) M abscisic acid (ABA) caused an increase in proline content, especially at higher concentrations, within 2-3 h. Even 3 h after the removal of ABA from the medium the plants continued to accumulate proline. The higher the concentration of the ABA, the higher was the proline level at 6 h. When the highest ABA concentration, 10(-4) M, was tested with polyethylene glycol (PEG) (-5.0 bars) in the medium, the ABA treatment resulted in a higher proline content than in control plants. The treatments "PEG alone" and "PEG + ABA" resulted in heavy accumulation of proline, especially, 3 h after releasing the plants from the stress. The proline content in PEG+ABA-treated plants was always higher than plants treated with PGE or ABA alone. In peas (Pisum sativum L. cv Alaska) the same trend occurred although to a lesser degree. These findings indicate an influence of ABA on proline accumulation in water-stressed plants.

Prediction of seed longevity at sub-zero temperatures and genetic resources conservation

THE International Board for Plant Genetic Resources (IBPGR) is encouraging the development of an international network of seed banks for the conservation of the genetic resources of the major crop species of the world and their wild relatives1. Most of the species in priority lists show ‘orthodox’ seed characteristics2, that is their longevity is prolonged in a defined manner by a reduction in moisture content (MC) (at least down to 5% MC, fresh weight basis) and temperature3. From a consideration of biological factors and the design and cost of seed storage facilities, IBPGR recommends that orthodox seeds are stored at −18 °C or less and at 5± 1% MC2. It is convenient to aim at −20 °C as the nominal temperature. Because of the accumulation of mutations associated with loss of viability4,5, IBPGR recommends regeneration of stocks (that is growing plants to provide new seeds from the old) when viability has fallen by 5% (ref. 2). To plan ancillary facilities and procedures, it is necessary to estimate regeneration intervals (time taken for viability to fall by 5%) for the major crop species. Such estimates pose three problems: there are genotypically controlled variations in longevity within a species; seed ‘quality’, determined by conditions before harvest and during processing, can affect subsequent longevity; and loss of viability at −20 °C is extremely slow, and so far it has been possible to predict regeneration interval only by questionable extrapolation from more favourable storage conditions5,6. We have examined these problems in barley (Hordeum distichum, L.) and have developed an approach which should make possible more accurate predictions from experiments lasting only 2 yr—even though fresh seed of most species shows no detectable loss of viability during this time.

The uptake of copper by barley roots in the presence of zinc

Summary The uptake of copper by intact barley roots (Hordeum distichum L.) was shown to be unaffected by the presence of zinc in uptake experiments lasting 2 and 24 h. Addition of zinc sulphate to the uptake medium did not alter the kinetic constants respective of the uptake of copper in concentration-dependent uptake experiments of 2 and 24 h duration. It is concluded that the uptake of copper by intact barley roots is mediated by a mechanism which is not influenced by the presence of zinc.

Separation and Some Properties of Large and Small Amyloplasts throughout Development in Barley Endosperm

A method is described whereby amyloplasts from immature barley (Hordeum distichum L.) endosperm could be separated into two populations of large and small amyloplasts at all stages of development. The small amyloplasts had more amylopectin than the large at early stages, but by 60 days after anthesis, the large had the greater proportion of amylopectin. Starch synthetase activity was associated with both types of amyloplast. The nucleotide specificity of the starch synthetase associated with each population varied independently throughout development. At 25 days after anthesis, the large amyloplasts were more susceptible than the small to alpha-amylolysis; however, at 38 and 60 days, the small amyloplasts became more susceptible.

Free and Protein‐bound β‐Amylases of Barley Grain. Characterization by Two‐dimensional Immunoelectrophoresis

AbstractThe β‐amylases of ungerminated barley (Hordeum distichum L. cv. Emir) were characterized by two‐dimensional immunoelectrophoretic techniques in order to elucidate the structure and physiological importance of the latent β‐amylase present in cereal grains. Two water‐soluble forms with partial immunochemical identity were detected. One of the enzyme forms was found to consist of aggregates between β‐amylase and an immunochemically distinct non‐active protein. Both β‐amylase and the protein could be released from the aggregates with β‐mercaptoethanol and, to some extent, with papain. β‐Mercaptoethanol increased the extractability of β‐amylase and of the non‐active protein. The aggregated form of β‐amylase was found to predominate in extracts made in the presence of papain. Possible functions of the non‐enzymatic protein in formation of latent β‐amylase is discussed.

SCREENING FOR HIGH-LYSINE CULTIVARS IN A BARLEY BREEDING PROGRAM

The UDY dye-binding method for determining protein levels in cereal grains was applied to an F2 population derived from a cross between OR 585, a two-rowed selection of barley (Hordeum distichum L. emend Lam.) possessing the "Hiproly" gene(s) for high lysine and TR 412, a two-rowed selection with a normal level of lysine. Seed of the two parental gentoypes produce different UDY absorbance values at similar protein levels. If UDY absorbance values are determined for the parental genotypes over a range of barley protein contents, the different regression lines for OR 585 and TR 412 parental barleys can be used to segregate F2 progeny that express the gene for high lysine. Determination of lysine by the UDY method closely agrees with lysine values determined by amino acid analysis.

Concentration Dependent Uptake of Copper by Barley Roots

AbstractThe time course of the uptake of copper by excised barley roots (Hordeum distichum L.) after 24 h shows other characteristics than after 2 h. A further investigation of the concentration dependent uptake of copper by intact roots and kinetic analysis demonstrates a biphasic pattern for 2 h uptake periods, and possibly monophasic behaviour for uptake periods of 20 min and 24 h.Plasmolysis data of cortex cells of barley roots indicate that concentrations above 80 μM Cu are unphysiological with regard to longer uptake periods.

Appearance and development of P700 oxidation and photosystem I activity in etio-chloroplasts prepared from greening barley leaves

The development of photosystem I activity of plastids isolated from greening barley (Hordeum distichum, L.) leaves was studied. The electron transport activity in photosystem I was measured as anthraquinone-mediated oxygen uptake and as light induced absorbance changes of the reaction centre molecule P700. P700 oxidation was observed after one hour of greening though an electron transport leading to oxygen uptake was observed after 30 minutes. Phenazine methosulphate had no effect on the oxidation of P700 until after four hours of greening. The ratio chlorophyll/P700 decreased from about 2300/l at one hour to 640/l at sixteen hours of greening. The light intensity dependence of the electron transport of photosystem I showed that the photosynthetic units gradually increased in size as the greening proceeded. The increase of the rate of the oxygen uptake, calculated on plastid basis, decreased after eight hours while the P700 content, calculated on plastid basis, increased continuously between three and sixteen hours. Chromatographic separations and fluorimetric analyses of the chlorophyll pigments showed that the reaction centre molecule could not be protochlorophyllide or chlorophyllide.

Genotypic and Environmental Influences on Germination and Callus Induction in Hordeum distichum

Different genotypes of barley were studied in their reactions against the synthetic auxin 2,4-D 1) during germination. The auxin treatment leads to callus formation in different locations in the seedlings, depending on the genotype. While in one genotype (initial line Haisa II) callus formation appeared in the root tips, in its mutant ( ert 16), differing in one gene, callus was derived from the embryo. The influence of seed size and genotype in this process is discussed.

Partial purification and characterization of the linoleate hydroperoxide isomerase from grains of Hordeum distichum

Linoleate hydroperoxide isomerase was mainly located in the embryos of barley grains and its activity decreased during germination. The enzyme partially purified from embryos converted 9-hydroperoxy, trans-10, cis-12-octadecadienoic acid to 9-hydroxy, 10-oxo, cis-12-octadecenoic acid and 13-hydroxy, 10-oxo, trans-11-octadecenoic acid in the ratio of ca 2:1.

Partial purification and characterization of the lipoxygenase from grains of Hordeum distichum

Lipoxygenase activities in ungerminated and germinating barley grains were found to be associated exclusively with the embryos. A lipoxygenase was extracted from ungerminated embryos and partially purified by fractional precipitation with ammonium sulfate and gel-filtration. Both the crude extracts and the purified preparation appeared to contain only a fatty acid type lipoxygenase which mainly converted linolele acid to 9-hydroperoxy, trans-10, cis-12-octadecadienoic acid. The purified enzyme was inhibited by its own products, hydroperoxides, but not by 1 mM cyanide, EDTA, Hg2+ or Cu2+.

Δ1-Pyrroline-5-carboxylic Acid Dehydrogenase in Barley, a Proline-accumulating Species

The characteristics of the enzyme Delta(1)-pyrroline-5-carboxylic acid dehydrogenase from etiolated barley (Hordeum distichum) shoots have been examined. The bulk of the enzyme activity was found in the 10,000g pellet fraction, this activity being displayed only after detergent treatment of the suspended pellet. The enzyme was most active at pH 8, and activity was NAD-dependent. Enzyme activity was unaffected by either mannitol or sucrose in the reaction mixture up to a concentration of 0.45 m but was strongly inhibited by Cl(-) and, to a lesser extent, SO(4) (2-). The inhibition attributable to KCl was reversed by increasing the concentration of Delta(1)-pyrroline-5-carboxylic acid in the reaction mixture.

Studies on Trypsin Inhibitor in Barley<subtitle>I. Purification and Some Properties</subtitle>

To clarify the properties and functions of a trypsin inhibitor from Japanese barley in comparison with the inhibitor from Pirkka barley, an inhibitor was isolated from the barley Hordeum distichum L var. emend Lamark by extraction with 1% NaCl, ammonium sulfate fractionation and repeated chromatography on DEAE-cellulose and CM-cellulose. The final purified preparation of the inhibitor was found to be homogeneous by both chromatographic and electrophoretic analysis. The inhibitor was thermostable and was stable over the broad pH range from 2 to 11. No inhibition was observed by heavy metal ions and many reagents at 10(-2) M, except that p-chloromercuribenzoate caused a 69% loss of activity. The inhibitor was subjected to isoelectric focusing at pH 7.51 and its molecular weight was calculated to be 14,200+/-900 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The apparent dissociation constant for the complex between the inhibitor and trypsin[EC 3.4.21.4] was 1.64 X 10(-7)M with casein as a substrate. One microgram of purified inhibitor inhibited 1.5 mug of pure trypsin in the hydrolysis of alpha-N-benzoyl-DL-arginine-p-nitroanilide. By chemical modification of arginyl residues in the inhibitor with 1,2-cyclohexanedione, the inhibitor was shown to be an arginine inhibitor. The inhibitor contained relatively many basic amino acids and few half cystines as compared with Pirkka barley trypsin inhibitor.

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.

RELATIONSHIPS OF VARIOUS PHYSICAL AND CHEMICAL CHARACTERS TO DIGESTIBLE ENERGY IN WHEAT AND BARLEY CULTIVARS

Seventeen cultivars of hard and soft spring wheat (Triticum aestivum L.), and 29 cultivars of two-row and six-row barley (Hordeum distichum and H. vulgare) were examined for bulk weight (BW), 1,000-kernel weight (KW) and plumpness, and analyzed for gross composition, amylose, gross energy (GE), β-glucan (barley only), and for sedimentation (wheat only). Digestion coefficients and digestible energy (DE) values of the cultivars were determined by mouse-feeding. The ranges in protein, starch, amylose, and GE varied from 5 to 15%, whereas ether extract, fiber, ash and β-glucan contents varied from 1 to 3%. Except for sedimentation in wheat, and plumpness in barley there were no major differences in physical or chemical characters between hard and soft wheats or between two- and six-row barley. In wheat, DE was significantly correlated with BW (−0.59, P < 0.05), KW (−0.53, P < 0.05), plumpness (−0.55, P < 0.05), fiber (+0.72, P < 0.01), ash (−0.52, P < 0.05), sedimentation (−0.57, P < 0.05) and GE (+0.97, P < 0.01). Digestion coefficient was significantly correlated with protein (−0.58, P < 0.05), ash (−0.56, P < 0.05), and sedimentation (−0.57, P < 0.05). In barley, DE was significantly correlated with protein (+0.41, P < 0.05) and GE (+0.82, P < 0.01), and digestion coefficient was significantly correlated with BW (+0.55, P < 0.01), plumpness (+0.45, P < 0.05), ether extract (+0.50, P < 0.01), and fiber (−0.52, P < 0.01). For use as selection criteria the most significant correlations were between DE and GE and sedimentation in wheat, and between DE and GE in barley.

Hybrid performance among six-rowed × two-rowed winter barleys (Hordeum vulgare L. and Hordeum distichum L.)

A two-rowed winter barley cultivar, Carstens, was crossed with 22 6-rowed barley cultivars and one 2-rowed cultivar. The parents and hybrids, which were 2-rowed, were grown at two locations in two seasons. An F2 generation of each cross was included in the second season. The hybrids and parents were compared for winter survival, heading date, height, number spike bearing tillers, rachis nodes per spike, 1000-kernel weight, and grain weight. The hybrid significantly exceeded the higher parent in most crosses for height, number rachis nodes per spike, and in every cross for 1000-kernel weight. Significant midparent heterosis was observed in most crosses for winter survival. Heterosis for grain weight was obtained in the 2-rowed × 2-rowed cross. The 2-rowed parents were distinctly less hardy than the 6-rowed parents and expression of characters like number of tillers and grain weight was confounded with winter survival. In hybrids from 6-rowed × 2-rowed crosses the increased number of rachis nodes per spike and heavier kernels contribute to higher grain yields, but these influences are offset by the restricted row number and fewer kernels per spike.

Phosphorylase activity in relation to starch synthesis in developing Hordeum distichum grain

Activity, control and primer requirements of starch phosphorylase in developing barley endosperm were investigated. Phosphorylase was detected in endosperm extracts from 3 days after anthesis. Unprimed activity was predominant between 2 and 10 days after anthesis, when it constituted 70–80% of total activity, but this proportion declined rapidly as the grain developed. The existence of at least 2 isoenzymes was indicated by studies of pH dependence and phosphate inhibition, and was further supported by acrylamide gel electrophoresis and column chromatography using DEAE-cellulose. The two isoenzymes which ere possibly both glyco proteins, appear in barley endosperm soon after anthesis. One appears capable of unprimed activity, and may be associated with the initiation of a-1,2 glucans, which then serve as primers for starch synthetase. This disappears by 13–15 days after anthesis. The other isoenzyme is capable of some unprimed activity but undergoes modification between 15 and 20 days after anthesis, resulting in the loss of unprimed activity. The relevance of the results to initiation of starch synthesis and to starch synthetase in amyloplasts is discussed.