Triticum Aestivum Var Research Articles

Dry Matter Intake and Digestion of Perennial and Annual Cool-Season Grasses by Sheep

Excess perennial cool-season grass production can be harvested as hay for feeding later. Thus, a series of experiments were conducted to estimate DMI and digestibility of perennial cool-season grasses relative to an annual cool-season grass hay. In Exp. 1, wheat (Triticum aestivum var. Pioneer 2174), tall wheatgrass (Thinopyrum ponticum var. Jose), smooth brome (Bromus inermis var. Lincoln), and intermediate wheatgrass (Thinopyrum intermedium var. Manska) were harvested in the spring as high-moisture hay and fed to lambs. At feeding, all 4 hays contained more (P < 0.05) ADF and less N than as standing forage. Apparent digestibility of the DM, NDF, and ADF fractions and DMI were not different (P > 0.10) among the hays used in this experiment. In Exp. 2, grasses were harvested as field-dried (DM >65%) hay from established stands of Jesup Max Q (Festuca arundinacea) and Nanyro (F. arundinacea) tall fescues, Harusakae meadow fescue (Festuca pratensis), and wheat (var. Pioneer 2174). Lambs fed wheat hay had greater (P < 0.05) DMI (69.3 g/kg BW0.75, respectively) compared with lambs fed Jessup or Nanyro (35.0 and 33.8 g/BW0.75), and lambs fed Harusakae hay had intermediate DMI (50.2 g/BW0.75). Digestibility of Jesup hay was greater (P < 0.05) than digestibility of the other 3 hays. Excess cool-season grasses can be harvested as high-moisture or field-dried hay, but harvested hays had greater concentrations of ADF and NDF and a lesser concentration of N than preharvest standing forage.

Soil Physicochemical Properties in a Grassland and Agroecosystem Receiving Varying Organic Inputs

The application of organic amendments in agroecosystems has been widely recommended, but the impact of their C/N ratio on the stabilization and sequestration of soil organic carbon (SOC) is often unaccounted for. The influence of the C/N ratio of amendments on soil physicochemical properties in a rice (Oryza sativa var. NDR97)–barley (Hordeum vulgare var. Lakhan) rotation tropical dryland agroecosystem was compared with an undisturbed grassland. Chemical fertilizer in the form of urea and three organic inputs (Sesbania aculeata shoot, low C/N ratio; air‐dried straw of wheat (Triticum aestivum var. Malviya 533), high C/N ratio; and S. aculeata shoot+wheat straw, high and low C/N ratio combined) carrying an equivalent amount of N, were added to plots of the agroecosystem once during each annual cycle. Soil water‐holding capacity (WHC), porosity, SOC, total N, and aggregate stability were improved in the wheat straw and S. aculeata shoot+wheat straw treatments, reaching levels comparable with the grassland. Soil WHC, porosity, and SOC influenced the productivity of the grassland and the agroecosystem. The grassland recorded highest SOC (53% higher relative to control) followed by the wheat straw (+47%), S. aculeata shoot+wheat straw (+37%) and soil total N was greatest in the S. aculeata shoot+wheat straw treatment (+37.5%). Aggregate stability and macroaggregate distribution were also higher in the wheat straw and S. aculeata shoot+wheat straw treatments, however, the microaggregate and silt + clay fractions showed a reverse trend. Management practices with a higher residue‐C return in the agroecosystem resulted in increased aggregate stability and aggregate‐associated SOC, with C storage attaining levels similar to the natural system.

Investigation on the Fusarium induced stress protein (FISP) in wheat: Immunolocalisation in root cells

Fusarium induced-stress-protein (FISP) of ∼51 kDa molecular mass was detected in seven day old germinated wheat (Triticum aestivum var Sonalika) seedlings infected with F. oxysporum for a period of seven days. This particular stress protein (FISP) of ∼51 kDa was over-expressed in the case of Fusarium infected seedlings compared to the untreated seedlings where the presence of this protein was insignificant. Localisation of this ∼51 kDa protein in root tissue by anti-CSAP (Cadmium Stress Associated Protein) antiserum showed a significantly higher number of gold particles in the case of Fusarium infected root tissue compared to the untreated control. A unique type of organised localisation of FISP around the plasma membrane and outer vacuolar membrane suggests its defensive role against Fusarium infection that might be a general stress protein against biotic and abiotic stresses.

A sulphur deficiency‐induced gene, sdi1, involved in the utilization of stored sulphate pools under sulphur‐limiting conditions has potential as a diagnostic indicator of sulphur nutritional status

A sulphate deficiency-induced gene, sdi1, has been identified by cDNA-amplified fragment length polymorphism (AFLP) analysis utilizing field-grown, nutrient-deficient wheat (Triticum aestivum var. Hereward). The expression of sdi1 was specifically induced in leaf and root tissues in response to sulphate deficiency, but was not induced by nitrogen, phosphorus, potassium or magnesium deficiency. Expression was also shown to increase in plant tissues as the external sulphate concentration in hydroponically grown plants was reduced from 1.0 to 0.0 mm. On this basis, sdi1 gene expression has potential as a sensitive indicator of sulphur nutritional status in wheat. Genome-walking techniques were used to clone the 2.7-kb region upstream of sdi1 from genomic DNA, revealing several cis-element motifs previously identified as being associated with sulphur responses in plants. The Arabidopsis thaliana gene most highly homologous to sdi1 is At5g48850, which was also demonstrated to be induced by sulphur deficiency, an observation confirmed by the analysis of microarray data available in the public domain. The expression of Atsdi1 was induced more rapidly than previously characterized sulphur-responsive genes in the period immediately following the transfer of plants to sulphur-deficient medium. Atsdi1 T-DNA 'knockout' mutants were shown to maintain higher tissue sulphate concentrations than wild-type plants under sulphur-limiting conditions, indicating a role in the utilization of stored sulphate under sulphur-deficient conditions. The structural features of the sdi1 gene and its application in the genetic determination of the sulphur nutritional status of wheat crops are discussed.

Influence of plant developmental stage on microbial community structure and activity in the rhizosphere of three field crops.

Seasonal shifts in rhizosphere microbial populations were investigated to follow the influence of plant developmental stage. A field study of indigenous microbial rhizosphere communities was undertaken on pea (Pisum satvium var. quincy), wheat (Triticum aestivum var. pena wawa) and sugar beet (Beta vulgaris var. amythyst). Rhizosphere community diversity and substrate utilization patterns were followed throughout a growing season, by culturing, rRNA gene density gradient gel electrophoresis and BIOLOG. Culturable bacterial and fungal rhizosphere community densities were stable in pea and wheat rhizospheres, with dynamic shifts observed in the sugar beet rhizosphere. Successional shifts in bacterial and fungal diversity as plants mature demonstrated that different plants select and define their own functional rhizosphere communities. Assessment of metabolic activity and resource utilization by bacterial community-level physiological profiling demonstrated greater similarities between different plant species rhizosphere communities at the same than at different developmental stages. Marked temporal shifts in diversity and relative activity were observed in rhizosphere bacterial communities with developmental stage for all plant species studied. Shifts in the diversity of fungal and bacterial communities were more pronounced in maturing pea and sugar beet plants. This detailed study demonstrates that plant species select for specialized microbial communities that change in response to plant growth and plant inputs.

Uptake of Zn and Fe by Wheat (Triticum aestivum var. Greina) and Transfer to the Grains in the Presence of Chelating Agents (Ethylenediaminedisuccinic Acid and Ethylenediaminetetraacetic Acid)

A way to decrease iron and zinc deficiency in humans is to biofortify foods by increasing the bioavailable contents in these elements. The aim of this work was to study if chelating agents could be used to increase the capture of Fe and Zn by wheat grains. Zn and/or Fe in combination with the chelating agents ethylenediaminedisuccinic acid (EDDS) or ethylenediaminetetraacetic acid (EDTA) were added at various times (i.e., at flower head formation, anthesis, and postanthesis) to spring wheat ( Triticum aestivum var. Greina) grown in nutrient solution. Treatments lasted for 2 weeks, and the plants were harvested at grain maturity. The shoots of treated plants accumulated higher Zn and/or Fe concentrations than untreated plants, depending on the treatment. The plants also accumulated significant concentrations of EDDS or EDTA in their shoots. Elevated Zn and Fe concentrations in the shoots did in most cases not lead to significantly higher Zn and Fe concentrations in the grains. The grains of plants treated with EDDS during flower head formation accumulated elevated Fe and Zn concentrations but at the cost of a reduction in yield. The control plants transferred higher percentages of Fe and Zn from the shoot into the grain than the treated plants. This indicates that EDTA and EDDS inhibited in most cases the translocation of Fe and Zn from the shoots into the grains. The amounts of EDDS and EDTA found in the grains of treated plants were very small. This indicates that there was little transfer of the chelates into the symplast and that the apoplastic pathway, which is important for the transport of chelants into the shoots, is efficiently blocked between shoots and seeds.

Amelioration of dense sodic subsoil using organic amendments increases wheat yield more than using gypsum in a high rainfall zone of southern Australia

Subsoil constraints are major limiting factors in crop production in many soils of southern Australia. A field study examined effects of deep incorporation of organic and inorganic amendments in 30–40 cm on soil properties, plant growth and grain yield of wheat ( Triticum aestivum var. Ambrook) on a Sodosol with dense sodic subsoil with or without lucerne history in a high rainfall region (long-term average annual rainfall 576 mm) of Victoria. Amendments were applied at a rate of 10–20 t ha −1. Deep ripping alone and deep ripping with gypsum did not significantly affect grain yields. In comparison, application of organic materials doubled biomass production and increased grain yield by 1.7 times. Organic amendment-treated plots produced 60% more grains per area than the untreated control. The crop extracted over 50 mm extra water from below 40 cm soil in organic amendment-treated plots than the untreated control. Nitrogen uptake was almost doubled (403 kg ha −1) in the organic amendment-treated plots than the untreated control (165 kg ha −1). The improved yield with amendments was related to an increase in plant available water in the hostile subsoil, and prolonged greenness of leaves and supply of nitrogen and other nutrients.

Identification of low temperature stabilizing genes, controlling chromosome synapsis or recombination, in short arms of chromosomes from the homoeologous group 5 of Triticum aestivum

Plants of common wheat Triticum aestivum var. Chinese Spring, lacking the short arms of homoeologous group 5 chromosomes were subjected to a cold treatment of 10oC, and the chiasma frequency in pollen mother cells in the first meiotic metaphase was recorded. The existence in the short arms of chromosomes 5A and 5B of Ltp genes identical in effect to that described for chromosome SDL is demonstrated. In the absence of chromosome arm 5DS a significant decrease in chiasmata along with only a slight reduction in chromosome pairing was observed after the cold treatment, suggesting the existence in 5DS of a gene partially controlling crossing-over at low temperatures. The results that were obtained allow us to propose the following designations for the genes with a stabilizing effect at low temperature: Ltpl in 5DL, Ltp2 in 5AS, Ltp3 in 5BS and Ltr, low temperature recombination, in 5DS.

Role of calcium–calmodulin in auxin-induced somatic embryogenesis in leaf base cultures of wheat (Triticum aestivum var. HD 2329)

Wheat leaf bases cultured for 1 day on 2,4-d (10 μM) display the induction of somatic embryogenesis. The induction of somatic embryogenesis by 2,4-d appears to be calcium-mediated as treatment of leaf bases with the calcium chelator, EGTA, prior to 2,4-d treatment, inhibited the induction of somatic embryogenesis. This sensitivity of auxin to reduced calcium levels can be reversed by calcium ions alone and not any other divalent cation like magnesium or zinc. Additionally, the expression of the three calcium-regulated genes, Triticum aestivum calmodulin binding protein kinase, calcium-dependent protein kinase, and putative calcium binding protein was analyzed in wheat leaf bases which suggest a specific role for Ca2+ in somatic embryogenesis. Application of the calcium ionophore, A23187, either alone or along with 2,4-d, induced somatic embryogenesis. This specificity for calcium was verified both by treatment with the calcium antagonist TMB8, and the elimination of calcium from the medium, resulting in reduction of somatic embryogenesis by 80%. Treatment with calcium channel blockers like verapamil and nifedipine, calcium antagonist, lanthanum, and calmodulin inhibitors chlorpromazine and fluphenazine, prior to the 2,4-d treatment, inhibited induction of somatic embryogenesis. The present study thus provides evidence for the involvement of calcium–calmodulin in the stimulus–response coupling of auxin-induced somatic embryogenesis in wheat leaf base system.

Yield Responses of Wheat (Triticum aestivum) To Vermicompost Applications

Earthworm digested wastes (vermicompost) are being produced in increasing quantities and there is much interest in developing new markets for these products. In this paper, the responses of wheat (Triticum aestivum var. Einstein and Xi19) to vermicompost additions and to combinations of vermicompost and inorganic NPK fertilizer in field and glasshouse environments are considered. Plant response was determined by measuring a range of ontogenetic parameters (plant growth, chlorophyll content, fertile ears, tiller number and grain yield). The individual treatments involved the addition of 1, 10 and 30 t ha−1 of vermicompost to soil, or the coapplication of 1, 10 and 30 t ha−1 of vermicompost plus NPK fertilizer where the N addition rate was normalized to 150 kg N ha−1. Photosynthetic pigment development, plant growth, and yield were reduced in all treatments in the absence of inorganic fertilizer. However, all coapplication treatments resulted in similar yields to NPK fertilizer alone in both field and glasshouse experiments. It is our conclusion that vermicompost alone cannot provide a viable substitute for inorganic fertilizer without causing a significant loss of yield; however, it may enhance soil quality if integrated into conventional arable cropping practices which use inorganic fertilizers.

AGRONOMIC IMPLICATIONS OF THE SUPPLY OF LIME AND GYPSUM BY-PRODUCTS TO PALEXERULTS FROM WESTERN SPAIN

A laboratory experiment with leaching columns reproducing the topmost portion (Ap and AB horizons) of a Palexerult from western Spain was conducted to compare the efficiency of limestone (L), gypsum (G), and various lime and gypsum by-products (sugar foam waste, phosphogypsum [PG], and red gypsum [RG]) to alleviate Al toxicity and improve soil productivity. The effect of the previous five amendments on composition changes in the exchange complex and the soil saturation extract was examined after one or two leaching cycles (equivalent to as many years of field precipitation). The productivity of the Ap horizon after the first leaching cycle was assessed by growing wheat (Triticum aestivum var. Jabato) in a greenhouse. The lime by-products increased the pH of the Ap horizon and the Ca content of the exchange complex to a greater extent than the gypsum amendments; in addition, the former minimized the Al content of the exchange complex and the saturation extract. Changes in the AB horizon were much less marked, and the sugar foam waste was a better liming material than limestone. The changes in the exchange complex and saturation extract from gypsum amendments followed a more complex pattern and affected both horizons (Ap and AB). The pH of the soil was initially decreased relative to the controls through a "salt effect" and then increased after the second leaching cycle, when most of the gypsum was leached from the soil. In both horizons, the Ca content was increased, and the Al content of the exchange complex decreased-albeit to a lesser extent than with the lime amendments in Ap; by contrast, exchangeable Mg and Na were lost in substantial amounts in the first leaching cycle; K losses were comparatively smaller. After the first leaching cycle, aluminum-fluoride ion pairs were the most active Al species in the extracts from Ap and AB in PG amended columns; on the other hand, the aluminum sulfate ion pairs were the most active in the extracts from the G- and RG-amended columns. After the second leaching cycle, the activity of Al3+-the most phytotoxic ionic species of Al-in the Ap extracts from all calcium carbonate-amended columns decreased, whereas that in the gypsum-amended soil only decreased in the PG-treated columns; in the AB horizon, however, the extracts from all gypsic amendments decreased the Al3+ activity, with respect to control and lime amendments. The calcium aluminum balance (Noble et al., 1988) was increased by all treatments. All lime and gypsum amendments-particularly sugar foam waste-increased productivity relative to the controls. Of the three gypsum amendments, RG had the greatest impact on productivity; this can be ascribed to its Zn content, which was very low in the natural soil.

Structural characterization, expression analysis and evolution of the red/far-red sensing photoreceptor gene, phytochrome C (PHYC), localized on the ‘B’ genome of hexaploid wheat (Triticum aestivum L.)

Phytochromes are a family of red/far-red light perceiving photoreceptors. The monocot phytochrome family is represented by three members, PHYA, PHYB and PHYC. We have isolated and characterized the first PHY gene member (TaPHYC) from common wheat, Triticum aestivum var. CPAN1676. It codes for a species of the photoreceptor, phyC, which is known to be light-stable in all plants analyzed so far. A sequence of 7.2 kb has been determined, which includes 3.42 kb of coding region. This is the second full-length PHYC gene sequenced from a monocot (first was from rice). TaPHYC gene shares structural similarities with the rice PHYC containing four exons and three introns in the coding region. The 5' UTR is 1.0-kb-long and harbors an upstream open reading frame (URF) encoding 28 aa. Southern blot analysis of TaPHYC indicates that it represents single locus in the wheat genome, although the possibility of additional loci cannot be completely ruled out. Chromosomal localization using nullisomic-tetrasomic lines of Triticum aestivum var. Chinese Spring places TaPHYC on chromosome 4B. PHYC represents a constitutively expressed gene in all the organs tested and under light/dark conditions. However, PHYC was found to be developmentally regulated showing maximal expression in 3-day-old dark-grown seedlings, which declined thereafter. In silico analysis has also been done to compare TaPHYC gene with the partial sequences known from other wheat species and cultivars. The presence of a topoisomerase gene immediately downstream of the PHYC gene, both in rice and wheat genomes, presents yet another example of synteny in cereals and its possible significance has been discussed.

Extraction, Purification, and Inhibitory Effect of Alpha - Amylase Inhibitor from Wheat (Triticum aestivum Var. Zarrin)

Plant alpha-amylase inhibitors show great potential as tools to engineer resistance of crop plants against pests. They are also drug-design targets for treatment of diabetes and digestion disorderes. These inhibitors also known as sensitizing agents in human. The numerous form of alpha-amylase inhibitors was reported. In this study alpha-amylase inhibitor was extracted from Iranian wheat cultivar (Triticum aestivum v zarrin), precipitated and purified by anion exchange fast protein liquid chromatography. Electrophoresis of purified protein showed 0.66 relative mobility. Total hydrolytic activity of human salivary and bacillus subtilis alpha-amylase were inhibited 97.07% and 89.97% respectively by collected purified alpha-amylase inhibitor.

Effects of sheared-root inoculum of Glomus intraradices on wheat grown at different phosphorus levels in the field

Abstract Growth and yield potential of wheat inoculated with the arbuscular mycorrhizal fungus Glomus intraradices were investigated at different phosphorus levels under field conditions. Surface sterilized wheat ( Triticum aestivum var. Swift) was infected with sheared-root inoculum at the rate of 0.5 g dry weight per 1000 seed and sown in P-deficient loamy and slightly acidic (pH 5.5) field plots fertilized with 0, 5, 10 and 20 kg ha −1 of commercial P. Plants inoculated had significantly higher dry weight and yield compared to controls. Mycorrhization of roots in both inoculated and control plants increased with P-level but decreased over time at higher P-levels. The mycorrhiza-mediated growth effect was higher at 5 and 10 kg than at 20 kg P ha −1 in terms of plant dry weight, number of grain per spike, and 1000 grain weight. It is suggested that sheared-root inoculum of G. intraradices may contribute to reducing P fertilizer applications.

Identification of the wheat seed protein CM3 as a highly active emulsifier using a novel functional screen.

Lyophilized albumin protein fractions were prepared from flour of four varieties of wheat: Triticum aestivum cvs. Mercia and Riband, Triticum aestivum var. spelta, and Triticum turgidum var. durum (Kamut). The dry powders were redissolved in sodium phosphate buffers at pH 3.0, 6.5, or 8.0 and at ionic strengths of 0.1 or 1.0 M to a concentration of 0.1% (w/v). Emulsions formed by sonication of protein solutions with n-hexadecane were aged at room temperature and separated into aqueous, interstitial, and interfacial phases. The distinct emulsion components were lyophilized and analyzed by RP-HPLC. A protein was observed to be preferentially located in the interfacial component and subsequently purified from a total albumin fraction and identified by N-terminal sequencing as CM3, an alpha-amylase inhibitor subunit. Measurement of the equilibrium surface tension of CM3 as a function of protein concentration demonstrated that it was at least as active as bovine beta-lactoglobulin, an established protein emulsifier. Furthermore, measurement of the surface dilational elastic modulus at an air/water interface demonstrated the formation of a viscoelastic film, while fluorescence and FT-IR spectroscopic measurements on adsorbed and nonadsorbed CM3 suggest that the secondary structure is essentially unchanged upon adsorption to an oil/water interface. It is concluded that functional screening is a valid approach to identify novel protein emulsifiers in complex mixtures.

Utilisation of Zinc from Zinc Fertiliser Bands: Effect of Concentrations of Zinc in Zinc Chloride and Zinc-Edta Fertiliser Bands on Root Growth and Zinc Uptake by Wheat

Factors affecting the extent of utilisation of zinc from zinc fertiliser bands include the extent of solubility and movement of zinc from the fertiliser band, the extent of root to zinc fertiliser contact as well as the concentration and extent root growth in the fertiliser band. Growth chamber and incubation studies were conducted to compare the extent of root growth and zinc uptake by wheat (Triticum aestivum var Columbus) from Zinc chloride (ZnCl2) and Zn-EDTA fertiliser bands when applied to a non-calcareous soil of pH 7.0 and low in DTPA-extractable Zn. The Zn fertilisers were uniformly mixed with 200 g of soil contained in acrylic cylinders. Concentrations and forms of water-soluble Zn in the fertiliser bands were determined from the incubation studies. Concentrations of Zn in the Zn-EDTA fertiliser bands were much greater than concentrations of Zn in the ZnCl2 bands. Whereas root growth was stimulated by low rates of ZnCl2, high rates of Zn (>0.8 mg Zn/cm3) resulted in a decrease in the amount as well as quality of roots recovered from the fertiliser band. Zn-EDTA reduced root growth into the fertiliser band for most of the rates of Zn applied. The results obtained showed that root growth into the fertiliser bands was closely related to the concentration of Zn in soil solution. Concentrations of Zn in the plant shots increased with increase in the amount of roots in the fertiliser bands as well as the concentration of Zn in soil solution.

The effect of different additives on the fermentation quality, aerobic stability and in vitro digestibility of pea/wheat bi‐crop silages containing contrasting pea to wheat ratios

Studies were conducted to compare the effects of using two microbial inoculants, a sulphite salt‐based additive, formic acid and quebracho tannins, on the fermentation quality, nutritive value and aerobic stability of pea/wheat bi‐crop silages. Spring peas (Pisum sativum var. Magnus) and spring wheat (Triticum aestivum var. Axona) were drilled together at rates that gave high (HP/W; 3:1) or low (LP/W; 1:3) pea to wheat ratios. The peas and wheat were harvested at the yellow wrinkled pods and late milk/early dough maturity stage, respectively, and conserved in 1·5‐kg polyethylene bag, laboratory silos. The bi‐crops were conserved without treatment (control) or treated with either of two lactic acid bacteria‐based inoculants [Lactobacillus buchneri; applied at 105 colony‐forming units (CFU) g–1 fresh weight (FW) or Lactobacillus plantarum (applied at 106 CFU g–1 FW)], sulphite salts (applied at the rate of 1 ml sulphite solution kg–1 FW), quebracho tannins (applied at 16 g kg–1 FW) and formic acid (applied at 2·5 g kg–1 FW). Six replicates were made for each treatment, and the silos were opened after 112 days of ensilage. The level of peas in the bi‐crop influenced the effectiveness of the additives. With the exception of sulphite salts, all the additives significantly reduced the soluble nitrogen (N) and ammonia‐N concentrations of all the silages. The ratio of lactic acid to acetic acid was generally lower in the LP/W silages than in the HP/W silages, and the additive treatments only increased the in vitro digestible organic matter in dry matter of the LP/W silages. Of all the additives evaluated, formic acid resulted in the least aerobic spoilage in HP/W bi‐crop silages. However, in the LP/W bi‐crops, additive treatment was not necessary for ensuring aerobic stability.

Recherche prospective sur la dualité entre caractéristiques morphologiques et capacités de compétition des végétaux : le cas des espèces adventices et du blé

Competitive abilities of plants were interpreted by measuring their morphological traits in interspecific competitive cultivation conditions. Measurements were realised by a comparative approach with interspecific cultivation of fourteen arable weeds growing with a domestic species cultivated at a large scale: the winter wheat ( Triticum aestivum var Darius). Results show that arable weeds characterised by an important biomass and allocation of biomass to the stems are responsible for a decrease in wheat biomass, and for the ear, a decrease in height, biomass and number of seeds. These results are discussed in view of predicting competitive abilities of arable weeds with a simple method and for the conservation of arable weeds since some of them are among the most threatened species of the European flora.

Resistance of wheat aleurone cell walls to acid and xylanase action

Isolated wheat (Triticum aestivum var. Potam) aleurone layers have a high capacity to acidify their environment, and secrete hydrolytic enzymes (endoxylanase, glucanase, α-amylase, proteases, etc.) under the control of GA3. Acidic pH and xylanases are found to be essential for cell wall relaxation in growing tissues, but aleurone is a non-growing, non-dividing tissue. In this tissue, we studied the effect of these loosening factors on aleurone cell walls.Exposure to pH 3.0 caused the release of carbohydrates and calcium ions from the pericarp, and a small amount of carbohydrates, mainly polysaccharides, from aleurone layers from which pericarp tissue had been removed. 50 percnt; of the total sugars released into the incubation medium by these isolated aleurone tissue was arabinose, but no xylose, calcium ions, or phenolic compounds were found. Acid preincubation decreased by 30 percnt; the susceptibility of aleurone cell walls to degradation by exogenously-applied endoxylanase, and also modified the architecture of cell wall as observed by autofluorescence of phenolic groups. These findings suggest that acid treatment and endoxylanase action, rather than having a loosening effect on aleurone cell wall, can have an opposite effect, increasing the resistance of aleurone cell walls to loosening.

Attraction to Gamma-Irradiated Wheat in the Angoumois Grain Moth

The olfactory orientation of insects plays a key role in the strategy of their trophic behavior, allowing them to reduce energy expenditures for finding a trophic substratum and determining its properties. Phytophagous insects are attracted by the smell of some plants (Sutherland, 1972), whereas the smell of other plants repels them (Alexander and Barton, 1943). The attitude toward a trophic substratum may change after damage to it by various species of animals and microorganisms (Rice, 1986). The purpose of this study was to reveal the ability of the Angoumois grain moth ( Sibotroga cerealella Oliv.) to distinguish between gamma-irradiated and normal spring wheat ( Triticum aestivum var lutenscens ). Grain samples were gamma-irradiated at a dose of 400 Gy in a GUPOS unit equipped with a 137 Cs source, and the background radiation level in the irradiated grain was controlled using a USIT-2 instrument. The effects of irradiation on the physiological state of grain was determined by analyzing the activity of the initial growth processes. The attitude of moths toward irradiated and normal grain was estimated from the number of egg masses and the extent of damage inflicted by hatching larvae during their development into adult insects. Grain samples (100 grains each) were placed in metal containers 3 cm in diameter and 4 cm in height and exposed in a thermostat (at 20 ∠ 1iC ) together with the ears of spring wheat infested by Angoumois grain moth. Ten containers with irradiated and normal grain were arranged in an alternating order at a distance of 10 cm from each other. In irradiated samples, no increase in the level of background radiation was revealed, but the initial growth processes proved to be strongly inhibited: seed vigor was indeterminate, and the laboratory germination rate decreased by a factor of 20.5 ( P > 0.99). The average rootlet length in five-day seedlings of irradiated grain was 7.5 times smaller than that in normal seedlings ( P ♢ 0.99) (table). During four months of observations, egg masses were found on 143 grains, of which 34.3% were irradiated and 65.7% were normal (confidence interval ∠ 4.2% at 95% significance level). The number of eggs per mass did not differ statistically and ranged from three to nine in both types of grain samples. A total of 59 adult moths emerged, of which 35.6% developed in irradiated and 64.4% in normal seeds (confidence interval ∠ 4.0% ). Hence, the development of insects from the egg to the adult state was completed in only one-third of infested grains. The corresponding ratios in normal and irradiated samples did not differ significantly, although irradiated grain became approximately 50% less attractive to egg-laying females.