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1.
The efficacy of Hanseniaspora uvarum against gray mold by adding ammonium molybdate (NH4–Mo) and the mode of actions were evaluated. The results showed that H. uvarum at 1 × 106 CFU ml−1 plus 1 mmol l−1 NH4–Mo greatly reduced gray mold in grape fruits. NH4–Mo at concentrations of 1, 5, 10 and 15 mmol l−1 significantly inhibited spore germination and mycelium growth of Botrytis cinerea. Population growth of H. uvarum was markedly inhibited by NH4–Mo at 5 mmol l−1in vitro and not affected by addition of NH4–Mo at 1 and 5 mmol l−1 in wounds combination of NH4–Mo and H. uvarum induced higher activities of peroxidase (POD), polyphenoloxidase (PPO), phenylalanine ammonialyase (PAL), superoxide dismutase (SOD), catalase (CAT) and β-1,3-Glucanase than individual application of H. uvarum or NH4–Mo. The enhancement of disease control may be directly because of the inhibitory effects of NH4–Mo on spore germination and mycelial growth of B. cinerea in vitro, and indirectly because of the induced defense reactions by NH4–Mo in grape berries.  相似文献   

2.
The fine structures and rheological behaviours of aqueous flour dispersions and of β-glucan, (1→3,1→4)-β-d-glucan isolates obtained from 18 registered varieties of normal covered barley seeds and four registered oat varieties, grown in the same location in Greece, were investigated. The β-glucan content of the barleys and oats varied between 2.5–5.4 and 2.1–3.9%, respectively (dry matter basis). Heat treatment of the barley and oat flour dispersions with 80% (v/v) ethanol, to inactivate endogenous β-glucanases, had a stabilizing effect on the viscosity profile of the flour slurries. The relationship between total β-glucan content and aqueous slurry viscosity (at 247 s−1) of the heat-treated barley flours was weak (r2=0.45, p<0.05, n=18). β-Glucans were isolated by water extraction at temperatures slightly below the gelatinization temperature of starch, enzymatic removal of starch and partial removal of contaminating proteins by adjustment to pH 4.0–4.5, and subsequent precipitation of the water-soluble β-glucans with 80% (v/v) ethanol. The cellulosic oligomers released by the action of a (1→3,1→4)-β-d-glucan hydrolase showed cellotriosyl and cellotetraosyl units, accounted for 91.1–92.1% for barley and between 92.4 and 94.1% for the oat preparations; the respective molar ratios of tri- to tetra-saccharides (DP3/DP4) ranged between 2.73–3.05 (barley) and 2.16–2.42 (oat). Steady shear measurements confirmed the random coil type behaviour of freshly prepared β-glucan solutions (5 and 7%, w/v). The rate at which shear thinning began was dependent on both concentration and molecular size of the polysaccharide. Most of the β-glucan dispersions followed the Cox–Merz rule, except Mucio, a variety with high Mw β-glucan (2.39×105). Viscoelastic characterization, at 8% (w/v), of three barley β-glucan aqueous dispersions differing in molecular size, indicated that the low molecular weight sample exhibited shorter gelation time and higher gelation rate (IE=[dlog G′/dt]max) than its higher molecular weight counterparts. Small deformation oscillatory measurements on gels of all barley β-glucan isolates (10% (w/v), 7 d storage, 25 °C) revealed a strong negative relationship (r2=0.88, p<0.01) between G′ (1 Hz, strain 0.1%) and apparent Mw of the polysaccharide.  相似文献   

3.
In this study, extraction of hemicelluloses from the carbohydrate-enriched residues was successfully carried out with organic solvent and the residue was used for bio-based energy production. The chemical composition and physico-chemical properties of six hemicelluloses released were elucidated by a combination of sugar analysis, molecular determination, Fourier transform infrared, and 1H, 13C and 2D-HSQC NMR spectroscopy. The results showed that the successful treatments resulted in a fractionation of the native hemicelluloses. The sugar analysis indicated that xylose (47.14-56.91%) was found to be the major sugar components and small amounts of glucose (14.1-19.06%) and mannose (12.41-18.09%) were also observed in these hemicellulosic fractions. Further studies by NMR spectroscopy exhibited that the acetylated hemicellulosic fraction had a main structure of (1 → 4)-linked β-d-xylopyranosyl backbone with 4-O-methyl-α-d-glucuronic acid as a side chain and a minor structure of linear β-(1 → 4)-linked glucomannans. Furthermore, these hemicelluloses possessed a low substituted degree which was beneficial for enzymatic saccharification.  相似文献   

4.
Cereals β-glucans are linear homopolysaccharides of consecutively linked (1→4)-β-d-glucosyl residues (i.e. oligomeric cellulose segments) that are separated by single (1→3)-linkages. β-Glucans display all the functional properties of viscous and gel forming food hydrocolloids combined with all the physiological properties of dietary fibres. This review focuses on the relationships between the molecular–structural characteristics of β-glucans and their physicochemical properties in aqueous dispersions and in food systems as well as their physiological functions in the gastro-intestinal tract. The physical properties of β-glucans, such as solubility and rheological behaviour in the solution and gel states, are controlled by their molecular features, such as their distribution of cellulosic oligomers, their linkage pattern and their molecular weight as well as by temperature and concentration. The technological and nutritional functionality of β-glucans is often related to their rheological behaviour. Incorporation of β-glucans into various products (bread, muffins, pasta, noodles, salad dressings, beverages, soups, reduced-fat dairy and meat products) showed that attributes, such as breadmaking performance, water binding and emulsion stabilising capacity, thickening ability, texture, and appearance appear to be related to the concentration, molecular weight and structure of the polysaccharide. The health benefits of β-glucans, such as reducing blood serum cholesterol and regulating blood glucose levels, are also correlated with the amount and molecular weight of the solubilised β-glucans in the gastro-intestinal tract.  相似文献   

5.
Spelt bran and hull were submitted to enzymatic treatment during 1 h, 4 h and 24 h to release arabinoxylans (AXs). Several enzymatic commercial preparations with mainly endo-xylanase activity from Trichoderma reesei (Rohalase WL), Thermomyces lanuginosus (Pentopan Mono conc. BG), Bacillus subtilis (Belfeed B MP and Grindamyl Powerbake 900), Humicola insolens (Ultraflo L), Aspergillus aculeatus (Shearzyme 2×), A. aculeatus plus T. reesei (Shearzyme Plus) were tested and combined with a commercial cellulolytic preparation from T. reesei (Celluclast 1.5L). The xylanolytic activity of the commercial enzyme preparations was heterogeneous. The production of monomers by the different enzymes was evaluated on oat spelt xylan. Spelt bran and hull hydrolysates were analysed in regard to their content of total and free sugars. Monomers of glucose were mainly released with Celluclast, Ultraflo L and Shearzyme 2×. The percentage of released AXs ranged from 18.1% to 69.7% for bran and 0.5% to 6.4% for hull (% of the AXs originally present in the substrate). The solution of AXs hydrolysed by endoxylanases from spelt bran contained polysaccharides with a degree of polymerisation (DP) of 2–71 while those hydrolysed with endoxylanases plus Celluclast had DPs were 1–1164. The hydrolysates from spelt hull had much lower DPs (between 2 and 17).  相似文献   

6.
Antifeedant, growth inhibitory and toxic effects of crude seed extracts of Annona squamosa and Annona atemoya from Fazenda Viveiro Bona, Parasisópolis – Minas Gerais, Brazil, were evaluated against the cabbage looper, Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) using different bioassays. Crude methanolic seed extracts deterred feeding of third instar T. ni larvae in a leaf disc choice bioassay. A. squamosa was ∼10 times more active as a feeding deterrent than A. atemoya (DC50 = 2.3 mg/ml vs. 20.1 mg/ml). A. squamosa was ∼three times more active as a growth inhibitor than A. atemoya (EC50 = 38.0 ppm vs. 117.0 ppm). Methanolic seed extracts of A. squamosa and A. atemoya were toxic to third instar T. ni larvae both through topical and oral application. A. squamosa was more toxic through feeding (LC50 = 167.5 ppm vs. 382.4 ppm) whereas, A. atemoya exerted greater toxicity via topical application (LC50 = 301.3 μg/larva vs. 197.7 μg/larva). Both A. squamosa and A. atemoya extracts reduced leaf area consumption and larval growth in a greenhouse experiment. Our results indicate that both A. squamosa and A. atemoya have potential for development as botanical insecticides, especially for local use in Brazil.  相似文献   

7.
The stress relaxation behaviour of barley kernels with differences in β-glucan was studied using the generalized Maxwell model for explaining the differences in quality. The relaxation moduli show that cultivar significantly affected the relaxation times (τ2 and τ3) and compressional viscosity (ηE2 and ηE3) of the 3 Maxwell elements and the pure elastic component (E0). These data were twice as high in cultivars with high β-glucans compared to low β-glucans. Protein and malt extract, as well as β-glucan, showed similar patterns to the corresponding cultivars from the same locations. Malt extract was correlated with both insoluble fibre (−0.71; P < 0.0007) and total fibre (−0.66; P < 0.006). High β-glucan cultivars presented relatively high soluble fibre, wort viscosity and presented higher relaxation times. Soluble fibre and the wort viscosity were correlated with relaxation times τ1, τ2, τ3. Also, β-glucans were correlated with τ3 and viscosity ηE3. The overall importance of the effect of β-glucans on viscoelasticity, malting and food quality as shown in this investigation is in agreement with earlier investigations.  相似文献   

8.
The stress relaxation behaviour of barley kernels with differences in β-glucan was studied using the generalized Maxwell model for explaining the differences in quality. The relaxation moduli show that cultivar significantly affected the relaxation times (τ2 and τ3) and compressional viscosity (ηE2 and ηE3) of the 3 Maxwell elements and the pure elastic component (E0). These data were twice as high in cultivars with high β-glucans compared to low β-glucans. Protein and malt extract, as well as β-glucan, showed similar patterns to the corresponding cultivars from the same locations. Malt extract was correlated with both insoluble fibre (−0.71; P < 0.0007) and total fibre (−0.66; P < 0.006). High β-glucan cultivars presented relatively high soluble fibre, wort viscosity and presented higher relaxation times. Soluble fibre and the wort viscosity were correlated with relaxation times τ1, τ2, τ3. Also, β-glucans were correlated with τ3 and viscosity ηE3. The overall importance of the effect of β-glucans on viscoelasticity, malting and food quality as shown in this investigation is in agreement with earlier investigations.  相似文献   

9.
Poor yields of East African highland bananas (Musa spp., AAA-EAHB) on smallholder farms have often been attributed to problems of poor soil fertility. We measured the effects of mineral fertilizers on crop performance at two sites over two to three crop cycles; Kawanda in central Uganda and Ntungamo in southwest Uganda. Fertilizers were applied at rates of 0N–50P–600K, 150N–50P–600K, 400N–0P–600K, 400N–50P–0K, 400N–50P–250K and 400N–50P–600K kg ha−1 yr−1. In addition 60Mg–6Zn–0.5Mo–1B kg ha−1 yr−1 was applied to all treatments, with the exception of the control plots which received no fertilizer. Fresh bunch mass and yield increased with successive cycles. Yield increases above the control ranged from 3.1 to 6.2 kg bunch−1 (average bunch weight for all treatments 11.5 kg bunch−1) and 2.2–11.2 Mg ha−1 yr−1 (average yield for all treatments 15.8 Mg ha−1 yr−1) at Kawanda, compared with 12.4–16.0 kg bunch−1 (average bunch weight for all treatments 14.7 kg bunch−1) and 7.0–29.5 Mg ha−1 yr−1 (average yield for all treatments 17.9 Mg ha−1 yr−1) at Ntungamo. The limiting nutrients at both sites were in the order K > P > N. Potassium, N and P foliar nutrient mass fractions were below previously established Diagnosis and Recommendation Integrated System (DRIS) norms, with the smallest K mass fractions observed in the best yielding plots at Ntungamo. Total nutrient uptakes (K > N > P) were higher at Ntungamo as compared with Kawanda, probably due to better soil moisture availability and root exploration of the soil. Average N, P and K conversion efficiencies for two crop cycles at both sites amounted to 49.2 kg finger DM kg−1 N, 587 kg finger DM kg−1 P and 10.8 kg finger DM kg−1 K. Calibration results of the model QUEFTS using data from Ntungamo were reasonable (R2 = 0.57, RMSE = 648 kg ha−1). Using the measured soil chemical properties and yield data from an experiment at Mbarara in southwest Uganda, the calibrated QUEFTS model predicted yields well (R2 = 0.68, RMSE = 562 kg ha−1). We conclude that banana yields can be increased by use of mineral fertilizers, but fertilizer recovery efficiencies need to improve substantially before promoting wide-scale adoption.  相似文献   

10.
Wastage of agricultural chemicals and ensuing environmental pollution is an issue, where ineffective spray deposition is a major concern with conventional pesticide application methods. Electrostatic spraying is known to be one of the most effective methods to improve leaf abaxial (underside) surface deposition, overall deposition, and distribution on the plant targets. Deposition of charged sprays on leaf abaxial and adaxial (upper) surfaces as influenced by the spray charging voltage (system), application speed (operational), target height and orientation (target) parameters was studied in the laboratory. An air-assisted electrostatic induction spray charging system attached to a moving carriage was used to apply charged spray at uniform application (ground) speeds. Spray deposition (101–71 μm NMD), determined using a fluorescent tracer technique increased with charging (0–5.5 mC kg−1) on leaf abaxial and decreased with charging on adaxial surface. The deposition was higher on abaxial (0.66–1.33 μg cm−2) at 30° below (horizontal plane) and on adaxial (0.78–1.79 μg cm−2) at 0° (horizontal) target orientation for lower (0.278 m s−1) application speed. At all target heights, abaxial deposition increased with charging voltage (0–4.0 kV) for medium application speed (0.417 m s−1) and adaxial deposition decreased with charging voltage for lower application speed (0.278 m s−1). The medium application speed with higher charging voltage was optimum for abaxial and adaxial deposition. The droplet velocity and charging voltage were the key factors for obtaining desired spray deposition on targets. All the selected factors including target orientation (O), application speed (S), target surface (L), and charging voltage (V), and their interactions except between O and S were significant at lower (0.35 m) and medium (0.65 m) target heights. All the factors and their interactions except between O and V were significant at higher (0.95 m) height. Electrostatically charged spray improved the underside (abaxial) and overall deposition. The deposition was substantially influenced by factors such as charging voltage, application speed, plant target height, and target orientation.  相似文献   

11.
Growing cotton during the tropical dry season avoids many insect pests endemic in the wet season. The impact of low mid-season radiation and night temperature that characterise the dry season, on the conversion of radiation to biomass (RUE) and the partitioning of this biomass were measured as these were largely unknown. Over three seasons, two Gossypium hirsutum (upland) cultivars and a Gossypium barbadense cultivar were sown from March to June at the Ord River (15.5°S), Western Australia. For the highest yielding March and April sowings, final biomass was similar to high yielding temperate grown cotton (∼30° latitude) and was generally greater than May or June sowings. However, biomass was accumulated differently: maximum growth rate was 6–12 g/m2/day for 78–134 days compared with 15–25 g/m2/day for 25–60 days reported for temperate grown cotton. RUE changed significantly with ontogeny, peaking between squaring and early flowering. The range in RUE of 1.2–2.0 g/MJ throughout the crop lifecycle for the upland cultivars was similar to temperate climates where biomass was corrected to a glucose equivalent. The RUE of 1.2–2.3 g/MJ measured over the lifecycle of G. barbadense cultivar was the first reported for this species. From first square to first flower the variation in RUE could be explained by a linear decline (p < 0.05) with temperature, which may limit vegetative biomass in May and June sowings and in cooler than average seasons for March and April sowings. Due to favourable temperatures and water supply, sowing in March would have the greatest risk of rank growth. It was concluded the low temperature and radiation during flowering and boll growth combined to reduce crop growth rate but high yields were achieved when the crop boll filling phase was extended. Management must be tailored to ensure a high proportion of boll growth (60–80%) can occur after vegetative growth has terminated.  相似文献   

12.
Widening the range of organic nutrient resources, especially N sources, is a major challenge for improving crop productivity of smallholder farms in southern Africa. A study was conducted over three seasons to evaluate different species of indigenous legumes for their biomass productivity, N2-fixation and residual effects on subsequent maize crops on nutrient-depleted fields belonging to smallholder farmers under contrasting rainfall zones in Zimbabwe. Under high rainfall (>800 mm yr−1), 1-year indigenous legume fallows (indifallows), comprising mostly species of the genera Crotalaria, Indigofera and Tephrosia, yielded 8.6 t ha−1 of biomass within 6 months, out-performing sunnhemp (Crotalaria juncea L.) green manure and grass (natural) fallows by 41% and 74%, respectively. A similar trend was observed under medium (650–750 mm yr−1) rainfall in Chinyika, where the indifallow attained a biomass yield of 6.6 t ha−1 compared with 2.2 t ha−1 for natural fallows. Cumulatively, over two growing seasons, the indifallow treatment under high rainfall at Domboshawa produced biomass as high as 28 t ha−1 compared with ∼7 t ha−1 under natural fallow. The mean total N2 fixed under indifallows ranged from 125 kg ha−1 under soils exhibiting severe nutrient depletion in Chikwaka, to 205 kg ha−1 at Domboshawa. Indifallow biomass accumulated up to 210 kg N ha−1, eleven-fold higher than the N contained in corresponding natural fallow biomass at time of incorporation. Application of P to indifallows significantly increased both biomass productivity and N2-fixation, translating into positive yield responses by subsequent maize. Differences in maize biomass productivity between indifallow and natural fallow treatments were already apparent at 2 weeks after maize emergence, with the former yielding significantly (P < 0.05) more maize biomass than the latter. The first maize crop following termination of 1-year indifallows yielded grain averaging 2.3 t ha−1, significantly out-yielding 1-year natural fallows by >1 t ha−1. In the second season, maize yields were consistently better under indifallows compared with natural fallows in terms of both grain and total biomass. The first maize crop following 2-year indifallows yielded ∼3 t ha−1 of grain, significantly higher than the second maize crop after 1-year indifallows and natural fallows. The study demonstrated that indigenous legumes can generate N-rich biomass in sufficient quantities to make a significant influence on maize productivity for more than a single season. Maize yield gains under indifallow systems on low fertility sandy soils exceeded the yields attained with either mineral fertilizer alone or traditional green manure crop of sunnhemp.  相似文献   

13.
In Argentina, delayed sowing causes a decrease in seed yield and in radiation use efficiency (RUE) of peanut crops (Arachis hypogaea L.), but it is not known if RUE reduction is mainly due to reduced temperature during late reproductive stages or to a sink limitation promoted by decreased seed number in these conditions. We analyzed seed yield determination and RUE dynamics of two cultivars (Florman and ASEM) in four irrigated field experiments (Expn) grown at three sites and five contrasting sowing dates (between 17 October and 21 December) in three growing seasons. An additional field experiment was performed with widely spaced plants (i.e. with no interference among them) to evaluate the effect of peg removal on RUE and leaf carbon exchange rate (CER). Seasonal dynamics of mean air temperature and irradiance, biomass production (total and pods), and intercepted photosynthetically active radiation (IPAR) were followed. Seed yield and seed yield components (pod number, seeds per pod, seed number and seed weight) were determined at final harvest. Crop growth rate (CGR) and pod growth rate (PGR) were computed for growth phases of interest. RUE values for crops sown until 14 November were 1.89–1.98 g MJ−1 IPAR, within the usual range. RUE decreased significantly for cv. Florman in the late sowing of Exp1 (29 November) and for both cultivars in Exp3 (21 December sowing). Across experiments, seed yield (4.5-fold variation relative to minimum) was strongly associated (r2 = 0.87, P < 0.0001) with variations in seed number (3.5-fold variation relative to minimum), and to a lesser extent (r2 ≤ 0.54, P ≤ 0.001) to variations in seed weight (1.9-fold variation relative to minimum). Seed number was positively related (P < 0.01) to CGR (r2 = 0.66) and to PGR (r2 = 0.72) during the R3–R6.5 phase (seed number determination window), while crop growth during the grain-filling phase (i.e. between R6.5 and final harvest) was positively associated with grain number (r2 = 0.80, P < 0.001). No association was found between RUE and mean air temperature, neither for the whole cycle nor for the phase between R6.5 and final harvest, which showed the largest temperature variation (16.4–22.4 °C) across experiments. Use of mean minimum temperature records (range between 13.8 and 18.5 °C) did no improve the relationship. However, grain-filling phase RUE showed a positive (r2 = 0.69, P = 0.003) linear response to seed number across experiments. This apparent sink limitation of source activity was consistent with the reduced RUE (from 2.73 to 1.42 g MJ−1 IPAR) and reduced leaf CER at high irradiance (from ca. 30 to 15 μmol m−2 s−1) for plants subjected to 75% peg removal.  相似文献   

14.
An active crop canopy reflectance sensor could be used to increase N-use efficiency in maize (Zea mays L.), if temporal and spatial variability in soil N availability and plant demand are adequately accounted for with an in-season N application. Our objective was to evaluate the success of using an active canopy sensor for developing maize N recommendations. This study was conducted in 21 farmers’ fields from 2007 to 2009, representing the maize production regions of east central and southeastern Pennsylvania, USA. Four blocks at each site included seven sidedress N rates (0–280 kg N ha−1) and one at-planting N rate of 280 kg N ha−1. Canopy reflectance in the 590 nm and 880 nm wavelengths, soil samples, chlorophyll meter (SPAD) measurements and above-ground biomass were collected at the 6th–7th-leaf growth stage (V6–V7). Relative amber normalized difference vegetative index (ANDVIrelative) and relative SPAD (SPADrelative) were determined based on the relative measurements from the zero sidedress treatment to the 280 kg N ha−1 at-planting treatment. Observations from the current study were compared to relationships between economic optimum N rate (EONR) and ANDVIrelative, presidedress NO3 test (PSNT), or SPADrelative that were developed from a previous study. These comparisons were based on an absolute mean difference (AMD) between observed EONR and the previously determined predicted relationships. The AMD for the relationship between EONR and ANDVIrelative in the current study was 46 kg N ha−1. Neither the PSNT (AMD = 66 kg N ha−1) nor the SPADrelative (AMD = 72 kg N ha−1) provided as good an indicator of EONR. When using all the observations from the two studies for the relationships between EONR and the various measurements, ANDVIrelative (R2 = 0.65) provided a better estimate of EONR than PSNT (R2 = 0.49) or SPADrelative (not significant). Crop reflectance captured similar information as the PSNT and SPADrelative, as reflected in strong relationships (R2 > 0.60) among these variables. Crop canopy reflectance using an active sensor (i.e. ANDVIrelative) provided as good or better an indicator of EONR than PSNT or SPADrelative, and provides an opportunity to easily adjust in-season N applications spatially.  相似文献   

15.
Twenty Cladobotryum dendroides isolates from Serbian Agaricus bisporus farms collected during 2003–2007, and the F56 strain of A. bisporus were tested in vitro for sensitivity to tea tree oil (Timorex 66 EC), a biofungicide, in comparison with prochloraz–manganese (Octave WP). The efficacies of tea tree oil and prochloraz–manganese were evaluated in a mushroom growing room, after application at standard product application rates and a combination of the two at respective proportion of 20:80%. Tea tree oil was considerably less toxic than prochloraz–manganese in vitro to C. dendroides isolates (ED50 112.9–335.8 mg l−1) and A. bisporus F56 strain (98.0 mg l−1), although neither fungicide was lethal to the pathogen. The biological efficiency of tea tree oil was higher than in treatments with the reference formulation of prochloraz–manganese. In our in vivo trials, no negative interference of the biofungicide with A. bisporus physiology was observed. Tea tree oil applied at the standard product application rate caused a significant reduction in cobweb disease levels in the A. bisporus growing room. Timorex 66 EC should be tested further in combination with other biofungicides to investigate the effectiveness of various mixtures for A. bisporus disease control.  相似文献   

16.
In maize, the effects of nitrogen (N) deficiencies on the determination of kernel number per plant (KNP) have been described only by changes in plant growth rate during the critical period for kernel set (PGRcp). We hypothesize that N availability affects KNP also through variations in biomass allocation to the ear, which determines a stable N concentration in this organ. Six maize hybrids of different breeding origin were evaluated in field experiments at two N levels (0 and 400 kg N ha−1 applied). Traits included were KNP and per apical ear (KNE1), and the allometric estimation of PGRcp, ear growth rate during the critical period (EGRcp), and N content and N concentration in different plant organs. We demonstrated that (i) N availability promoted differences among genotypes (G) in the response of EGRcp and KNP to PGRcp, (ii) variations in KNE1 were explained by EGRcp (r2 = 0.64) and by ear N content at silking + 12 d (r2 = 0.64), and (iii) ear N concentration was a highly conservative trait (range between 10.47 and 15.98 mg N g biomass−1) as compared to N concentration in vegetative tissues (range between 4.94 and 18.04 mg N g biomass−1). Three response patterns were detected among hybrids, one for which the relationship between EGRcp and PGRcp did not vary between N levels and experiments, a second one for which N availability affected this relationship, and a third one for which the response was affected by the year (Y) effect. These results, together with the high correlation between EGRcp and ear N content (r2 = 0.88), evidenced the importance of both photo-assimilate and N availability on EGRcp and KNP determination. Values of 1.5–2.3 g ear−1 d−1 during the critical period and 0.49–0.70 g of N ear−1 at silking + 12 d were determined as thresholds for maximizing KNE1, and both could be easily estimated by means of allometric models.  相似文献   

17.
Plant responses to water deficit need to be monitored for producing a profitable crop as water deficit is a major constraint on crop yield. The objective of this study was to evaluate physiological responses of cotton (Gossypium hirsutum) to various environmental conditions under limited water availability using commercially available varieties grown in South Texas. Soil moisture and variables of leaf gas exchange were measured to monitor water deficit for various varieties under different irrigation treatments. Lint yield and growth variables were also measured and correlations among growth parameters of interest were investigated. Significant differences were found in soil moisture, leaf net assimilation (An), stomatal conductance (g), transpiration rate (Tr), and instantaneous water use efficiency (WUEi) among irrigation treatments in 2006 while no significant differences were found in these parameters in 2007. Some leaf gas exchange parameters, e.g., Tr, and leaf temperature (TL) have strong correlations with An and g. An and WUE were increased by 30–35% and 30–40%, respectively, at 600 μmol (CO2) m−2 s−1 in comparison with 400 μmol (CO2) m−2 s−1. Lint yield was strongly correlated with g, Tr, WUE, and soil moisture at 60 cm depth. Relative An, Tr, and TL started to decrease from FTSW 0.3 at 60 cm and FTSW 0.2 at 40 cm. The results demonstrate that plant water status under limited irrigation management can be qualitatively monitored using the measures of soil moisture as well as leaf gas exchange, which in turn can be useful for describing yield reduction due to water deficit. We found that using normalized An, Tr, and TL is feasible to quantify plant water deficit.  相似文献   

18.
The partitioning behavior of the glutenin proteins was evaluated in aqueous two-phase systems (ATPSs) formed by sulfate salts (lithium or sodium) and poly(ethylene glycol) (PEG) with average molar mass of 1500 g mol−1 or 4000 g mol−1. The partition coefficients for the glutenin proteins in each ATPS were investigated as a function of the temperature (278.2 K–318.2 K), tie line length (TLL) and electrolyte nature. In all ATPS, the majority of glutenin proteins spontaneously concentrate in the polymer-rich phase (Kp > 1). The partition coefficient is very dependent on the salt nature and the ATPS formed by PEG + lithium sulfate presents higher Kp values as compared with the ATPS formed PEG + sodium sulfate. An increase of molar mass of polymer promotes a decrease of Kp. Thermodynamic parameters of transfer (ΔtrG, ΔtrH and ΔtrS) were obtained by the application of the Van’t Hoff equation (VHE). The values obtained by VHE indicate that the transfer of glutenin proteins to the polymer-rich phase has an enthalpic origin.  相似文献   

19.
The holoparasitic weed Orobanche cumana (sunflower broomrape) constrains sunflower (Helianthus annuus) production in many countries. The development of efficient control strategies requires an understanding of the processes underlying the complex environment–host–parasite interrelations. Growth and development of O. cumana and sunflower were quantified under field conditions in southeastern Romania. Sunflower hybrid Florom 350 was sown at two dates, in plots infested with 0, 50, 200 and 1600 viable O. cumana seeds kg−1 dry soil, under low-input (rainfed, low nitrogen supply) and high-input (irrigated, high nitrogen supply) conditions. Sunflower shoot biomass reached peak values of 760–1287 g m−2 between the end of anthesis and physiological maturity. Seed yield varied from 221 to 446 g m−2. Sunflower biomass and yield were affected by all experimental factors. Seed yield responded positively to delaying sowing from early April to late May as well as to irrigation and fertilisation, and negatively to O. cumana infestation. Yield reductions, which were a product of reduced seed number and size, amounted to 13%, 25% and 37% at parasite seed densities of 50, 200 and 1600 viable seeds kg−1 soil, respectively. Maximum O. cumana attachment numbers, recorded in late-sown high-input crops in 2004, ranged from 11 m−2 in plots with 50 parasite seeds kg−1 soil to 188 m−2 with 1600 seeds kg−1 soil. Parasite attachment number was a function of crop sowing date, water and nutrient supply, seedbank density, and sunflower biomass and root length density, via mechanisms of parasite seed stimulation, host carrying capacity and intraspecific competition. Delayed sowing and improved water and nitrogen supply were associated with increases in parasite number that neutralised yield-boosting effects of irrigation and fertilisation at the highest infestation level. Sunflower shoot biomass was significantly reduced by O. cumana infection, with reductions affecting organs in the order head > stem > leaves. Most of the discrepancy between infected and non-infected plants was accounted for by O. cumana biomass. Parasites mainly acted as an extra sink for assimilates during sunflower generative growth and impaired host photosynthesis to a much lesser degree. Results suggest that similar mechanisms govern infection level and host–parasite biomass partitioning across different Orobanche–host systems.  相似文献   

20.
The objectives of this study were to determine the effects of genotype on chemical components of barley which influence nutritional value. Six barley (Hordeum vulgareL.) isotypes, expressed in Compana (CI 5438) and Betzes (CI 6398) cultivars with genetic combinations non-waxy (WXWX) and waxy (wxwx) starch in covered (NN) and hulless (nn) kernels and long-awn (LK2LK2) and short-awn (lk2lk2) traits, were grown in 1987, 1988 and 1989. Analyses were made for protein, fat, starch, free sugars, total dietary fibre (TDF ), TDF components and extract viscosity. The hulless gene reduced TDF by preventing the hulls from adhering to the kernel, thus concentrating the remaining components. Waxy barleys contained less (P<0·001) starch, but more (P<0·001) free sugars and ether extract (P<0·001). Increased (P<0·02) TDF in waxy barleys was due to an increase (P<0·001) in total and soluble β-glucans. The short-awn gene had no effect other than to increase (P<0·04) extract viscosity, and to reduce test weight (P<0·008) and % plump kernels (P<0·03). The expression of the hulless and waxy genes in barley is desirable for use in human food products due to increased levels of soluble dietary fibre, particularly β-glucans, but reduces malting potential and feed value for poultry.  相似文献   

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