Explore the vast range of titles available.

Temperature is one of the most important factors that determine plant growth, development, and yield. Accurate summarization of plant temperature response is thus a prerequisite to successful crop systems modelling and application of such models to management. This paper reports on a general equation that can be used to simulate the temperature response of plants. The equation reads as r=Rmax(Tmax-TTmax - Topt) (TTopt)ToptTmax - Topt, where r is the daily rate of growth (or development) at any temperature, Toptis the optimum temperature, Tmaxis the maximum temperature, and Rmaxis the maximum rate of growth or development at Topt. It has the smallest number of parameters possible to simulate the plant response to the full range of temperatures relevant to plant growth and development. The equation was shown to successfully simulate the growth and development of maize, bean, wheat, barley, sorghum, and lambsquarters. The adjusted R -square of fit ranged from 0.747 to 0.998, mostly greater than 0.9. For one maize dataset that contains independent data, the equation was shown to be highly predictive. The equation could find application in crop germplasm classification, crop modelling and environmental control of artificial crop production systems.

Wild oat is a significant weed of cropping systems in the Canadian Prairies. Wild oat resistance to herbicides has increased interest in the use of nonchemical management strategies. Harvest weed seed control techniques such as impact mills or chaff collection have been of interest in Prairie crops, with wild oat identified as a key target. To evaluate the effects of crop rotation maturity, harvest management, and harvest weed seed control on wild oat, a study was conducted from 2016 to 2018 at four locations in the Canadian Prairies. Two-year crop rotations with either early, normal, or late-maturing crops were implemented before barley was seeded across all rotations in the final year. In addition, a second factor of harvest management (swathing or straight cut) was included in the study. Chaff collection was used in this study to quantify wild oat seeds that were targetable by harvest weed seed control techniques. The hypothesis was that earlier maturing crops would result in increased wild oat capture at harvest and, therefore, lower wild oat populations. Wild oat density and wild oat biomass were lowest in the early maturing rotations. In addition, wild oat exhibited lower biomass in swathed crops than straight-cut crops. Wild oat seedbank levels reflected a similar trend with the lowest densities occurring in early maturing rotation, then the normal maturity rotation, and the late maturing rotation, which had the highest seedbank densities. Wild oat densities increased in all crop rotations; however, only harvest weed seed control and crop rotation were implemented as control measures. Wild oat numbers in the chaff were not reflective of the earliness of harvest. Crop yields suggest that competitive winter wheat stands contributed to the success of the early maturing rotations compared to other treatments. Early maturing rotations resulted in reduced wild oat populations, likely through a combination of crop competitiveness and rotational diversity, and harvest weed seed control management effects from earlier maturing crops. Nomenclature: Wild oat, Avena fatua L.; barley, Hordeum vulgare L.

Two contrasting barley ( Hordeum vulgare L.) cultivars, i.e. Kepin No. 7 (salt sensitive) and Jian 4 (salt tolerant), were grown hydroponically to study the effect of exogenous silicon (Si) on time dependent changes of the activities of major antioxidant enzymes and of lipid peroxidation in roots under salt stress. Enzymes included: superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and glutathione reductase (GR). Three treatments with three replicates were investigated consisting of a control (basal nutrients with neither NaCl nor Si added), 120 mmol/L −1 NaCl, and 120 mmol/L −1 NaCl +1.0 mmol/L −1 Si. Plant roots were harvested 2, 4 and 6 days after treatment and assayed for activities of the antioxidant enzymes and the concentrations of reduced glutathione (GSH) and malondialdehyde (MDA), and electrolytic leakage percentage (ELP). The activities of SOD, POD and CAT in roots of salt-stressed plants were significantly stimulated at Day 2 compared to control plants, but considerably decreased at Day 4 and onward. GR activity in roots of salt-stressed plants remained unchanged at Day 2, but significantly decreased at Day 4 and onward. However, exogenous Si significantly enhanced these enzyme activities in roots of salt-stressed plants compared to Si-deprived salt treatments. This Si effect was time-dependent and became stronger as the experiments continued. The tendency of change in the activities of antioxidant enzymes and the concentration of GSH coincided with the concentration of MDA, the end product of lipid peroxidation, and the ELP. Higher activities of antioxidant enzymes, and higher concentration of GSH, but lower concentration of MDA and lower ELP were noted in cultivar Jian 4 compared to Kepin No. 7, implying genotypic differences with Jian 4 being less susceptible to stress-dependent membrane lipid peroxidation. The effects of Si-enhanced salt tolerance are discussed with respect to cell membrane integrity, stability and function in barley.

The influence of constant (9, 13 and 19 h) and reciprocally-interchanged photoperiods [at terminal spikelet (TS) or triple mound (TM)] on leaf, tiller and primordium development were examined using photoperiod-responsive cultivars of spring wheat, ‘UQ 189’ and spring barley, ‘Arapiles’. In both species, constant longer photoperiod reduced the duration from sowing (S) to double ridge (DR), as expected. However, photoperiod sensitivity was not restricted to this mainly vegetative phase. There was also a marked increase or reduction in the duration of reproductive phases between TS/TM and heading (H) when plants were transferred to shorter or longer photoperiods respectively, compared with controls. These responses were largely independent of the photoperiod during previous phases although minor effects of the previous photoperiod were observed. For both species, the time course of leaf emergence was linear, or bi-linear, depending on the final leaf number on the main stem. The rate of leaf emergence was faster for the first six to eight leaves than for the leaves appearing subsequently. The rate of emergence of early-formed leaves was independent of photoperiod whereas the rate of emergence of later leaves varied with photoperiod. Photoperiod also affected the dynamics of tillering. The rate of leaf primordium initiation was little affected by variation in photoperiod, but the rate of spikelet initiation increased with increases in photoperiod. The rates of leaf and spikelet primordium initiation were both substantially higher in barley than in wheat. The fact that the reproductive phase from TS/TM to H was largely independent of the duration of the previous phase provides evidence that this phase might be genetically manipulated to increase the time for floret development and hence grain number.

We have generated a telomere-specific probe by the polymerase chain reaction and used it to localize chromosome telomeres of ten unrelated angiosperm species in in situ. Concatenation of the simple monomers, 5′-(TTTAGGG)-3′, derived from the sequence of Arabidopsis thaliana telomeres, yielded a stable, versatile and reliable probe that gave a signal of high intensity following fluorescence in situ hybridization. Most species, including those with known karyotype rearrangements, showed telomere label only at chromosome termini. These findings are discussed in the context of the chromosomal events responsible for generating and stabilizing karyotype change in plants.

Barley (Hordeum vulgare L.) is among the world's earliest domesticated and most important crop plants. It is diploid with a large haploid genome of 5.1 gigabases (Gb). Here we present an integrated and ordered physical, genetic and functional sequence resource that describes the barley gene-space in a structured whole-genome context. We developed a physical map of 4.98 Gb, with more than 3.90 Gb anchored to a high-resolution genetic map. Projecting a deep whole-genome shotgun assembly, complementary DNA and deep RNA sequence data onto this framework supports 79,379 transcript clusters, including 26,159 'high-confidence' genes with homology support from other plant genomes. Abundant alternative splicing, premature termination codons and novel transcriptionally active regions suggest that post-transcriptional processing forms an important regulatory layer. Survey sequences from diverse accessions reveal a landscape of extensive single-nucleotide variation. Our data provide a platform for both genome-assisted research and enabling contemporary crop improvement.

Barley yellow dwarf disease (BYD) is transmitted by aphids and is caused by different strains of Barley yellow dwarf virus (BYDV) and Cereal yellow dwarf virus (CYDV). Economically it is one of the most important diseases of cereals worldwide. Besides chemical control of the vector, growing of tolerant/resistant cultivars is an effective way of protecting crops against BYD. The Ryd3 gene in barley (Hordeum vulgare L.) confers tolerance to BYDV-PAV and BYDV-MAV and the locus was previously mapped on the short arm of barley chromosome 6H near the centromere. We applied a strategy for high-resolution mapping and marker saturation at the Ryd3 locus by exploiting recent genomic tools available in barley. In a population of 3,210 F2 plants, 14 tightly linked markers were identified, including 10 that co-segregated with Ryd3. The centromeric region where Ryd3 is located suffers suppressed recombination or reduced recombination rate, suggesting potential problems in achieving (1) map-based cloning of Ryd3 and (2) marker selection of the resistance in breeding programmes without the introduction of undesirable traits via linkage drag.

Although it is commonly accepted that root exudation enhances plant-microbial interactions in the rhizosphere, experimental data on the spatial distribution of exudates are scarce. Our hypothesis was that root hairs exude organic substances to enlarge the rhizosphere farther from the root surface. Barley (Hordeum vulgare 'Pallas' - wild type) and its root-hairless mutant (brb) were grown in rhizoboxes and labelled with 14CO2. A filter paper was placed on the soil surface to capture, image and quantify root exudates. Plants with root hairs allocated more carbon (C) to roots (wild type: 13 %; brb: 8 % of assimilated 14C) and to rhizosheaths (wild type: 1.2 %; brb: 0.2 %), while hairless plants allocated more C to shoots (wild type: 65 %; brb: 75 %). Root hairs increased the radial rhizosphere extension three-fold, from 0.5 to 1.5 mm. Total exudation on filter paper was three times greater for wild type plants compared to the hairless mutant. Root hairs increase exudation and spatial rhizosphere extension, which probably enhance rhizosphere interactions and nutrient cycling in larger soil volumes. Root hairs may therefore be beneficial to plants under nutrient-limiting conditions. The greater C allocation below ground in the presence of root hairs may additionally foster C sequestration.