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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Grass and forage science 58 (2003), S. 0 
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Daily net canopy photosynthesis (Pn) of cocksfoot (Dactylis glomerata L.) was predicted for combinations of temperature, herbage nitrogen (N) concentration and water status from the integration of models of leaf photosynthesis of the light-saturated photosynthetic rate (Pmax), photosynthetic efficiency (α) and the degree of curvature (θ) of leaf light-response curves. The effect on Pn, maximum Pn (Pn max) and the optimum leaf area index (LAI at Pn max) was examined when any one of these factors was limiting. The ranges that gave the optimum values of Pn (Pn max = 30·8–33·5 g CO2m−2 d−1) for temperature (19–22°C) and N concentration (40–50 g N kg−1 DM) were smaller than those for net leaf photosynthesis. Also, Pn fell to 0 at a lower level of water stress (pre-dawn leaf water potential, ψlp = −12·5 bar) than for Pmax. The canopy photosynthesis model was then used to compare predicted and measured dry matter (DM) production for cocksfoot pastures grown under a diverse range of environmental conditions with field data from New Zealand and Argentina. To predict DM production leaf area index and leaf canopy angle were included from field measurements. The model explained about 0·85 of the variation in cocksfoot DM production for the range of 6·5–134 kg DM ha−1 d−1. The canopy model overestimated the DM production by 0·10 which indicates that a further Pmax function for leaves of different ages and a partitioning sub-model may be needed to improve predictions of DM production.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Grass and forage science 57 (2002), S. 0 
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Maximum light-saturated photosynthetic rate (Pmax) and stomatal conductance (gs) of field-grown cocksfoot (Dactylis glomerata L.) leaves in a silvopastoral system were measured at different times under moderate (850–950 µmol m−2 s−1 photosynthetic photon flux density, PPFD) and severe shade (85–95 µmol m−2 s−1 PPFD). Also Pmax and gs were measured after 30, 60 and 180 min of severe shade to determine the lag in the rise of photosynthesis rate from low to high irradiance levels (induction state). The highest Pmax and gs values obtained were 26·5 µmol CO2 m−2 s−1 and 0·41 mol H2O m−2 s−1 in non-limiting conditions with full sunlight (1900 µmol m−2 s−1 PPFD). These values were defined as standardized dimensionless Pmaxs=1 and gss=1 for comparison of treatment effects. The Pmaxs under severe shade decreased by 0·004 units per minute from 1 to 180 min and reached a steady-state of 0·37 units after 140 min. Under moderate shade, Pmaxs decreased by 0·002 units per minute from 1 to 120 min and reached a steady-state of 0·76 units. The time required to reach full induction on return to full sun (Pmaxs=1) was 15 min after 30 min of severe shade and 37 min after 180 min of shade. Mathematical equations were derived to describe the changes in Pmaxs and gss under severe and moderate shade and during induction. The rate of change of gss was slower than for Pmaxs on entering shade and also slower during the subsequent induction process. This indicated other factors in addition to gs were operating in the reduction and increment of Pmax and a two-step model to explain this is proposed. The defined photosynthetic responses of cocksfoot leaves to fluctuating light regimes could be used to develop quantitative predictions of Pmax for inclusion in a canopy photosynthesis model of silvopastoral systems.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2494
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A simple multiplicative model using temperature, foliage nitrogen (N) concentration and water status was developed to predict the maximum photosynthetic rate (Pmax) of field-grown cocksfoot (Dactylis glomerata L.) leaves when none, one, two or all the factors were limiting. The highest Pmax was 27·4 μmol CO2 m–2 s−1 in non-limited conditions, which was defined as the standardized Pmax value dimensionless (Pmaxs=1). Pmaxs increased 0·058 units per °C from 10°C to the optimum range (19–23°C) (Pmaxs=1) and then declined 0·077 units of Pmaxs per °C from 23 to 31°C. Pmaxs=1 was also measured from 59 to 52 g N kg−1 dry matter (DM) foliage N. Pmaxs then decreased at the rate of 0·115 units per 10 g N kg−1 DM from 52 to 26 g N kg−1 DM, and 0·409 units of Pmaxs per 10 g N kg−1 DM from 26 to 15 g N kg−1 DM. For predawn leaf water potential (ψlp), Pmaxs=1 was measured from −0·1 to −1·2 bar but declined linearly at a rate of 0·078 units per bar of ψlp from −1·2 to −14·0 bar because of a linear decrease in stomatal conductance. An interaction between low N content (≤20 g N kg−1 DM) and high temperature (〉23°C) was also detected. Together, this multiplicative model accounted for 0·82 of the variation in Pmaxs.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 89 (1967), S. 4213-4214 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 90 (1968), S. 5284-5286 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 93 (1971), S. 3817-3818 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 114 (1995), S. 0 
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Wild relatives are a potential source of genetic diversity to lentil (Lens culinaris Medik). The objective of this research was to obtain viable interspecific hybrids between the domesticated lentil and its wild relatives.The paper details the results of a number of interspecific crosses among L. culinaris, L. orientalis, L. odemensis, L. ervoides and L. nigricans. Viable hybrids were produced between L. culinaris × L. orientalis, L. culinaris × L. nigricans, L. culinaris × L. ervoides and between L. culinaris × L. odemensis. Further viable hybrids were obtained between L. culinaris and L. ervoides, which have the potential to be a ‘bridge’ in hybridization to L. culinaris for specific L. nicrigans lines which proved recalcitrant in L. culinaris × L. nigricans crosses. This is the first time that four wild species of lentils have been used successfully in hybridization with cultivated lentils, and viable hybrids produced. This paper also suggests that the artificial supplement of GA3, hormone is needed after fertilization for the normal growth of the hybrid embryo, possibly as the natural GA3 production is restricted with alien pollinations in cultivated lentils in both F1 and backcross hybrids.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 121 (2002), S. 0 
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Ascochyta blight, caused by Ascochyta lentis, is one of the most globally important diseases of lentil. Breeding for host resistance has been suggested as an efficient means to control this disease. This paper summarizes existing studies of the characteristics and control of Ascochyta blight in lentil, genetics of resistance to Ascochyta blight and genetic variations among pathogen populations (isolates). Breeding methods for control of the disease are discussed. Six pathotypes of A. lentis have been reported. Many resistant cultivars/lines have been identified in both cultivated and wild lentil. Resistance to Ascochyta blight in lentil is mainly under the control of major genes, but minor genes also play a role. Current breeding programmes are based on crossing resistant and high-yielding cultivars and multilocation testing. Gene pyramiding, exploring slow blighting and partial resistance, and using genes present in wild relatives will be the methods used in the future. Identification of more sources of resistance genes, good characterization of the host-pathogen system, and identification of molecular markers tightly linked to resistance genes are suggested as the key areas for future study.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Anther culture (AC) was carried out on a fertile triploid hybrid between Hordeum vulgare L. (cultivated barley) and H. bulbosum L, (bulbous barley grass) to determine whether AC-derived regenerants differed from progeny obtained through selfing and backcrossing. Chromosome counts were carried out on all plants and DNA was extracted from them to prepare Southern blots for molecular analysis. To identify true recombinants, the blots were probed with rye repetitive sequence probes (pSc119.1 and pScl19.2). which hybridize strongly and specifically to H. bulbosum DNA. Twenty probes that detect single- or low-copy sequences were hybridized with Southern blots containing restricted DNA extracted from 25 AC-derived plants, 11 selfed and six backcrossed progeny that showed hybridizations with pScll9. Although restriction fragment length polymorphisms (RFLPs) were only observed using probes that map to four of the possible 14 chromosome arms, an introgression associated with chromosome 6HS was frequently observed among plants derived from AC. selfing and backcrossing. Plants from AC differed from selfed and backcrossed progeny in their chromosome number; unique RFLP bands that were occasionally observed may indicate chromosomal rearrangements.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 96 (1974), S. 4673-4674 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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