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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 24 (1984), S. 0 
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The growth and competition of wild oats (Avena fatua L.) emerging at different times, and the time of onset of competition by them were studied using natural populations in spring barley. In one experiment in 1972, wild oats emerging in the 0–0⋅5, 0⋅5–2⋅5, 2⋅5–4 crop leaf stages at densities of 54, 46, 15 m −2 respectively were allowed to compete all season with the crcp. These gave rise to 82, 17 and l% of all seed shed and caused 16%, and two non-significant yield losses respectively. In two other experiments in 1973, nearly all the wild oats that caused yield losses had emerged by the crop 2˙45 leaf stage. Where wild oats emerging up to the crop 2⋅5 leaf stage were removed, the later ones did not compensate by making extra growth. In one of these experiments in which densities of crop and weed were 416 and 414 m 2, and in the other where they were 295 and 294 m 2 respectively, grain yield losses were significant if the wild oats remained in the crop until the crop had 2⋅5–4⋅5 leaves and 4⋅5–6⋅5 leaves respectively. In a third experiment in 1973 with initial densities of 464 wild oats and 336 barley plants m −2, and where a top dressing of nitrogen was given at the crop 3–4 leaf stage, unlike the other two experiments in 1973 where all nitrogen was applied at sowing, no yield losses resulted unless the wild oats remained in the crop until after the crop 6 leaf stage.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Weed research 25 (1985), S. 0 
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: A study was made of the caryopsis weights of Avena fatua grown in the field and in pots and of the competitive ability of A. fatua from heavy seed (≥18 mg) and light reed (≤11 mg) grown at a depth of either 25 or 75 mm with spring barley sown at 25 mm.The weight of field- and pot-grown caryopses of A. fatua types fA, fB and fC ranged from 3 to 25, 5 to 23, and 5 to 25 mg respectively. With one exception, both the field- and pot-grown samples showed a double normal distribution pattern. The mean weights of pot-grown primary and secondary caryopses of fA, fB and fC were 15 and 9, 19 and 11, and 18 and 11 mg respectively.In a competition experiment, A. fatua grown from heavy seeds sown at 75 mm depth with an equal number of barley produced 47% more panicles, 54% more seed and 56% more dry weight per plant than plants from light seeds. When barley and both seed weights of A. fatua were sown at 25 mm depth these differences were smaller, being 21, 28 and 34% respectively.When the barley was at Zadoks stage 87, and when the barley and A. fatua were grown at equal densities at 25 mm depth, the dry weight of barley was reduced from 10·4 to 7·7, and to 5·8 g per plant by light- and heavy-seeded A. fatua, respectively. When the barley was grown at 25 mm and the A. fatua at 75 mm, the weight per barley plant was reduced to 9·5 and 7·2 g by A. fatua plants grown from light and heavy seeds respectively. Reductions in numbers of grain were caused mainly by a reduction in the number of fertile heads.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-3180
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The emergence and development of A fatua were studied in 23 spring barly fields in 1972 and nine in 1973 nautarally infested with yhe weed. Emergence occurred up to the four-leaf stages of the crop. The mean number of days from drilling to 50% emergence of A fatua plants was 22 in 1972 and 36 in 1973.The majority of seeds were shed by early emerging plants in 1972, 79% and in 1973. 59% of A fatua plants had emerged by the two-leaf stage of the crop and these plants produced 97 and 89% respectively of all the seed shed. In both years, A fatua plants emerging before the crop produced five times as many seeds per plant as those emerging between the crop two and three-leaf stages. The earliest emerging plants were also the heaviest and had most stems per plant.In both years there was a significant relationship between the density of A fatua plants in the crop in spring and their mortality.A large variation occured between the sites in the number of A fatua plants that emerged by a given crop leaf stage. In 1973.insufficient numbers of sites were investigatesd to derive a relationship between time to A fatua emergence and crop yield loss, but in 1972, a given density of A fatua plants emerging at an early stage caused agreater crop yields loss than the same density emerging later. This was also evident to aleser extent in data derived from a similar series of 15 experiments in 1971.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Plant growth regulation 28 (1999), S. 129-132 
    ISSN: 1573-5087
    Keywords: dormancy ; Lactuca sativa ; lettuce seeds ; Brassica napus ; rapeseed ; combustion products ; Salix viminalis ; Themeda triandra ; Triticum aestivum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In darkness, dormancy was imposed on seeds of lettuce (Lactuca sativa L. cv. Grand rapids) by high temperature and on seeds of oilseed rape (Brassica napus L. cv. Apex) by osmotic stress using polyethylene glycol (PEG 8000). In both cases, dormancy was broken by incubating the seeds in aqueous extracts of combustion products from Salix viminalis wood chips or Themeda triandra leaves. Dormancy of rapeseed, but not lettuce, was also broken by a solution of smoke from burnt straw of Triticum aestivum. The greatest stimulation from burnt vegetation was achieved with an aqueous extract of pyrolysed willow wood chips, which had been subjected to temperatures of up to 800 °C during combustion in a down-draught gasifier. This suggests that some biologically active substances obtained from combustion of plant tissues are highly heat-stable.
    Type of Medium: Electronic Resource
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