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  • Electronic Resource  (3)
  • nitrogen  (2)
  • Ant  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Insectes sociaux 41 (1994), S. 43-61 
    ISSN: 1420-9098
    Keywords: Ant ; caste ; polyethism ; division of labor ; Ponerinae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We examined division of labor and colony demography in the antPonera pennsylvannica. Observation of three colonies with individually marked workers revealed a high degree of interindividual behavioral variation and a rough but consistent division of labor between brood tenders and foragers. This division was present both in colonies consisting entirely of workers produced in the previous summer and in colonies containing freshly eclosed ants. Two colonies showed typical age-based polyethism, with young ants focusing on brood care and overwintered ants on foraging. No such age basis was detected in the third colony. This difference may relate to variability in brood production schedules. Colonies showing temporal polyethism had two peaks of brood production and thus had relatively large brood populations when the first young workers eclosed, while the third colony had only one peak and little brood for the young workers to tend. Even if young ants have a lower threshold for brood care, it may have been concealed in the latter situation. Demographic data indicate that natural colonies produce one brood per year and that workers typically eclose into colonies with relatively low brood care demands. This suggests that overwintered workers do most of a colony's work and that the division of labor among overwintered ants is the more important one under natural conditions. The basis of this division is as yet unknown. These results also suggest that small colony size, univoltine brood schedule and a close association between foraging and brood care do not preclude division of labor among specialized castes, as has been suggested for another ponerine species (Traniello 1978).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5036
    Keywords: nitrogen ; precoditioning ; roots ; sycamore
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Acer pseudoplatanus L. trees were grown in sand culture for 2 years and, in 1988, supplied with either 1.0 mol N m-3 (low N) or 6.0 mol N m-3 (high N) to precondition their growth. In 1989, the same trees received either high or low nitrogen, producing four treatments; High N in 1988/High N in 1989; High N in 1988/Low N in 1989; Low N in 1988/Low N in 1989; and Low N in 1988/High N in 1989. Plant growth was affected by N supply in both years. In 1989 the Low N/High N treated trees had the same overall mass, leaf mass and stem girth as the High N/High N treatment. Early spring growth of foliage and roots was conditional on nitrogen supplied in the previous season. Later, the rapid increases in leaf, stem and root growth under high N was through root uptake. Internal partitioning of growth was affected, with the Low N/High N treatment producing more new leaves on axillary shoots, and more new white roots on existing structures, than the Low N/Low N treatment. Despite effects of the N preconditioning on the structure of both canopy and root system, nitrogen uptake was solely dependent on the current nitrogen supply.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5036
    Keywords: borescope ; cherry ; nitrogen ; persistence ; root ; season
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The persistence of white roots in cherry (Prunus avium) grown under two levels of nitrogen (high and low), was studied directly using a non-destructive borescope system. Plant growth and nitrogen uptake was increased by the extra nitrogen. Persistence times of white roots were significantly affected by several factors such as nitrogen level, time of appearance and depth in the pot. Suberisation of white roots tended to be late in the growing season, and roots produced in the middle of May persisted as white for significantly longer (5.9 weeks) than those produced in early July (2.5 weeks). Also, roots that appeared at the foot of the pot remained white for longer (5.6 weeks) than roots at the surface of the pot (2.7 weeks). Results also suggest that white root persistence was greater for trees with the lower rate of application of nitrogen (4.5 weeks under low nitrogen compared to 3.6 under high nitrogen).
    Type of Medium: Electronic Resource
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