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  • evolution
  • nitrogen
  • wheat
  • Springer  (79)
  • Royal Society
  • 1985-1989  (79)
  • 1987  (79)
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  • 1985-1989  (79)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 43 (1987), S. 851-860 
    ISSN: 1420-9071
    Keywords: Social insects ; Isoptera ; caste differentiation ; reproductive biology ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The hemimetabolous termites have a very different caste system from social Hymenoptera in which only true imagoes participate in all social tasks. In termites, the imagoes are restricted to reproduction. The termite solidiers have no equivalent in other social insects. They are unique both in their post-embryonic development and their exclusively defensive function. At maturity they keep their molting gland and therefore should be considered as stabilized, differentiated immatures. They appeared monophyletically, early in the evolution of termites. The definition of the worker caste and the current theories explaining its evolution are reexamined after a critical reappraisal of data on post-embryonic development. On the basis of ontogenic, morphologic and functional criteria, we define termite workers as individuals diverging early and irreversibly from the imaginal development, with a morphology typical of their caste but largely of larval appearance, and taking part in most of the social tasks. Such a truly eusocial worker caste is observed in all advanced phyla: Termitidae, Hodotermitidae, andSchedorhinotermes (Rhinotermitidae), but apparently also in one morphologically primitive termite,Mastotermes darwiniensis. This distribution can only be explained by postulating a polyphyletic origin of the worker caste in termites. In all other primitive termites, most of the work is done by temporary helpers (late larvae and nymphs). In these societies, pseudergates are redefined as individuals separating late from the imaginal line, functioning as workers, but not constituting the main working force in the natural society. The particularity of the caste system in termites results from two fundamental peculiarities of their post-embryonic development: -A certain dissociation of molt, growth, and differentiation. -A relative independence in the ontogeny of their different organs.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 43 (1987), S. 297-300 
    ISSN: 1570-7458
    Keywords: green peach aphid ; Myzus persicae ; potato ; Solanum tuberosum ; maturity ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 44 (1987), S. 31-35 
    ISSN: 1570-7458
    Keywords: host quality ; nitrogen ; survival ; Leptinotarsa decemlineata ; Lycopersicon esculentum ; plant virus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Résumé Pour vérifier l'hypothèse selon laquelle une contamination par un virs végétal peut accroître la consommation de plantes délaissées ou partiellement résistantes, nous avons examiné les interactions entre Leptinotarsa decemlineata Say, Lycopersicon esculentum Mill., et le virus de la mosaïque du tabac (TMV). La survie des larves de L. decemlineata a augmenté avec la contamination par TMV; les teneurs en azote et en tomatine étaient toutes deux plus élevées dans les plantes contaminées par le virus. La survie a augmenté linéairement avec la teneur en azote, mais sans dépendre de la teneur en tomatine. L'influence positive pour L. decemlineata de la contamination par le virus peut être attribuée au moins en partie à la teneur en azote plus élevée. Nos résultats correspondent à l'hypothèse selon laquelle la consommation de plantes délaissées ou partiellement résistantes peut être augmentée par la contamination virale, et que cette contamination peut faciliter l'adaptation d'insectes phytophages sur des plantes marginalement consommables.
    Notes: Abstract Infection by tobacco mosaic virus improved the suitability of tomato, Lycopersicon esculentum Mill. for survival of Colorado potato beetle, Leptinotarsa decemlineata (Say), larvae. This improvement was due, at least in part, to the increase in total nitrogen content of virus-infected plants. The simultaneous increase in tomatine content had no discernable effect on L. decemlineata survival. Our results are consistent with the suggestions that virus infection may improve the suitability of partially resistant or non-preferred hosts, and that virus infection may facilitate the adaption of phytophagous insects to such ‘marginal’ host plant species.
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  • 4
    ISSN: 1436-5073
    Keywords: steel ; nitrogen ; microarea ; Auger spectrometry ; electron probe microanalysis ; standards
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 12 (1987), S. 119-137 
    ISSN: 1573-0867
    Keywords: fertiliser ; nitrogen ; regression ; response ; winter wheat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Measurements were made of yield of dry matter, plant-N content, and the distribution of mineral-N down the soil profile in 10 fertiliser-N experiments. In one of them detailed measurements were made throughout growth. Rate of N-uptake by the crop was unaffected by the amount of mineral-N in the upper 90 cm of soil when it was above about 30 kg N ha−1. The %N in plants that received ample N-fertiliser declined with increase in plant mass according to a previously derived equation. During senescence there was an apparent loss of N from the crop. N-nutrition in the different experiments had little effect on the partition of assimilate between grain and straw. At harvest grain and straw weights were well related by a linear model which had the same gradient but different intercepts for each experiment. Grain %N was about four times greater than straw %N. Regression analysis supported the view that high evaporative conditions or temperatures during the growing period induced earlier harvest dates, less grain relative to straw, and a higher %N in the plant when ample N-fertiliser was applied but not when N-fertiliser was withheld. Other analyses indicated that cereal roots were generally unable to extract mineral nitrogen from the soil when the concentration was less than about 0.18 kg N ha−1 cm−1, that at low levels of N-nutrition the recovery of available inorganic-N from soil by the grain and straw was about 80%, and that the average mineralisation rates from early spring to shortly after harvest date varied between 0.22 and 0.88 kg N ha−1 d−1 from site to site.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 12 (1987), S. 201-218 
    ISSN: 1573-0867
    Keywords: relative effectiveness ; apatites ; wheat ; initial and residual effectiveness ; bicarbonate extractable phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The initial and residual agronomic effectiveness of six apatite rock phosphates from India, one from the USA (North Carolina) and one from Australia (Queensland) were evaluated in a pot trial with wheat on a lateritic soil. All of the Indian rock phosphates were very poor sources of phosphorus. Values of initial effectiveness relative to monocalcium phosphate ranged from 〈 0.0001 to 0.02 and from 〈 0.0001 to 0.008 for measurements based on yield and phosphorus uptake respectively. The residual effectiveness relative to freshly applied monocalcium phosphate was determined by growing a second crop on the fertilized soils. The effectiveness of the Indian rock phosphates remained very low ranging from 〈 0.0001 to 0.002 and from 〈 0.0001 to 0.0004 for yield and phosphorus uptake respectively. Queensland and North Carolina rock phosphates were much superior to the Indian sources with initial effectiveness values in terms of yield of 0.08 and 0.37 and residual effectiveness values of 0.02 and 0.15 respectively. For each crop there was a single relationship between yield and phosphorus uptake (i.e. internal efficiency) for all phosphorus sources showing that variations in yield response were due solely to differences in phosphorus availability. Sodium bicarbonate extractable phosphorus values for fertilized soils sampled shortly after fertilization were not predictive of yield unless different calibration curves were used for the different phosphorus fertilizers.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 13 (1987), S. 191-197 
    ISSN: 1573-0867
    Keywords: chemical extractants ; critical levels ; semi-arid region soils ; wheat ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To find critical tissue levels of Zn for wheat, and to evaluate various chemical extractants, a screen-house experiment was conducted on 21 diverse soils representing semi-arid regions in Haryana State, India. The extractants differed in the amounts of Zn extracted and the order was: 0.1 N HC1 〉 EDTA-NH4OAc 〉 EDTA-(NH4)2CO3 〉 DTPA + CaCl2. The amounts (mg kg−1) of extractable Zn associated with a yield reduction of 20% were: DTPA + CaCl2, 0.60; EDTA — (NH4)2CO3, 0.80; EDTA-NH4OAc, 0.92 and 0.1 N HCl, 1.20. The corresponding critical Zn concentration in ten weeks old plants was found to be 17 mg gm−1. The DTPA + CaCl2 method gave the best correlation (r = 0.85) between extracted Zn and Bray's per cent yield. It is recommended for assessing Zn status of soils of semi-arid region.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 14 (1987), S. 135-142 
    ISSN: 1573-0867
    Keywords: nitrogen ; phosphorus ; soil and crop residues management practices ; maize yield ; Plinthudult ; Cameroon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The shortening of fallow period in several areas in tropical Africa has reduced soil fertility and exposed soils to erosion and run-off. Fertilizer application and crop conservation practices are needeed to sustain high crop yield and to conserve the natural resource base for upland crop production in the continent. Field trials were carried out to evaluate the effect of fertilizer application and soil and crop residues management practices on yield of maize (Zea mays L.) planted on a Plinthudult soil at Bertoua, Eastern Cameroon. Maize yields increased significantly with nitrogen and phosphorus fertilizer application. Under the rainfall pattern prevailing in the area, the amount of nitrogen required for maximum yield was higher in the second season. On the other hand, the amount of phosphorus required for maximum yield appeared to decrease with time. The burning of crop residues and weeds prior to planting together with no-till practive gave higher yield of maize than other soil and crop residues management practices.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 11 (1987), S. 25-41 
    ISSN: 1573-0867
    Keywords: fertilizer ; high analysis nutrient compounds ; nitrogen ; phosphorus ; Rhodes grass ; slow-release ; sulphur ; Townsville stylo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The fertilizer potential of two unusual N-P compounds with cage structures was evaluated in pot experiments where plants were repetitively cut over 400 days. One of the compounds, hexamethyl-hexaaza-tetraphosphaadamantane (APA), having 41.6% P and 28.2% N, showed high fertilizer capability. After more than 400 days, dry matter yield of Rhodes grass given APA was 83–102% of that given conventional N-P sources, and yield of Townsville stylo 60–70%. Curves for N and P uptakes over time were of sigmoidal form, with the steepest parts between days 40 and 120, suggesting a slow-release feature. However growth was depressed up to day 40, presumably by some toxic factor associated with the decomposition of the APA. This toxicity was avoided if some conventional fertilizer was applied with the APA. The other compound, the tetrasulphide of APA (APAS) had only limited fertilizer potential. Plants did absorb P and S at least from this compound, but Townsville stylo yield was only 32–38% of that with conventional fertilizers, and Rhodes grass yield not much greater than from control pots. The possible slow-release feature, and the toxic effect, did not occur with APAS.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Cellular and molecular life sciences 43 (1987), S. 1094-1099 
    ISSN: 1420-9071
    Keywords: Cognitive processes ; metabolism ; evolution ; biomathematical models ; cell proliferation ; cell growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A model for cellular proliferation is described according to which proliferation ensues when metabolism evolves towards commitment to DNA synthesis, and inhibition of proliferation occurs when enzymic interactions are iterated within a few metabolic pathways, another limiting factor being the supply of metabolites. The model successfully describes cellular growth and division as a ‘cognitive process’ based on interaction within enzymic elements and the genome, and affords an explanation in these terms of some empirical phenomena which have previously been understood only as isolated observations.
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