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  • 1
    ISSN: 1432-1939
    Keywords: Biennial plants ; Carbon partitioning ; Nitrogen partitioning ; Storage ; Harvest index
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Growth and nitrogen partitioning were investigated in the biennial monocarp Arctium tomentosum in the field, in plants growing at natural light conditions, in plants in which approximately half the leaf area was removed and in plants growing under 20% of incident irradiation. Growth quantities were derived from splined cubic polynomial exponential functions fitted to dry matter, leaf area and nitrogen data. Main emphasis was made to understanding of the significance of carbohydrate and nitrogen storage of a large tuber during a 2-years' life cycle, especially the effect of storage on biomass and seed yield in the second season. Biomass partitioning favours growth of leaves in the first year rosette stage. Roots store carbohydrates at a constant rate and increase storage of carbohydrates and nitrogen when the leaves decay at the end of the first season. In the second season the reallocation of carbohydrates from storage is relatively small, but reallocation of nitrogen is very large. Carbohydrate storage just primes the growth of the first leaves in the early growing season, nitrogen storage contributes 20% to the total nitrogen requirement during the 2nd season. The efficiency of carbohydrate storage for conversion into new biomass is about 40%. Nitrogen is reallocated 3 times in the second year, namely from the tuber to rosette leaves and further to flower stem leaves and eventually into seeds. The harvest index for nitrogen is 0.73, whereas for biomass it is only 0.19.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Plant and soil 68 (1982), S. 353-359 
    ISSN: 1573-5036
    Keywords: Anoxia ; Oxygen flux ; Primula
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Pitfalls in the use of the platinum micro-electrode method of determining soil oxygen flux are described, together with an example of its use. Interpretation of current measurements as oxygen fluxes is possible only if, a) an oxygen limitation to current has been demonstrated, and then b) a suitable applied potential is used. Oxygen flux values in a well drained soil can be as low as those in a seasonally waterlogged soil. However such low flux values are usually of short duration.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 73 (1987), S. 109-115 
    ISSN: 1432-1939
    Keywords: Flowerhed photosynthesis ; Carbon balance ; Competition ; Arctium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The gas exchange of flowerheads was determined in Arctium tomentosum and A. lappa during their development. The light, temperature and CO2 responses were used to estimate flowerhead photosynthesis and the in situ contribution of carbon assimilation to the carbon requirement of the plant for supporting a flowerhead. Changes in vapour pressure deficit had no effect on flowerhead photosynthesis rates and were not included in the model. In both species assimilatory capacity correlated with total bract chlorophyll content. Light, temperature and CO2 response curves were very similar in form between species, differing only in absolute rates. During all stages of development, flowerheads always exhibited a net carbon loss, which was mainly determined by temperature. The respiration rate decreased in the light, the difference of CO2 exchange in the dark and in the light was interpreted as photosynthesis. This rate was larger in A. lappa than in A. tomentosum. 30% of the total C requirement of A. lappa flowerheads was photosynthesized by its bracts, the total contribution offlowerhead photosynthesis in A. tomentosum was only 15%. The potential competitive advantages of variation in flowerhead photosynthesis are discussed.
    Type of Medium: Electronic Resource
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