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  • 1
    Electronic Resource
    Electronic Resource
    Uptake of SO2 in shoots of Scots pine: field measurements of net flux of sulphur in relation to stomatal conductance (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 5 (1982), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. Net fluxes of gaseous sulphur compounds, water vapour and carbon dioxide to current- and one-year-old shoots of Scots pine were simultaneously measured in the field. The shoots were fumigated in temperature-controlled assimilation chambers with sulphur dioxide at concentrations ranging from 40 to 250 μg m−3 (15–95 ppb). The hypothesis that stomatal opening regulates the uptake of sulphur dioxide was tested. The following conclusions were reached concerning the dry deposition of sulphur dioxide to a dry coniferous shoot.There was a marked diurnal variation in the uptake rate of sulphur dioxide. The net deposition velocity of sulphur was about three times higher during the day than during the night during July-October. Stomatal opening was not the primary factor controlling the dry deposition rate of sulphur dioxide. The net dry deposition rate was significantly smaller than the calculated rate based on stomatal conductances for water vapour.Part of this deviation could be explained by re-emission of reduced sulphur compound(s) from the needles. The re-emission of sulphur was a light-dependent process and might be of great significance for the sulphur balance calculations.A variable deposition velocity should be used in atmospheric transport models to account for the diurnal and seasonal variation in the surface resistance of a dry canopy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11587612
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Gas exchange in a 20-year-old stand of Scots pine (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 54 (1982), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The rates of net photosynthesis and transpiration of one-year-old shoots were measured in situ in five different positions within the crown of a young Scots pine (Pinus sylvestris L.). Measurements were carried out on south- and north-facing shoots on the third and sixth whorls, respectively, and on an east-facing shoot on the ninth whorl. In another investigation the rates of gas exchange of one-year-old shoots on the third whorl of eight different trees were studied. The measurements were made during June and July, 1977, under non-limiting conditions of soil water. The daily rates of net photosynthesis in whorls three and six followed the light conditions closely, with higher rates for the south side of each whorl and higher for whorl three than six. On whorl nine the shoot had a higher light compensation point and a low rate of photosynthesis at light saturation compared to the other shoot positions. The quantum yield for the shoot on the lowest whorl, as estimated from the linear part of the light response curve, was 50% lower than for shoots on whorl three and six.The variation in transpiration rates was pronounced within the crown as an effect of differences in the absolute value and diurnal course of stomatal conductance. The variation in net photosynthesis was small between different trees while the variation in transpiration was much higher. Thus the variation in water use efficiency was great. It is concluded that it is possible to extrapolate measurements of net photosynthesis from individual trees up to a stand level without introducing large errors in the estimate. More caution must be paid before extrapolating tree transpiration up to stand transpiration. However, before an extrapolation of gas exchange is made from tree to stand level the variation in net photosynthesis and transpiration rate within the crown must be known.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1982.tb00570.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Gas exchange in a 20-year-old stand of Scots pine (1982)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 54 (1982), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Net photosynthesis of current and one-year-old shoots in Scots pine (Pinus sylvestris L.) was measured during a two-year period (1977–1978). The measurements were carried out in Central Sweden using a system that allowed in situ measurements throughout the year. The photosynthetically active period, defined as months with a positive carbon dioxide balance, was nine months per year for one-year-old shoots and six months for current shoots. The daily rates of net photosynthesis were low in spring and late autumn and 95% of the annual photosynthetic production occurred from May to October. In spring net photosynthesis was limited by a low photosynthetic capacity and a restricted access to water caused by the frozen ground. It took more than three months in spring and early summer to restore full photosynthetic capacity in the one-year-old shoots, but the rate of recovery varied considerably between the two years. In late autumn the rates of photosynthesis were mainly limited by low photon flux densities.The seasonal patterns of photosynthesis were similar between the two years, and even though there were pronounced differences for individual months, the total annual photosynthetic production of the two years only differed by 1.4% for the one-year-old shoots. The differences in photosynthetic production for current shoots were much higher as an effect of different rates of needle development and differences in photosynthetic capacity during the two years. An estimate of the carbon balance of the current shoots showed that the shoots had not photosynthesized their own weight in terms of carbon until late August (1978) or early September (1977), which means that their photosynthetic production was of minor importance for the formation of stem wood.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1982.tb00569.x
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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