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  • 1
    Electronic Resource
    Electronic Resource
    The carbon gain benefits of solar tracking in a desert annual (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 1 (1978), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. A comparison between two sympatric winter desert annuals, Camissonia claviformis and Malvastrum rotundi folium showed that both gained similar amounts of carbon during a spring day, although by very different means. Camissonia has horizontally fixed leaves which have a very high photosynthetic capacity. The temperature optimum of photosynthesis for this species is near 20°C. Malvastrum has leaves with a lower photosynthetic capacity and a photosynthetic temperature optimum near 30°C. Leaves of the latter species remain normal to the sun throughout the course of the day. The tracking response and high temperature optimum for photosynthesis of Malvastrum result in a high daily carbon gain and also a high water-use efficiency.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1978.tb02045.x
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  • 2
    Electronic Resource
    Electronic Resource
    Photosynthetic gas exchange and the stable isotope composition of leaf water: comparison of a xylem-tapping mistletoe and its host (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 16 (1993), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Photosynthetic gas exchange and the stable isotopic composition of foliage water were measured for a xylem tapping mistletoe, Phoradendron juniperinum, and its host tree, Juniperus osteosperma, growing in southern Utah. The observed isotopic composition of water extracted from foliage was compared to predictions of the Craig-Gordon model of isotopic enrichment at evaporative sites within leaves. Assimilation rates of juniper were higher and stomatal conductance was lower than the values observed for the mistletoe. This resulted in lower intercellular/ ambient CO2 values in the juniper tree relative to its mistletoe parasite. For mistletoe, the observed foliage water hydrogen and oxygen isotopic enrichment was less than that predicted by the model. In juniper, foliage water hydrogen isotopic enrichment was also lower than that predicted by the evaporative enrichment model. In contrast, the oxygen isotopic enrichment in juniper foliage water was slightly greater than that predicted for the evaporative sites within leaves. Hydrogen isotopic enrichment in mistletoe foliage shows systematic variation with stem segment, being highest near the tips of the youngest stems and decreasing toward the base of the mistletoe, where isotopic composition is close to that of stem water in the host tree. In a correlated pattern, mid-day stomatal conductance declined abruptly in mistletoe foliage of increasing age.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1993.tb00480.x
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  • 3
    Electronic Resource
    Electronic Resource
    Water uptake by plants: perspectives from stable isotope composition (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Stable isotope studies of hydrogen and oxygen stable isotope ratios of water within plants are providing new information on water sources, competitive interactions and water use patterns under natural conditions. Variation in the utilization of summer rain by aridland species and limited use of stream water by mature riparian trees are two examples of how stable isotope studies have modified our understanding of plant water relations. Analyses of xylem sap and tree rings have the potential of providing both short-term and long-term information on plant water use patterns.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1992.tb01657.x
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  • 4
    Electronic Resource
    Electronic Resource
    Differential uptake of summer precipitation among co-occurring trees and shrubs in a pinyon-juniper woodland (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Measurements of the ratio of deuterium to hydrogen (D/H) in stem xylem water were used to determine the relative uptake of summer precipitation by four co-occurring plant species in southern Utah. The species compared included two trees, Juniperus osteosperma and Pinus edulis, and two shrubs, Artemisia tridentata and Chrysothamnus nauseousus. There were significant differences among species in the relative use of summer precipitation. Chrysothamnus nauseosus had stem water D/H ratios in May through August 1990 that were not significantly different from that of groundwater. In contrast, the other three species had stem water D/H ratios that were intermediate between the groundwater value and summer precipitation values, indicating that a mixture of both precipitation and groundwater was being used by these species. The two tree species generally had higher D/H values than did A. tridentata indicating a higher average uptake of summer precipitation, although the roots of J. osteosperma and P. edulis may not be as responsive to small precipitation events as A. tridentata. There was a strong negative correlation between stem water D/H ratios and predawn water potential, which suggests a relationship between plant rooting pattern and water source use. In addition, water-use efficiency during photosynthetic gas exchange, calculated from leaf carbon isotope composition, differed among species and was strongly correlated with differences in the relative uptake of summer precipitation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1992.tb02150.x
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  • 5
    Electronic Resource
    Electronic Resource
    Photoperiod and photosynthetic capacity in Lotus scoparius (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 9 (1986), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Leaves of Lotus scoparius Nutt., a Mediterranean-climate shrub, exhibited higher photosynthetic capacities when grown under winter (10/14 h, day/night) than summer (14/10 h) photo-periods, even though total daily photon irradiance was higher under summer photoperiods. Photosynthetic dependence on natural variations in photo-period, such that activity was higher under photo-periods associated with expected precipitation, may be a more dependable environmental parameter than total irradiance in temperate habitats with winter-spring precipitation patterns and where seasonal cloudiness may cause total daily irradiance levels to be highly variable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1365-3040.ep11616364
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  • 6
    Electronic Resource
    Electronic Resource
    Nitrogen isotope composition of tomato (Lycopersicon esculentum Mill. cv. T-5) grown under ammonium or nitrate nutrition (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Studies that quantify plant δ15N often assume that fractionation during nitrogen uptake and intra-plant variation in δ15N are minimal. We tested both assumptions by growing tomato (Lycopersicon esculetum Mill. cv. T-5) at NH4+ or NO−3 concentrations typical of those found in the soil. Fractionation did not occur with uptake; whole-plant δ15N was not significantly different from source δ15 N for plants grown on either nitrogen form. No intra-plant variation in δ15N was observed for plants grown with NH+4. In contrast. δ15N of leaves was as much as 5.8% greater than that of roots for plants grown with NO−3. The contrasting patterns of intra-plant variation are probably caused by different assimilation patterns. NH+4 is assimilated immediately in the root, so organic nitrogen in the shoot and root is the product of a single assimilation event. NO−3 assimilation can occur in shoots and roots. Fractionation during assimilation caused the δ15N of NO−3 to become enriched relative to organic nitrogen; the δ15N of NO−3 was 11.1 and 12.9% greater than the δ15N of organic nitrogen in leaves and roots, respectively. Leaf δ15N may therefore be greater than that of roots because the NO−3 available for assimilation in leaves originates from a NO−3 pool that was previously exposed to nitrate assimilation in the root.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00010.x
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  • 7
    Electronic Resource
    Electronic Resource
    On the role of orientation in reducing photoinhibitory damage in photosynthetic-twig desert shrubs (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Quantum yields for O2 evolution were measured in photosynthetic twigs and leaves of Hymenoclea salsola and Senecio douglasii, two common shrubs of the deserts of western North America. When exposed to long-term drought, quantum yields of leaves and twigs remained constant up to the point of leaf abscision in both species. As water stress developed further, quantum yields began to decline in twigs; the extent of this quantum yield reduction was dependent on incident photon flux density. The reduction in quantum yield in twigs, which have a near-vertical orientation, was greatly accelerated when twigs were reoriented to the near-horizontal inclination typical of leaves. The reductions in quantum yield were not rapidly reversible and are interpreted as indicating photoinhibitory damage. The results are discussed in terms of the role that a near-vertical orientation might serve in maintaining photosynthetic structures through a drought period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1992.tb00977.x
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  • 8
    Electronic Resource
    Electronic Resource
    Modification of paraheliotropic leaf movement in Phaseolus vulgaris by photon flux density (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 14 (1991), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract. The effects of modification of photon flux density (PFD, 400-700 nm) on paraheliotropic leaf movement were examined in Phaseolus vulgaris L. under controlled environmental conditions. The cosine of the angle of incidence to directional PFD (cos(i)), a measure of leaf movement, was linearly and negatively related to PFD. That is, leaflets progressively oriented away from a direct light beam in response to increasing PFD. The minimum PFD causing paraheliotropic movement was approximately 25 μmol m−2 s−1. When PFD was varied, tissue temperature changed due to an altered energy balance. Since a change in pulvinus temperature can affect leaf movement, experiments were conducted to distinguish the effects of PFD signal and pulvinis temperature. Leaflets oriented to reduce incident PFD levels in response to increasing PFD (either white light or blue light) when pulvinis temperature was kept constant. From these results, we conclude that changes in PFD signals alone can control paraheliotropic leaf movements. Phaseolus vulgaris grown outdoors oriented their leaflets to face towards the sun in the morning and again in late afternoon, but avoided the sun's direct rays at midday. This diurnal pattern of paraheliotropic leaf movements can be explained on the basis of known paraheliotropic movements in response to PFD and air temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1991.tb01510.x
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  • 9
    Electronic Resource
    Electronic Resource
    Carbon isotope composition of C4 grasses is influenced by light and water supply (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 19 (1996), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The carbon isotope composition of C4 grasses has the potential to be used as an indicator of changes in the isotopic composition and concentration of atmospheric CO2, especially for climate reconstruction. The usefulness of C4 grasses for this purpose hinges on the assumption that their photosynthetic discrimination against 13C remains constant in a wide range of environmental conditions. We tested this assumption by examining the effects of light and water stress on the carbon isotope composition of C4 grasses using different biochemical subtypes (NADP-ME, NAD-ME, PCK) in glasshouse experiments. We grew 14 different C4 grass species in four treatments: sun-watered, sun-drought, shade-watered and shade-drought. Carbon isotope discrimination (Δ) rarely remained constant. In general, Δ values were lowest in sun-watered grasses, greater for sun-drought plants and even higher for plants of the shade-watered treatment. The highest Δ values were generally found in the most stressed grasses, the shade-drought plants. Grasses of the NADP-ME subtype were the least influenced by a change in environmental variables, followed by PCK and NAD-ME subtypes. Water availability affected the carbon isotope discrimination less than light limitation in PCK and NAD-ME subtypes, but similarly in NADP-ME subtypes.In another experiment, we studied the effect of increasing light levels (150 to 1500 μmol photons m−2 s−1) on the Δ values of 18 well-watered C4 grass species. Carbon isotope discrimination remained constant until photon flux density (PFD) was less than 700 μmol photons m−2 s−1. Below this light level, Δ values increased with decreasing irradiance for all biochemical subtypes. The change in A was less pronounced in NADP-ME and PCK than in NAD-ME grasses. Grasses grown in the field and in the glasshouse showed a similar pattern. Thus, caution should be exercised when using C4 plants under varying environmental conditions to monitor the concentration or carbon isotopic composition of atmospheric CO2 in field/glasshouse studies or climate reconstruction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1996.tb00331.x
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  • 10
    Electronic Resource
    Electronic Resource
    Ecophysiology of two solar tracking desert winter annuals (1982)
    Springer
    Oecologia 54 (1982), S. 41-49 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The seasonal course of water relations in field populations of two leaf solar tracking desert winter annuals was examined. Measurements were made of leaf movements in relation to leaf conductance and water potential. Malvastrum rotundifolium maintained solar tracking movements up to the wilting point of the plant (-4 MPa). Lupinus arizonicus altered its morphology through paraheliotropic leaf movements as leaf water potentials declined to-1.8 MPa. Diurnal patterns of leaf conductance showed marked seasonal trends, with gas exchange activity being restricted to early morning hours as water availability declined. Studies of potted plants showed that L. arizonicus was not able to alter its osmotic potential in response to drought, while M. rotundifolium underwent a 1.86 MPa reduction in osmotic potential. The significance of the two contrasting patterns is discussed in terms of observed plant distribution and origin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00541105
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