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  • 1
    Electronic Resource
    Electronic Resource
    Temperature and humidity effects on branchlet gas-exchange in white spruce: an explanation for the increase in transpiration with branchlet temperature (1999)
    Springer
    Trees 14 (1999), S. 161-168 
    Details
    ISSN: 0931-1890
    Keywords: Key words Picea glauca ; Transpiration ; Stomatal conductance ; Photosynthesis ; Water viscosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  In situ gas-exchange data, for branchlets of white spruce [Picea glauca (Moench) Voss.] in a mature mixed-wood boreal forest in central Canada (53°44´N 105°14´W), were subjected to a multiple regression analysis. Vapor pressure deficit (VPD) and branchlet temperature (tleaf) were both significant predictors (P〈0.0001) of stomatal conductance to water vapor (gsw) and net photosynthesis (An), together explaining 67 and 64% of the variation in gsw and An, respectively. Since VPD and tleaf were autocorrelated in these field data, but also to further explore the nature of independent effects of temperature and humidity on water and CO2 exchange in white spruce, steady-state gas-exchange was performed on well-watered greenhouse-grown seedlings of white spruce. Results from laboratory experiments supported the following conclusions: (1) Transpiration (E) increases with VPD to an inflection point that increases linearly with tleaf. This tleaf effect on E could not be explained by trends in VPD, RH, An or PFD. Rather, our data support a model in which E and gsw are influenced by the balance between ’supply’ and ’loss’ of water to and from leaf tissue, respectively. The supply of water appears to be in accordance with Darcy’s law, where supply of water is proportional to the driving gradient in pressure/ tension, specific permeability (k), and inverse of water viscosity (n –1). Approximately half of the increase in E could be explained by the linear increase in n –1 with increasing tleaf. We propose that increases in k explain the remainder of the increase in E with tleaf. (2) VPD and tleaf appear to have independent effects on gsw. In contrast, RH effects on gsw or E were subtle and could be explained by a combination of effects of tleaf and VPD. (3) An was affected primarily by tleaf, being reduced at low (10°C) and high (40°C) temperatures, and only indirectly by humidity parameters via stomatal conductance, viz. intercellular CO2 concentrations. Our results have implications for the prediction of water fluxes from plants and canopies in areas where plant temperatures vary diurnally or seasonally.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004680050220
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  • 2
    Electronic Resource
    Electronic Resource
    Low-temperature photosynthetic performance of a C4 grass and a co-occurring C3 grass native to high latitudes (2004)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 27 (2004), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The photosynthetic performance of C4 plants is generally inferior to that of C3 species at low temperatures, but the reasons for this are unclear. The present study investigated the hypothesis that the capacity of Rubisco, which largely reflects Rubisco content, limits C4 photosynthesis at suboptimal temperatures. Photosynthetic gas exchange, chlorophyll a fluorescence, and the in vitro activity of Rubisco between 5 and 35 °C were measured to examine the nature of the low-temperature photosynthetic performance of the co-occurring high latitude grasses, Muhlenbergia glomerata (C4) and Calamogrostis canadensis (C3). Plants were grown under cool (14/10 °C) and warm (26/22 °C) temperature regimes to examine whether acclimation to cool temperature alters patterns of photosynthetic limitation. Low-temperature acclimation reduced photosynthetic rates in both species. The catalytic site concentration of Rubisco was approximately 5.0 and 20 µmol m−2 in M. glomerata and C. canadensis, respectively, regardless of growth temperature. In both species, in vivo electron transport rates below the thermal optimum exceeded what was necessary to support photosynthesis. In warm-grown C. canadensis, the photosynthesis rate below 15 °C was unaffected by a 90% reduction in O2 content, indicating photosynthetic capacity was limited by the capacity of Pi-regeneration. By contrast, the rate of photosynthesis in C. canadensis plants grown at the cooler temperatures was stimulated 20–30% by O2 reduction, indicating the Pi-regeneration limitation was removed during low-temperature acclimation. In M. glomerata, in vitro Rubisco activity and gross CO2 assimilation rate were equivalent below 25 °C, indicating that the capacity of the enzyme is a major rate limiting step during C4 photosynthesis at cool temperatures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2004.01196.x
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  • 3
    Electronic Resource
    Electronic Resource
    Photosynthetic pathway alters xylem structure and hydraulic function in herbaceous plants (2003)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 26 (2003), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Plants using the C4 photosynthetic pathway have greater water use efficiency (WUE) than C3 plants of similar ecological function. Consequently, for equivalent rates of photosynthesis in identical climates, C4 plants do not need to acquire and transport as much water as C3 species. Because the structure of xylem tissue reflects hydraulic demand by the leaf canopy, a reduction in water transport requirements due to C4 photosynthesis should affect the evolution of xylem characteristics in C4 plants. In a comparison of stem hydraulic conductivity and vascular anatomy between eight C3 and eight C4 herbaceous species, C4 plants had lower hydraulic conductivity per unit leaf area (KL) than C3 species of similar life form. When averages from all the species were pooled together, the mean KL for the C4 species was 1.60 × 10−4 kg m−1 s−1 MPa−1, which was only one-third of the mean KL of 4.65 × 10−4 kg m−1 s−1 MPa−1 determined for the C3 species. The differences in KL between C3 and C4 species corresponded to the two- to three-fold differences in WUE observed between C3 and C4 plants. In the C4 species from arid regions, the difference in KL was associated with a lower hydraulic conductivity per xylem area, smaller and shorter vessels, and less vulnerable xylem to cavitation, indicating the C4 species had evolved safer xylem than the C3 species. In the plants from resource-rich areas, such as the C4 weed Amaranthus retroflexus, hydraulic conductivity per xylem area and xylem anatomy were similar to that of the C3 species, but the C4 plants had greater leaf area per xylem area. The results indicate the WUE advantage of C4 photosynthesis allows for greater flexibility in hydraulic design and potential fitness. In resource-rich environments in which competition is high, an existing hydraulic design can support greater leaf area, allowing for higher carbon gain, growth and competitive potential. In arid regions, C4 plants evolved safer xylem, which can increase survival and performance during drought events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2478.2003.01119.x
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  • 4
    Electronic Resource
    Electronic Resource
    Interactions between atmospheric CO2 concentration and phosphorus nutrition on the formation of proteoid roots in white lupin (Lupinus albus L.) (2002)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 25 (2002), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Atmospheric [CO2] affects photosynthesis and therefore should affect the supply of carbon to roots. To evaluate interactions between carbon supply and nutrient acquisition, the [CO2] effects on root growth, proteoid root formation and phosphorus (P) uptake capacity were studied in white lupin (Lupinus albus L.) grown hydroponically at 200, 410 and 750 µmol mol−1 CO2, under sufficient (0·25 mm P) and deficient (0·69 µm P) phosphorus. Plant size increased with increasing [CO2] only at high P. Both P deficiency and increasing [CO2] increased the production of proteoid clusters; the increase in response to increased [CO2] was proportionally greater from low to ambient [CO2] than from ambient to high. The activity of phosphoenol pyruvate carboxylase in the proteoid root, the exudation of organic acids from the roots, and the specific uptake of P increased with P deficiency, but were unaffected by [CO2]. Increasing [CO2] from Pleistocene levels to those predicted for the next century increased plant size and allocation to proteoid roots, but did not change the specific P uptake capacity per unit root mass. Hence, rising [CO2] should promote nutrient uptake by allowing lupins to mine greater volumes of soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2002.00883.x
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  • 5
    Electronic Resource
    Electronic Resource
    Photosynthetic performance at low temperature of Bouteloua gracilis Lag., a high-altitude C4 grass from the Rocky Mountains, USA (2000)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 23 (2000), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The mechanisms controlling the photosynthetic performance of C4 plants at low temperature were investigated using ecotypes of Bouteloua gracilis Lag. from high (3000 m) and low (1500 m) elevation sites in the Rocky Mountains of Colorado. Plants were grown in controlled-environment cabinets at a photon flux density of 700 μmol m−2 s−1 and day/night temperatures of 26/16 °C or 14/7 °C. The thermal response of the net CO2 assimilation rate (A) was evaluated using leaf gas-exchange analysis and activity assays of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), phosphoenolpyruvate carboxylase (PEPCase) and pyruvate,orthophosphate dikinase (PPDK). In both ecotypes, a reduction in measurement temperature caused the CO2-saturated rate of photosynthesis to decline to a greater degree than the initial slope of A versus the intercellular CO2 response, thereby reducing the photosynthetic CO2 saturation point. As a consequence, A in normal air was CO2-saturated at sub-optimal temperatures. Ecotypic variation was low when grown at 26/16 °C, with the major difference between the ecotypes being that the low-elevation plants had higher A; however, the ecotypes responded differently when grown at cool temperature. At temperatures below the thermal optimum, A in high-elevation plants grown at 14/7 °C was enhanced relative to plants grown at 26/16 °C, while A in low-elevation plants grown at 14/7 °C was reduced compared to 26/16 °C-grown plants. Photoinhibition at low growth temperature was minor in both ecotypes as indicated by small reductions in dark-adapted Fv/Fm. In both ecotypes, the activity of Rubisco was equivalent to A below 17 °C but well in excess of A above 25 °C. Activities of PEPCase and PPDK responded to temperature in a similar proportion relative to Rubisco, and showed no evidence for dissociation that would cause them to become principal limitations at low temperature. Because of the similar temperature response of Rubisco and A, we propose that Rubisco is a major limitation on C4 photosynthesis in B. gracilis below 17 °C. Based on these results and for theoretical reasons associated with how C4 plants use Rubisco, we further suggest that Rubisco capacity may be a widespread limitation upon C4 photosynthesis at low temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.2000.00599.x
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamic photo-inhibition and carbon gain in a C4 and a C3 grass native to high latitudes (2004)
    Oxford, UK : Blackwell Science Ltd
    Plant, cell & environment 27 (2004), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: C4 plants are rare in the cool climates characteristic of high latitudes and altitudes, perhaps because of an enhanced susceptibility to photo-inhibition at low temperatures relative to C3 species. In the present study we tested the hypothesis that low-temperature photo-inhibition is more detrimental to carbon gain in the C4 grass Muhlenbergia glomerata than the C3 species Calamogrostis Canadensis. These grasses occur together in boreal fens in northern Canada. Plants were grown under cool (14/10 °C day/night) and warm (26/22 °C) temperatures before measurement of the light responses of photosynthesis and chlorophyll fluorescence at different temperatures. Cool growth temperatures led to reduced rates of photosynthesis in M. glomerata at all measurement temperatures, but had a smaller effect on the C3 species. In both species the amount of xanthophyll cycle pigments increased when plants were grown at 14/10 °C, and in M. glomerata the xanthophyll epoxidation state was greatly reduced. The detrimental effect of low growth temperature on photosynthesis in M. glomerata was almost completely reversed by a 24-h exposure to the warm-temperature regime. These data indicate that reversible dynamic photo-inhibition is a strategy by which C4 species may tolerate cool climates and overcome the Rubisco limitation that is prevalent at low temperatures in C4 plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.2004.01246.x
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  • 7
    Electronic Resource
    Electronic Resource
    Interactive effects of low atmospheric CO2 and elevated temperature on growth, photosynthesis and respiration in Phaseolus vulgaris (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 21 (1998), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: For most of the past 250 000 years, atmospheric CO2 has been 30–50% lower than the current level of 360 μmol CO2 mol–1 air. Although the effects of CO2 on plant performance are well recognized, the effects of low CO2 in combination with abiotic stress remain poorly understood. In this study, a growth chamber experiment using a two-by-two factorial design of CO2 (380 μmol mol–1, 200 μmol mol–1) and temperature (25/20 °C day/night, 36/29 °C) was conducted to evaluate the interactive effects of CO2 and temperature variation on growth, tissue chemistry and leaf gas exchange of Phaseolus vulgaris. Relative to plants grown at 380 μmol mol–1 and 25/20 °C, whole plant biomass was 36% less at 380 μmol mol–1× 36/29 °C, and 37% less at 200 μmol mol–1× 25/20 °C. Most significantly, growth at 200 μmol mol–1× 36/29 °C resulted in 77% less biomass relative to plants grown at 380 μmol mol–1× 25/20 °C. The net CO2 assimilation rate of leaves grown in 200 μmol mol–1× 25/20 °C was 40% lower than in leaves from 380 μmol mol–1× 25/20 °C, but similar to leaves in 200 μmol mol–1× 36/29 °C. The leaves produced in low CO2 and high temperature respired at a rate that was double that of leaves from the 380μmol mol–1× 25/20 °C treatment. Despite this, there was little evidence that leaves at low CO2 and high temperature were carbohydrate deficient, because soluble sugars, starch and total non-structural carbohydrates of leaves from the 200μmol mol–1× 36/29 °C treatment were not significantly different in leaves from the 380μmol mol–1× 25/20 °C treatment. Similarly, there was no significant difference in percentage root carbon, leaf chlorophyll and leaf/root nitrogen between the low CO2× high temperature treatment and ambient CO2 controls. Decreased plant growth was correlated with neither leaf gas exchange nor tissue chemistry. Rather, leaf and root growth were the most affected responses, declining in equivalent proportions as total biomass production. Because of this close association, the mechanisms controlling leaf and root growth appear to have the greatest control over the response to heat stress and CO2 reduction in P. vulgaris.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3040.1998.00290.x
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature effects on the photosynthetic response of C3 plants to long-term CO2 enrichment (1995)
    Springer
    Plant ecology 121 (1995), S. 67-77 
    Details
    ISSN: 1573-5052
    Keywords: Acclimation ; CO2 enrichment ; Gas exchange ; Photosynthesis ; Temperature responses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To assess the long-term effect of increased CO2 and temperature on plants possessing the C3 photosynthetic pathway, Chenopodium album plants were grown at one of three treatment conditions: (1) 23 °C mean day temperature and a mean ambient partial pressure of CO2 equal to 350 μbar; (2) 34 °C and 350 μbar CO2; and (3) 34 °C and 750 μbar CO2. No effect of the growth treatments was observed on the CO2 reponse of photosynthesis, the temperature response of photosynthesis, the content of Ribulose-1,5-bisphosphate carboxylase (Rubisco), or the activity of whole chain electron transport when measurements were made under identical conditions. This indicated a lack of photosynthetic acclimation in C. album to the range of temperature and CO2 used in the growth treatments. Plants from every treatment exhibited similar interactions between temperature and CO2 on photosynthetic activity. At low CO2 (〈 300 μbar), an increase in temperature from 25 to 35 °C was inhibitory for photosynthesis, while at elevated CO2 (〉 400 μbar), the same increase in temperature enhanced photosynthesis by up to 40%. In turn, the stimulation of photosynthesis by CO2 enrichment increased as temperature increased. Rubisco capacity was the primary limitation on photosynthetic activity at low CO2 (195 μbar). As a consequence, the temperature response of A was relatively flat, reflecting a low temperature response of Rubisco at CO2 levels below its km for CO2. At elevated CO2 (750 μbar), the temperature response of electron transport appeared to control the temperature dependency of photosynthesis above 18 °C. These results indicate that increasing CO2 and temperature could substantially enhance the carbon gain potential in tropical and subtropical habitats, unless feedbacks at the whole plant or ecosystem level limit the long-term response of photosynthesis to an increase in CO2 and temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00044673
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