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  • 1
    Electronic Resource
    Electronic Resource
    Contrasting patterns of photosynthetic acclimation and photoinhibition in two evergreen herbs from a winter deciduous forest (1996)
    Springer
    Oecologia 107 (1996), S. 446-455 
    Details
    ISSN: 1432-1939
    Keywords: Forest understory ; Photosynthetic acclimation ; Photoinhibition ; Leaf longevity ; Nitrogen allocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between the microclimate within an Oak-Hickory forest and photosynthetic characters of two resident evergreen herbs with contrasting leaf phenologies was investigated on a monthly basis for 1 full year. Heuchera americana has leaf flushes in the spring and fall, with average leaf life spans of 6–7 months. Hexastylis arifolia produces a single cohort of leaves each spring with a leaf life span of 12–13 months. We predicted that among evergreen plants inhabiting a seasonal habitat, a species for which the frequency of leaf turnover is greater than the frequency of seasonal extremes would have a greater annual range in photosynthetic capacity than a species that only produced a single flush of leaves during the year. Photosynthetic parameters, including apparent quantum yield, maximum photosynthetic capacity (Pmax), temperature of maximum photosynthesis, photochemical efficiency of PSII and leaf nitrogen (N) and chlorophyll concentrations, were periodically measured under laboratory conditions in leaves sampled from natural populations of both species. Mature leaves of both species acclimated to changing understory conditions with the mean seasonal differences being significantly greater for Heuchera than for Hexastylis. Area based maximum photosynthetic rates at 25°C were approximately 250% and 100% greater in winter leaves than summer leaves for Heuchera and Hexastylis respectively. Nitrogen concentrations were highest in winter leaves. Chlorophyll concentrations were highest in summer leaves. Low Pmax/N values for these species suggest preferential allocation of leaf nitrogen into non-photosynthetic pools and/or light-harvesting function at the expense of photosynthetic enzymes and electron transport components. Despite the increase in photosynthetic capacity, there was evidence of chronic winter photoinhibition in Hexastylis, but not in Heuchera. Among these ecologically similar species, there appears to be a trade-off between the frequency of leaf production and the balance of photosynthetic acclimation and photoinhibition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00333934
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  • 2
    Electronic Resource
    Electronic Resource
    Photosynthetic responses of Miconia species to canopy openings in a lowland tropical rainforest (1993)
    Springer
    Oecologia 94 (1993), S. 49-56 
    Details
    ISSN: 1432-1939
    Keywords: Miconia ; Tropics ; Rainforest ; Photosynthetic acclimation ; Canopy gaps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We examined the photosynthetic acclimation of three tropical species of Miconia to canopy openings in a Costa Rican rainforest. The response of photosynthesis to canopy opening was very similar in Miconia affinis, M. gracilis, and M. nervosa, despite differences in growth form (trees and shrubs) and local distributions of plants (understory and gap). Four months after the canopy was opened by a treefall, photosynthetic capacity in all three species had approximately doubled from closed canopy levels. There were no obvious signs of high light damage after treefall but acclimation to the gap environment was not immediate. Two weeks after treefall, Amax, stomatal conductance, apprarent quantum efficiency, and dark respiration rates had not changed significantly from understory values. The production of new leaves appears to be an important component of light acclimation in these species. The only variables to differ significantly among species were stomatal conductance at Amax and the light level at which assimilation was saturated. M. affinis had a higher stomatal conductance which may reduce its water use efficiency in gap environments. Photosynthesis in the more shade-tolerant M. gracilis saturated at lower light levels than in the other two species. Individual plant light environments were assessed after treefall with canopy photography but they explained only a small fraction of plant variation in most measures of photosynthesis and growth. In conclusion, we speculate that species differences in local distribution and in light requirements for reproduction may be more strongly related to species differences in carbon allocation than in carbon assimilation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317300
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  • 3
    Electronic Resource
    Electronic Resource
    Response to long- and short-term salinity in populations of the C4 nonhalophyte Andropogon glomeratus Walter B.S.P. (1988)
    Springer
    Oecologia 75 (1988), S. 73-77 
    Details
    ISSN: 1432-1939
    Keywords: Ahdropogon glomeratus ; Genetic differentiation ; Growth response ; Salinity ; Stress tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This research was undertaken to investigate differences in salt tolerance under conditions in which salinity is increased gradually and maintained for long periods or increased rapidly and maintained for shorter periods. The responses of populations of a C4 nonhalophytic grass, Andropogon glomeratus, to long- and short-term salinity were measured under controlled environment conditions. Additionally, plants from a salt marsh population and an inland population were transplanted into a salt marsh and their survival compared. The relative growth reductions in the salt marsh and the inland populations under long-term salinity were similar. Survival of seedlings of 4 populations inundated with full-strength seawater over a relatively short period indicated differential capacities to tolerate soil salinities imposed in a manner similar to tidal inundation in a salt marsh. The greater survival of plants from the marsh population transplanted into the salt marsh further indicated genetic differentiation between the populations. These results indicate that genetic differentiation to salt tolerance in A. glomeratus is better reflected by survival after shortterm salinity events, rather than growth inhibition due to long-term salinity imposed gradually.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378816
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Physiological responses in two populations of Andropogon glomeratus Walter B.S.P. to short-term salinity (1988)
    Springer
    Oecologia 75 (1988), S. 78-82 
    Details
    ISSN: 1432-1939
    Keywords: Andropogon glomeratus ; A-Ci curves ; Osmotic adjustment ; Photosynthesis ; Salinity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Andropogon glomeratus is a C4 nonhalophytic grass which exhibits population differentiation for tolerance to short-term salinity exposure. To investigate possible physiological mechanisms whch enable salt-tolerant individuals to survive short-term inundation, gas exchange and water relations parameters were measured before and during a 5-day watering treatment of half-strength synthetic seawater in plants from a tolerant and a non-tolerant population. Photosynthetic recovery was followed for 10 days after the salinity treatment. Photosynthetic CO2 uptake was substantially inhibited in both populations. Stomatal conductances decreased and intercellular CO2 concentrations increased, indicating non-stomatal factors were primarily responsible for the decrease in CO2 uptake. After termination of the salinity treatment photosynthetic capacity increased more rapidly in the tolerant population and reached the pretreatment level after 6 days, whereas the nontolerant population did not recover fully after 10 days. A-Ci curves measured before and after the salinity treatment indicated a decrease in the carboxylation efficiency, and suggested a proportionately greater metabolic inhibition relative to the increase in the stomatal limitation. Osmotic adjustment occurred in a 2-day period in the tolerant population, but there was no change in the osmotic potentials or the water potential at the point of turgor loss in the nontolerant population. Thus short-term salt tolerance in the marsh population is associated with rapid osmotic adjustment and recovcry of photosynthetic capacity shortly after the end of the salinity exposure, rather than maintenance of greater photosynthesis during the salinity treatment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00378817
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    Paper (German National Licenses)
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