Photosynthetic Capacity and PSII Efficiency of the Evergreen Alpine Cushion Plant Saxifraga paniculata during Winter at Different Altitudes (original) (raw)
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Functional Ecology, 2000
Microclimate was measured and photosynthetic responses to a climate warming manipulation were compared for the evergreen shrub Artemisia tridentata and the herbaceous forb Erigeron speciosus in the Rocky Mountains, Colorado, USA. 2. Soil was warmer and drier under infra-red heaters compared with control plots. 3. Midday xylem pressure potential did not differ for A. tridentata on heated vs control plots but was lower for E. speciosus on heated plots compared with controls. Leaf temperatures did not vary for the two species on heated or control plots. 4. There were no significant treatment or species differences in the diurnal patterns of CO 2 assimilation or stomatal conductance to water vapour. Also, there were no differences in responses to leaf temperature. 5. The quantum yield for CO 2 assimilation over a range of PPFD was lower for plants on heated plots. There was a marked difference between species in the pattern of stomatal conductance to water vapour over a range of PPFD, but no differences as a result of the heating treatment. 6. The quantum efficiency of PSII electron transport was significantly affected by heating. Non-radiative energy dissipation was greater for A. tridentata compared with E. speciosus . There was recovery of F V / F M for A. tridentata but not for E. speciosus . 7. Heating appears to affect plants via changes in soil water content rather than by increasing leaf temperature. The deciduous species E. speciosus appears to undergo some permanent closure of PSII on heated plots, in contrast to the evergreen shrub A. tridentata . Such differences may help explain the increase in above-ground biomass accumulation in response to heating for shrubs, compared with the decrease observed for deciduous herbaceous species.
Differences in Microsite, Plant Form, and Low-Temperature Photoinhibition in Alpine Plants
Arctic, Antarctic, and Alpine Research, 2000
Low temperatures and high sunlight, factors that are characteristic of high elevations, may lead to the low-temperature photoinhibition of photosynthesis (LTP). Exposure and photosynthetic responses to low temperature and high sunlight were compared among current-year seedlings of the conifers Abies lasiocarpa and Picea engelmannii, and the snowbank perennials Caltha leptosepala and Erythronium grandiflorum, in the alpine treeline ecotone. The ratio of silhouette (sunlit) to total leaf area of whole plants was greatest in A. lasiocarpa (0.33), 25% lower in P. engelmannii (0.25), and at least 36% lower in the snowbank perennials than for A. lasiocarpa. This indicated less structural avoidance of high sunlight in the conifer seedlings, particularly A. lasiocarpa. CO 2 assimilation (A,at) in A. lasiocarpa was reduced 40% due to frosts, high sunlight (22%), and their combination (90%). A sa ' was much less affected by frosts and high sunlight in P. engelmannii and especially the perennials. Following frost and high sunlight exposure, diurnal reductions in maximum photosynthetic efficiency, indicated by the chlorophyll fluorescence ratio FJFmcorresponded to species differences in A,a,' A substantially greater degree of slowly-reversible, or irreversible LTP (44% reduction in predawn FJF m) occurred in the microclimate above snow for A. lasiocarpa compared to the other species. It appears that a higher resistance to LTP in the perennials may contribute to their greater occurrence in microsites with lower temperatures and higher sunlight compared to the conifer seedlings.
The role of photoperiodism in alpine plant development
Arctic, Antarctic, and Alpine Research, 2003
BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.
Adaptation of the Long-Lived Monocarpic Perennial, Saxifraga longifolia to High Altitude
Plant physiology, 2016
Global change is exerting a major effect on plant communities altering their potential capacity for adaptation. Here, we aimed at unveiling mechanisms of adaptation to high altitude in an endemic long-lived monocarpic, Saxifraga longifolia, by combining demographic and physiological approaches. Plants from three altitudes (570, 1100 and 2100 m a.s.l.) were investigated in terms of leaf water and pigment contents, and activation of stress defense mechanisms. The influence of plant size on physiological performance and mortality was also investigated. Levels of photoprotective molecules α-tocopherol, carotenoids and anthocyanins) increased in response to high altitude (1100 relative to 570 m a.s.l.), which was paralleled by reduced soil and leaf water contents and increased ABA levels. The more demanding effect of high altitude on photoprotection was however partly abolished at very high altitudes (2100 m a.s.l.) due to improved soil water contents, with the exception of α-tocopherol ...
Response of Saxifraga oppositifolia L. to simulated climate change at three contrasting latitudes
Global Change Biology, 1997
Saxifraga oppositifolia, a widespread circum-arctic and alpine plant species, was exposed to increased temperature at three ITEX sites of different latitudes: Val Bercla in the Swiss Alps (46°N), Latnjajaure in mid-alpine Northern Sweden (68°N), and Alexandra Fjord, Ellesmere Island (79°N) in the Canadian High Arctic. Phenology, growth, and reproduction were monitored for 2 or 3 consecutive years. Increased temperature had little influence on the phenology of S. oppositifolia, although flowering period was somewhat longer and pollination earlier in the experimental plots. A decrease in the density of flowers on each plant was noted at two sites over 3 years, with a slightly larger decrease in the warmed plots. The few changes observed in reproductive variables (e.g. fruit : flower ratio) are mostly assigned to increased shading by taller growing neighbouring plants of other species, thus limiting performance of the shade-intolerant S. oppositifolia. It is assumed that survival of this species, especially at the lower limits of its altitudinal and latitudinal distribution, will depend on seed dispersal to new, open habitats.
Photosynthesis and photoinhibition in a tropical alpine giant rosette plant,Lobelia rhynchopetalum
New Phytologist, 1997
Dedicated to Prof. Dr Benno Parthier, Institute of Plant Biochemistry, Halle, on the occasion of his 65th birthday SDMMARY Carbodioxide uptake, oxygen evolution and chlorophyll fluorescence of leaves of Lobelia rhynchopetalum Hemsl., a giant rosette plant of the tropical alpine regions of Ethiopia, were studied under field conditions at 4000 m above sea level. Our objective was to investigate the photosynthetic adaptation to the combination of wide fluctuation in diurnal temperature, high photon flux densities (PFD) and low CO^ partial pressure encountered in these regions. At an ambient CO^ partial pressure of c 17 Pa, maxinial rates of CO^ uptake were low, ranging between 4 and 6 //.mol m"^ s"'. Such rates, however, required high PFDs and were obser\'ed only at levels of 1500 /fmol photons m"^ s"^. Carbon dioxide uptake was significantly inhibited when PFD was > 2000 fimoX photons m"' s"'. On the other hand, at saturating CO^ levels, maximal photosyntbetic oxygen evolution was higher (30 //mol O^ m"^ s"'), saturating at the same PFD as CO^ uptake. Quantum efficiency of CO.^ uptake (0-006 mol CO^ mol photons"', at high altitude and a low CO^ partial pressure of 17 Pa) and even of oxygen evolution under CO.^-saturating conditions in the leaf O^ electrode (0-05 mol O^ mol photons"^) indicated reduced photosynthetic efficiency. Electron transport rate (FTR) was strongly correlated with the leaf temperature. Non-photochemical quenching (NPQ) responded inversely to leaf temperature and stomatal conductance. The results indicated that in the morning, when the sun irradiates the partly frozen leaves with closed stomata, NPQ is the principal mechanism by which Lobelia leaves protect their photosynthetic apparatus. However, during tbe day, the predominant upright inclination of tbe leaves significantly contributes to protecting the leaves from excess light absorption. A comparison of the chlorophyll fluorescence of young and old leaves revealed that the former had high ETR and quantum efficiency of photos> ntbetic electron transport but a lower capacity for NPQ. Extremely high NPQ values but low ETR and low quantum efficiency w^ere recorded for the old lea\es. Thus, in the course of maturation the leaves apparently lose photosynthetic efficiency but increase their capability for protective non-photochemical quenching.
Arctic, Antarctic, and Alpine Research, 2003
We investigated carbon isotope discrimination of two morphs of Saxifraga oppositifolia and other plant species in a glacier foreland in the High Arctic at Ny-Å lesund, Svalbard, Norway. At this site, soil conditions vary considerably along with the progress of primary succession within a small area. We compared growth forms and d 13 C values, which reflect long-term leaf gas exchange characteristics, of plants growing in different successional stages with different soil conditions. Even though the soil mass water content (water mass/ dry mass) increased from 10% to 140% with the progress of succession, the water and nitrogen content of the soil had negligible effects on the d 13 C values of the observed species. The d 13 C values were determined mainly by species and growth forms. We compared two morphs of S. oppositifolia, the prostrate form (P-form) and the cushion form (C-form), on the same riverbank in the glacier foreland. Regardless of the successional stage, the d 13 C values of the C-form were about 2& more negative than those of the Pform. The ground cover area per plant mass (GA) of the C-form was less than 30% that of the P-form, and the product of GA and stomatal conductance appears to be an important factor in the relationship between transpiration and photosynthesis of a whole plant. We suggest that the relationship between GA and the root mass fraction is a crucial factor affecting the water utilization in high arctic environments. We also examined the relationship between life form and water utilization for other phototrophs, including lichens, mosses, narrow-leaved grasses, perennials, and shrubs.