Modifications in Photosynthetic Pigments and Chlorophyll Fluorescence in 20-Year-Old Pine Trees after a Four-Year Exposure to Carbon Dioxide and Temperature Elevation (original) (raw)
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Global Change Biology, 1996
Trees growing in natural systems undergo seasonal changes in environmental factors that generate seasonal differences in net photosynthetic rates. To examine how seasonal changes in the environment affect the response of net photosynthetic rates to elevated CO2/ we grew Pinus taeda L. seedlings for three growing seasons in open-top chambers continuously maintained at either ambient or ambient + 30 Pa CO2. Seedlings were grown in the ground, under natural conditions of light, temperature and nutrient and water availability. Photosynthetic capacity was measured bimonthly using net photosynthetic rate vs. intercellular CO2 partial pressure (A-C,) curves. Maximum Rubisco activity (Vc^ax) a"*^ ribulose 1,5-bisphosphate regeneration capacity mediated by electron transport (/max) a"^ phosphate regeneration (PiRC) were calculated from A-C; curves using a biochemically based model. Rubisco activity, activation state and content, and leaf carbohydrate, chlorophyll and nitrogen concentrations were measured concurrently with photosynthesis measurements. This paper presents results from the second and third years of treatment.
Tree Physiology, 1996
Effects of needle water potential (Ψ l) on gas exchange of Scots pine (Pinus sylvestris L.) grown for 4 years in open-top chambers with elevated temperature (ET), elevated CO 2 (EC) or a combination of elevated temperature and CO 2 (EC + ET) were examined at a high photon flux density (PPFD), saturated leaf to air water vapor pressure deficit (VPD) and optimal temperature (T). We used the Farquhar model of photosynthesis to estimate the separate effects of Ψ l and the treatments on maximum carboxylation efficiency (V c,max), ribulose-1,5-bisphosphate regeneration capacity (J), rate of respiration in the light (R d), intercellular partial pressure of CO 2 (C i) and stomatal conductance (G s). Depression of CO 2 assimilation rate at low Ψ l was the result of both stomatal and non-stomatal limitations on photosynthetic processes; however, stomatal limitations dominated during short-term water stress (Ψ l < −1.2 MPa), whereas nonstomatal limitations dominated during severe water stress. Among the nonstomatal components, the decrease in J contributed more to the decline in photosynthesis than the decrease in V c,max. Long-term elevation of CO 2 and temperature led to differences in the maximum values of the parameters, the threshold values of Ψ l and the sensitivity of the parameters to decreasing Ψ l. The CO 2 treatment decreased the maximum values of V c,max , J and R d but significantly increased the sensitivity of V c,max , J and R d to decreasing Ψ l (P < 0.05). The effects of the ET and EC + ET treatments on V c,max , J and R d were opposite to the effects of the EC treatment on these parameters. The values of G s , which were measured simultaneously with maximum net rate of assimilation (A max), declined in a curvilinear fashion as Ψ l decreased. Both the EC + ET and ET treatments significantly decreased the sensitivity of G s to decreasing Ψ l. We conclude that, in the future, acclimation to increased atmospheric CO 2 and temperature could increase the tolerance of Scots pine to water stress.
Tellus B, 2007
In earlier studies the seasonal dynamics of photosynthetic capacity in northern conifers has been explained as a slow response to the ambient temperature. We tested this concept with Scots pine (Pinus sylvestris L.). We analysed the seasonal dynamics of photosynthetic efficiency in Scots pine at the timberline in Finnish Lapland, and in a southern boreal forest in Southern Finland. The relationship between the daily photosynthetic efficiency and leaf temperature history was determined from continuous measurements of shoot CO 2 exchange. The shoot CO 2 exchange and photosynthetic efficiency showed similar seasonal patterns in the northern and in the southern locations, following daily mean temperature with a delay. The relationship between the temperature history and photosynthetic efficiency appeared to be near sigmoidal both in the northern and in the southern trees. The relationship was also consistent from year-to-year, thus the seasonal course of photosynthetic efficiency can be predicted accurately from the ambient temperature using a sigmoidal relationship. A rapid decrease of photosynthetic efficiency was observed when daytime temperature dropped below zero or frost had occurred in the previous night. The difference in the rate of acclimation of photosynthetic efficiency between the north and the south was small.
Frontiers in plant science, 2014
Understanding the seasonality of photosynthesis in boreal evergreen trees and its control by the environment requires separation of the instantaneous and slow responses, as well as the dynamics of light reactions, carbon reactions, and respiration. We determined the seasonality of photosynthetic light response and respiration parameters of Scots pine (Pinus sylvestris L.) in the field in southern Finland and in controlled laboratory conditions. CO2 exchange and chlorophyll fluorescence were measured in the field using a continuously operated automated chamber setup and fluorescence monitoring systems. We also carried out monthly measurements of photosynthetic light, CO2 and temperature responses in standard conditions with a portable IRGA and fluorometer instrument. The field and response measurements indicated strong seasonal variability in the state of the photosynthetic machinery with a deep downregulation during winter. Despite the downregulation, the photosynthetic machinery re...
Impacts of seasonal air and soil temperatures on photosynthesis in Scots pine trees
Tree Physiology, 2002
Seasonal courses of light-saturated rate of net photosynthesis (A 360 ) and stomatal conductance (g s ) were examined in detached 1-year-old needles of Scots pine (Pinus sylvestris L.) from early April to mid-November. To evaluate the effects of soil frost and low soil temperatures on gas exchange, the extent and duration of soil frost, as well as the onset of soil warming, were manipulated in the field. During spring, early summer and autumn, the patterns of A 360 and g s in needles from the control and warm-soil plots were generally strongly related to daily mean air temperatures and the frequency of severe frosts. The warm-soil treatment had little effect on gas exchange, although mean soil temperature in the warm-soil plot was 3.8°C higher than in the control plot during spring and summer, indicating that A 360 and g s in needles from control trees were not limited by low soil temperature alone. In contrast, prolonged exposure to soil temperatures slightly above 0°C severely restricted recovery of A 360 and especially g s in needles from the cold-soil treatment during spring and early summer; however, full recovery of both A 360 and g s occurred in late summer. We conclude that inhibition of A 360 by low soil temperatures is related to both stomatal closure and effects on the biochemistry of photosynthesis, the relative importance of which appeared to vary during spring and early summer. During the autumn, soil temperatures as low as 8°C did not affect either A 360 or g s .
Tree Physiology, 1996
To detect seasonal and long-term differences in growth and photosynthesis of loblolly pine (Pinus taeda L.) exposed to elevated CO 2 under ambient conditions of precipitation, light, temperature and nutrient availability, seedlings were planted in soil representative of an early, abandoned agricultural field and maintained for 19 months in the field either in open-top chambers providing one of three atmospheric CO 2 partial pressures (ambient, ambient +15 Pa, and ambient +30 Pa) or in unchambered control plots. An early and positive response to elevated CO 2 substantially increased total plant biomass. Peak differences in relative biomass enhancement occurred after 11 months of CO 2 treatment when biomass of plants grown at +15 and +30 Pa CO 2 was 111 and 233% greater, respectively, than that of plants grown at ambient CO 2 . After 19 months, there was no significant difference in biomass between +15 Pa CO 2 -treated plants and ambient CO 2 -treated plants, whereas biomass of +30 Pa CO 2 -treated plants was 111% greater than that of ambient CO 2 -treated plants. Enhanced rates of leaf-level photosynthesis were maintained in plants in the elevated CO 2 treatments throughout the 19-month exposure period despite reductions in both leaf N concentration and ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity during the first 11 months of CO 2 exposure. Reductions in Rubisco activity indicated photosynthetic adjustment to elevated CO 2 , but Rubisco-mediated control of photosynthesis was small. Seasonal shifts in sink strength affected photosynthetic rates, greatly magnifying the positive effects of elevated CO 2 on photosynthesis during periods of rapid plant growth. Greater carbon assimilation by the whole plant accelerated plant development and thereby stimulated new sinks for carbon through increased plant biomass, secondary branching and new leaf production. We conclude that elevated CO 2 will enhance photosynthesis and biomass accumulation in loblolly pine seedlings under high nutrient conditions; however, reductions over time in the relative biomass response of plants to elevated CO 2 complicate predictions of the eventual magnitude of carbon storage in this species under future CO 2 conditions.
Global Change Biology, 2012
Leaf responses to elevated atmospheric CO 2 concentration (C a ) are central to models of forest CO 2 exchange with the atmosphere and constrain the magnitude of the future carbon sink. Estimating the magnitude of primary productivity enhancement of forests in elevated C a requires an understanding of how photosynthesis is regulated by diffusional and biochemical components and up-scaled to entire canopies. To test the sensitivity of leaf photosynthesis and stomatal conductance to elevated C a in time and space, we compiled a comprehensive dataset measured over 10 years for a temperate pine forest of Pinus taeda, but also including deciduous species, primarily Liquidambar styraciflua. We combined over one thousand controlled-response curves of photosynthesis as a function of environmental drivers (light, air C a and temperature) measured at canopy heights up to 20 m over 11 years (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006) to generate parameterizations for leaf-scale models for the Duke free-air CO 2 enrichment (FACE) experiment. The enhancement of leaf net photosynthesis (A net ) in P. taeda by elevated C a of +200 lmol mol À1 was 67% for current-year needles in the upper crown in summer conditions over 10 years. Photosynthetic enhancement of P. taeda at the leaf-scale increased by two-fold from the driest to wettest growing seasons. Current-year pine foliage A net was sensitive to temporal variation, whereas previous-year foliage A net was less responsive and overall showed less enhancement (+30%). Photosynthetic downregulation in overwintering upper canopy pine needles was small at average leaf N (N area ), but statistically significant. In contrast, co-dominant and subcanopy L. styraciflua trees showed A net enhancement of 62% and no A net -N area adjustments. Various understory deciduous tree species showed an average A net enhancement of 42%. Differences in photosynthetic responses between overwintering pine needles and subcanopy deciduous leaves suggest that increased C a has the potential to enhance the mixed-species composition of planted pine stands and, by extension, naturally regenerating pine-dominated stands.
Plant Science, 2012
Norway spruce (Picea abies L. Karst) grown under ambient (365-377 mol (CO 2 ) mol −1 ; AC) and elevated (700 mol (CO 2 ) mol −1 ; EC) CO 2 concentrations within glass domes with automatically adjustable windows and on an open-air control site were studied after 8 years of treatment. The effect of EC on photosynthesis, mesophyll structure and phenolics accumulation in sun and shade needles was examined. Photosynthetic assimilation and dark respiration rates were measured gasometrically; the structural parameters of mesophyll were determined using confocal microscopy and stereological methods. The contents of total soluble phenolics and lignin were assessed spectrophotometrically, and localizations of different phenolic groups were detected histochemically on needle cross-sections.
Planta, 1998
Photosynthetic CO 2 uptake, the photochemical eciency of photosystem II, the contents of chlorophyll and chlorophyll-binding proteins, and the degree of frost hardiness were determined in three-year-old Scots pine (Pinus sylvestris L.) trees growing in the open air but under controlled daylength. The following conditions were compared: 9-h light period (short day), 16-h light period (long day), and natural daylength. Irrespective of induction by short-day photoperiods or by subfreezing temperatures, frost hardening of the trees was accompanied by a long-lasting pronounced decrease in the photosynthetic rates of one-year-old needles. Under moderate winter conditions, trees adapted to a long-day photoperiod, assimilated CO 2 with higher rates than the short-day-treated trees. In the absence of strong frost, photochemical eciency was lower under shortday conditions than under a long-day photoperiod. Under the impact of strong frost, photochemical eciency was strongly inhibited in both sets of plants. The reduction in photosynthetic performance during winter was accompanied by a pronounced decrease in the content of chlorophyll and of several chlorophyll-binding proteins [light-harvesting complex (LHC)IIb, LHC Ib, and a chlorophyll-binding protein with MW 43 kDa (CP 43)]. This observed seasonal decrease in photosynthetic pigments and in pigment-binding proteins was irrespective of the degree of frost hardiness and was apparantly under the control of the length of the daily photoperiod. Under a constant 9-h daily photoperiod the chlorophyll content of the needles was considerably lower than under long-day conditions. Transfer of the trees from short-day to long-day conditions resulted in a signi®cantly increased chlorophyll content, whereas the chlorophyll content decreased when trees were transferred from a long-day to a short-day photoperiod. The observed changes in photosynthetic pigments and pig-ment-binding proteins in Scots pine needles are interpreted as a reduction in the number of photosynthetic units induced by shortening of the daily light period during autumn. This results in a reduction in the absorbing capacity during the frost-hardened state.