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• Information on the genetic variation of plant response to elevated CO2 (e[CO2]) is needed to understand plant adaptation and to pinpoint likely evolutionary response to future high atmospheric CO2 concentrations. • Here, quantitative trait loci (QTL) for above- and below-ground tree growth were determined in a pedigree – an F2 hybrid of poplar ( Populus trichocarpa and Populus deltoides), following season-long exposure to either current day ambient CO2 (a[CO2]) or e[CO2] at 600 µl l−1, and genotype by environment interactions investigated. • In the F2 generation, both above- and below-ground growth showed a significant increase in e[CO2]. Three areas of the genome on linkage groups I, IX and XII were identified as important in determining above-ground growth response to e[CO2], while an additional three areas of the genome on linkage groups IV, XVI and XIX appeared important in determining root growth response to e[CO2]. • These results quantify and identify genetic variation in response to e[CO2] and provide an insight into genomic response to the changing environment. [ABSTRACT FROM AUTHOR]

• The consequences of increasing atmospheric carbon dioxide for long-term adaptation of forest ecosystems remain uncertain, with virtually no studies undertaken at the genetic level. A global analysis using cDNA microarrays was conducted following 6 yr exposure ofPopulus ×  euramericana(clone I-214) to elevated[CO2] in a FACE (free-air CO2 enrichment) experiment.• Gene expression was sensitive to elevated[CO2] but the response depended on the developmental age of the leaves, and< 50 transcripts differed significantly between different CO2 environments. For young leaves most differentially expressed genes were upregulated in elevated[CO2], while in semimature leaves most were downregulated in elevated[CO2].• For transcripts related only to the small subunit of Rubisco, upregulation in LPI 3 and downregulation in LPI 6 leaves in elevated CO2 was confirmed byanova. Similar patterns of gene expression for young leaves were also confirmed independently across year 3 and year 6 microarray data, and using real-time RT–PCR.• This study provides the first clues to the long-term genetic expression changes that may occur during long-term plant response to elevated CO2.New Phytologist(2005)doi: 10.1111/j.1469-8137.2005.01450.x© New Phytologist(2005) [ABSTRACT FROM AUTHOR]

• The consequences of increasing atmospheric carbon dioxide for long-term adaptation of forest ecosystems remain uncertain, with virtually no studies undertaken at the genetic level. A global analysis using cDNA microarrays was conducted following 6 yr exposure ofPopulus ×  euramericana(clone I-214) to elevated[CO2] in a FACE (free-air CO2 enrichment) experiment.• Gene expression was sensitive to elevated[CO2] but the response depended on the developmental age of the leaves, and< 50 transcripts differed significantly between different CO2 environments. For young leaves most differentially expressed genes were upregulated in elevated[CO2], while in semimature leaves most were downregulated in elevated[CO2].• For transcripts related only to the small subunit of Rubisco, upregulation in LPI 3 and downregulation in LPI 6 leaves in elevated CO2 was confirmed byanova. Similar patterns of gene expression for young leaves were also confirmed independently across year 3 and year 6 microarray data, and using real-time RT–PCR.• This study provides the first clues to the long-term genetic expression changes that may occur during long-term plant response to elevated CO2.New Phytologist(2005)doi: 10.1111/j.1469-8137.2005.01450.x© New Phytologist(2005) [ABSTRACT FROM AUTHOR]

Investigates the effects of elevated carbon dioxide on leaf development in three genotypes of Populus. Decline in the nitrogen content of leaf; Measurement of leaf production and longevity; Impact of elevated carbon dioxide on plant epidermal cells.

Root growth and respiration in elevated CO2 (700 μmol mol-1) was studied in three tree species, Fraxinus excelsior L., Quercus petraea, L. and Pinus sylvestris L. grown in open-top chambers (OTCs) during a long-term exposure (20 months), during which root systems were allowed to develop without restriction imposed by pots. Root growth, measured as root length using root in-growth bags was increased significantly in trees exposed to elevated CO2, although the magnitude of the response differed considerably between species and with time of sampling, the greatest effect observed after 6 months in ash (ratio of elevated: ambient, e:a; 3.40) and the smallest effect observed in oak (e:a; 1.95). This was accompanied by changes in specific root length, with a significant decrease in all species after 6 months, suggesting that root diameter or root density were increased in elevated CO2. Increases in root length might have resulted from an acceleration in root cell expansion, since epidermal cell size was significantly increased in the zone of elongation in ash root tips (P < 0.05). Contrasting effects of elevated CO2 were observed for root carbohydrates, with significant increases in soluble sugars for all species (P < 0.05), but both increases and decreases in starch content were observed, depending on species, and producing a significant interaction between species and CO2 (P < 0.001). Exposure to elevated CO2 increased the total root d. wt for whole trees of all three species after 8 months of exposure, although the magnitude of this effect, in contrast to the root in-growth study, was greatest in Scots pine and smallest in ash. No significant effect of elevated CO2 was observed on the root: shoot ratio. Further detailed analysis of whole root systems after 20 months confirmed that species differences in root responses to elevated CO2 were apparent, with increased coarse and fine root production in elevated CO2 for Scots pine and ash respectively. Lateral root number was increased in elevated CO2 for all species, as was mean root diameter. Root respiration rates were significantly reduced in elevated CO2 for all three species. These results provide firm evidence that exposure of trees to future CO2 concentrations will have large effects on root system development growth, carbohydrate status and respiration. The magnitude and direction of such effects will differ, depending on species. The consequences of such responses for the three species studied are discussed. [ABSTRACT FROM AUTHOR]

This study investigated the effects of carbon dioxide (CO2) enrichment and soil water deficit on the water use efficiency (WUE) and growth of Sanguisorba minor Scop. (salad burnet) and Anthyllis vulneraria L. (kidney vetch), growing in controlled environments. Instantaneous WUE (IWUE) increased in both species in elevated CO2, with a higher average increase in unwatered (UW) A. vulneraria over the drying cycle. Total plant WUE of A. vulneraria increased in elevated CO2 and under water deficit: the UW plants in elevated CO2 had higher WUE and reduced water loss. By contrast, thee was only an effect of water supply on S. minor: total plant WUE increased and water loss decreased in the UW plants in both CO2 treatments. Total apparent root length (ARL) of both species increased with CO2 enrichment and in UW S. minor total ARL was increased. By contrast, for A. vulneraria, total ARL of UW plants increased in ambient CO2, but decreased in elevated CO2 as compared with well-watered (WW) plants. Shoot dry weight (SDW) and root dry weight increased in both species (WW and UW) with CO2 enrichment. For UW S. minor, SDW decreased relative to WW plants in both CO2 treatments. By contrast, ANOVA showed no significant effect of water supply on SDW oft vulneraria. Leaflet length increased in both species in elevated CO2 and decreased following drought. Cell wall tensiometric extensibility (%P) increased in expanding leaves of S. minor in elevated CO2 and for both species %P decreased in the UW plants as compared with those WW. Leaf water potential (Ψ) of both species was lower in growing leaves of WW plants in elevated CO2. Water deficit reduced the Ψ of growing leaves in both CO2 treatments. [ABSTRACT FROM AUTHOR]

Leaf extension was stimulated following exposure of three interamerican hybrid poplar clones (Populus trichocarpa × P. deltoides); 'Unal', 'Boelare', and 'Beaupre' and a euramerican clone 'Primo' (Populus nigra × P. deltoides) to elevated CO2 in controlled environment chambers. For all three interamerican clones the evidence suggests that this was the result of increased leaf cell expansion associated with enhanced cell wall extensibility (WEx), measured as tensiometric increases in cell wall plasticity. For the interamerican clone 'Boelare', there was also a significant increase in cell wall elasticity following exposure to elevated CO2 (P ≤ 0.001). The effect of elevated CO2 in stimulating cell wall extensibility was confirmed in a detailed spatial analysis of extensibility made across the lamina of expanding leaves of the clone 'Boelare. For two of the interamerican hybrids, 'Unal' and 'Beaupre', both leaf cell water potential (ψ) and turgor pressure (P) were lower in elevated than in ambient CO2. By contrast, no significant effects on the cell wall properties or leaf water relations for the euramerican hybrid 'Primo' were observed following exposure to elevated CO2, suggesting that the mechanism for increased leaf extension in elevated CO2 differed, depending on clone. The cumulative total length of leaves of 'Boelare' grown in elevated CO2 was significantly increased (P ≤ 0.05) and since leaf number was not significantly increased in any inter-american clone it is hypothesized that final leaf size was stimulated in elevated CO2 for these clones. By contrast, there was no significant effect of CO2 on cumulative total leaf length for the euramerican clone 'Primo', but leaf number was significantly increased by elevated CO2. [ABSTRACT FROM AUTHOR]

Diurnal measurements of leaf or leaflet extension, water relations and cell wall extensibility (&phis;) were made on young growing leaves of four chalk downland herbs (Sanguisorba minor Scop., Lotus corniculatus L., Anthyllis vulneraria L. and Plantago media L.) growing in controlled environment cabinets and exposed to either ambient or elevated CO2. This study revealed differences in the effect of CO2 and the control of leaf growth between the four species. Leaf extension rate (LER) increased significantly at night (average over 8 h) in elevated CO2 for S. minor, A. vulneraria and P. media with a significant increase over the first 4 h of darkness for S. minor, L. corniculatus and P. media, whilst for S. minor and P. media average day-time LER (over 16 h) also increased significantly in elevated CO2 as compared with ambient CO2. Water potential (Ψ), solute potential (Ψ), turgor pressure (P), yield turgor (Y) and the effective turgor for growth (Pe) were measured using psychrometers. Solute potentials of S. minor, A. vulneraria and P. media decreased significantly following exposure to elevated CO2 with a significant reduction in Ψ, during the day in A. vulneraria. Turgor pressure increased significantly in elevated CO2 as compared with ambient CO2 in A. vulneraria but there was no effect of elevated CO2 on P in the other species. No effects of CO2 on Ψ, Y or Pe were observed. Leaf cell wall extensibility (&phis;) increased significantly in leaves of S. minor, L. corniculatus and P. media exposed to elevated CO2, whereas in A. vulneraria, there was no effect of CO2 on extensibility. These results suggest that the mechanism by which elevated CO2 promotes leaf growth differs between species since in S. minor, L. corniculatus and P. media. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the impact of ambient (345 μl l-1)and elevated (590 μl l-1)CO2 on the root and shoot growth of four native chalk grassland herbs: Sanguisorba minor Scop. (salad burnet), Lotus corniculatus L. (birdsfoot trefoil), Anthyllis vuineraria L. (kidney vetch) and Plantago media L. (hoary plantain). Elevated CO2 had contrasting effects on both shoot and root growth of the four species studied. Both leaf expansion and production were stimulated by elevated CO2 for S. minor L. corniculatus and P. media, whilst for A. vulneraria, only leaflet shape appeared to be altered by elevated CO2, with the production of broader leaflets, compared with those produced in ambient CO2. After 100 d shoot biomass was enhanced in elevated CO2for S. minor and L. corniculatus, whilst there was no effect of elevated CO2 on shoot biomass for A. vulnerariaor P. media. Contrasting effects of CO2 were also apparent for measurements of specific leaf area (SLA), which increased for L. corniculatus, decreased for A. vulneraria and remained unaltered for S. minor and P. media in elevated compared with ambient CO2. Elevated CO2 also had contrasting effects on both the growth and morphology of roots. rite accumulation of root biomass was stimulated following exposure to elevated CO2 for S. minor and L. corniculatus whilst there was no effect on root biomass for A. vulneraria or P. media. Root length was measured on three occasions during the 100 d and revealed that exposure to elevated CO2 promoted root extension in S. minor, L. cornicvlatus and P. media, but not in A. vulneraria. Specific root length (SRL, length per unit dry weight) was increased in elevated CO2 for one species, P. media, whilst the root to shoot ratio of all four species remained unchanged by CO2. These results show that four native herbs differ in their response to CO2, suggesting that the structure of this plant community may be altered in the future. [ABSTRACT FROM AUTHOR]

Transplants of beech (Figus sylvatica L.) were grown in open-top chambers ventilated with either charcoal-filtered or unfiltered air. From May until September measurements of stomatal conductance to water vapour (g.) were made on trees in the chambers. On six out of seven occasions, leaves which had expanded during the first Hush (initial shoot extension, during May) in unfiltered air, had lower stomatal conductances, compared with those grown in filtered air; this was significant on three occasions (P < 0.05). Leaves which expanded later in the season (second flush or lammas growth) responded differently to the air quality treatments, with greater stomatal conductances recorded for trees exposed to unfiltered air. Measurements of leaf (psychrometry) and shoot (pressure bomb) water relations indicated that air quality had little effect on turgor pressure (P). Values of solute (φs) and water (φw) potential were higher for trees grown in unfiltered air. Trees were transported to the laboratory for measurement of photosynthesis (A), transpiration (E) and stomatal conductance (gs). Measurements of CO2 uptake were also made whilst the CO2 concentration within the leaf (Ci) was experimentally controlled (A/C, analysis). This revealed that higher rates of photosynthesis for lammas leaves grown in unfiltered air were due to enhanced regeneration of RuBP (increased Jmax P < 0.08). Carboxylation efficiency (dA/dCi) and percentage stomatal limitation were not significantly altered by air quality. Jmax and dA/dCi were similarly reduced following exposure to drought regardless of the air quality treatment. [ABSTRACT FROM AUTHOR]

The primary aim of the study was to quantify the effects of photosynthetically-active radiation (PAR) on extension of leaves of silver birch (Betula pendula Roth.) and sycamore (Acer pseudoplatanus L.). Plants grown at 250 μmol m-2 s1 were exposed to a range of fluence rates (0 680 μmol m-2 s-1) whilst enclosed in Perspex chambers in which temperature, vapour pressure deficit and photoenvironment were all controlled. Measurements of leaf extension, water relations, and cell wall extensibility (WEX) were made at the end of a 3 h exposure period. For leaves of birch, reducing the fluence rate resulted in reduced leaf extension and a lowering of WEX. Exposure of sycamore seedlings for 3 h to different values of PAR had little effect on the growth of leaves and WEX remained constant. The characteristics of net photosynthesis also differed for the two species and photosynthesis and wall loosening may be linked. Since natural woodland shadelight, in addition to reduced PAR, also has reduced R/FR ratio, a second group of seedlings were placed in a photoenvironment which simulated shadelight (low PAR, R/FR) for 28 d. This treatment reduced extension rate and final leaf size for both species. Measurements of extension, water relations and WEX made when seedlings were exposed to shadelight whilst held in the Perspex chambers revealed differences in the control of leaf growth for the two species. It is confirmed that leaves of birch are highly responsive to changes in PAR with cell wall loosening the most likely process controlling this response. [ABSTRACT FROM AUTHOR]

Leaf growth of first year seedlings of silver birch (Betula pendula Roth,) and sycamore (Acer pseudoplatanus L.) was measured continuously using linear variable transducers (LVTDs) when shoots were enclosed in small Perspex chambers, in which temperature, vapour pressure deficit (VPD) and photon fluence rate were all controlled. A new method was used to measure the yield turgor (Y) of growing leaves. The VPD of air in the chamber was altered so that transpiration rate was changed. Turgor pressures, measured using thermocouple psychrometers, and growth rates varied as a result of this treatment, and the relationship between leaf growth and turgor pressure (P) and the turgor pressure at which growth ceased (F) could he measured within a very short time period using well-watered plants. The value of Y was constant for illuminated and darkened leaves of both species, but Y was higher for sycamore leaves (Y = 0.250 MPa) compared with the value for birch leaves (Y = 0.071 MPa). Cell wall extensibility (m, MPa[sup-1]h[sup-1]) was calculated from the slope of the line relating turgor pressure to growth. For leaves of birch, there was a significant increase in pu when leaves were illuminated (m, dark = 1.3 x 10[sup-2] MPa[sup-1]h[sup-1]; m, light = 4.6 x 10[sup-2] MPa[sup-1]), similar in magnitude to the increase in wall extensibility measured previously by mechanical analysis of killed leaf tissue (WEX, the plasticity of tissue subjected to a uni-axial stress). No change in was detected when darkened sycamore leaves were illuminated (mn, dark = 4.2 x l0[sup-2] MPa[sup-1] h[sup-1]; m, light = 4.4 x 10[sup-2] MPa[sup-1] h[sup-1]). The results confirm earlier work on the factors controlling the diurnal patterns of leaf growth of these two species and suggest that leaf growth of birch is primarily limited by cell wall loosening hut that the growth of sycamore leaves may be limited by leaf turgor. [ABSTRACT FROM AUTHOR]

Leaf extension of one-year-old seedlings of silver birch (Betula pendula Roth.) and sycamore (Acer pseudoplatanus L.), was measured using linear variable transducers (LVDTs) interfaced to a microcomputer. Birch and sycamore seedlings exhibited contrasting patterns of leaf extension during a diurnal cycle with a 16 h photoperiod. Birch leaves grew more rapidly when illuminated; growth during the photoperiod was approximately doubled when compared with growth in the dark. Mean relative growth rates±SE at 'lights-on + 3 h' and 'lights-off+5 h' were 0.0136±0.0016 and 0.0066±0.0005 h-1 respectively. In direct contrast, growth of sycamore leaves was increased when leaves were darkened; mean relative growth rates ± SE at 'lightson± 3 h' and 'lights-off+ 5 h' were 0.0056±0.0005 and 0.0094±0.0008 h-1 respectively. When leaves of birch and sycamore were darkened, increased leaf turgor was measured in both species, but only in sycamore was this higher night-time turgor associated with a higher rate of leaf growth. Cell wall extensibility (WEX), ah indication of the ability of cell walls to loosen and extend irreversibly, and cell surface pH were assessed in darkened and illuminated leaves of both species. An increase in WEX was measured when birch leaves were illuminated (P<0.001) and this was accompanied by a decline in cell surface pH (P<0.001). However, when leaves of sycamore were illuminated, WEX declined (P < 0.05) and cell surface pH increased (P< 0.001). The ability of these species to survive beneath a woodland canopy is discussed in relation to the cellular factors controlling their leaf growth. [ABSTRACT FROM AUTHOR]

Leaf extension was stimulated following exposure of three interamerican hybrid poplar clones (Populus trichocarpa × P. deltoides); 'Unal', 'Boelare', and 'Beaupre' and a euramerican clone 'Primo' (Populus nigra × P. deltoides) to elevated CO2 in controlled environment chambers. For all three interamerican clones the evidence suggests that this was the result of increased leaf cell expansion associated with enhanced cell wall extensibility (WEx), measured as tensiometric increases in cell wall plasticity. For the interamerican clone 'Boelare', there was also a significant increase in cell wall elasticity following exposure to elevated CO2 (P ≤ 0.001). The effect of elevated CO2 in stimulating cell wall extensibility was confirmed in a detailed spatial analysis of extensibility made across the lamina of expanding leaves of the clone 'Boelare. For two of the interamerican hybrids, 'Unal' and 'Beaupre', both leaf cell water potential (ψ) and turgor pressure (P) were lower in elevated than in ambient CO2. By contrast, no significant effects on the cell wall properties or leaf water relations for the euramerican hybrid 'Primo' were observed following exposure to elevated CO2, suggesting that the mechanism for increased leaf extension in elevated CO2 differed, depending on clone. The cumulative total length of leaves of 'Boelare' grown in elevated CO2 was significantly increased (P ≤ 0.05) and since leaf number was not significantly increased in any inter-american clone it is hypothesized that final leaf size was stimulated in elevated CO2 for these clones. By contrast, there was no significant effect of CO2 on cumulative total leaf length for the euramerican clone 'Primo', but leaf number was significantly increased by elevated CO2. [ABSTRACT FROM AUTHOR]

* Information on the genetic variation of plant response to elevated CO(2) (e[CO(2)]) is needed to understand plant adaptation and to pinpoint likely evolutionary response to future high atmospheric CO(2) concentrations. * Here, quantitative trait loci (QTL) for above- and below-ground tree growth were determined in a pedigree - an F(2) hybrid of poplar (Populus trichocarpa and Populus deltoides), following season-long exposure to either current day ambient CO(2) (a[CO(2)]) or e[CO(2)] at 600 microl l(-1), and genotype by environment interactions investigated. * In the F(2) generation, both above- and below-ground growth showed a significant increase in e[CO(2)]. Three areas of the genome on linkage groups I, IX and XII were identified as important in determining above-ground growth response to e[CO(2)], while an additional three areas of the genome on linkage groups IV, XVI and XIX appeared important in determining root growth response to e[CO(2)]. * These results quantify and identify genetic variation in response to e[CO(2)] and provide an insight into genomic response to the changing environment.