Biomedical subjects

Penny J Tricker

Publications and source records attributed to Penny J Tricker.

3 recordsLinked to original sources

PubMed2005

Stomatal conductance and not stomatal density determines the long-term reduction in leaf transpiration of poplar in elevated CO2.

Using a free-air CO2 enrichment (FACE) experiment, poplar trees (Populus x euramericana clone I214) were exposed to either ambient or elevated [CO2] from planting, for a 5-year period during canopy development, closure, coppice and re-growth. In each year, measurements were taken of stomatal density (SD, number mm(-2)) and stomatal index (SI, the proportion of epidermal cells forming stomata). In year 5, measurements were also taken of leaf stomatal conductance (gs, micromol m(-2) s(-1)), photosynthetic CO2 fixation (A, mmol m(-2) s(-1)), instantaneous water-use efficiency (A/E) and the ratio of intercellular to atmospheric CO2 (Ci:Ca). Elevated [CO2] caused reductions in SI in the first year, and in SD in the first 2 years, when the canopy was largely open. In following years, when the canopy had closed, elevated [CO2] had no detectable effects on stomatal numbers or index. In contrast, even after 5 years of exposure to elevated [CO2], gs was reduced, A/E was stimulated, and Ci:Ca was reduced relative to ambient [CO2]. These outcomes from the long-term realistic field conditions of this forest FACE experiment suggest that stomatal numbers (SD and SI) had no role in determining the improved instantaneous leaf-level efficiency of water use under elevated [CO2]. We propose that altered cuticular development during canopy closure may partially explain the changing response of stomata to elevated [CO2], although the mechanism for this remains obscure.

Analysis of Variance↗

PubMed2005

The transcriptome of Populus in elevated CO2.

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 of Populus x euramericana (clone I-214) to elevated [CO(2)] in a FACE (free-air CO(2) enrichment) experiment. Gene expression was sensitive to elevated [CO(2)] but the response depended on the developmental age of the leaves, and < 50 transcripts differed significantly between different CO(2) environments. For young leaves most differentially expressed genes were upregulated in elevated [CO(2)], while in semimature leaves most were downregulated in elevated [CO(2)]. For transcripts related only to the small subunit of Rubisco, upregulation in LPI 3 and downregulation in LPI 6 leaves in elevated CO(2) was confirmed by anova. 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 CO(2).

Adaptation, Physiological↗

PubMed2003

Spatial and temporal effects of free-air CO2 enrichment (POPFACE) on leaf growth, cell expansion, and cell production in a closed canopy of poplar.

Leaf expansion in the fast-growing tree, Populus x euramericana was stimulated by elevated [CO(2)] in a closed-canopy forest plantation, exposed using a free air CO(2) enrichment technique enabling long-term experimentation in field conditions. The effects of elevated [CO(2)] over time were characterized and related to the leaf plastochron index (LPI), and showed that leaf expansion was stimulated at very early (LPI, 0-3) and late (LPI, 6-8) stages in development. Early and late effects of elevated [CO(2)] were largely the result of increased cell expansion and increased cell production, respectively. Spatial effects of elevated [CO(2)] were also marked and increased final leaf size resulted from an effect on leaf area, but not leaf length, demonstrating changed leaf shape in response to [CO(2)]. Leaves exhibited a basipetal gradient of leaf development, investigated by defining seven interveinal areas, with growth ceasing first at the leaf tip. Interestingly, and in contrast to other reports, no spatial differences in epidermal cell size were apparent across the lamina, whereas a clear basipetal gradient in cell production rate was found. These data suggest that the rate and timing of cell production was more important in determining leaf shape, given the constant cell size across the leaf lamina. The effect of elevated [CO(2)] imposed on this developmental gradient suggested that leaf cell production continued longer in elevated [CO(2)] and that basal increases in cell production rate were also more important than altered cell expansion for increased final leaf size and altered leaf shape in elevated [CO(2)].

Algorithms↗