Deltoides Clones Research Articles

Modelling the effects of elevated atmospheric CO2 on crown development, light interception and photosynthesis of poplar in open top chambers

An open‐top chamber experiment was carried out to examine the likely effects of elevated atmospheric [CO2] on architectural as well as on physiological characteristics of two poplar clones (Populus trichocarpa × P. deltoides clone Beaupré and P. deltoides × P. nigra clone Robusta). Crown architectural parameters required as input parameters for a three‐dimensional (3D) model of poplar structure, such as branching frequency and position, branch angle, internode length and its distribution pattern, leaf size and orientation, were measured following growth in ambient and elevated [CO2 ] (ambient + 350 μmol mol–1) treated open‐top chambers. Based on this information, the light interception and photosynthesis of poplar canopies in different [CO2] treatments were simulated using the 3D poplar tree model and a 3D radiative transfer model at various stages of the growing season. The first year experiments and modelling results showed that the [CO2] enrichment had effects on light intercepting canopy structure as well as on leaf photosynthesis properties. The elevated [CO2] treatment resulted in an increase of leaf area, canopy photosynthetic rate and above‐ground biomass production of the two poplar clones studied. However, the structural components responded less than the process components to the [CO2] enrichment. Among the structural components, the increase of LAI contributed the most to the canopy light interception and canopy photosynthesis; the change of other structural aspects as a whole caused by the [CO2] enrichment had little effect on daily canopy light interception and photosynthesis.

Short-rotation coppiced vs non-coppiced poplar: A comparative study at two different field sites

Five different poplar ( Populus) clones were grown during the period 1987–1989 in short-rotation, high-density intensive field plantations at two sites, i.e. Afsnee (near Gent, Belgium) and Orsay (Paris-Sud, France). Different cultural management regimes were applied at the two sites: in Orsay all trees were coppiced after the first or establishment year (1987) and grown for two more years in a coppiced regime, while in the Afsnee plantation trees were grown in a non-coppiced regime and harvested only after three years. Stem volume index (calculated) growth and production were monitored during the three years of the study (1987–1989). They are being reported for all five clones as a function of time, as well as of cumulative temperature and radiation. Significant differences in the climatological conditions between both sites were observed, with the experimental site in Orsay having higher average and cumulative temperature and radiation than the site in Afsnee, 280 km NNE of Orsay. Significant clonal differences were observed during all three years of the study at both experimental field sites. During the establishment year, growth of height and volume index was always higher for all clones in Orsay as compared to Afsnee mainly because of the larger temperature and radiation sums in Orsay. Moreover, the growing season was consistently longer in Orsay. Volume index data showed that the coppiced system yielded overall less above-ground volume after two or three years, but significant clonal variation was observed. However, the coppiced system enhanced intrinsic growth performance, as shown by the absolute and relative growth rates. Volume index of the P. trichocarpa × P. deltoides clones was generally higher than that of the P. trichocarpa clones and that of the euramerican poplar clone Robusta ( P. deltoides × P. nigra) at both sites and in all three years. The largest volume production was realised by clone Beaupré in the three-year-old rotation.

Selection of poplar clones for the lower valley of the Colorado River, Argentina

Summary Ten tree attributes were used to evaluate the performance of 25 Populus deltoides clones in a selection trial in southern Buenos Aires, Argentina. A hierarchical cluster procedure was used to group clones on a multivariate basis. Three Argentinian selections (clones INTA 347-69, 186-68 and 71-67) and one Italian selection (clone Fierolo) were recommended for larger trials across the region. Cluster analysis was an appropriate tool for selecting genotypes with acceptable growth rate, desirable form and resistance to canker disease, rust and wind damage.

Growth and Physiology of One-year old Poplar ( Populus) Under Elevated Atmospheric CO 2 Levels

The effects of elevated atmospheric CO 2 concentrations on the ecophysiological responses (gas exchange, chlorophyll a fluorescence, Rubisco activity, leaf area development) as well as on the growth and biomass production of two poplar clones (i.e. Populus trichocarpa × P. deltoides clone Beaupré and P. × euramericana clone Robusta) were examined under open top chamber conditions. The elevated CO 2 treatment (ambient + 350 μmol mol -1) stimulated above-ground biomass of clones Robusta and Beaupré after the first growing season by 55 and 38%, respectively. This increased biomass production under elevated CO 2 was associated with a significant increase in plant height, the latter being the result of enhanced internode elongation rather than an increased production of leaves or internodes. Both an increased leaf area index (LAI) and a stimulated net photosynthesis per unit leaf contributed to a significantly higher stem biomass per unit leaf area, and thus to the increased above-ground biomass production under the elevated CO 2 concentrations in both clones. The larger LAI was caused by a larger individual leaf size and leaf growth rate; the number of leaves was not altered by the elevated CO 2 treatment. The higher net leaf photosynthesis was the result of an increase in the photochemical (maximal chlorophyll fluorescence Fm and photochemical efficiency Fv/Fm) as well as in the biochemical (increased Rubisco activity) process capacities. No significant differences were found in dark respiration rate, neither between clones nor between treatments, but specific leaf area significantly decreased under elevated CO 2 conditions.

Organic solute accumulation and dehydration tolerance in three water-stressed Populus deltoides clones.

The relationship between osmotic potential, water-soluble organic solutes and electrolyte leakage was investigated in three greenhouse-grown eastern cottonwood (Populus deltoides Bartr.) clones. The Ohio Red (from southern Ohio) and Platte (from eastern Nebraska) clones were selected because they differ in dehydration tolerance, gas exchange and osmotic potential. A third clone, Wildcat (from western Nebraska) was included because of its origin in a very dry area. Plants were either watered daily (control) or watered every 4-6 days (preconditioned). A third group of plants was watered daily until it was water-stressed at the end of the experiment (nonconditioned). Leaves for osmotic potential and water-soluble solute determinations were sampled at predawn after plants were rewatered. All clones showed osmotic adjustment ranging from 0.23 to 0.48 MPa. Organic solutes contributed up to 48% of the total osmotic adjustment. The solutes that contributed at least -0.05 MPa each to leaf osmotic potential in any clone were sucrose, malic acid, glucose, fructose, myoinositol and salicin. Fructose and glucose concentrations were unchanged or declined in preconditioned Ohio Red and Platte but increased in Wildcat. The Ohio Red clone had the highest sucrose concentration in both well-watered and preconditioned plants, and a lower injury index (more membrane stability) than Wildcat in the preconditioned plants, whereas nonconditioned Platte displayed the greatest electrolyte leakage of all clones and treatments. Cell membrane stability was correlated to osmotic potential and sucrose concentration only in Ohio Red.

Gas exchange characteristics of Populus trichocarpa, Populus deltoides and Populus trichocarpa x P. deltoides clones.

Responses of net photosynthesis, dark respiration, photorespiration, transpiration, and stomatal conductance to irradiance, temperature, leaf-to-air vapor density difference (VDD), and plant water stress were examined in two Populus trichocarpa clones (one from a moist, coastal climate in western Washington and one from a dry, continental climate in eastern Washington), one P. deltoides clone, and two P. trichocarpa x P. deltoides clones. Light saturation of photosynthesis in greenhouse-grown trees occurred at about 800 micromol m(-2) s(-1) for P. deltoides, P. trichocarpa x P. deltoides, and the eastern Washington ecotype of P. trichocarpa, but at about 600 micromol m(-2) s(-1) for the western Washington ecotype of P. trichocarpa. Average net photosynthesis (at saturating irradiance and the optimum temperature of 25 degrees C) was 20.7, 18.8, 18.2 and 13.4 micromol CO(2) m(-2) s(-1) for P. deltoides, P. trichocarpa x P. deltoides, and the eastern and western Washington clones of P. trichocarpa, respectively. In all clones, net photosynthesis decreased about 14% as VDD increased from 3 to 18 g H(2)O m(-3). Stomatal conductance decreased sharply with decreasing xylem pressure potential (XPP) in all clones except the western Washington clone of P. trichocarpa. Stomata in this clone were insensitive to changes in XPP and did not control water loss. Complete stomatal closure (stomatal conductance < 0.05 cm s(-1)) occurred at about -2.0 MPa in the eastern Washington clone of P. trichocarpa and around -1.25 MPa in the P. deltoides and P. trichocarpa x P. deltoides clones. Transpiration rates were highest in the P. trichocarpa x P. deltoides clone and lowest in the western Washington clone of P. trichocarpa. The P. deltoides clone and eastern Washington clone of P. trichocarpa had the highest water use efficiency (WUE) and the western Washington clone of P. trichocarpa had the lowest WUE. The hybrids were intermediate. It was concluded that: (1) gas exchange characteristics of eastern and western Washington clones of P. trichocarpa reflected adaptation to their native environment; (2) crossing the western Washington clone of P. trichocarpa with the more drought resistant P. deltoides clone produced plants better adapted to the interior Pacific Northwest climate, although the stomatal response to soil water deficits in the hybrid was conservative compared with that of the eastern Washington clone of P. trichocarpa; and (3) introducing eastern Washington clones of black cottonwood into breeding programs is likely to yield lines with favorable growth characteristics combined with enhanced WUE and adaptation to soil water deficits.

Phenolic Composition of Bud Exudates of Populus deltoides

Abstract Bud exudate of Populus deltoides clones originating from six central and eastern American states was examined by gas chromatography/mass spectrometry and the components were identified. The principal components of the bud exudate were the flavone galangin, the flavanone pinocembrin and the flavanonol pinobanksin, together with the related compounds pinocembrin chalcone, pinobanksin methyl ether and pinobanksin-3-acetate. The bud exudate composition was very different from that seen in a North American poplar of the section Tacamahaca, P. balsamifera. The bud exudates from all P. deltoides specimens were similar excepting that from Vermont.

Gibberellins and heterosis in poplar

To investigate the possible involvement of gibberellins (GAs) in heterosis of hybrid poplar, six poplar clones were studied, including two Populus deltoides clones and two interspecific hybrid clones (P. ×euramericana = P. deltoides × P. nigra) originating from crosses with each of the P. deltoides clones. In field conditions in Ontario, Canada, the interspecific hybrids were consistently taller and had greater shoot dry weights than their parental P. deltoides clones. Shoot dry weights and heights were highly correlated across the six clones, as clonal rankings for these parameters were identical. Endogenous GA-like substances were extracted, purified, chromatographed on silica gel partition columns, and quantified by the cv. Tan-ginbozu dwarf rice bioassay. Bioactive peaks were further chromatographed on reversed-phase C18 HPLC and again bio-assayed. Statistically significant differences in concentrations of total GA-like substances were observed. With one exception, the rankings for the concentrations of GA-like substances and those of GA1-like plus GA19-like substances were similar to the rankings for height growth. Gibberellins A1 and A19 have been identified from the tissue of hybrid poplar by capillary gas chromatography – selected ion monitoring (GC–SIM), and GA1 was also identified by GC–SIM in this tissue. In three of four comparisons, interspecific hybrids contained significantly higher concentrations of GA-like activity than their corresponding parental clones. Thus, a correlation was observed between the concentration of endogenous GA-like activity and hybrid vigor for height growth and shoot dry weight in poplar.

Evidence for nonstomatal inhibition of net photosynthesis in rapidly dehydrated shoots of Populus

Results are presented on the decline of net photosynthesis during the application of rapid water stress to excised shoots of different Populus L. clones. Six clones were selected from the species Populustrichocarpa Torr. &amp; Gray, Populusdeltoides Bartr., and from the hybrid Populustrichocarpa × Populusdeltoides, taking into account the differences in stomatal behaviour between and within these species. The two most productive P. trichocarpa clones and the hybrid clone, characterized by a reduced ability to close stomata during leaf desiccation, showed, nevertheless, a sharp reduction of net photosynthesis at water potentials lower than −1.5 MPa. In contrast, the inhibition of net assimilation in the P. deltoides clone, caused by water stress, was accompanied by a reduction in stomatal conductance. In all studied clones the decrease in net photosynthetic rate followed closely the point of turgor loss of the leaves, indicating a possible relationship between nonstomatal inhibition of photosynthesis and protoplast volume shrinkage.

Poplar rusts in Australia with comments on potential conifer rusts

Melampsora medusae Thum. and M. larici-populina Kleb. have been recorded in Australia for the first time. Their detection, spread and host range are described. M. medusae has the wider host range, but occurs mainly on Populus deltoides clones and hybrids. M. laricipopulina occurs mainly on P. nigra var. italica. Detailed descriptions are given of both rusts, and their geographic distribution listed. The possible effect of these rusts on Australian forestry is discussed, and several other rusts in Australia with known conifer aecial hosts elsewhere are listed.