Populus Canescens Research Articles

Ability of transgenic poplars with elevated glutathione content to tolerate zinc(2+) stress

Phytoremediation potentials of four poplar lines, Populus nigra (N-SL clone), Populus canescens, and two transgenic P. canescens clones were investigated using in vitro leaf discs cultures. The transgenic poplars overexpressed a bacterial gene encoding γ-glutamylcysteine synthetase in the cytosol (11ggs) or in the chlopoplasts (6LgI), and therefore, they contained an elevated level of glutathione. Leaf discs of poplar clones were exposed to different concentrations of ZnSO 4 for 21 days. Zinc(2+) was phytotoxic only at high concentrations (10 −2 to 10 −1 M) at all P. canescens lines, but P. nigra was more sensitive. Transgenic poplars showed elevated heavy metal uptake as compared to the nontransformed clones. Treatments with zinc(2+) strongly induced the activity of glutathione S-transferase enzyme in untransformed poplar lines but to a lesser extent in the transgenic clones. These results suggest that transgenic poplars are more suitable for phytoremediation of soils contaminated with zinc(2+) than wild-type plants.

Physical, mechanical and natural decay resistance properties of lesser known and lesser utilized Diospyros mespiliformis, Tyrachylobium verrucosum and Newtonia paucijuga timber species from Tanzania

Some physical and mechanical properties together with the natural decay resistance of the lesser known and lesser utilized timbers of Diospyros mespiliformis, Tyrachylobium verrucosum and Newtonia paucijuga, species from Tanzania were determined. The physical and strength properties of the timber species were determined following the methods of BS 373 (1957), Lavers (1969) and Ishengoma and Nagoda (1991). Natural decay resistance was determined using the brown-rot fungi (Coniophora puteana and Goeophyllum trabeum) and the white rot fungus (Coriolus versicolor) for both heartwood and sapwood in accordance with EN 113 (1993). Results show that, D. mespiliformis and T. verrucosum are high density timbers with basic densities of 719 and 745 kg/m3, respectively, while N. paucijuga is a medium density timber with a basic density of density 607 kg/m3. With the exception of radial cleavage strength, which were comparable for all the timbers tested, T.verrucosum had higher strength properties than D. mespiliformis. Newtonia. paucijuga showed lowest strength value specifically in modulus of rupture (MOR), modulus of elasticity (MOE) and compressive strength than the other timbers tested. The work to maximum load, shear and radial cleavage strength of D. mespiliformis and N. paucijuga were comparable. If these timber species are promoted, D. mespiliformis and T. verrucosum can substitute Cassiporea malosana and Newtonia paucijuga can substitute Populus canescens. Natural durability ratings according to EN 350-1 (1993) were as follows; N. paucijuga—1 (durable), D. mespiliformis—5 (not durable) and T. verrucosum—5 (not durable).

STUDY OF ROOT INVASION OF SEWER PIPES AND POTENTIAL AMELIORATIVE TECHNIQUES

The invasion of sewer pipes by tree roots is a major cost to both the corporations managing urban infrastructure and to private landowners. There are a number of factors that may result in the growth of roots into and around the pipes. These include pipe material factors such as degradation of aging pipes and damage caused to pipes and environmental factors such as site conditions, tree proximity and tree species. Research into these issues will help in developing more efficient methods of controlling root invasion, benefiting both the management of sewer flow and the urban landscape. A study of root invasions in suburban Melbourne was carried out to examine relationships between site factors and root blockages. Common factors found associated with tree root blockages were Eucalyptus and Melaleuca species over 4m high within 6 m of sewers, pipe depth 2 m or less, rubber ring joined 150 mm diameter vitreous clay, 30 to 60 years old, soil types with sandy topsoils, and blockages occurring most frequently when temperatures and evaporation were at their lowest i.e. August to October. An experiment was conducted to evaluate chemical and physical treatments for preventing root growth in disturbed soil with high nutrient content and readily available moisture (modeling leaking sewers). Over a period of 177 days significant inhibition was achieved with the chemical treatments dichlobenil (278 g/m and 1392 g/m), copper sulphate (1.5 g Cu/kg soil and 7.5 gCu/kg soil), oryzalin (1031 g/m) and trifluralin (260 g/m) and the physical treatments slaked lime (ratio of 10 soil:1 lime and 10 soil:5 lime) and cement slurry. The potential for the use of these treatments in areas where tree roots have damaged sewers is discussed. INTRODUCTION The degree of harmony between trees and urban infrastructure depends on the levels of understanding of how, why and when tree root damage arises and what prevention strategies are available. Tree impacts on infrastructure such as sewers can be a major cost to the managers of utilities and other urban infrastructure managers (Schrock 1985; Baker, 1980; McPherson and Peper 1996). Soil disturbance during installation creates pathways for roots to grow from the surface towards the pipe. Essentially, these root growth corridors contain favourable sized pores that can hold water and air, similar those found in topsoil. If pipes have been damaged and leak, then root growth will eventually exploit such regions. Tree roots, incorrect installation procedures, other underground service operators or material degradation, may all cause damage. This paper reports on a study, which investigated the factors associated with sewer blockage in metropolitan Melbourne and which investigated techniques that could be used to minimise tree root growth in disturbed soils such as found near sewer pipes. MATERIALS AND METHODS The survey was conducted in two parts. The first was an investigation of site factors associated with tree root blockages in the year 1999 by South East Water (SEW). Proc. IC on Urban Horticulture Eds: R. Junge-Berberovic et al. Acta Hort 643, ISHS 2004 114 Sites where blockages had occurred were visited and specific information about the site recorded. The second part was an analysis of factors associated with tree root blockages that occurred in the four years 1997 to 2000. This component of the study did not involve site visits but it used the available information on blockages recorded by SEW. The study of 1999 blockages recorded data on trees, geology and soil. The study of 1997-2000 blockages examined a range of factors that may have influenced blockages. In December 1999, a site with 85 trees planted in four rows was selected at Burnley College. The trees were Eucalyptus globulus, Eucalyptus saligna, Eucalyptus camaldulensis, Eucalyptus melliodora and Populus canescens. Holes were dug the trees and then soil sections were then were backfilled with treated sandy loam soil. The treated soil section was watered and fertilised periodically to simulate a soil that is situated close to a leaking pipe. The concept of this experiment was based on studies by Nazer and Clark (1982) and Wagar and Barker (1993). There were twelve treatments (nine chemical, two physical, and one control (no treatment)). The treated cores were excavated after 177 days and the root mass in each was measured. The treatments used are displayed in Table 1. The cement slurry and compaction are categorised as ‘physical treatments’ because they act as a physical barrier to root growth. There were five replicates of each treatment.

Plant regeneration and Agrobacterium-mediated transformation of two elite aspen hybrid clones from in vitro leaf tissues

An efficient regeneration and transformation system was developed for two elite aspen hybrid clones (Populus canescens × P. grandidentada and P. tremuloides × P. davidiana). Callus was induced from in vitro leaf explants on modified Murashige and Skoog medium (MSA) and woody plant medium (WPM) containing four different combinations of cytokinins and auxins. Callus tissues regenerated into shoots on WPM medium supplemented with 2.0 mgl−1 (9.12 μM) zeatin or 0.01 mgl−1 (0.045 μM) thidiazuron. P. canescens × P. grandidentata exhibited the higher callus and shoot production. In vitro leaf explants from the two hybrid clones were cocultivated with Agrobacterium tumefaciens strain EHA105 harboring the binary Ti plasmid pBI121 carrying the uidA gene encoding for β-glucuronidase (GUS) and the npt II gene encoding for neomycin phosphotransferase II. Transformation was confirmed by GUS assays, polymerase chain reaction, and Southern blot analyses. Agrobacterium concentration, acetosyringone, and pH of the cocultivation medium were evaluated for enhancing transformation efficiency with the clone P. canescens × P. grandidentata.

Radial patterns of sap flow in woody stems of dominant and understory species: scaling errors associated with positioning of sensors.

We studied sap flow in dominant coniferous (Pinus sylvestris L.) and broadleaf (Populus canescens L.) species and in understory species (Prunus serotina Ehrh. and Rhododendron ponticum L.) by the heat field deformation (HFD) method. We attempted to identify possible errors arising during flow integration and scaling from single-point measurements to whole trees. Large systematic errors of -90 to 300% were found when it was assumed that sap flow was uniform over the sapwood depth. Therefore, we recommend that the radial sap flow pattern should be determined first using sensors with multiple measuring points along a stem radius followed by single-point measurements with sensors placed at a predetermined depth. Other significant errors occurred in the scaling procedure even when the sap flow radial pattern was known. These included errors associated with uncertainties in the positioning of sensors beneath the cambium (up to 15% per 1 mm error in estimated xylem depth), and differences in environmental conditions when the radial profile applied for integration was determined over the short term (up to 47% error). High temporal variation in the point-to-area correction factor along the xylem radius used for flow integration is also problematic. Compared with midday measurements, measurements of radial variation of sap flow in the morning and evening of sunny days minimized the influence of temporal variations on the point-to-area correction factor, which was especially pronounced in trees with a highly asymmetric sap flow radial pattern because of differences in functioning of the sapwood xylem layers. Positioning a single-point sensor at a depth with maximum sap flow is advantageous because of the high sensitivity of maximum sap flow to water stress conditions and changes in micro-climate, and because of the lower random errors associated with the positioning of a single-point sensor along the xylem radius.

A mechanistic analysis of penetration of glyphosate salts across astomatous cuticular membranes.

Penetration of glyphosate salts across isolated poplar (Populus canescens (Aiton) Sm) cuticular membranes (CM) was studied using Na+, K+, NH4+, trimethylsulfonium+ (TMS) and isopropylamine+ (IPA) as cations. After droplet drying, humidity over the salt residues on the outer surfaces of the CM was kept constant, and cuticular penetration was monitored by sampling the receiver solution facing the inner surfaces of the CM. Glyphosate salts disappeared exponentially with time from the surfaces of the CM. This first-order process could be quantitatively described using rate constants (k) or half-times (time for 50% penetration; t1/2). Humidity strongly affected the velocity of penetration, as k increased by factors of 5.3 (K-glyphosate), 6.9 (TMS-glyphosate), 7.1 (NH4-glyphosate), 8.5 (Na-glyphosate) and 10.5 (IPA-glyphosate) when humidity was increased from 70 to 100%. Depending on the type of cation and humidity, t1/2 varied between 4 and 70h, but the humidity effect was statistically significant only at 100% humidity, when half-times were highest with IPA-glyphosate and lowest with TMS-glyphosate. Glyphosate acid penetration was measured only at 90% humidity and found to be extremely slow (t1/2 = 866 h). Adding 0.2 g litre-1 of a wetter (alkylpolyglucoside) to the donor increased IPA-glyphosate rate constants by about four times, but increasing concentration produced no further increase in k. When donors contained 0.2 g litre-1 wetter, further additions of 4 g litre-1 Ethomeen T25 did not change rate constants measured with IPA-glyphosate at 90% humidity, while Genapol C-100 and diethyl suberate increased k by only 35%. Concentration of IPA-glyphosate (1, 2 and 4 g litre-1) did not influence k at 90% humidity, and pH of donor solutions (4.0, 7.7, 9.5) had no effect on k of K-glyphosate at 90% humidity. Temperature (10 to 25 degrees C) had only a small influence on velocity of penetration of IPA-glyphosate and K-glyphosate, as energies of activation amounted to only 4.26 and 2.92 kJ mole-1, respectively. These results are interpreted as evidence for penetration of glyphosate salts in aqueous pores.

Effects of rhizospheric bicarbonate on net nitrate uptake and partitioning between the main nitrate utilising processes in Populus canescens and Sambucus nigra

Increased levels of rhizospheric dissolved inorganic carbon have repeatedly been demonstrated to enhance plant growth by up to 80%, although carbon from dark fixation accounts for only 1–3% of total plant carbon gain. This study, therefore, aimed at investigating the effects of bicarbonate on nitrate uptake, assimilation and translocation to shoots. Clonal saplings of poplar (Populus canescens(Ait.) Sm.) and elder (Sambucus nigraL.) were grown hydroponically for 35 days in a nutrient solution containing 0, 0.5 and 1 mM bicarbonate and 2 mM nitrate as the sole nitrogen source at pH 7.0. Net nitrate uptake, root nitrate accumulation and reduction, and export of nitrogenous solutes to shoots were measured after incubating plants with 15N-labelled nitrate for 24 h. Net nitrate uptake increased non-significantly in plant species (19–61% compared to control plants) in response to 1 mM bicarbonate. Root nitrate reduction and nitrogen export to shoots increased by 80 and 95% and 15 and 44% in poplar and elder, respectively. With enhanced root zone bicarbonate, both species also exhibited a marked shift between the main nitrate utilising processes. Poplar plants increasingly utilised nitrate via nitrate reduction (73–88% of net nitrate uptake), whereas the proportions of export (20–9%) and storage in roots (7–3%) declined as plants were exposed to 1 mM external bicarbonate. On the other hand, elder plants exhibited a significant increase of root nitrate reduction (44–66%) and root nitrate accumulation (6–25%). Nitrate translocation to elder shoots decreased from 50 to 8% of net nitrate uptake. The improved supply of nitrogen to shoots did not translate into a significant stimulation of growth, relative growth rates increased by only 16% in poplar saplings and by 7% in elder plants.

Phenotypic plasticity of the phenology of seven European tree species in relation to climatic warming

ABSTRACTTo evaluate the potential responses of individual trees to climatic warming, phenological observations of clones of Larix decidua (Mill.), Betula pubescens (Ehrh.), Tilia cor‐data (Mill.), Populus canescens (Ait.), Quercus robur (L.), Fagus sylvatica (L.) and Picea abies (L.) relocated over a large latitudinal range in Europe were analysed. The magnitude of the response of the clone was compared to that of genetically different trees of the same species in part of the latitudinal range, which were assumed to have adapted to their local climates. It was found that the responses of the date of leaf unfolding and the date of leaf fall in the clones to temperature were similar in magnitude to those in the genetically different trees. This demonstrates that trees possess considerable plasticity and are able to respond phenotypically to a major change in their local climate.For the clones of Larix decidua and Quercus robur the duration of the growing season may decrease with increasing temperature, because leaf fall is advanced more than leaf unfolding. In Betula pubescens and Populus canescens, leaf unfolding and leaf fall are advanced equally, whereas in Tilia cordata and Fagus sylvatica the date of leaf fall seems to be unaltered but the date of leaf unfolding advances with increasing temperature. These differences in the duration of the growing season at increased temperature may alter the competitive balance between the species.Descriptive dynamic models showed that most of the variance in the date of leaf unfolding can be accounted for by temperature. However, a generally applicable model of leaf fall based on temperature and/or photoperiod could not improved the null model, i.e. the mean date of leaf fall, because of variability in other environmental factors.The lowest temperatures around the dates of leaf unfolding and leaf fall differed among the clones. The hypothesis that the survival of the clones is curtailed by spring frosts was supported. Thus, these lowest temper‐tures around leaf unfolding may represent thresholds below which the species cannot survive. It is argued that these thresholds may be a particularly sensitive means to evaluate the impact of climatic warming on the geographical distribution of tree species.

A Case Study inPopulus canescensto Estimate the Leaf Area Index

SYNOPSIS A 25-year old Populus canescens stand was selected for sampling to estimate the one-side leaf surface area per unit ground area. A portable area meter was used to determine leaf surface areas of a sample of branches of the first order. Different unweighted and weighted regression equations were compared to estimate leaf surface area. The estimated tree leaf areas were regressed on D.B.H., with unit weight being assigned to the single observation.

CARBOHYDRATE COMPOSITION AND INVERTASE ACTIVITY IN POPLAR LEAF TISSUES INFECTED BY MILLAMPSORA AECIDIOIDES (D.C.) SCHROETER

SummaryQualitative analyses of ethanol‐soluble carbohydrates of rust‐infected poplar leaves were similar to those of other rust infections. Sucrose was the most abundant ethanol‐soluble carbohydrate in both healthy and infected leaf tissues. Mannitol, arabitol and trehalose were detected in low concentrations at the site of infection. Mannose formed a significant proportion of the insoluble carbohydrates in the pustule disc. Activities of both acid and alkaline invertase, assayed by two methods, were similar in both healthy and infected tissues. These results are discussed in relation to those of other biotrophic infections and it is suggested that the Populus canescens Aiton Sm./Melampsora aecidioides (D.C.) Schroeter relationship may be a benign one.

A phytosociological study of orange Kloof, Table Mountain, South Africa

The present survey forms part of a larger research project of the entire Table Mountain Nature Reserve. The aim of the study was to classify the vegetation into uniform ecological units suitable for management pur poses. Apart from the natural vegetation, the area also supports a number of exotics (Populus canescens, Quer cus robur and Acacia melanoxylon stands, Pinus spp. planta tions and Eucalyptus spp. belts.

Illustrations of the British Flora: a Series of Wood Engravings, with Dissections, of British Plants

THE appearance of the fifth revised edition of the “Illustrations of the British Flora” completes the repuBlication of “Bentham's Handbook of the British Flora.” It is universally acknowledged that both the text (now called the Handbook) and the illustrations have been of great use to several generations of botanical students, especially beginners. It is, however, unfortunate that the two volumes have been reissued without more drastic alterations having been made. A considerable number of serious mistakes are perpetuated, as, for example, in Fig. 933, where the leaves of Populus canescens are figured as P. alba, and in Fig. 935, where the catkins of one species and the leaves of another are figured under the name of P. nigra.