LIFE‐HISTORY EVOLUTION AND DENSITY‐DEPENDENT GROWTH IN EXPERIMENTAL POPULATIONS OF YEAST

We studied the evolution of the correlation between growth rate r and yield K in experimental lineages of the yeast Saccharomyces cerevisiae. First, we isolated a single clone every approximately 250 generations from each of eight populations selected in a glucose‐limited medium for 5000 generations at approximately 6.6 population doublings per day (20 clones per line × 8 lines) and measured its growth rate and yield in a new, galactose‐limited medium (with ～1.3 doubling per day). For most lines, r on galactose increased throughout the 5000 generations of selection on glucose whereas K on galactose declined. Next, we selected these 160 glucose‐adapted clones in the galactose environment for approximately 120 generations and measured changes in r and K in galactose. In general, growth rate increased and yield declined, and clones that initially grew slowly on galactose improved more than did faster clones. We found a negative correlation between r and K among clones both within each line and across all clones. We provide evidence that this relationship is not heritable and is a negative environmental correlation rather than a genetic trade‐off.     

Bacterial growth properties at low optical densities

A method for accurate quantification of growth rate and yield of bacterial populations at low densities was developed with a modified version of a stepwise linear model for fitting growth curves based on optical density measurements, and adapted to measurements at low optical densities in 96-well microtiter plates. The method can be used for rapid and precise estimates of growth rate and yield, based on optical density measurements of large numbers of cultures of Escherichia coli. E. coli B lines were serially propagated at low glucose concentration during a long-term evolution experiment. Growth rate and yield of populations sampled from each of 12 lines that evolved for 20,000 generations under these conditions and two ancestral clones was measured. Populations were grown at three different glucose concentrations. Consistent with earlier findings, statistical analysis showed that both exponential growth rate and yield per unit of glucose differed significantly between the three glucose concentrations tested. Significant adaptation of the evolved populations to the nutrient conditions in which they evolved for 20,000 generations was observed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Influence of carbon source on shoot multiplication and adventitious bud regeneration in in vitro beech cultures

Experiments were performed to determine the effects ofcarbon source and concentration on shootmultiplication in shoot cultures of Fagussylvatica (one clone) and F. orientalis (twoclones) and on the induction of adventitious shootbuds from leaf and internode explants of F.orientalis. In general, glucose was the best carbonsource for both axillary branching and adventitiousshoot regeneration. Shoot-tip explants grown on 3–4%glucose medium produced more shoots than those onsucrose or fructose. For maximum shoot length, glucosemedium was best for two of the three clones, and 4%sucrose for the other. The number of shoots was theparameter most influenced by glucose concentration inthe adventitious shoot regeneration experiments, thenumber increasing with sugar concentration. The lowesthyperhydricity rate occurred in the presence ofsucrose in both species. Shoot growth and quality wasnegatively affected by fructose supplied media. Theuse of filter-sterilized rather than autoclavedfructose neither stimulated shoot growth nor reducedthe incidence of hyperhydricity in all three clones.The response of shoot cultures to differentcarbohydrate treatments appears to some extent to begenotype dependent.     

Engineering the expression level of cytosolic nucleoside diphosphate kinase in transgenic Solanum tuberosum roots alters growth,respiration and carbon metabolism

Nucleoside diphosphate kinase (NDPK) is a ubiquitous enzyme that catalyzes the transfer of the γ‐phosphate from a donor nucleoside triphosphate to an acceptor nucleoside diphosphate. In this study we used a targeted metabolomic approach and measurement of physiological parameters to report the effects of the genetic manipulation of cytosolic NDPK (NDPK1) expression on physiology and carbon metabolism in potato (Solanum tuberosum) roots. Sense and antisense NDPK1 constructs were introduced in potato using Agrobacterium rhizogenes to generate a population of root clones displaying a 40‐fold difference in NDPK activity. Root growth, O₂ uptake, flux of carbon between sucrose and CO₂, levels of reactive oxygen species and some tricarboxylic acid cycle intermediates were positively correlated with levels of NDPK1 expression. In addition, NDPK1 levels positively affected UDP‐glucose and cellulose contents. The activation state of ADP‐glucose pyrophosphorylase, a key enzyme in starch synthesis, was higher in antisense roots than in roots overexpressing NDPK1. Further analyses demonstrated that ADP‐glucose pyrophosphorylase was more oxidized, and therefore less active, in sense clones than antisense clones. Consequently, antisense NDPK1 roots accumulated more starch and the starch to cellulose ratio was negatively affected by the level of NDPK1. These data support the idea that modulation of NDPK1 affects the distribution of carbon between starch and cellulose biosynthetic pathways.     

Sequence conservation among the glucose transporter from the cyanobacterium Synechocystis sp. PCC 6803 and mammalian glucose transporters

Synechocystis sp. PCC 6803 is capable of facultative photoheterotrophy with glucose as the sole carbon source. Eight mutants that were unable to take up glucose were transformed with plasmids from pooled gene banks of wild-type Synechocystis DNA prepared in an Escherichia coli vector that does not replicate in Synechocystis. One mutant (EG216) could be complemented with all gene banks to restore ability for photoheterotrophic growth. One of the gene banks was fractionated into single clones and plasmid DNA from each clone used to complement EG216. This yielded a 1.5 kb DNA fragment that was sequenced. It contained one complete open reading frame (gtr) whose putative gene product displayed high sequence conservation with the xylose transporter of E. coli and the mammalian glucose transporters. Further, the isolated gtr gene interrupted in vitro by a kanamycin resistance cassette could be used to construct mutants from wild-type Synechocystis sp. PCC 6803 that lacked a functional glucose transporter, thus confirming the identity of the gtr gene with the glucose transporter gene. This is the first prokaryotic glucose transporter known to share a sequence relationship with mammalian glucose transporters and the first sugar transporter from a cyanobacterium characterized at the sequence level.     

Relationship between cell size and specific thrombopoietin productivity in chinese hamster ovary cells during dihydrofolate reductase-mediated gene amplification

When parental Chinese hamster ovary (CHO) cell clones that are capable of producing thrombopoietin (TPO) were subjected to high methotrexate (MTX) concentrations, clonal variations in cell growth were apparent. In the clones that had no significant enhancement in specific TPO productivity (q _Tpo) when a higher level of MTX was administered, their growth was not depressed significantly nor their cell size changed significantly. On the other hand, those clones that showed a significant enhancement inq _Tpo at higher a MTX dosage, cell growth was depressed initially but recovered during successive sub-cultures. Furthermore, their cell size increased, which suggested that changes in cell size may be indicative of an enhancedq _Tpo. When the enhancement of theq _Tpo of 9 clones after a high MTX dosage was plotted against the extent of the increase of their size, there was a linear correlation (r ²=0.80,P<0.001, ANOVA), which suggested that an enhancement ofq _Tpo after high MTX administration can be measured by the increase in their cell size. Taken together, our data demonstrate that the selection of amplified CHO cell clones with enhancedq _Tpo can be done based upon their increased size and growth pattern. This facilitates the development of highly productive recombinant CHO cell lines.     

NH4 : NO3 nutrition influence on biomass productivity and root respiration of poplar and willow clones

Nitrogen fertilization often improves the yield of intensively managed, short‐rotation coppices. However, information of N nutrition form on the growth of common species and clones used for biomass production is limited. Thus, this study aims at evaluating N form effects on the growth of two Salicaceae clones. Cuttings of the poplar clone Max 4 (Populus maximovizcii × P. nigra) and the willow clone Inger (Salix triandra × S. viminialis) were fertilized in a pot experiment with four ratios of nitrate (NO₃^?) to ammonium (50%, 62.5%, 75% and 87.5% NO₃^? balanced with ammonium (NH₄⁺) to constant total N) for one growing season and under stable soil pH. Plants were harvested for analysis of biomass and morphology of leaves, stem and roots. Respiration of fine and coarse roots (RR) was determined and related to biomass growth. Salix cv. Inger accumulated more total dry matter than Populus cv. Max 4. In both Salicaceae clones, the total biomass was significantly influenced by the nitrate ratio and greatest in plants fertilized with 50% NO₃^? of the total N supply. Both clones possess a different leaf and root morphology, but no significant influence of the NO₃^? ratio on the morphology was found. Fine RR rates differed significantly between clones, with significantly greater fine RR in Max 4; 87.5% NO₃^? fertilization increased the fine RR. Fine RR and total accumulated plant biomass were closely related. Our study is the first to show the tremendous influence of fine root respiration, especially including the carbon‐intensive reduction of NO₃^? to NH₄⁺, on the aboveground growth of Salicaceae clones. Ways to improve yield in SRC are thus to lower the assimilate consumption by fine roots and to match fertilization regimes to the used clones or vice versa.     

Genotypic variability and stability of poplars and willows grown onnitrate-contaminated soils

Abstract

Phyto-recurrent selection is an established method for selecting tree genotypes for phytoremediation. To identify promising Populus (poplar) and Salix (willow) genotypes for phytotechnologies, our objectives were to (1) evaluate the genotypic variability in survival, height, and diameter of poplar and willow clones established on soils heavily contaminated with nitrates; and (2) assess the genotypic stability in survival and diameter of selected poplar clones after one and eleven growing seasons. We tested 27 poplar and 10 willow clones planted as unrooted cuttings, along with 15 poplar genotypes planted as rooted cuttings. The trees were tested at an agricultural production facility in the Midwestern, United States. After 11 growing seasons, using phyto-recurrent selection, we surveyed survival and measured the diameter of 27 poplar clones (14 unrooted, 13 rooted) that were selected based on superior survival and growth throughout plantation development. Overall, willow exhibited the greatest survival, while poplar had the greatest height and diameter. At 11 years after planting, superior clones were identified that exhibited above-average diameter growth at the establishment- and rotation-age, most of which had stable genotypic performance over time. Selection of specific clones was favorable to genomic groups, based on the geographic location and soil conditions of the site.     

Phosphorus availability mediates plasticity in life-history traits and predator–prey interactions in Daphnia

We analysed growth plasticity of two Daphnia pulex clones under low‐phosphorus (LP) and high phosphorus (HP) conditions, in the presence of Chaoborus kairomones to examine how food quality (P‐availability) might impact life‐history responses and vulnerability to predation. Overall, clone 1 grew faster, and was larger at maturity. Under HP, both clones responded to kairomones by increasing growth, age and size at maturity, and decreasing fecundity. Under LP, both clones suffered reduced growth, and fecundity. However, the magnitude of response to kairomones depended on a clone by P‐availability interaction. Chaoborus presented a 1 : 1 clonal mixture under HP or LP, consumed more individuals under LP. Moreover, fewer clone 1 individuals were consumed. Studying the effects of P‐availability on life histories, and predator–prey interactions may help us understand the mechanisms generating and maintaining plasticity, as well as influencing genotypic diversity and microevolutionary processes in natural populations.     

Glucose Utilization by Euglena gracilis var. bacillaris: Short-Term Metabolic Studies*

SYNOPSIS. In tryptone media, optimal growth of nonphotosynthetic Euglena gracilis var. bacillaris on glucose occurred with 1% (w/v) glucose at pH 3.5, and required a previous adaptive period in glucose medium. In short term metabolic experiments, glucose uptake was greatly stimulated by small concentrations of tryptone or succinate; effects of shaking suggested that CO₂ has a similar stimulatory effect. Glucose utilization was highly dependent on glucose concentration, with an apparent threshold at about 2 mM and increasing steeply with glucose concentration above this value. In tracer experiments, about 90% of the glucose carbon consumed was assimilated, and about 10% released as CO₂. Glucose did not stimulate respiration even during rapid glucose utilization. Tracer studies indicated oxidation of endogenous substrates was depressed by an amount which just compensated for the respiration due to glucose. The conditions which allowed rapid glucose utilization by “resting”E. gracilis var. bacillaris were the same as those known previously to be required for growth on glucose. It was therefore concluded that these factors act directly on the main pathways of glucose metabolism.     

Effects of carbon source and concentration on development of lingonberry (<Emphasis Type="Italic">Vaccinium vitis-idaea</Emphasis> L.) shoots cultivated <Emphasis Type="Italic">in vitro</Emphasis> from nodal explants

Summary Carbohydrate type and concentration and their interactive effects on in vitro shoot proliferation of three lingonberry (Vaccinium vitis-idaea ssp. vitis-idaea L.) cultivars (‘Regal’, ‘Splendor’, and ‘Erntedank’) and two V. vitis-idaea ssp. minus (Lodd) clones (‘NL1’ and ‘NL2’) were studied. Nodal explants were grown in vitro on medium with 2 μM zeatin and either glucose, sorbitol, or sucrose at a concentration of 0, 10, 20, or 30 gl⁻¹. The interactive effects of carbohydrate type and concentration and genotype were important for shoot proliferation. The best response was afforded by sucrose at 20 gl⁻¹ both in terms of explant response and shoot developing potential, although glucose supported shoot growth equally well, and in ‘NL1’ at 10 gl⁻¹ it resulted in better in vitro growth than sucrose. Carbohydrate concentration had little effect on shoot vigor. The genotypes differed in terms of shoots per explant, length, and vigor, leaves per shoot, and callus formation at the base of explants; this was manifested with various types and concentrations of carbohydrate. Changing the positioning of explants on the medium from vertically upright to horizontal increased the shoot and callus size, but decreased shoot height and leaves per shoot. Proliferated shoots were rooted on a peat:perlite (1∶1, v/v) medium and the plantlets were acclimatized and eventually established in the greenhouse.     

The effect of salt stress and abscisic acid on proline production,chlorophyll content and growth of <Emphasis Type="Italic">in vitro</Emphasis> propagated shoots of <Emphasis Type="Italic">Eucalyptus camaldulensis</Emphasis>

Three clones, selected for their variation in salt tolerance, were examined regarding their growth and physiological responses on exposure to salt (NaCl) and abscisic acid (ABA) in vitro. The shoot proline levels significantly increased in two salt tolerant clones when exposed to 100 mM NaCl in the shoot multiplication medium. In contrast, proline in a salt sensitive clone did not change in comparison to the control treatment. When 10 M ABA was included in the medium all clones had an increase in proline regardless of whether they were salt tolerant or salt sensitive, linking proline production to the stress hormone ABA. Callus production was so variable that it was not possible to produce callus of consistent texture, colour and growth for all three clones. For the two clones where consistent growth was achievable, both the salt tolerant and salt sensitive clones increased proline production when exposed to salt. This response, however, was greater in the salt tolerant clone. Other parameters examined were growth (dry weight) and shoot chlorophyll content. These characteristics did not correlate with the salt tolerance of the clones, with similar weights being produced on non salt and salt media and similar chlorophyll in both salt sensitive and salt tolerant clones regardless of the medium in which they were grown. The production of proline is considered with regard to selection for differences in salt tolerance in vitro.     

Kinetics of glucose stimulatory effect on silica deposition and growth of natural populations of Fragilaria crotonensis

Diatoms are known to exploit organic substrates for growth; however, convincing evidence that they can utilize dissolved organic carbon under natural conditions is not available. In 2008–2009, we performed in situ experiments examining the effect of glucose addition on silica deposition kinetics and growth rates of Fragilaria crotonensis in the eutrophic ?ímov Reservoir (Czech Republic). Silica deposition kinetics was measured at 4‐h intervals over a 24‐h incubation with PDMPO [2‐(4‐pyridyl)‐5{[4‐dimethylaminoethyl‐aminocarbamyl)‐methoxy] phenyl}oxazole] fluorescence probe. A significant stimulatory effect of glucose supplemented at the concentration of 10^?4 M on Fragilaria silification was observed at 20 and 24 h. Fragilaria growth rates almost doubled upon glucose enrichment compared with the untreated control at 24 h. In addition, we conducted a dose‐response experiment testing the glucose additions from 10^?8 to 10^?3 M in a 24‐h incubation. Glucose stimulated both Fragilaria silification and growth at concentrations >10^–7 M, which might occasionally occur in a reservoir as a result of accidental contamination of water by organic pollution.     

Somatic embryogenesis and plant regeneration from floral explants of cacao (Theobroma cacao L.) using thidiazuron

Summary A procedure for the regeneration of cacao (Theobroma cacao) plants from staminode explants via somatic embryogenesis was developed. Rapidly growing calli were induced by culturing staminode explants on a DKW salts-based primary callus growth (PCG) medium supplemented with 20 g glucose per L, 9 μM 2,4-D, and thidiazuron (TDZ) at various concentrations. Calli were subcultured onto a WPM salts-based secondary callus growth medium supplemented with 20 g glucose per L, 9 μM 2,4-D, and 1.4 nM kinetin. Somatic embryos were formed from embryogenic calli following transfer to a hormone-free DKW salts-based embryo development medium containing sucrose. The concentration of TDZ used in PCG medium significantly affected the rate of callus growth, the frequency of embryogenesis, and the number of somatic embryos produced from each responsive explant. A TDZ concentration of 22.7 nM was found to be the optimal concentration for effective induction of somatic embryos from various cacao genotypes. Using this procedure, we recovered somatic embryos from all 19 tested cacao genotypes, representing three major genetic group types. However, among these genotypes, a wide range of variation was observed in both the frequency of embryogenesis, which ranged from 1 to 100%, and the average number of somatic embryos produced from each responsive explant, which ranged from 2 to 46. Two types of somatic embryos were identified on the basis of their visual appearance and growth behavior. A large number of cacao plants have been regenerated from somatic embryos and established in soil in a greenhouse. Plants showed morphological and growth characteristics similar to those of seed-derived plants. The described procedure may allow for the practical use of somatic embryogenesis for clonal propagation of elite cacao clones and other applications that require the production of a large number of plants from limited source materials.     

Requirements for in vitro propagation of seven nitrogen-fixing Alnus species

Studies on the in vitro propagation of Alnus crispa, A. glutinosa, A. incana, A. japonica, A. rubra, A. sinuata and A. viridis indicated interspecific as well as intraspecific variations in their requirements for in vitro culture. The WPM and Blaydes media supported, respectively, growth of A. glutinosa and A. crispa but not that of both species, while the MS medium induced equal or significantly better growth than WPM and Blaydes media for both species. The optimum type and concentration of sugar to be used in the multiplication medium varied with species. Only A. glutinosa showed good growth on sucrose while glucose was optimum for all other species but at different concentrations. All species rooted in 3 weeks on half-strength MS medium including 1 M IBA. All clones of A. glutinosa and A. rubra rooted 100%, whereas easy-to-root and difficult-to-root clones were observed in the other species. In the rooting medium, glucose promoted rooting of the difficult-to-root clones better than sucrose. Survival following transfer to an artificial substrate was 100% for all species. Nodulation tests using pure cultures of two Frankia strains showed 100% nodulation on all Alnus clones.     

Intraspecific diversity and distribution of the cosmopolitan species Pseudo‐nitzschia pungens (Bacillariophyceae): morphology,genetics, and ecophysiology of the three clades

Three clades of Pseudo‐nitzschia pungens, determined by the internal transcribed space (ITS) region, are distributed throughout the world. We studied 15 P. pungens clones from various geographical locations and confirmed the existence of the three clades within P. pungens, based on ITS sequencing and described the three subgroups (IIIaa, IIIab, and IIIb) of clade III. Clade III (clade IIIaa) populations were reported for the first time in Korean coastal waters and the East China Sea. In morphometric analysis, we found the ultrastructural differences in the number of fibulae, striae, and poroids that separate the three clades. We carried out physiological tests on nine clones belonging to the three clades growing under various culture conditions. In temperature tests, only clade III clones could not grow at lower temperatures (10°C and 15°C), although clade I and II clones grew well. The estimated optimal growth range of clade I clones was wider than that of clades II and III. Clade II clones were considered to be adapted to lower temperatures and clade III to higher temperatures. In salinity tests, clade II and III clones did not grow well at a salinity of 40. Clade I clones were regarded as euryhaline and clade II and III clones were stenohaline. This supports the hypothesis that P. pungens clades have different ecophysiological characteristics based on their habitats. Our data show that physiological and morphological features are correlated with genetic intraspecific differentiation in P. pungens.     

Influence of pectin and glucose on growth and polygalacturonase production by Aspergillus niger in solid-state cultivation

The solid-state production of endo- and exo-polygalacturonases (PG) by Aspergillus niger was studied in a media containing wheat bran, salts, and different citric pectin and/or glucose concentrations. Kinetic analysis of the process indicated that the formation of PG and the growth of A. niger are associated processes. By increasing citric pectin from 0 to 16% (w/w), the maximum A. niger concentration (X _m) was raised from 94 to 121 mg/g dry medium suggesting that pectin can be used by A. niger as a growth substrate besides its role as an inducer. With 16% (w/w) pectin, 281 U exo-PG/gdm and 152 U endo-PG/gdm were obtained. Otherwise, pectin concentrations from 20 to 30% (w/w) hindered both production and growth. A. niger concentrations of 108–113 mg/gdm were achieved in runs with glucose from 5 to 12% (w/w), whereas at 16 and 20% (w/w) glucose, lower X _m values (ca. 100 mg/gdm) were measured. The addition of glucose to the wheat bran medium, up to 10% (w/w) led to maximum endo-PG titers slightly lower than those found in the absence of glucose. Nevertheless, exo-PG formation in these media was strongly increased and activities over 370 U/gdm were achieved. The results suggest that in experiments with pectin concentrations until 16% (w/w), exo-PG production was repressed by pectin-degradation products although these same substances had favored biomass growth. When glucose concentrations over 10% (w/w) were added to the media, the maximum activities of both enzymes decreased drastically, suggesting that glucose at high concentrations also exerts a repressive effect on PG production.     

Genetic variability in growth rates of marine dinoflagellates

The growth rates of thirty clones of Prorocentrum micans, twenty-two clones of Gonyaulax excavata and fifteen clones of Scrippsiella trochoidea, isolated from eight different water samples were measured under two environmental conditions. There was significant genetic variability in growth rates between clones. The amount of genetic variability between clones ranged from 10–27% (coefficient of variation) in Prorocentrum micans, 31–52% in Gonyaulax excavata and 11–20% in Scrippsiella trochoidea. Unlike Gonyaulax excavata and Scrippsiella trochoidea many different Prorocentrum micans clones had identical growth rates.Supported by Spanish CAICYT, grant num. 2409/83.     

Participation of the intracellular enzymes in the control of mutational processes

Summary The influence of UV-specific endonuclease and medium composition on the frequency and spectrum of genic mutations in Escherichia coli KI2 uvr ⁺ (with normal repair enzymes) and urv A6 (defective in UV-specific endonuclease) was studied. Mutations at the locus glu (gene controlling assimilation of glucose) were induced by ultra-violet irradiation and hydroxylamine treatment. To identify mutant colonies, triphenyl tetrazolium chloride (TTC) was added to the medium since it coloured the mutant colonies bright crimson and readily permitted distinction between pure mutant clones (complete mutations) and mixed clones (mosaic or sector mutations).A maximum mutation frequency after UV-irradiation was observed in E. coli uvr ⁺ cells but not in the E. coli uvr A6 strain. The curve of mutagenesis with a maximum was found in both studied strains after treatment by hydroxylamine which did not cause DNA damage recognized by UV-specific endonuclease.The highest frequency of mutations (at the point of maximum) in the series of experiments with enriched growth medium was almost 10 times higher than in the series of the experiments with poor medium.It was established that in bacteria with normal repair enzymes the frequency of complete mutations was higher than the frequency of mosaic mutations. It was also observed that the rate of UV-mutagenesis was higher in the case of E. coli uvr ⁺.The study of the distribution of mosaic mutant sectors in experiments with bacteria suspended in either a nutrient broth or a buffer during UV-irradiation revealed that the size of mutant sectors was rather variable and that the differences in the number of nucleoids per cell did not always determine the distribution of mutant sector sizes.Abbreviations HA Hydroxylamine hydrochloride - TTC Triphenyl tetrazolium chloride - TCA Trichloroacetic acid Other papers of this series are: Soyfer 1972; Soyfer et al. 1977; Soyfer and Kartel 1978     

Genetic variation and productivity of Populus trichocarpa and its hybrids. X. Trait correlations in young black cottonwood from four river valleys in Washington

 A common-garden study of Populus trichocarpa Torr. & Gray was established in spring 1986 with 128 clones collected from sites along two mesic (Hoh and Nisqually) and two xeric (Dungeness and Yakima) river valleys in Washington. Two replicate plantations, one in Puyallup and the other in Wenatchee, Wash., were established with this material. Over 2 years data were taken on stem growth, leaf/crown characters, spring/autumn phenology, and the incidence of Melampsora occidentalis leaf rust. Combining clones from all four sources, correlation/regression analyses were used to examine clonal stability of traits between test sites and trait relationships with stem growth; broad-sense heritabilities (H ²) and genetic correlations revealed the genetic strength of these traits. At Puyallup, many leaf/crown traits predicted stem growth moderately to very well (r ²>0.50), e.g., total leaf area (TLA) to diameter gave an r ² of 0.91 and current-terminal leaf size, of 0.79. Some regressions were quadratic, suggesting a threshold level in a trait (e.g., leaf size) beyond which stem growth levels off. Upper-crown TLA was more closely related to height than TLA of the lower sylleptics, but the reverse was true for diameter. A decline in r ² values from upper to lower crown positions was sharper for correlations of TLAs with height than with diameter. Thus, leaf area allocation seems to differentially affect stem growth. When autumn leaf fall (LF) and rust incidence (R) were regressed with growth, r ² values ranged from 0.58 to 0.71, but those of spring flush (SF) were only 0.10 to 0.12. Early LF and high R, both negatively affecting growth, had a strong geographic component as it occurred mainly on lower-elevation Yakima clones. At Wenatchee, field conditions were harsher and microsites more variable, so trait/growth relationships were weaker. Genetic correlations with growth revealed similar trends as phenotypic analyses. Unlike leaf/crown traits, clonal scores of LF, SF, and R were fairly stable across the two test sites (r ²: 0.58–0.80). These traits also showed strong genetic control (H ²: 0.96–0.98). The trait/growth relationships as well as trait stability within clones have implications for selecting clonal stock in poplar culture and conservation. Received: 23 February 1998 / Accepted: 7 May 1998