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Virulence of a nucleopolyhedrovirus to Neodiprion abietis (Hymenoptera: Diprionidae).

Different larval stages of balsam fir sawfly, Neodiprion abietis (Harris) (Hymenoptera: Diprionidae), were challenged by different concentrations of a nucleopolyhedrovirus in the laboratory to determine larval susceptibility to the virus and to test treatment effects of the virus on the sawfly survivors. The results indicated that younger larvae were more susceptible to the virus than older instars. The speed of larval death depended on the larval age and the virus concentration. Generally, the virus killed second or third instars in approximately 5 d and fourth or fifth instars in 10-12 d at concentrations of 10(7) polyhedral inclusion bodies (PIB) /ml. The virus had profound treatment effects on sawfly survivors. Feeding activity of the survivors was reduced by > 40% compared with that of the control group, pupal weight by approximately 25%, and adult emergence by > 30%. There was also a higher percentage of male adults in the virus-treated groups than in the control.

Animals↗

Influence of larval stage and virus inoculum on virus yield in insect host Neodiprion abietis (Hymenoptera: Diprionidae).

Virus yield produced by dead larvae of balsam fir sawfly, Neodiprion abietis (Harris) (Hymenoptera: Diprionidae), that had been infected at four different larval stages (second, third, fourth, or fifth instar) with two virus concentrations (10(5) polyhedral inclusion bodies (PIB) /ml or 10(7) PIB/ml), were analyzed and compared to determine the effects of instar and amount of virus inoculum on virus production. The results indicate that both larval stage and inoculation dosage significantly affect virus yield. On average, each dead larva produced 1.36-12.21 x 10(7) PIB, depending upon larval age and virus concentration of inoculation. Although each dead larva produced more PIB when it was inoculated in the fourth or fifth stage, inoculation of these larvae did not result in the highest virus yield because of low larval mortality. In terms of net virus return, third instars would maximize virus yield when they are inoculated with a virus concentration that can cause 95-100% larval mortality.

Animals↗

How do water transport and water storage differ in coniferous earlywood and latewood?

The goal of this research project was to determine the water transport behaviour of earlywood versus latewood in the trunk of 21-year-old Douglas-fir [Pseudostuga menziesii (Mirb.) Franco] trees. Specific conductivity (k(s)) and the vulnerability of xylem to embolism were measured on a single growth ring and in a subset of earlywood and latewood samples within the same ring. Earlywood/latewood ratio, trunk water potential (Psi) and relative water content (RWC) were used to predict differences in conductivities and vulnerability to embolism. Earlywood has about 11 times the k(s) of latewood, and up to 90% of the total flow occurred through the earlywood. Earlywood's vulnerability to embolism followed the same trend as that of the whole wood, with 50% loss of conductivity at -2.2 MPa (P(50)). Latewood was more vulnerable to embolism than earlywood at high Psi, but as Psi decreased, the latewood showed very little further embolism, with a P(50) <-5.0 MPa. The lowest trunk Psi estimated in the field was about -1.4 MPa, indicating that latewood and earlywood in the field experienced about 42% and 16% loss of k(s), respectively. The higher vulnerability to embolism in latewood than in earlywood at field Psi was associated with higher water storage capacity (21.8% RWC MPa(-1) versus 4.1% RWC MPa(-1), latewood and earlywood, respectively). The shape of the vulnerability curve suggests that air seeding through latewood may occur directly through pores in the margo and seal off at lower pressure than earlywood pores.

Tracheophyta↗

In vivo 13C NMR metabolite profiling: potential for understanding and assessing conifer seed quality.

High-resolution 13C MAS NMR spectroscopy was used to profile a range of primary and secondary metabolites in vivo in intact whole seeds of eight different conifer species native to North America, including six of the Pinaceae family and two of the Cupressaceae family. In vivo 13C NMR provided information on the total seed oil content and fatty acid composition of the major storage lipids in a non-destructive manner. In addition, a number of monoterpenes were identified in the 13C NMR spectra of conifer seeds containing oleoresin; these compounds showed marked variability in individual seeds of Pacific silver fir within the same seed lot. In imbibed conifer seeds, the 13C NMR spectra showed the presence of considerable amounts of dissolved sucrose presumed to play a protective role in the desiccation-tolerance of seeds. The free amino acids arginine and asparagine, generated as a result of storage protein mobilization, were detected in vivo during seed germination and early seedling growth. The potential for NMR to profile metabolites in a non-destructive manner in single conifer seeds and seed populations is discussed. It is a powerful tool to evaluate seed quality because of its ability to assess reserve accumulation during seed development or at seed maturity; it can also be used to monitor reserve mobilization, which is critical for seedling emergence.

Carbon Isotopes↗

The evolution of Ty1-copia group retrotransposons in gymnosperms.

A diverse collection of Ty1-copia group retrotransposons has been characterized from the genome of Picea abies (Norway spruce) by degenerate PCR amplification of a region of the reverse transcriptase gene. The occurrence of these retrotransposable elements in the gymnosperms was investigated by Southern blot hybridization analysis. The distribution of the different retrotransposons across the gymnosperms varies greatly. All of the retrotransposon clones isolated are highly conserved within the Picea (spruce) genus, many are also present in Pinus (pine) and/or Abies (fir) genera, and some share strongly homologous sequences with one or more of cedar, larch, Sequoia, cypress, and Ginkgo. Further subclones of one of the most strongly conserved retrotransposon sequences, Tpa28, were obtained from Ginkgo and P. abies. Comparisons of individual sequence pairs between the two species show nucleotide cross-homologies of around 80%-85%, corresponding to nucleotide substitution rates similar to those of nuclear protein-coding genes. Analysis of Tpa28 consensus sequences reveals that strong purifying selection has acted on this retrotransposon in the lineages connecting Ginkgo and Picea. Collectively, these data suggest, first, that the evolution of the Ty1-copia retrotransposon group in the gymnosperms is dominated by germ line vertical transmission, with strong selection for reverse transcriptase sequence, and, second, that extinction of individual retrotransposon types has been comparatively rare in gymnosperm species lineages compared with angiosperms. If this very high level of sequence conservation is a general property of the retrotransposons, then their extreme sequence diversity implies that they are extremely ancient, and the major element lineages seen today may have arisen early in eukaryote evolution. The data are also consistent with horizontal transmission of particular retrotransposons between species, but such a mechanism is unnecessary to explain the results.

Amino Acid Sequence↗

Modeling shoot water contents in high-elevation Picea rubens during winter.

During the winter of 1990-1991, a meteorological tower was established at an 880-m elevation site within the spruce-fir zone on Mt. Moosilauke, New Hampshire, USA. Hourly means of air, needle and trunk temperatures, wind velocity, relative humidity and solar radiation were recorded. On a weekly basis, shoots that had elongated during the preceding growing season were collected from four red spruce (Picea rubens Sarg.) trees and their relative water contents (RWC) determined. Cuticular resistances of needles from these shoots were measured four times during the winter.Measured meteorological parameters were used in a previously developed model to simulate changes in red spruce shoot RWC during the winter. The modeled results were compared to measured shoot RWCs. The predictive power of the model was improved when it was modified to include measured values of cuticular resistance and needle and trunk temperatures. The new version of the model accurately predicted RWC from late December 1990 to the beginning of April 1991, after which spring recharge appeared to occur. We conclude that water lost from foliage was easily replaced by stored reserves and that uptake of water by the roots was not required to maintain an adequate foliar water content during the winter.

Journal Article↗

Seasonal biochemical changes in coniferous forest canopies and their response to fertilization.

Seasonal changes in concentrations of total nitrogen, free amino acids, chlorophyll, starch and sugar were measured in foliage from fertilized and unfertilized conifer forests in New Mexico and Oregon. In the New Mexico Douglas-fir (Pseudotsuga menziesii var glauca (Beissn.) Franco) forest, fertilization resulted in elevated foliar nitrogen concentrations on all dates, from an average of 9 mg g(-1) in unfertilized trees to 14 mg g(-1) in fertilized trees. In the Oregon western hemlock (Tsuga heterophylla (Raf.) Sarg.) forest, fertilization increased total N by only 15%, from 13 mg g(-1) in unfertilized trees to 15 mg g(-1) in fertilized trees. Foliar nitrogen concentrations on a weight basis were lowest in winter and spring, but did not vary seasonally when expressed on a leaf area basis. Chlorophyll concentrations increased with fertilization and had greater seasonal variation than did total nitrogen concentrations. Chlorophyll concentrations were significantly higher during the growing season than in the winter and spring months. Fertilization did not result in major changes in the proportion of total nitrogen in chlorophyll at either the Oregon or the New Mexico site. Concentrations of free amino acids varied with date and fertilization treatment; in New Mexico, amino acids were highest in the winter sample, whereas in Oregon, they were lowest in winter and spring. At both sites, amino acid concentrations were significantly higher in fertilized trees than in control trees on most dates and the ratios of amino acid-N to total N were also significantly higher in fertilized trees. For both sites, starch concentrations were nearly zero for most of the year, but increased sharply just before bud break and initiation of new growth in the spring. Although fertilization resulted in increased nitrogen concentrations in foliage at both sites, the response in New Mexico was much greater than in Oregon. These results are in agreement with forest productivity data that suggest that growth in the New Mexico site is limited by nitrogen, whereas in the Oregon site it is not.

Journal Article↗

Interaction between indole-3-acetic acid and ethylene in the control of tracheid production in detached shoots of Abies balsamea.

We investigated the interaction between indole-3-acetic acid (IAA) and ethylene in the regulation of the seasonal periodicity of tracheid production in 1-year-old balsam fir (Abies balsamea (L.) Mill.) cuttings collected at different times during the dormant period. The cuttings were left with their buds intact or were debudded and treated either apically with IAA or 2-chloroethylphosphonic acid (Ethrel) in lanolin, laterally with IAA or Ethrel in lanolin, or basally with Ethrel, Co(2+) or Ag(+) in deionized water. The treated cuttings were then cultured for up to 5 weeks under controlled environment conditions favorable for cambial growth. No change in ethylene evolution was detected during the rest-quiescence transition, when IAA-induced tracheid production increased. The induction of cambial reactivation by IAA was associated with a rise in ethylene evolution, but there was no consistent relationship among IAA concentration, tracheid number and ethylene emission. Neither Ethrel, Co(2+) nor Ag(+) affected tracheid production when applied basally, except for 10 and 100 micro M Ethrel and 100 micro M Co(2+), which were inhibitory. In contrast, ethylene evolution was promoted by Ethrel and inhibited by Co(2+), whereas Ag(+) had no effect. Similarly, applying Ethrel apically or laterally increased ethylene evolution, but did not promote tracheid production except in the treatment in which 1 mg Ethrel g(-1) lanolin was applied laterally to cuttings treated apically with 0.1 mg IAA g(-1) lanolin, and in the treatment in which 10 mg Ethrel g(-1) lanolin was applied laterally to budded cuttings. We conclude that (1) ethylene evolution is not specifically associated with IAA-induced tracheid production, (2) ethylene does not mimic the promoting effect of IAA on tracheid production, and (3) ethylene can promote tracheid production, but only when its application results in a localized unphysiologically high concentration in the cambial region, which, in turn, induces an accumulation of IAA.

Journal Article↗

Pollen management for intensive seed orchard production.

Artificially increasing pollen supply (supplemental mass pollination (SMP)) to conifer seed orchards has the potential to increase seed yields and improve the genetic worth of seed crops that would otherwise suffer from the detrimental effects of pollen contamination and unbalanced paternal contribution. However, success rates, measured as the proportion of seed fertilized by SMP, have been low. This review examines the concepts underlying SMP and presents data for two SMP field trials with Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and white/Engelmann spruce (Picea glauca (Moench) Voss, Picea engelmannii Parry ex Engelm.). The trial results are discussed with respect to pollen fertility, pollination technique, and competing pollen cloud density. I also summarize methods for ensuring the successful handling of pollen ex situ.

Journal Article↗

Laterally applied Ethrel causes local increases in radial growth and indole-3-acetic acid concentration in Abies balsamea shoots.

The terminal (1-year-old) shoot of quiescent, two-year-old balsam fir (Abies balsamea (L.) Mill.) seedlings was ringed with lanolin containing 0, 1 or 10 mg g(-1) Ethrel, an ethylene-generating compound, and cultured for 6 weeks under environmental conditions favorable for growth. Bud break and the elongation of the current-year terminal shoot were monitored, and the subjacent previous-year terminal shoot that had been treated with Ethrel was harvested to measure stem radial growth by microscopy, shoot ethylene evolution by gas chromatography, and cambial region indole-3-acetic acid (IAA) concentration by combined gas chromatography-mass spectrometry. Compared with the lanolin controls, Ethrel at 1 and 10 mg g(-1) did not affect bud break or longitudinal growth, but stimulated tracheid production and bark increment up to about 2-fold at the application site, though not above or below it. In addition, the 1 and 10 mg g(-1) Ethrel treatments increased the cambial region IAA concentration about 3-fold and the evolution of ethylene at least 40-fold at the application site, compared with unwounded portions of both treated and control shoots. The 10 mg g(-1) Ethrel treatment also stimulated ethylene evolution about 10-fold, both above and below the application site. However, this stimulation was not associated with an elevation in cambial region IAA concentration. Similarly, the lanolin control treatment increased ethylene evolution at the application site about 10-fold, without affecting the cambial region IAA concentration. Our results suggest that the localized stimulation of radial growth in woody shoots ringed with Ethrel is mediated by an increase in IAA concentration, which in turn is induced by a threshold, abnormally high concentration of Ethrel-derived ethylene.

Journal Article↗

Root growth potential as an indicator of drought stress history.

Container-grown quiescent Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) seedlings were air dried to plant water potentials of -0.2, -2.2 or -3.8 MPa (unstressed, moderate, and severe stress treatments, respectively). Trees from each treatment were either placed in root mist chambers held at 10, 20, or 28 degrees C for 28 days and root growth potential (RGP) and plant water potential (PWP) measured weekly, or potted in a 1/1 mix of peat and vermiculite, watered only once, and height growth and survival recorded after 10 weeks in an unheated greenhouse. Root growth potential of unstressed trees was greater than that of moderately stressed trees at all temperatures. Root growth potential of severely stressed trees was zero. Predawn plant water potentials of unstressed and moderately stressed trees were initially high, fell to -0.5 to -0.8 MPa, and then increased. Predawn plant water potential of severely stressed trees declined continuously over the 28-day experiment. Survival and height growth of the severely stressed trees were reduced compared to the unstressed and moderately stressed trees. Among the root growth potential measurements, RGP measured after 7 days at 10 degrees C was most sensitive to drought stress history and revealed differences in vigor that were not apparent from the survival and height growth data.

Journal Article↗

Influence of ectomycorrhizal fungal inoculation on growth and root IAA concentrations of transplanted conifers.

We determined whether in vitro plant growth regulator production by mycorrhizal fungi is correlated with conifer seedling growth and root IAA concentrations. Container-grown seedlings of interior Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), lodgepole pine (Pinus contorta Dougl.) and ponderosa pine (Pinus ponderosa Dougl.) were inoculated at seeding with ectomycorrhizal fungi having a high, moderate or low capacity to produce either IAA or ethylene in vitro. Inoculated seedlings were grown for one season in the nursery, harvested in December, cold stored over winter and then transplanted to either a nursery field or a forest site in the spring. Seedling morphology and endogenous IAA in roots were measured immediately after cold storage and again six and 12 months after transplanting. Morphological responses to inoculation varied among different mycorrhizal fungi. Free IAA concentration of roots was increased in some inoculation treatments for all conifer species. In seedlings transplanted to a nursery field, in vitro ethylene-producing capacity of the ectomycorrhizal fungi was highly correlated with more morphological features than in vitro IAA-producing capacity. Both IAA- and ethylene-producing capacity were significantly correlated with more morphological features in seedlings transplanted to a forest site than in seedings transplanted to a nursery field. One year after transplanting, only in vitro IAA-producing capacity was correlated with endogenous IAA concentration of roots of the inoculated seedlings. We conclude that growth responses of conifer seedlings can be partially influenced by IAA and ethylene produced by ectomycorrhizal fungal symbionts.

Journal Article↗

Shoot structure, light interception, and distribution of nitrogen in an Abies amabilis canopy.

We studied the effects of variation in shoot structure and needle morphology on the distributions of light and nitrogen within a Pacific silver fir (Abies amabilis (Dougl.) Forbes) canopy. Specifically, we investigated the role of morphological shade acclimation in the determination of resource use efficiency, which is claimed to be optimal when the distribution of nitrogen within the canopy is directly proportional to the distribution of intercepted photosynthetically active radiation (PAR). Shoots were collected from different heights in the crowns of trees representing four different size classes. A new method was developed to estimate seasonal light interceptance (SLI, intercepted PAR per unit needle area) of the shoots using a model for the directional distribution of above-canopy PAR, measurements of shoot silhouette area and canopy gap fraction in different directions. The ratio SLI/SLI(o), where the reference value SLI(o) represents the seasonal light interceptance of a spherical surface at the shoot location, was used to quantify the efficiency of light capture by a shoot. The ratio SLI/SLI(o) doubled from the top to the bottom of the canopy, mainly as a result of smaller internal shading in shade shoots than in sun shoots. Increased light-capturing efficiency of shade shoots implies that the difference in intercepted light by sun shoots versus shade shoots is much less than the decrease in available light from the upper to the lower canopy. For example, SLI of the five most sunlit shoots was only about 20 times greater than the SLI of the five most shaded shoots, whereas SLI(o) was 40 times greater for sun shoots than for shade shoots. Nitrogen content per unit needle area was about three times higher in sun needles than in shade needles. This variation, however, was not enough to produce proportionality between the amounts of nitrogen and intercepted PAR throughout the canopy.

Journal Article↗

Freezing behaviors in leaf buds of cold-hardy conifers visualized by NMR microscopy.

1H-Nuclear magnetic resonance (NMR) microscopy was used to study freezing behavior in wintering leaf buds of Momi fir (Abies firma Sieb. et Zucc.) and Japanese red pine (Pinus densiflora Sieb. et Zucc.). The images acquired predominantly reflected the density of mobile (i.e., non-ice) protons mainly from unfrozen water. By comparing images taken at various subfreezing temperatures, we determined which tissues produced the high and low temperature exotherms detected by differential thermal analyses. Typical extra-organ freezing was successfully imaged in leaf buds of A. firma. The bud scales readily froze at -7 degrees C, but shoot primordia remained supercooled to -14 degrees C in December buds and to -21 degrees C in March buds. The size of supercooled shoot primordia was reduced with decreasing temperature, indicating a gradual decrease in water content of the shoot primordia. In contrast, the signal from shoot primordia of P. densiflora disappeared between -7 and -14 degrees C, corresponding to the high temperature exotherm at -8 degrees C, indicating extracellular freezing of the shoot primordia. The xylem and bark tissues readily froze at -7 degrees C in A. firma and between -7 and -14 degrees C in P. densiflora. We conclude that NMR microscopy can noninvasively provide more spatially specific information about freezing behavior in leaf buds than traditional methods such as differential thermal analysis. In particular, it allows the organized and harmonized freezing behaviors in complex organs to be visualized directly thereby revealing the diversity of mechanisms involved in freezing behaviors.

Journal Article↗

Stomatal behavior of four woody species in relation to leaf-specific hydraulic conductance and threshold water potential.

Midday stomatal closure is mediated by the availability of water in the soil, leaf and atmosphere, but the response to these environmental and internal variables is highly species specific. We tested the hypothesis that species differences in stomatal response to humidity and soil water availability can be explained by two parameters: leaf-specific hydraulic conductance (K(L)) and a threshold leaf water potential (Psi(threshold)). We used a combination of original and published data to estimate characteristic values of K(L) and Psi(threshold) for four common tree species that have distinctly different stomatal behaviors: black cottonwood (Populus trichocarpa Torr. & Gray.), Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), red alder (Alnus rubra Bong.) and western hemlock (Tsuga heterophylla (Raf.) Sarg.). We used the values to parameterize a simple, nonelastic model that predicts stomatal conductance by linking hydraulic flux to transpirational flux and maintaining Psi(leaf) above Psi(threshold). The model successfully predicted fundamental features of stomatal behavior that have been reported in the literature for these species. We conclude that much of the variation among the species in stomatal response to soil and atmospheric water deficits can be explained by K(L) and Psi(threshold). The relationship between Psi(threshold) and xylem vulnerability to cavitation differed among these species.

Journal Article↗

Dependence of winter water relations of mature high-elevation Picea engelmannii and Abies lasiocarpa on summer climate.

Water relations of Engelmann spruce (Picea engelmannii Parry) and subalpine fir (Abies lasiocarpa (Hook.) Nutt.) trees growing at an elevation of 3230 m on Mt. Evans, Colorado, USA, were studied during the winters of 1995-1996 and 1996-1997. During both winters, current-year and 1-year-old shoots were collected weekly and their relative water contents (RWC) determined. Measured meteorological parameters were used in a conifer winter water relations model, WINWAT, to simulate changes in shoot RWC of P. engelmannii and A. lasiocarpa during the winter. The model failed to predict shoot RWCs in 1996-1997 when calibrated with 1995-1996 data. The cold early summer of 1995 inhibited xylem formation, which appears to have caused lower rates of water recharge to the needles during the 1995-1996 winter than during the 1996-1997 winter. We conclude that summer climate strongly affects winter water relations in these subalpine species, and that changes in both summer and winter climate must be considered when predicting future ranges of these species.

Altitude↗

Relationship between carbohydrate concentration and root growth potential in coniferous seedlings from three climates during cold hardening and dehardening.

Greenhouse-cultured, container-grown seedlings of Aleppo pine (Pinus halepensis Mill.), radiata pine (Pinus radiata D. Don), and interior Douglas-fir (Pseudotsuga menziesii var. glauca (Beissn.) Franco) were cold acclimated and deacclimated in growth chambers over 24 weeks. Needle and root cold hardiness and root growth potential (RGP) were measured weekly. Root, needle and stem analyses for soluble sugars and starch were performed biweekly. In all tissues, there was a close correspondence between cold hardiness and the absolute concentration of soluble sugars, as well as between the increase and decrease in concentration of soluble sugars during cold hardening and dehardening, respectively, supporting the theory that soluble sugars function as cryoprotectants in plant tissues. The magnitude of starch concentration did not parallel the magnitude of the cold hardiness attained, and changes in starch concentration were related to production and consumption factors, rather than timing of changes in cold hardiness. The rise and fall of RGP paralleled the rise and fall of total carbohydrate concentration in roots. The behavior of the three species was surprisingly similar, considering the different climates to which they are adapted.

Carbohydrates↗

Response of old-growth conifers to reduction in stand density in western Oregon forests.

The positive growth response of healthy young trees to density reduction is well known. In contrast, large old trees are usually thought to be intrinsically limited in their ability to respond to increased growing space; therefore, density reduction is seldom used in stands of old-growth trees. We tested the null hypothesis that old-growth trees are incapable of responding with increased growth following density reduction. The diameter growth response of 271 Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), ponderosa pine (Pinus ponderosa Dougl. ex Laws) and sugar pine (Pinus lambertiana Dougl.) trees ranging in age from 158 to 650 years was examined 20 to 50 years after density reduction. Density reduction involved either light thinning with removal of less vigorous trees, or shelterwood treatments in which overstory trees were not removed. Ratios of basal area growth after treatment to basal area growth before treatment, and several other measures of growth, all indicated that the old trees sometimes benefited and were not harmed by density reduction. Growth increased by 10% or more for 68% of the trees in treated stands, and nearly 30% of trees increased growth by over 50%. This growth response persisted for at least 20 years. During this 20-year period, only three trees in treated stands (1.5%) exhibited a rapid decrease in growth, whereas growth decreased in 64% of trees in untreated stands. The length of time before a growth response to density reduction occurred varied from 5 to 25 years, with the greatest growth response often occurring 20 to 25 years after treatment. These results have important implications both for the basic biology of aging in woody plants as well as for silvicultural practices in forests with old-growth trees.

Forestry↗