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Non-mycorrhizal species such as Banksia (Proteaceae) that depend on root exudates to acquire phosphorus (P) are prominent in south-western Australia, a biodiversity hotspot on severely P-impoverished soils. We investigated the consequences of an exudate-releasing P-mobilising strategy related to control of iron (Fe) acquisition in two Banksia species, B. attenuata R.Br. and B. laricina C. Gardner, that differ greatly in their geographical distribution and rarity. We undertook solution culture experiments to measure root-mediated Fe reduction (FeR) in non-cluster and cluster roots at four stages of cluster-root development, and whole root systems for plants grown at 2 to 300 μM Fe (as Fe-EDTA). As a positive control, we used Pisum sativum (cv. Dunn) to validate the FeR assay. Unlike typical Strategy I species, both Banksia species showed no significant variation in FeR, for either cluster or non-cluster roots, when grown at a wide range of Fe supply. For roots of different developmental stages, we measured a range for B. attenuata cluster roots of 0.13 ± 0.03 to 1.29 ± 0.14 μmol Fe3+ reduced g−1 FW h−1 and 0.56 ± 0.11 to 1.10 ± 0.24 μmol Fe3+ reduced g−1 FW h−1 in non-cluster roots. Similarly, for B. laricina cluster-roots, FeR ranged from 0.22 ± 0.07 to 1.21 ± 0.37 μmol Fe3+ reduced g−1 FW h−1, and in non-cluster roots from 0.56 ± 0.11 to 0.71 ± 0.08 μmol Fe3+ reduced g−1 FW h−1. We also observed only minor differences for whole-root system FeR, and even though B. attenuata showed signs of leaf Fe deficiency in the 2 μM Fe treatment, its FeR was the lowest of both species across all treatments at 0.079 ± 0.009 μmol Fe3+ reduced g−1 FW h−1, compared with the fastest rate of 0.20 ± 0.014 μmol Fe3+ reduced g−1 FW h−1 for B. laricina in the 28 μM Fe treatment. Taking plants through a pulse from low to high Fe, then back to low Fe supply did not elucidate any significant response in FeR. Although Fe acquisition is tightly controlled in the investigated Banksia species, such control is not based on regulation of FeR, which challenges the model that is commonly accepted for Strategy I species.

Due to its contribution to plant drought tolerance, arbuscular mycorrhizae (AM) may play an important role in the revegetation of degraded pastures in semi-arid and arid regions. Salsola laricina, an important forage plant in Iran, belongs to predominantly non-mycotrophic Chenopodiaceae, but field observations suggest that it forms functional mycorrhizae. We therefore, established a greenhouse experiment to test the mycorrhizal response of this species at four levels of soil moisture and to determine the contribution of AM to the drought tolerance of this species. The plants were grown in sterilized soil and either left non-inoculated or inoculated with four AM fungal isolates originating from an S. laricina field site to investigate also the functional variability of sympatric AM fungal species. Root colonization of S. laricina by AM fungi was found in all the inoculated treatments, and mycorrhizae clearly improved the plants' growth and P uptake. The mycorrhizal responses, i.e., the differences between mycorrhizal and non-mycorrhizal plants, were most pronounced at the lowest soil moisture level of 25% field capacity, which strongly suggests that mycorrhiza contributes to the drought tolerance of S. laricina. Differential effects of the four inoculated AM fungal isolates, independent of their root colonization levels, indicate differential compatibility of the isolates with this host plant species. The findings of the study have important implications for the revegetation of degraded pastures with S. laricina, as they show that AM should be considered in this process.

Larix laricina (eastern larch, tamarack) is a transcontinental North American conifer with a prominent disjunction in the Yukon isolating the Alaskan distribution from the rest of its range. We investigate whether in situ persistence during the last glacial maximum (LGM) or long‐distance postglacial migration from south of the ice sheets resulted in the modern‐day Alaskan distribution. We analyzed variation in three chloroplast DNA regions of 840 trees from a total of 69 populations (24 new sampling sites situated on both sides of the Yukon range disjunction pooled with 45 populations from a published source) and conducted ensemble species distribution modeling (SDM) throughout Canada and United States to hindcast the potential range of L. laricina during the LGM. We uncovered the genetic signature of a long‐term isolation of larch populations in Alaska, identifying three endemic chlorotypes and low levels of genetic diversity. Range‐wide analysis across North America revealed the presence of a distinct Alaskan lineage. Postglacial gene flow across the Yukon divide was unidirectional, from Alaska toward previously glaciated Canadian regions, and with no evidence of immigration into Alaska. Hindcast SDM indicates one of the broadest areas of past climate suitability for L. laricina existed in central Alaska, suggesting possible in situ persistence of larch in Alaska during the LGM. Our results provide the first unambiguous evidence for the long‐term isolation of L. laricina in Alaska that extends beyond the last glacial period and into the present interglacial period. The lack of gene flow into Alaska along with the overall probability of larch occurrence in Alaska being currently lower than during the LGM suggests that modern‐day Alaskan larch populations are isolated climate relicts of broader glacial distributions, and so are particularly vulnerable to current warming trends., Range disjunctions represent natural laboratories to examine the interplay between long‐distance migration and refugial persistence in biome development. Larix laricina (larch) is a transcontinental North American conifer with a disjunction in the Yukon isolating its Alaskan distribution. Using chloroplast‐microsatellite analysis and species distribution modeling, we provide evidence for the glacial persistence and long‐term isolation of larch in Alaska.

Objectives Gypsophila species have very high medicinal and commercial importance and contain interesting natural substances. However, there is no report on the essential oil or fatty acid composition of any Gypsophila species. This prompted us to investigate the essential oil and fatty acid composition of Gypsophila laricina Schreb. Materials and Methods Plant materials were collected during the flowering period. The essential oil composition of the aerial parts of G. laricina Schreb. was analyzed by gas chromatography and gas chromatography-mass spectrometry. The fatty acid compositions were analyzed by gas chromatography-mass spectrometry. Results Sixty-six and ten compounds were identified in the essential oil and fatty acid of G. laricina Schreb., respectively. The major components of the essential oil were hexadecanoic acid (27.03%) and hentriacontane (12.63%). The main compounds of the fatty acid were (Z,Z)-9,12- octadecadienoic acid methyl ester (18:2) 40.4%, (Z)-9-octadecenoic acid methyl ester (18:1) 35.0%, and hexadecanoic acid methyl ester (16:0) 13.0%. Conclusion The results showed that the fatty acid composition is rich in polyunsaturated fatty acids. The essential oils of G. laricina Schreb. were dominated by fatty acid derivatives and n-alkanes. We think the results obtained from this research will stimulate further research on the chemistry of Gypsophila species.

Essentialoil composition of Gypsophila turcicaHamzaoğlu, Gypsophila pinifoliaBoiss. & Hausskn., G. tuberculosa Hub.-Mor., G. eriocalyxBoiss. and G. laricina Schreb. were analyzed by means of gas chromatography-massspectrometry (GC-MS). Thirty six, fourty four, sixty six, forty one and sixtyone compounds were identified in the essential oils of G. turcica, G. pinifolia,G. laricina, G. tuberculosa and G. eriocalyxrespectively. The major components were determined hentriacontane (12.93 ±0.4%), 1-octadecanol (8.97 ± 0.1%), hexahydrofarnesyl acetone (6.9 ± 0.09%) andpentacosane (6.63 ± 0.08%) in G. turcica oil, hexadecanoic acid (17.6 ±0.4%), 1-tetradecanol (7.6 ± 0.1%) and phytol (5.63 ± 0.05%) in G. pinifoliaoil, octacosane (6.83%), eicosanal (6.19%), triacontane (6.03%) and heneicosane(5.78%) for G. eriocalyx, hexadecanoic acid (25.3%, 27.0%) and hentriacontane(13.0%, 12.6%) for G. tuberculosa and G. laricina,respectively. Antibacterial activity of G. eriocalyx, G. tuberculosis and G. laricinawere investigated against Gram negative (Escherichiacoli) and Gram positive (Staphylococcusaureus) bacteria., Essential oil composition of Gypsophila turcica Hamzaoğlu, Gypsophila pinifolia Boiss. & Hausskn., G. tuberculosa Hub.-Mor., G. eriocalyx Boiss. and G. laricina Schreb. were analyzed by means of gas chromatography-mass spectrometry (GC-MS). Thirty six, fourty four, sixty six, forty one and sixty one compounds were identified in the essential oils of G. turcica, G. pinifolia, G. laricina, G. tuberculosa and G. eriocalyx respectively. The major components were determined hentriacontane (12.93 ± 0.4%), 1-octadecanol (8.97 ± 0.1%), hexahydrofarnesyl acetone (6.9 ± 0.09%) and pentacosane (6.63 ± 0.08%) in G. turcica oil, hexadecanoic acid (17.6 ± 0.4%), 1-tetradecanol (7.6 ± 0.1%) and phytol (5.63 ± 0.05%) in G. pinifolia oil, octacosane (6.83%), eicosanal (6.19%), triacontane (6.03%) and heneicosane (5.78%) for G. eriocalyx, hexadecanoic acid (25.3%, 27.0%) and hentriacontane (13.0%, 12.6%) for G. tuberculosa and G. laricina, respectively. Antibacterial activity of G. eriocalyx, G. tuberculosis and G. laricina were investigated against Gram negative (Escherichia coli) and Gram positive (Staphylococcus aureus) bacteria.

Three new isopimarane-type diterpenoids, botrysphins G-I (1–3), a new muurolane-type sesquiterpenoid, 11,12-dihydroxylentideusether (4), and two new triketides, 4-dechlorobotrysphone C (5) and 4,5-dihydroxy-3-methoxy-6-undecanoyloxy-2-cyclohexen-1-one (6), together with one known diterpenoid, sphaeropsidin A (7), one sesquiterpenoid, lentideusether (8), and one triketide sphaeropsidone (9), were isolated from culture of the fungus Botrysphaeria laricina associated with the moss Rhodobryum umgiganteum. The structures of the new compounds were established on the basis of extensive spectroscopic techniques including HRMS and 1D and 2D NMR data. Compounds 1 and 2 exhibited NO inhibitory activity with IC50 values of 13.9 μM and 41.9 μM, respectively. At the same time, these two compounds showed quinone reductase inducing activity with 2.7-fold of induction for 1 at 12.5 μM and 1.6-fold for 2 at 25.0 μM.

The phenology of trees is highly susceptible to changing global temperatures. Leaf budburst advances with increasing spring temperatures, but can also be delayed when warmer winters reduce chilling exposure. Results from long-term observations show that increasing temperatures have triggered advanced budburst in the past decades, but some studies also show that budburst advance has slowed recently. Here, we conducted an experiment with five temperate deciduous tree species (Acer rubrum L., Larix laricina (Du Rois) K. Koch, Populus tremuloides Michx., Quercus ellipsoidalis E. j. Hill, Betula papyrifera Marsh.) and one invasive species (Rhamnus cathartica L.) in Minnesota, USA, to assess the impact of chilling on the timing of leaf budburst. We collected twigs over two winter seasons (2011/2012 and 2012/2013) on a biweekly basis and exposed them to spring-like temperatures of 21 °C/16 °C day and night, long day photoperiod (16 h). We found a significant relationship of advanced budbreak with increased chilling for all species tested (P < 0.001) and significant differences in the timing to budburst among all species (P < 0.001). Acer rubrum responded strongly to chilling, showing a very steep linear decline in days to budburst with increased exposure to chilling. On the other end of the spectrum, L. laricina responded least to increases in chilling. These results suggest that rising global temperatures will likely have diverse impacts on tree species with potential implications for species interactions such as competition.

Three new triketides, botrysphones A-C (1-3) and six new isopimarane-type diterpenoids, botrysphins A-F (4-9), together with the known triketides sphaeropsidone (10) and chlorosphaeropsidone (11) and diterpenoids sphaeropsidins A and B (12 and 13), were obtained from culture of the fungus Botrysphaeria laricina associated with the moss Rhodobryum umgiganteum. The structures of the new compounds were established on the basis of extensive spectroscopic techniques including HRMS and 1D and 2D NMR data. Compounds 7 and 12 showed significant quinone reductase inducing activity in Hepa 1c1c7 cells.

Ethnopharmacological relevance Larix laricina , a native tree of North America, is a highly respected medicinal plant used for generations by Indigenous Peoples across its range, including the Cree of northern Quebec who use the bark to treat symptoms of diabetes. This study investigates the antioxidant capacity and bioavailability of active constituents identified in L. laricina bark extracts. Materials and methods (1) Oxygen radical absorbance capacity (ORAC) assay was employed to test antioxidant capacity of organic extracts (80% ethanol) from bark of L. laricina as well as fractions, isolated compounds, and media samples collected during permeability assays. (2) Caco-2 cell monolayer cultures were used to determine the permeability of identified antioxidants, which were quantified in basolateral media samples using liquid chromatography – tandem mass spectrometry (HPLC-ESI-MS/MS). Results Crude ethanolic extract possessed strong antioxidant potential in vitro (7.1±0.3 Trolox equivalents (TE) μM/mg). Among the 16 L. laricina fractions obtained by chromatographic separation, fraction 10 (F10) showed the highest antioxidant capacity (21.8±1.7 µm TE/mg). Among other identified antioxidants, the stilbene rhaponticin (isolated from F10) was the most potent (24.6±1.1 µm TE/mg). Caco-2 transport studies revealed that none of the identified compounds were detectable in basolateral samples after 2-h treatment with crude extract. In monolayers treated with F10 (60% rhaponticin), small quantities of rhaponticin were increasingly detected over time in basolateral samples with an apparent permeability coefficient (P app ) of 1.86×10 −8 cm/s (0–60 min). To model potential effects on blood redox status, we evaluated the antioxidant capacity of collected basolateral samples and observed enhanced activity over time after exposure to both extract and F10 (75 μg/mL) relative to control. Conclusions By profiling the antioxidant constituents of L. laricina bark, we identified rhaponticin as the most potent oxygen radical scavenger and observed low permeability in Caco-2 cell monolayers but an increase in basolateral antioxidant capacity.

The current view of the geographical ranges of lichens is often distorted by overly narrow or overly broad applications of names and by insufficient survey of most regions of the world. Here we present several cases where species of Teloschistaceae formerly thought to be limited to rather small territories in the western or eastern parts of Eurasia are in fact widespread in northern Eurasia. We support our findings with ITS nrDNA data in several new trees showing relationships in the genera Athallia, Calogaya, Caloplaca, Flavoplaca and Gyalolechia. The widespread species have little in common, except that most of them reproduce both sexually and asexually, and we discuss the possible influence of the combined reproduction on geographical range. Calogaya bryochrysion, Calogaya saxicola, Gyalolechia epiphyta and Gyalolechia ussuriensis are new combinations. Calogaya alaskensis is a younger synonym for C. bryochrysion. The generally arctic-alpine Calogaya bryochrysion also occurs on the bark of solitary trees in dry parts of the Altai Mountains. The Australian Flavoplaca cranfieldii is a younger synonym of F. flavocitrina. Gyalolechia epiphyta has been described numerous times, from different regions and substrata, as Caloplaca juniperi, C. laricina, C. tarani, Gyalolechia arizonica and G. juniperina. The name Gyalolechia xanthostigmoidea has recently been used for G. epiphyta, but it represents a distinct taxon. Gyalolechia ussuriensis is closely related to and morphologically indistinguishable from G. persimilis, but they have a different ecology and distribution and we regard them as distinct species. Caloplaca juniperina Tomin is lectotypified.

Certain tree species of Aquilaria and Gyrinops of family Thymelaeaceae are capable of producing a valuable resin called agarwood as a result of a self-defense mechanism to protect the internal tissue damage caused by pathogenic microorganisms entering via wounds occurred due to natural or artificial causes. The aromatic properties of agarwood oil are extraordinary high and therefore it is extensively used for incense, perfume and for traditional medicine in different parts of the world. Among the microorganisms which are capable of causing agarwood formation inducement, fungal species are believed to be the most influential agents. The ability of agarwood production in Gyrinops walla, believed to be endemic to Sri Lanka was recently identified. Due to the legal constraints of exporting agarwood and other products extracted from G. walla, Aquilaria crassna was introduced to the country as a high income plantation crop by private sector companies. However, studies were not conducted to identify the associated fungi in these species when grown under the climatic and geological conditions of Sri Lanka, which could be potential inocula for producing agarwood in artificial manner. Therefore the present study attempted to identify the associated fungal species in various parts of G. walla and A. crassna grown in the wet zone in Sri Lanka. For this reason, leaves, un-infected normal stem tissues and agarwood formed stem tissues were extracted from G. walla and A. crassna trees growing in Neboda and Ingiriya region respectively by non-destructive sampling. Those tissues were surface sterilised and separately grown in Potato Dextrose Agar at room temperature for 7 days in the laboratory. The morphological and genetic characteristics were then used for the identification of different fungal species. Trichoderma harzianum, Botryosphaeria laricina, Aspergillus terreus, A. sojae, A. niger, Fusarium sp, one unidentified Botryosphaeria sp and Sarcinomyces sp were identified in the agarwood resinous tissues extracted from G. walla. B. laricina, A. terreus, one unidentified Botryosphaeria sp and F. equiseti were identified from non-resinous stem tissue samples while T. harzianum, Colletotrichum gloeosporioide sand A. terreus were identified from the leaves of G. walla. B. laricina and one unidentified Aspergillus sp were identified from resinous tissue samples of A. crassna while B. laricina and Diaparthe amygdale were identified from non-resinous tissues and leaf samples respectively. The tests are currently underway to identify the most influential fungal species among the above to form agarwood in artificial manner. Keywords: Gyrinops walla, Aquilaria, Associated fungi, Agarwood, Fungal species Acknowledgement: Sadaharitha Plantations Limited and the Centre for Forestry and Environment, University of Sri Jayewardenepura.

Background. Changing climatic conditions cause changes in tree phenology, which is important for the survival of species and their spread in local ecosystems. This study concentrated on long-term (1957–2016 or 1980–2016) observations of 11 conifer species introduced to Lithuania with the aim to evaluate the response of their bud swelling phenophase to climate warming, considering the hardiness zones of their natural habitats. Materials and Methods. Sequences of the start date of the bud swelling phenophase of 11 introduced conifer species (Abies veitchii, Larix decidua, L. kaempferi, L. laricina, L. × marschlinsii, L. sibirica, L. sukaczewii, Picea mariana, Pinus mugo, Taxus baccata and Thuja occidentalis) were analysed. Data were collected from the paper archives of Kaunas Botanical Garden of Vytautas Magnus University (VMU). Sequences of bud swelling start dates were transformed into sequences of number of days from the beginning of the year. Results. Results indicated an advance of the bud swelling phenophase of ten conifer species introduced to Lithuania (the speed of changes varied from –0.10 to –0.98 days/year in the 1980–2016 period) and a delay of Larix sukaczewii (respectively, +0.12 days/ year) of the bud swelling phenophase, mainly influenced by the March temperature. Conclusions. The connection between the observed conifer species hardiness zone of the natural habitat and the reaction of the bud swelling phenophase to climate warming could be observed only when species from one genus were compared. To confirm this phenomenon, a research on a larger amount of introduced species with wider habitat hardiness zone options is needed in future.

Exotic larch (Larix decidua Mill., Larix kaempferi (Lamb.) Carr. and Larix sibirica Ledeb.) and their hybrids have been introduced into Canada to test adaptation and growth for reforestation purposes. For tree breeding opera- tions, provenance trials and seed orchards of exotic larches and their hybrids have been established in arboreta adjacent to natural forest stands of the indigenous species Larix laricina (Du Roi) K. Koch. This proximity offers an opportunity to measure spontaneous hybridization and the recruitment of hybrids. Using a combination of two chloroplast and three mitochondrial DNA markers, we estimated the rate of spon- taneous hybridization taking place between native (L. laricina) and exotic (L. decidua, L. kaempferi, L. sibirica) species of larch in two arboreta. More than 5,000 seeds and 1,000 recruits from the two experimental sites were sampled and genetically identified. The occurrence of sponta- neous hybridization between L. laricina and the exotics was found both in seeds and from recruits freely established near the plantations. A low hybridization rate (3 % or less) was observed among the seeds of L. laricina maternal trees. Spontaneous native-exotic hybrids were also observed to es- tablish and survive in the environment under the current climatic conditions at a similarly low rate. However, a much higher and variable rate of establishment was observed for recruits with exotic components (up to 34.6 % at one site). These results indicate that the spontaneous hybridization and the recruitment of hybrid and exotic recruits do occur and should be taken into consideration in the management and establishment of plantations of fast-growing species with ex- otic components.

Understanding the natural revegetation of forests disturbed by the dumping of mine wastes is vital for the success of reclamation strategies. The Gunnar gold mine tailings pond in southeast Manitoba has remained largely unvegetated since the mine was closed in 1942, with limited vegetation developed on one side of the pond. We examined the natural Picea mariana/Larix laricina forest that has developed on the pond to determine how the plant community develops and what changes in the tailings are associated with this development. Vegetation sampled along transects showed a consistent pattern of succession from Equisetum palustre to Salix spp., and Populus balsamifera, to Larix laricina and finally to P. mariana. Larix laricina and P. mariana are moving into the site at the rate of 1.5 m per year with L. laricina invading 4 years ahead of P. mariana. Both tree species show a similar pattern of annual growth, showing positive correlations with spring precipitation, a pattern also occurring on L. laricina growing on a nearby site. The establishment of E. palustre was accompanied by initially rapid decreases in compaction and conductivity of the tailings, and an increase in inorganic nitrogen. Surface organic matter depth, coarse organic matter mass, and soil organic carbon increased at a constant rate, whereas subsurface coarse organic matter had an initial rapid increase followed by a gradual increase. As fern allies (and specifically members of the Equisetaceae family) have a number of properties that facilitate succession on mine wastes, their use should be explored further.

Larix laricinaK. Koch is a medicinal plant belonging to traditional pharmacopoeia of the Cree of Eeyou Istchee (Eastern James Bay area of Canada).In vitroscreening studies revealed that, like metformin and rosiglitazone, it increases glucose uptake and adipogenesis, activates AMPK, and uncouples mitochondrial function. The objective of this study was to evaluate the antidiabetic and antiobesity potential ofL. laricinain diet-induced obese (DIO) C57BL/6 mice. Mice were subjected for eight or sixteen weeks to a high fat diet (HFD) or HFD to whichL. laricinawas incorporated at 125 and 250 mg/kg either at onset (prevention study) or in the last 8 of the 16 weeks of administration of the HFD (treatment study).L. laricinaeffectively decreased glycemia levels, improved insulin resistance, and slightly decreased abdominal fat pad and body weights. This occurred in conjunction with increased energy expenditure as demonstrated by elevated skin temperature in the prevention study and improved mitochondrial function and ATP synthesis in the treatment protocol.L. laricinais thus a promising alternative and complementary therapeutic approach for the treatment and care of obesity and diabetes among the Cree.

To help assess the risk of establishment of Phytophthora ramorum in eastern Canada, detached leaves/needles of six eastern native forest species were inoculated with P. ramorum and the amount of necrosis and sporulation was determined. Inoculation was also performed by plant dipping. Balsam fir (Abies balsamea), sugar maple (Acer saccharum), yellow birch (Betula alleghaniensis), white ash (Fraxinus americana), tamarack (Larix laricina) and red oak (Quercus rubra) were the species tested. Rhododendron ‘Nova Zembla’, which is putatively sensitive to the pathogen, was also included in the assays. The degree of necrosis on detached leaves was particularly high on F. americana and B. alleghaniensis. This susceptibility was also confirmed after wounding in the plant-dip experiment in which Q. rubra was also susceptible. For the coniferous species, needle necrosis was higher on A. balsamea than on L. laricina. Reisolation assays and PCR detection of P. ramorum were generally positive when necrosis occur...

Summary 1. Rank reversals in species performance are theoretically important for structuring communities, maintaining diversity and determining the course of forest succession. Species growth ranks can change with ontogeny or in different microenvironments, but interactions between ontogeny and the environment are not well-understood because of the lack of long-term forest competition studies. While early differences in growth among species may reflect intrinsic differences in shade-tolerance and physiology, ontogenetic trends in growth and variation in neighbourhood density and composition may change or even reverse early patterns of growth rankings. 2. We experimentally studied spatial and temporal patterns of species interactions and growth for three northern tree species: Larix laricina , Picea mariana and Pinus strobus . We compared species size and growth rankings over an 11-year period, for different species mixtures planted at four density levels in north-eastern Minnesota, USA. 3. The benefits of different growth strategies changed with ontogeny and density leading to reversals in the size rank of competing species over time and space. High-density stands promoted dominance and resource pre-emption by L. laricina , whereas lower-density stands favoured gradual accumulation of biomass and eventual dominance by P. strobus . In the absence of strong neighbour competition, ontogenetic trends in growth had greater influence on growth patterns. 4. Species interactions affected the productivity of mixed stands vs. monocultures. Species generally grew more in monoculture than when planted with P. strobus at low density, or with L. laricina at high density. Only L. laricina and P. mariana showed potential for greater overall productivity, or over-yielding, when planted together than alone, probably because of improved resource uptake by the highly stratified canopy. 5. Synthesis . Density predictably determined whether size-asymmetric growth or ontogenetic growth trends would drive early establishment and growth patterns. Variation in vertical and horizontal structure that results from early competitive dynamics can influence the successional trajectory or character of the mature forest. This study extends previous efforts to identify the causes of rank reversals in communities and understand the importance of temporal changes beyond the early years of seedling establishment.

A molecular phylogeny of Larix comprising 12 species was constructed from the sequence analysis of the paternally inherited cpDNA trnT-trnF region of 46 individuals. The most parsimonious tree split Larix into three sister clades: one clade was composed of two North American species, the other two were short-bracted and long-bracted species of Eurasia respectively except that L. sibirica was clustered in the long-bracted clade. The difference between the present cpDNA phylogeny and previous nrDNA ITS phylogeny in the position of L. sibirica seems to suggest that ancient cytoplasmic gene flow might exist between sections Larix and Multiserialis. The short-bracted L. laricina and long-bracted L. occidentalis have an identical sequence of the trnT-trnF region, which implies that the bract length divergence among North American larches might have occurred recently or chloroplast capture happened during the early differentiation of the two species. The cpDNA results also shed some light on the biogeography of Larix.

We detected nucleotide polymorphisms within the genus Gremmeniella in DNA sequences of β-tubulin, glyceraldehyde phosphate dehydrogenase, and mitochondrial small subunit rRNA (mtSSU rRNA) genes. A group-I intron was present in strains originating from fir (Abies spp.) in the mtSSU rRNA locus. This intron in the mtSSU rRNA locus of strains isolated from Abies sachalinensis (Fridr. Schmidt) M.T. Mast in Asia was also found in strains isolated from Abies balsamea (L.) Mill. in North America. Phylogenetic analyses yielded trees that grouped strains by host of origin with strong branch support. Asian strains of Gremmeniella abietina (Lagerberg) Morelet var. abietina isolated from fir (A. sachalinensis) were more closely related to G. abietina var. balsamea from North America, which is found on spruce (Picea spp.) and balsam fir, and European and North American races of G. abietina var. abietina from pines (Pinus spp.) were distantly related. Likewise, North American isolates of Gremmeniella laricina (Ettinger) O. Petrini, L.E. Petrini, G. Laflamme, & G.B. Ouellette, a pathogen of larch, was more closely related to G. laricina from Europe than to G. abietina var. abietina from North America. These data suggest that host specialization might have been the leading evolutionary force shaping Gremmeniella spp., with geographic separation acting as a secondary factor.Key words: Gremmeniella, geographic separation, host specialization, mitochondrial rRNA, nuclear genes.

Genetic variation at 16 allozyme loci was studied in both American (Larix occidentalis Nutt., L. laricina (Du Roi) C. Koch, L. lyallii Parl.) and Eurasian (L. sibirica Ledeb., L. gmelinii Rupr., L. olgensis A. Henry, L. kaempferi (Lamb.) Carr. (=L. leptolepis (Sieb. et Zucc.) Endl.), L. kamtschatica (Rupr.) Carr. and L. decidua (Mill. )) larch species. Species with a limited range, such as L. olgensis and L. lyallii, had lower genetic variation than species with a wider range. Population differentiation within species was of the same order of magnitude among species. The resulting phylogeny indicates a clear separation between American and Eurasian species. This result is in agreement with recent palaeontological findings that suggest that gene flow between American and Eurasian species has been unlikely since the last glaciation.

The nuclear ribosomal DNA (nrDNA) internal transcribed spacer (ITS) region has been characterized in the sister genera Larix and Pseudotsuga (Pinaceae). Complete sequences were obtained for seven species of Larix from North America and Eurasia and five species of Pseudotsuga from western North America and eastern Asia. ITS region lengths ranged from 1759 to 1770 bp in Larix and from 1564 to 1571 bp in Pseudotsuga. In both genera, ITS1 is three times as long as the 5.8S plus ITS2 and contains subrepeats as observed in other genera of Pinaceae. Secondary structure models predicted that the subrepeats fold into terminal stem and loop domains. ITS polymorphism detected within individuals of Larix and Pseudotsuga suggests a slow rate of concerted evolution among nrDNA loci. Except for the placement of L. sibirica, phylogenetic analyses of the ITS region agreed with previously reported restriction site analyses of Larix and Pseudotsuga. The data were not consistent with phylogenetic hypotheses for Larix based primarily upon ovulate cone characters, failing to support a derivation of the North American L. laricina from a short-bracted Eurasian lineage. The phylogenetic hypothesis did not conflict with a stepping stone model of evolution for Pseudotsuga, but a basal lineage could not be inferred for either genus.

Summary Fungi identified as Sphaeropsis sapinea (or synonyms) have been reported from Larix. Lack of pathogenicity tests, confusion about the identity of isolates mentioned in previous literature, and existence of distinct populations (A and B morphotypes) of the pathogen indicated the need to evaluate the ability of S. sapinea to cause disease of larch. Elongating snoot tips of Larix decidua, Larix laricina, and known hosts of the pathogen, Pinus banksiana and Pinus resinosa, were inoculated with water-agar plugs colonized with an A or a B isolate, or sterile plugs (controls). Each of five replications included five seedlings for each treatment-species combination. After 6 weeks, no symptoms had developed on control seedlings, but two-way analyses of variance revealed significant effects of isolate morpnotype and host on both incidence and severity of disease (values of p ≤ 0.01). The A isolate killed almost all shoot tips, but the B isolate killed from no P. resinosa shoots to 56% of L. laricina shoots. The average length of shoot killed by the A isolate was also greater than that killed by the B isolate. Response to the B isolate again varied among species, with greater average lengths of shoot killed on the larches (compared with the pines). Both A and B morphotypes of 5. sapinea should be considered among the fungi encountered on L. decidua and L. laricina.

UNLABELLED PREMISE OF THE STUDY Treelines are temperature-sensitive ecotones that should be able to expand in response to global warming; however, they are also controlled by ecological constraints. These constraints can create bottlenecks for tree regeneration, hindering treeline advances. Near Kangiqsualujjuaq (Nunavik, subarctic Quebec), previous studies suggested successful recruitment of Larix laricina above the altitudinal treeline, while Picea mariana establishment remains scarce. We studied regeneration of both species to identify factors responsible for such contrasting responses. • METHODS We measured seeds and wings to evaluate species dispersal potential. We compared seed viability and tolerance to shrub leachates with germination trials. To evaluate seedbed preferences, we compared seedling occurrence on the different seedbeds with seedbed relative abundance in the field. • KEY RESULTS Seed germination was similar between L. laricina and P. mariana, whereas dispersal potential was higher for the latter. Germination of P. mariana seeds was more strongly inhibited by shrub leachates than were L. laricina seeds. In the field, we found only a few Picea seedlings, but numerous seedlings of Larix had established disproportionally on several seedbeds. While Betula glandulosa, mosses, and Vaccinium uliginosim impeded Larix establishment, numerous seedlings were found on lichens, mineral soil, and liverworts. The low occurrence of suitable seedbeds for Picea, mainly mineral soil, could explain the seedling scarcity of this species. • CONCLUSIONS This study highlighted that allelopathy and unsuitable seedbeds could contribute to regeneration failure of P. mariana in eastern Nunavik and emphasizes the need to consider ecological preferences of species before predicting treeline expansion under a warmer climate.

The effects of climate on radial growth of Larix laricina (Du Roi) K. Koch, Picea glauca (Moench) Voss, and Picea mariana (Mill) BSP were investigated in the Hudson Bay Lowlands of northern Manitoba. The objective was to characterize spatial and temporal variations in growth of trees across the forest-tundra ecotone. Along a 250 km transect, 299 trees were sampled in three zones: northern forest, central tundra, and southern forest. Ring-width indices were compared with climate through correlation- and response-function analyses. Numerous years of suppressed growth at the three locales resulted from cooling that followed major volcanic eruptions at much lower latitudes. Temperatures during July of the current year and autumn of the previous year were most limiting, particularly for L. laricina, which was temperature-sensitive across the region. A weakened growth response to temperature during the 1940-60 period was likely due to atmospheric circulation shifts. Most chronologies were intercorrelated, which suggests common environmental forcing, though environmental influences differed in the southern forest (particularly for P. mariana). The source of this disparity has yet to be determined.

The efflux of CO2 from roots of Pinusbanksiana Lamb., Pinuscontorta Dougl., Piceaglauca (Moench) Voss, Piceamariana (Mill.) B.S.P., and Larixlaricina (Du Roi) K. Koch were measured under anaerobic and aerobic conditions at 5, 15, and 25 °C. Piceamariana showed an anaerobic to aerobic CO2 efflux ratio that was significantly higher than all other species at 5 °C. Larixlaricina showed higher levels of anaerobic and aerobic CO2 efflux rates than the other four species. These data suggest that Piceamariana roots have higher overall increases in fermentation rates with onset of anoxia at 5 °C, and L. laricina roots have high fermentation and respiration rates at 5 °C. These features may be indicative of metabolic adaptations to cold, flooded peatland soils of Canadian boreal forests. A redox dye test showed O2 diffusion from roots of Pinus spp. and L. laricina at each temperature level. Thus these species have some ability to transport O2 to root tissues and sustain limited respiration under anaerobic conditions. Black and white spruce did not show any O2 diffusion from roots at any temperature.

From the Neolithic to the 16th century AD in age, 18 archaeological sites in the Western and Northern Islands of Scotland have yielded wood and charcoal of Abies, Larix cf. laricina, Pinus section Strobus and especially Picea . All these exotic taxa very probably had a North American provenance and were beached by the North Atlantic Current. The archaeological contexts indicate that the driftwood was often used as fuel and occasionally for constructional purposes.

L'hybridization interspecifique offre a l'amelioration des perspectives interessantes pour la creation varietale, notamment pour la combinaison de caracteres complementaires favorables et par valorisation de l'heterosis. Dans cette perspective, plusieurs croisements controles entre le meleze laricin (Larix laricina)―adapte aux sols hydromorphes―et les melezes d'Europe (L decidua) et du Japon (L kaempferi) ont ete tentes, certains avec succes tels le croisement entre le meleze laricin et le meleze du Japon et celui de l'hybride triple (L laricina×(L decidua×L kaempferi)) (...)

Fertile and vegetative remains of Larix altoborealis sp. nov. have been recovered from sediments of the Eocene Buchanan Lake Formation of Axel Heiberg Island, Canadian High Arctic. Palynological and megafossil diversity and abundance data indicate that Larix was a subordinate member within a regionally diverse, mixed forest of broad-leaved and needle-leaved deciduous and needle-leaved evergreen taxa. Vegetative remains include leafy-leading shoots as well as branches with attached brachioblasts and needle fascicles. Cuticular analyses reveal that epidermal cells have distinctive undulatory anticlinal wall patterns bearing small projections. Seed cones are 14–30 mm long, 10–15 mm wide and are elliptical to ovoid, with 35 to 70 scales per cone. Ovuliferous scales are rounded to emarginate, each cone scale bearing two adaxial, winged seeds. Subtending each cone scale is a bract possessing a distinct apical tooth which does not exceed the length of the cone scale. The cuticular patterns of L. altoborealis needles are at present unique among Larix, but cone morphology indicates a relationship to the short-bracted taxa that are currently widely distributed in the boreal forests of North America and Eurasia, including L. laricina, L. sibirica, L. gmelini. Examination of bracts from L. altoborealis sp. nov. and all extant Larix indicates that bract morphology is distinctive for each species and is useful in identification. A phylogenetic scheme is developed for Larix based upon the seed-cone morphology, including features of the bract, and distribution patterns of extant and extinct species of Larix. Larix altoborealis sp. nov. is the first unequivocal report of pre-Oligocene Larix and provides insight into the early evolution and distribution of the genus.

Primordial shoot explants excised from buds of one Larix decidua tree, about 30 years old, produced more adventitious buds, elongating into shoots, when grown on half strength Litvay medium than when grown on other basal media. Thidiazuron and N6-benzyladenine (BA) were equally effective in adventitious bud induction. In a comparative study of 30-year-old L. decidua, L. leptolepis, L. eurolepis, and L. laricina trees, explants from L. eurolepis and L. decidua produced a high number of cultures with adventitious buds that elongated into shoots; those from L. leptolepis were less productive, and those from L. laricina failed to form adventitious buds. The highest response was obtained with material collected in August and September, and in March and April; the lowest response occurred in explants from the October collection.

summary A comparison is made of the phenologies of infructescence, follicle and seed growth development of two species of Banksia with particular reference to nutrient provision of dissimilarly sized seeds and associated mechanical defence costs. Follicles and seeds of B. attenuata developed sequentially while the smaller seeded B. laricina, exhibited an almost synchronous pattern of development. Seed nitrogen loading, assayed by temporal changes in amino pool sizes in different parts of the seed, was confined to a relatively short period (± 3 months) prior to infructescence desiccation in both species. Prolonged infructescence development in the larger seeded B. attenuata cannot therefore be interpreted simply as a mechanism for extending time available for mobilization of scarce nutrients within the plant, but may be a result of selective pressures related to the development of large woody structures around the seeds which provide mechanical defence against predators. Both Banksia spp. make relatively large investments of carbon, but not of nitrogen, in defence structures (up to 5·5 g per seed in B. attenuata) which in plants with low photosynthetic rates could have associated penalties in terms of N required for photosynthetic enzymes. Sequential development of follicle and then seed assumes significance, since nitrogen used in photosynthesis to provide carbon to the follicle can subsequently be mobilized from the leaf and redeployed in seed protein synthesis. The often held view that larger seeds require longer maturation periods is not universal as, in the Banksia spp. examined, defence costs and photosynthetic capacity might play a more dominant role in determining seed developmental patterns.

Forty-four isolates of Gremmeniella abietina from different European regions and laboratory strains of G. abietina and Ascocalyx abietis, which originated from regenerated protoplasts, were characterized morphologically and by protein electrophoresis. On the basis of the electrophoretic profiles of all isolates tested, the North American race of G. abietina is not present in Europe. Isolates from Pinus cembra and two Finnish isolates differed slightly from the tester strain for the European race; their electromorphs were very similar to that of the European race on other hosts but differences were noticed that would support the maintenance of the variety cembrae. Gremmeniella abietina var. balsamea, common on Abies balsamea and Picea spp. in Quebec, Canada, seems to be absent from the European counterparts Abies alba and Picea abies. The isolates from P. abies belong unequivocally to the European race of G. abietina. European isolates of G. laricina were morphologically and electrophoretically indistinguishable from the North American ones. The P. cembra and Larix decidua endophytes showed the same electrophoretic profile as the isolates from diseased pines identified as Brunchorstia pinea var. cembrae. No changes in the electrophoretic patterns of laboratory strains derived from regenerated protoplasts, compared with those of the original isolates, were observed. Two isolates from Abies do not belong to any known species of Brunchorstia; on the basis of morphological, electrophoretic, and immunological evidence they belong to a taxon taxonomically close to G. abietina. Key words: Gremmeniella abietina, protein electrophoresis, Pinus cembra, Picea abies, European isolates.

Kaempferol-3-p-coumarylglucoside (KCG) was isolated from ether fractions of acetone-extracted freeze-dried needles of all larch species investigated. In each case, KCG was found as one of the main flavonoids, whereas often a variety of closely related, acylated flavonoids was present in either low to very low concentration. For example, the KCG complex of L. leptolepis needles on alkaline hydrolysis produced traces of ferulic acid besides p-coumaric acid, indicating the possible presence of a kaempferol- 3-ferulylglycoside (KFG). Because of the low concentration, KFG could not be isolated from L. leptolepis needles, but was obtained from L. decidua, a species with lower concentrations of KCG. Freeze-dried needles of L. decidua were KCA. Traces of KCA were also found in needles extracted with 70% EtOH; chlorophyll etc. was of L. laricina. removed with CCl₄, and the extract was separated on a polyamide column and on paper. In addition to KCG, 4 new acylated glycosides were isolated and identified by standard methods as: the 3- ferulylglucosides of kaempferol, quercetin, iso- rhamnetin and syringetin. A fifth compound could not be completely freed from KCG, but was iden- tified as kaempferol-3-p-coumarylarabinoside-KCA. Traces of KCA were also found in needles of L. Laricina.

Time of shoot initiation and cessation, and rate and duration of lateral shoot elongation of full-sib families of Larix decidua Mill., L. laricina (Du Roi) C. Koch, and interspecific hybrids between L. decidua and L. kaempferi (Lamb.) Carriere, L. kaempferi x decidua, L. laricina x decidua, and L. laricina x kaempferi were explored in relation to hybrid vigor determined by height growth after 5 years. Height growth of L. laricina and L. decidua families was significantly less than height growth of the interspecific hybrids. Differences were observed for all lateral shoot elongation traits among L. laricina, L. decidua, and the interspecific hybrids. Lateral shoots of L. laricina families were the first to both initiate and cease elongation, and grew for the shortest period of time. Overall, the length of the shoot elongation period and date of cessation of shoot growth were significantly correlated with total height growth after 5 years, but the time of shoot initiation was not. Rate of elongation of lateral shoots was strongly correlated with growth increment in 1996, but was weakly correlated with total height growth after 5 years. Hybrid vigor in Larix seems to be partly a function of late cessation or increased duration of shoot elongation, or both.

Measurements of the photosynthetic response to midsummer irradiance were made for 11 species representing the dominant trees, understory shrubs, herbaceous plants and moss species in an old black spruce (Picea mariana (Mill.) B.S.P.) boreal forest ecosystem. Maximum rates of photosynthesis per unit foliage area at saturating irradiance, A(max), were highest for aspen (Populus tremuloides Michx.), reaching 16 micromol m(-2) s(-1). For tamarack (Larix laricina (Du Roi) K. Kock) and P. mariana, Amax was only 2.6 and 1.8 micromol m(-2) s(-1), respectively. Values of A(max) for understory shrubs and herbaceous plants were clustered between 9 and 11 micromol m(-2) s(-1), whereas A(max) of feather moss (Pleurozium schreberi (Brid.) Mitt.) reached only 1.9 micromol m(-2) s(-1). No corrections were made for differences in shoot structure, but values of photosynthetic light-use efficiency were similar for most species (70-80 mmol CO2 mol(-1)); however, they were much lower for L. laricina and P. mariana (15 mmol CO2 mol(-1)) and much higher for P. schreberi (102 m;mol CO2 mol(-1)). There was a linear relationship between Amax and foliage nitrogen concentration on an area basis for the broad-leaved species in the canopy and understory, but the data for P. mariana, L. laricina and P. schreberi fell well below this line. We conclude that it is not possible to scale photosynthesis from leaves to the canopy in this ecosystem based on a single relationship between photosynthetic rate and foliage nitrogen concentration.

The genus Larix belongs to the pine family, and has 10 species and a large number of subspecies and hybrids. It is widely distributed across North America, Asia and Europe. Three species are endemic to North America and seven occur in Europe and Asia. In North America, L. occidentalis (western larch) and L. lyalli (Alpine larch) grow in subalpine regions whereas L. laricina L. (tamarack) is mainly restricted to boreal zones. In Europe, Larix decidua (European larch) constitutes the only species and is localised at the subalpine level. In North Asia, Larix russica often referred to as L. sibirica (Siberian larch) and L. gmelinii (Asian larch) dominate the Siberian forest landscape. Southern Asia accounts for a wide variety of Larix species ranging from the mountain conditions of L. mastersiana (Masters larch, southwestern China) to the high elevation forests of L. griffithiana (Sikkim larch) in the Himalayan Mountains (Nepal, Tibet) and L. potaninii (Chinese larch) in southwestern China to the island environment of L. kaempferi referred to as L. leptolepis (Japanese larch) in Japan (Schmidt 1992).

Melampsora larici-populina Kleb. was reported for the first time in eastern North America during 2002, on Populus spp., its telial host (1). M. larici-populina, a heteroecious rust, alternates between species of Populus and Larix. Since M. larici-populina was observed again in 2003, we investigated the possibility that its basidiospores may infect larch (Larix spp.) resulting in spermogonia and aecia. Identification of Melampsora species from aeciospore morphology is difficult but urediniospores are distinctive. This is important since the native M. medusae also alternates between Populus and Larix spp. During the spring of 2004, aecia were observed on needles of exotic (Larix decidua Mill. and L. leptolepis (Siebold and Zucc.) Gordon) and indigenous (L. laricina (K. Koch)) larch in an arboretum in Lotbinière (Quebec, Canada) where M. larici-populina has previously been found. Larch needles with yellow blister-like fructifications were collected in May 2004 and fixed on top of petri plates to allow aeciospore release onto leaves of Jackii poplar (Populus balsamifera L. × P. deltoides Marsh.). After approximately 10 days, uredinia appeared on the abaxial surface of the poplar leaves. Some of the many needles collected yielded uredinia cultures on Jackii poplars. The majority of these cultures were identified as being M. larici-populina; one was M. medusae. M. larici-populina urediniospores were 32 to 48 μm long and possessed a characteristic apical bald spot. DNA was extracted from aecia and uredinia, and the internal transcribed spacer (ITS) of the ribosomal RNA gene was amplified in real-time polymerase chain reaction (PCR) by specific primers for M. medusae or M. larici-populina created from sequences (GenBank Accession Nos. AY429656 and AY429657). The 120 base pairs target fragments amplified only with the M. larici-populina specific primers with the 14 samples that were identified as M. larici-populina by morphological characteristics of the urediniospores. No PCR amplification was obtained with M. medusae primers. These results were not unexpected since larch has been previously reported as an aecial host of M. larici-populina elsewhere (2). The ability of M. larici-populina to overwinter and complete its life cycle has important consequences since it proves that it is established and can go through sexual reproduction. A complete life cycle in eastern North America may allow M. larici-populina to generate pathogenic variation that will challenge poplar breeders in this region. References: (1) L. Innes et al. Plant Dis. 88:85, 2004. (2) G. Newcombe et al. Plant Dis. 78:1218, 1994.

Needle blight of larch caused by Mycosphaerella laricina seriously limits the productivity of susceptible trees in the north central and northeastern United States. Adventitious shoots, derived from cotyledon tissue culture, of selected European larch (Larix decidua) and a hybrid larch were inoculated in vitro with three isolates of M. laricina.

Observations on the biology of Botryosphaeria pseudotsugae Funk were made in south central British Columbia, Canada. The fungus was associated with heavily cankered Douglas-fir (Pseudotsuga menziesii) that were also attacked by bark insects, miners, and borers. Cultural characteristics and observations on ascus and ascospore structure are also presented. Other ascomyctes associated with the cankers were Caliciopsis pseudotsugae, Stuartella suttonii, Lachnellula ciliata, Tympanis laricina, Durandiella pseudotsugae, and Dermea pseudotsugae.

Infection experiments with Ascocalyx abietina and A. laricina, on cembra pine, mountain pine, and larch between 1979 and 1985 gave very varying results from one year to another. Moderate to very severe disease only occurred after incubation on favourable sites in the subalpine zone. The intensity of disease may depend on local site and microclimatic conditions for infection. Successful infections occurred especially in autumn. An annual infection rate of 10 to 15 percent can endanger an afforestation: in an afforestation in Avers, 50 percent of the trees were killed in some 5 years.

SUMMARY Four phenolics were positively identified in Larix needles as vitexin, syringetin-3-glucoside, p-hydroxybenzaldehyde, and vanillin. A fifth compound was tentatively identified as a 3' substituted myricetin-3-glucoside.

Five new combinations are proposed in the genus Encoeliopsis, E. bresadolae (Rehm), E. ericae (Fr.), E. laricina (Ettl.), E. ledi (Alb. & Schw. ex Fr.), and E. oricostata (Cash), together with a detailed discussion of the nomenclatural problems involving the type species, E. rhododendri (Ces. ex DeNot.) Nannf.

The endophytic system (ES) of Arceuthobium pusillum in Picea mariana, a compatible host, ramified throughout branchlets composing witches' brooms, and its cells contained numerous nonmembranebound droplets composed largely of neutral fats which occupied much of the cytoplasmic volumes and which persisted in senescent cells. The ES in the less compatible Larix laricina was found to persist mostly in tissues adjacent to and in spur shoots, and, in less vigorous infections, it accumulated fewer lipid droplets. In more successful infections of larch, many droplets were observed. Although the droplets probably serve for storage of high-energy fats, their accumulation in L. laricina appears to be reflected in the degree of success which the parasite has in this host. The more successful the infection, the more abundant are lipid droplets. Rapid lipid synthesis by the parasite may help to maintain a sharp carbohydrate diffusion gradient from host to parasite. The lipid droplets in both hosts were often in physical contact with smaller, single membrane-bound, evenly staining bodies which may have been involved in synthesis or use of these lipids. Germinating seeds, aerial shoots, and ES of the parasite in both hosts contained functional chloroplasts that structurally resemble those in the Gramineae that use the C4-dicarboxylic acid pathway.

Functional sieve cells are present for the entire year in the secondary phloem of Larix laricina (Du Roi) K. Koch, Abies balsamea (L) Mill, and Picea mariana (Mill.) BSP. With regard to a given year's growth increment, all but the last-formed sieve cells (one to four layers) cease functioning in the same season in which they are derived from the cambium. The last-formed sieve cells overwinter and remain functional throughout the next growing season. Toward the end of April, undifferentiated cells in the outer margin of the cambial zone begin to differentiate into sieve cells. About a week later, cambial activity (cell division) commences All early phloem is produced before new xylem differentiation begins, that is, by mid-May in A. balsamea and by the end of May in L. laricina and P. mariana Most sieve cells are differentiated by early September Cessation of function begins by the end of September with the formation of definitive callose on the overwintering sieve cells and continues to sieve cells of the...

Azotobacter spp., Azospirillum spp., and Desulfovibrio spp., were identified as the predominant nitrogen-fixing bacteria associated with seedling root sections collected from natural stands of Pinusbanksiana Lamb., Piceamariana (Mill.) B.S.P., and Larixlaricina (Du Roi) K. Koch growing in Alberta. Samples from the sandy upland habitat of P. banksiana exhibited lower average rates of nitrogen fixation relative to the wet lowland occupied by P. mariana and L. laricina. Average nitrogen-fixing capacity (by acetylene reduction) was greater among bacteria isolates from L. laricina than those from P. mariana. Azospirillum spp. were strongly associated with P. mariana, while Azotobacter spp. were isolated more frequently from L. laricina.

Encoeliopsis laricina (Ettlinger) Groves is shown to be the chief fungus associated with a shoot-blight disease of western larch (Larix occidentalis Nutt.) in the Kootenay region of British Columbia, Canada. Symptoms are described and biological characteristics of the fungus are given.