Showing papers in "Botany in 2004"
TL;DR: The potential contribution of extraradical mycorrhizal mycelium to sustainable agriculture and maintenance of biodiversity is assessed and technologies that promise new vistas and improved fine-scale resolution of the dynamic spatial and temporal functioning of these networks in soil are highlighted.
Abstract: Extraradical mycelia of mycorrhizal fungi are normally the �hidden half� of the symbiosis, but they are powerful underground influences upon biogeochemical cycling, the composition of plant communities, and agroecosystem functioning. Mycorrhizal mycelial networks are the most dynamic and functionally diverse components of the symbiosis, and recent estimates suggest they are empowered by receiving as much as 10% or more of the net photosynthate of their host plants. They often constitute 20%�30% of total soil microbial biomass yet are undetected by standard measures of biomass used by soil scientists and agromomists. Mycorrhizal mycelia provide extensive pathways for carbon and nutrient fluxes through soil, often exceeding tens of metres per gram of soil. We consider the amounts of photosynthate �power� allocated to these mycelial networks and how this is used in fungal respiration, biomass, and growth and in influencing soil, plant, and ecosystem processes. The costs and functional �benefits� to plants linking to these networks are fungal specific and, because of variations in physiology and host specificity, are not shared equally; some plants even depend exclusively on these networks for carbon. We briefly assess the potential contribution of extraradical mycorrhizal mycelium to sustainable agriculture and maintenance of biodiversity and highlight technologies that promise new vistas and improved fine-scale resolution of the dynamic spatial and temporal functioning of these networks in soil.Key words: arbuscular mycorrhiza, ectomycorrhiza, extraradical mycelium, hyphal networks.
608 citations
TL;DR: What unites mycorrhizas in heathland and boreal forest biomes is their apparent affinity for acidic organic soils of inherently low accessibility of the major nutrients nitrogen (N) and phosphorus (P).
Abstract: The importance of mycorrhizas in heathland and boreal forest biomes, which together cover much of the landmass of the Northern Hemisphere and store most of the global stocks of carbon, is reviewed....
486 citations
TL;DR: The significance of this approach is discussed, and some possible ways of enhancing biocontrol by mycorrhizal fungi are discussed, as currently they can be sold as plant growth promoters without any form of costly registration.
Abstract: More than 80 disease biocontrol products are on the market worldwide, but none of these contain mycor rhizal fungi. This is despite ample evidence that both arbuscular mycorrhizal fungi and ectomyc...
461 citations
TL;DR: In future, isotopic tracers, morphological observations, microsatellite techniques, and fluorescent dyes will be useful in the study of networks in nature, which have the potential to influence patterns of seedling establishment, interplant competition, and mycorrhizal networks.
Abstract: It is well known from laboratory studies that a single mycorrhizal fungal isolate can colonize different plant species, form interplant linkages, and provide a conduit for interplant transfer of is...
363 citations
TL;DR: The disturbance-severity model, along with the linked response factors and regeneration mechanisms, provide a framework for evaluating how this species-rich and ecologically important layer responds to natural disturbances.
Abstract: Most work on the disturbance ecology of North American forests has focused on the tree canopy and woody understory, with little consideration of the herbaceous layer. Understanding how this species...
287 citations
TL;DR: Using the evidence available, it is concluded that mycorrhizas can occupy vari- ous positions along the continuum from parasitism to mutualism, depending on the specific plant and fungal genotypes and their abiotic and biotic environments.
Abstract: Mycorrhizas are considered to be classic mutualisms. Here, we define mutualism as a reciprocal increase in fitness of the symbionts, and we review the evidence for mycorrhizal mutualism at the comm...
269 citations
TL;DR: There are scarce data connecting water relations in Azospirillum-inoculated wheat suffering drought during anthesis with the yield and mineral content of grains.
Abstract: There are scarce data connecting water relations in Azospirillum-inoculated wheat suffering drought during anthesis with the yield and mineral content of grains. Azospirillum brasilense Sp245-inocu...
254 citations
TL;DR: Only a few species of truffles have been produced in commercial quantities, although methods have been developed that may see the cultivation of species such as Cantharellus cibarius, Lyophyllum shimeji Hongo, and Lactarius deliciosus.
Abstract: There are about 2500 recorded species of edible mushrooms The most expensive and sought after of these mushrooms belong to the mycorrhizal group and include Tuber melanosporum Vitt (Perigord blac
187 citations
TL;DR: Recovery experiments showed that exposure of seeds to various salinity and temperature regimes had little effect on viability of seeds.
Abstract: Limonium stocksii (Boiss.) Kuntze (Plumbaginaceae) is a perennial, woody shrub distributed at Hawks Bay, Karachi, Pakistan. Experiments were carried out to investigate seed germination responses of...
152 citations
TL;DR: Biotechnology science linked to this industrial activity needs to be reinforced, particularly with regards to the development of molecular probes for monitoring arbuscular mycorrhizal inocula in the field and increasing knowledge on the ecophysiolog...
Abstract: The development of an industrial activity producing microbial inocula is a complex procedure that involves for companies not only the development of the necessary biotechnological know-how, but als...
148 citations
TL;DR: Nuclear small-subunit ribosomal DNA sequences were determined for 65 members of the Gigartinales and related orders to support ordinal status for the Plocamiales, to which the Pseudoanemoniaceae and Sarcodiaceae are provisionally transferred.
Abstract: Nuclear small-subunit ribosomal DNA sequences were determined for 65 members of the Gigartinales and related orders. With representatives of 15 families of the Gigartinales sensu Kraft and Robins included for the first time, our alignment now includes members of all but two of the ca. 40 families. Our data continue to support ordinal status for the Plocamiales, to which we provisionally transfer the Pseudoanemoniaceae and Sarcodiaceae. The Halymeniales is retained at the ordinal level and consists of the Halymeniaceae (including the Corynomorphaceae), Sebdeniaceae, and Tsengiaceae. In the Halymeniaceae, Grateloupia intestinalis is only distantly related to the type species, Grateloupia filicina, but is closely affiliated with the genus Polyopes. The Nemastomatales is composed of the Nemastomataceae and Schizymeniaceae. The Acrosymphytaceae (now including Schimmelmannia, formerly of the Gloiosiphoniaceae) and the Calosipho niaceae (represented by Schmitzia) have unresolved affinities and are considered as ...
TL;DR: The possible function of several plant responses in the regulation of mycorrhizal association and some of the signals exchanged are still a matter of debate and will be discussed further on.
Abstract: Abundant data are available on some aspects of the arbuscular mycorrhizal symbiosis, for example, plant nutrition, but because of difficulties immanent to arbuscular mycorrhizal fungi, such as the ...
TL;DR: Multiple studies have produced compelling evidence that the ectomycorrhizal habit has developed convergently in multiple lineages of fungi and the case for third-party annotations of sequences is argued.
Abstract: The three biggest advances in fungal molecular phylogenetics in the last few years have been (1) the huge expansion in data sets, (2) the development of nonribosomal loci for phylogenetic analysis, and (3) the use of increasingly sophisticated types of analyses In addition, advances in parallel computing hold great promise for dramatic increases in speed of analysis These changes have had, or will have, a direct impact on mycorrhizal ecology through the use of sequence-based identification and an indirect impact through the conclusions drawn from such studies One problem in the field has been the accidental addition of erroneous sequences to the public databases through a variety of means, including polymerase change reaction contamination We discuss several examples, suggest ways to identify errors, and argue the case for third-party annotations of sequences Multiple studies have produced compelling evidence that the ectomycorrhizal habit has developed convergently in multiple lineages of fungi and
TL;DR: The role of symbiosis in evolution and the evolution and ecology of symbiotic theory are discussed, and research on mycorrhizas has been paradigmatic for revealing the dynamic nature of symbia and the inherent complexities of costbenefit accounting across the parasitismmutualism continuum.
Abstract: Two facets of symbiosis theory are discussed: the role of symbiosis in evolution and the evolution and ecology of symbiosis. Research on symbiosis developed in virtual conflict with the aims and do...
TL;DR: The roots or other subterranean organs of most plants develop symbioses, mycorrhizas, with fungal symbionts, and a new category has been proposed for symbiotic associations of some leafy liverworts.
Abstract: The roots or other subterranean organs of most plants develop symbioses, mycorrhizas, with fungal symbionts. Historically, mycorrhizas have been placed into seven categories based primarily on stru...
TL;DR: A significant correlation of species richness to tree density, a richness decrease as the number of vegetation layers in- creases, and a preferential fruiting of some species near Q. ilex or Arbutus unedo L. iles showed that richness and production were greatly enhanced in canopy gaps, highlighting the importance of forest structure and large woody debris for fungal conservation.
Abstract: We collected and mapped epigeous fruitbodies of both ectomycorrhizal (ECM) and saprobic fungi in an old- growth Quercus ilex L. Mediterranean forest within a permanent transect of 6400 m 2 over three consecutive fruiting seasons. Out of 5382 fruitbodies, a total of 234 species were found, including 166 and 68 ECM and saprobic taxa, re- spectively. Both communities were mainly composed of rare species. Two genera, Russula and Cortinarius, accounted for 34.4% of ECM fruitbodies and 50% of species diversity. The three most abundant ECM species were Laccaria laccata (Scop.: Fr.) Berk. & Broome, Inocybe tigrina R. Heim, and Lactarius chrysorrheus Fr. The fruiting ECM com- munity encompassed a few Mediterranean species and numerous broad host range temperate species. We also analysed the fruiting patterns in relation to forest structure, host composition, and natural canopy gaps. The results showed (i )a significant correlation of species richness to tree density, (ii) a richness decrease as the number of vegetation layers in- creases, and (iii) a preferential fruiting of some species near Q. ilex or Arbutus unedo L. Another noteworthy feature was that richness and production were greatly enhanced in canopy gaps. Selective fruiting was also observed among species. These results highlight the importance of forest structure and large woody debris for fungal conservation.
TL;DR: Seed germination decreased with the increase in salinity, and more than 10% of the seeds germinated at 900 mmol/L NaCl, while ethephon almost completely reverted the effect of salinity.
Abstract: Ceratoides lanata (Pursh) J.T. Howell is a shrub with numerous annual branchlets from the family Chenopodiaceae and is widely distributed in brackish water playas of northern Utah. Seeds had no dormancy, and about 90% of the seeds germinated in nonsaline control. Seed germination decreased with the increase in salinity, and more than 10% of the seeds germinated at 900 mmol/L NaCl. Almost all seeds germinated in less than 24 h, and no additional seed germinated after this time. Gibberellic acid had no effect in alleviating salinity effects; however, kinetin and fusicoccin substantially alleviated the effect of salinity on germination, while ethephon almost completely reverted the effect of salinity.Key words: Ceratoides lanata, gibberellic acid, ethephon, fusicoccin, halophytes, kinetin.
TL;DR: In the absence of secretory organs, the anatomical modifica- tions in this species are related to metabolic adaptations, such as an early development of the endodermal barrier for ion exclusion, to allow survival in high salinity.
Abstract: Seedlings of Prosopis strombulifera (Lam.) Benth. were grown hydroponically in Hoagland's solution with addition of 25 mmol/L NaCl every 48 h until final salt concentrations of 250, 500, and 700 mmol/L were reached. Control plants were grown without salt. Salinity induced anatomical changes in roots (young and mature zones), hypo- cotyls, young stems, and leaflets. The diameters of the young zone of roots of plants grown in increasing salt concen- trations were smaller than those of controls, with reduced number of cortex layers and reduced size of the vascular system. The roots from tolerant plants showed precocious suberization and (or) lignification of the endodermal cells and early activity of the pericycle. Hypocotyl diameter was reduced along with a reduction in secondary phloem. Roots and hypocotyls showed abundant phellem formation. The stem diameter of young tolerant plants was notably dimin- ished and less tissue lignification occurred. In stems and leaflets of treated plants, NaCl stimulated the production of tannins. In the leaflets, vascular bundles were similar in size. Groups of elongated parenchyma cells with many chloro- plasts surrounded the bundles. These results suggest that in the absence of secretory organs, the anatomical modifica- tions in this species are related to metabolic adaptations, such as an early development of the endodermal barrier for ion exclusion, to allow survival in high salinity.
TL;DR: Rhizobium leguminosarum Jordan bv.
Abstract: Rhizobium leguminosarum Jordan bv. viceae strains from pea and lentil root nodules were tested for control of damping-off of pea (Pisum sativum L., host) and sugar beet (Beta vulgaris L., nonhost) ...
TL;DR: The clonal shrub Cornus drummondii C.A. Mey.
Abstract: The clonal shrub Cornus drummondii C.A. Mey. is rapidly increasing in cover and displacing mesic grassland species in the central USA as a consequence of fire suppression. We assessed the impact of...
TL;DR: The results suggest that above- ground competition may be more important than belowground competition for structuring understory boreal forest communities, and both the structure and total amount of standing crop will be important for the outcome of species interactions.
Abstract: Increased nitrogen (N) input in boreal forests has previously been shown to induce a shift from Vaccinium myrtillus L. to Deschampsia flexuosa (L.) Trin. as the dominant understory species. We investigated the relative impor- tance of increased light and N for this shift, in a field experiment. We increased light availability, that is, we reduced aboveground competition from V. myrtillus, and increased N by adding 50 kg Nha -1 . Increased light availability had a positive effect on both the growth rate and final biomass of D. flexuosa. Although N addition increased the uptake of fertilizer N by both species, it had no effect on the growth or biomass of either species. Thus, aboveground competi- tion from V. myrtillus prevented expansion of D. flexuosa, regardless of N treatment. The results suggest that above- ground competition may be more important than belowground competition for structuring understory boreal forest communities. As light availability is important, both the structure and total amount of standing crop will be important for the outcome of species interactions.
TL;DR: It is proposed that researchers should not assume mycorrhizas are mutualistic based upon structural characteristics or limited functional studies showing bilateral exchange and should view them as occupying a wider range on the symbiotic continuum, including commensalism and antagonism, and recommended that comparative studies of mycor rhizas incorporate other types of root associations that have traditionally been considered antagonistic.
Abstract: Some views of mutualism, where the fitness of two symbiotic partners is higher in association than when apart, assume that they necessarily evolve towards greater benefit for the partners. Most mutualisms, however, seem prone to conflicts of interest that destabilize the partnership. These conflicts arise in part because mutualistic outcomes are conditional, depending upon complex interactions between environmental, developmental, and genotypic factors. Mutualisms are also subject to exploitation or cheating. Although various compensating mechanisms have been pro- posed to explain how mutualism can be maintained in the presence of exploiters, none of these mechanisms can elimi- nate exploitation. In this paper we explore various compensating mechanisms in mycorrhizas, examine the evidence for exploitation in mycorrhizas, and conclude that mycorrhizal mutualisms exhibit characteristics that are more consistent with a concept of reciprocal parasitism. We propose that researchers should not assume mycorrhizas are mutualistic based upon structural characteristics or limited functional studies showing bilateral exchange and should view mycorrhizas as occupying a wider range on the symbiotic continuum, including commensalism and antagonism. We recommend that comparative studies of mycorrhizas incorporate other types of root associations that have traditionally been considered antagonistic.
TL;DR: The experiment shows that light availability and herbivory affect the development and defence of Q. pyrenaica seedlings, and both factors decreased biomass and chemical defence, which could affect the seedlings' future performance.
Abstract: Many biotic and abiotic factors affect seedling establishment in woody plants. In Mediterranean environments, the major factors affecting tree regeneration are light, water, and herbivory. We inves...
TL;DR: The abundance of Lobaria pulmonaria (L.) Hoffm.
Abstract: Orographic precipitation over interior mountains has resulted in the formation of the inland temperate rainforest, where certain stands are potentially antique and support a rich flora of epiphytic macrolichens. We documented macrolichen diversity across three age-classes in forests of the Interior CedarHemlock biogeoclimatic zone (i.e., ICHwk3 subzone) east of Prince George, British Columbia. Our objectives were to report changes in lichen communities with stand age, identify potential indicators of antiquity, and investigate the functional role of dominant species in the ecosystem. We identified 41 taxa, including 4 alectorioid lichens, 21 foliose chlorolichens, and 16 old-growth-associated chlorolichens and cyanolichens. Older forests supported more species than young or mature forests. The abundance of Lobaria pulmonaria (L.) Hoffm. was strongly correlated with this increase in diversity and may therefore be an appropriate indicator of stand age in the ICH. The increase in L. pulmonaria and other N2-...
TL;DR: The apparent response to relatively small but presumably long-term differences in nitrogen abundance suggests that sporocarp production by macrofungi could be an effective bioindicator and should be considered in determination of critical loads for atmospheric nitrogen deposition to temperate and boreal forests.
Abstract: We characterized the epigeous macrofungus communities in two old-growth conifer forests by collecting sporocarps. Despite the similarity in dominant tree species in the two forests, the macrofungus...
TL;DR: Given its unique nature in terms of extent, health, and composition, and given the effect of plant hybrid zones on the ecology and evolution of their associated organisms, it is hoped that the current study will facilitate future research targeting conservation of this riparian forest in its full genetic complexity.
Abstract: Three species of Populus (Salicaceae) overlap and hybridize in southern Alberta, Canada. Variation in leaf morphology throughout the region identifies five genetically distinct zones. The drainage of the Oldman River contains a pure zone of balsam poplar (Populus balsamifera L.), a pure zone of plains cottonwood (Populus deltoides Marsh.), plus overlap and hybrid zones of balsam poplar - narrowleaf cottonwood (Populus angustifolia James) and balsam poplar - narrowleaf cottonwood - plains cottonwood. The drainage of the Red Deer River contains a pure zone of bal- sam poplar, a pure zone of plains cottonwood, plus an overlap and hybrid zone of balsam poplar - plains cottonwood. Zones on both drainages coincide with an elevational gradient. Overlap and hybrid zones extend at least 700 river km (the length obtained by measuring distances between sites of hybridization on a river and its tributaries) combined across the two drainages. Principal components analyses on leaf morphology identify a pattern of bidirectional intro- gression between sect. Tacamahaca (balsam poplar, narrowleaf cottonwood) species. These analyses also identify a pattern of unidirectional introgression between Tacamahaca and sect. Aigeiros (plains cottonwood) species, with F1 hybrids backcrossing only with the Tacamahaca parent. This pattern of unidirectional introgression subsequently was assessed and supported with data from the drainages of Ashley Creek and the Ogden River, Utah, which contain hybrid and overlap zones between narrowleaf cottonwood (Tacamahaca) and Fremont cottonwood, Populus fremontii S. Wat- son (Aigeiros). Given its unique nature in terms of extent, health, and composition, and given the effect of plant hybrid zones on the ecology and evolution of their associated organisms, it is hoped that the current study will facilitate future research targeting conservation of this riparian forest in its full genetic complexity.
TL;DR: Chromosome counts in this study confirmed ploidy expectations for all populations examined, and the need to calibrate DNA content measures with chromosome counts was demonstrated by a deviation from the expected 2:1 ratio between tetraploid and diploid values among European populations.
Abstract: Protocols were developed for both chromosome counts and flow cytometry to assess ploidy level and DNA content for populations of Arabidopsis lyrata L. sampled from Europe (Arabidopsis lyrata subsp....
TL;DR: The data available indicate that spontaneous hybridization among bryophytes is not uncommon and has an important, though still not completely understood, evolutionary significance.
Abstract: Despite being recognized as a widespread and evolutionary important phenomenon among vascular plants, interspecific hybridization among bryophytes has been strongly underestimated. In the present review, we summarize knowledge about bryophyte hybrids that are found in nature. Mechanisms of reproductive isolation in bryophytes are compared with those in vascular plants. The morphological and genetic features of sporophytic hybrids and their gametophytic progeny are discussed, as well as some inferences about hybrid fitness. The data available indicate that spontaneous hybridization among bryophytes is not uncommon and has an important, though still not completely understood, evolutionary significance. The existence of many allopolyploid taxa supports this conclusion. Finally we suggest some methods for further investigation of hybridization among bryophytes in nature. (Less)
TL;DR: Sources of phenotypic variance was investigated in a common garden study of populations of Elymus glaucus Buckley (blue wildrye) from the Blue Mountain Ecological Province of northeastern Oregon and adjoining Washington to develop a framework for guiding seed movement and preserving adaptive patterns of genetic variation in ongoing restoration work.
Abstract: Source-related phenotypic variance was investigated in a common garden study of populations of Elymus glaucus Buckley (blue wildrye) from the Blue Mountain Ecological Province of northeastern Oregon and adjoining Washington The primary objective of this study was to assess geographic patterns of potentially adaptive differentiation in this self-fertile allotetraploid grass, and use this information to develop a framework for guiding seed movement and preserving adaptive patterns of genetic variation in ongoing restoration work Progeny of 188 families were grown for 3 years under two moisture treatments and measured for a wide range of traits involving growth, morphology, fecundity, and phenology Variation among seed sources was analyzed in relation to physiographic and climatic trends, and to various spatial stratifications such as ecoregions, watersheds, edaphic classifications, etc Principal component (PC) analysis extracted four primary PCs that together accounted for 67% of the variance in measure
TL;DR: The fact that the partners of the AM symbiosis exchange such "pheromonal" active molecules during the presymbiotic stage of their interaction suggests the existence of other cross-signaling molecule during the symbiotic stage.
Abstract: During 400 million years of genomegenome interaction, plants and arbuscular mycorrhizal (AM) fungi have become highly interdependent, both ecologically and physiologically. As a result, the differ...