Publications by authors named "Martin Weih"

36 Publications

The Effects of Host Plant Genotype and Environmental Conditions on Fungal Community Composition and Phosphorus Solubilization in Willow Short Rotation Coppice.

Front Plant Sci 2021 5;12:647709. Epub 2021 Jul 5.

Department of Microbiology, Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University, Torun, Poland.

Phosphorus (P) is an essential plant nutrient. Low availability of P in soil is mainly caused by high content of FeO in the clay fraction that binds to P making it unavailable. Beneficial microbes, such as P solubilizing microorganisms can increase the available P in soil and improve plant growth and productivity. In this study, we evaluated the effects of environmental conditions (climate, soil parameters), plant genotype, and level of plant association (rhizosphere or endophytic root organism) on the abundance and diversity of phosphorus solubilizing microorganisms in a production system. We hypothesized that a lower number of endophytic fungi may possess the ability to solubilize P compared to the number of rhizosphere fungi with the same ability. We also expect that the plant genotype and the experimental site with its environmental conditions will influence fungal diversity. Two genotypes grown in pure and mixed cultures were investigated for their fungal microbiome community and diversity in the rhizosphere and endosphere during two growing seasons. We found that the rhizosphere fungal community was more diverse. A general dominance of Ascomycota () and Basidiomycota () was observed. The classes and were more frequent in the endosphere, while and were more abundant in the rhizosphere. Plot-specific soil properties (pH, total organic carbon, and nitrogen) significantly influenced the fungal community structure. Among the culturable fungal diversities, 10 strains of phosphate solubilizing fungi (PSFs) from roots and 12 strains from rhizosphere soil were identified using selective media supplemented with di-calcium and tri-calcium phosphates. The fungal density and the number of PSF were much higher in the rhizosphere than in the endosphere. was the dominant genus of PSF isolated from both sites; other less frequent genera of PSFs were , and . Overall the main factors controlling the fungal communities (endophytic vs. rhizosphere fungi) were the soil properties and level of plant association, while no significant influence of growing season was observed. Differences between genotypes were observed for culturable fungal diversity, while in metagenomic data analysis, only the class showed a significant effect from the plant genotype.
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http://dx.doi.org/10.3389/fpls.2021.647709DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8287252PMC
July 2021

Evidence for magnesium-phosphorus synergism and co-limitation of grain yield in wheat agriculture.

Sci Rep 2021 04 27;11(1):9012. Epub 2021 Apr 27.

Department of Plant Biology, Swedish University of Agricultural Sciences, 750 07, Uppsala, Sweden.

Modern crop production is characterized by high nitrogen (N) application rates, which can influence the co-limitation of harvested yield by other nutrients. Using a multidimensional niche volume concept and scaling exponents frequently applied in plant ecological research, we report that increased N and phosphorus (P) uptake in a growing wheat crop along with enhanced grain biomass is associated with more than proportional increase of other nutrients. Furthermore, N conversion efficiency and grain yield are strongly affected by the magnesium (Mg) to P ratio in the growing crop. We analyzed a field trial in Central Sweden including nine wheat varieties grown during two years with contrasting weather, and found evidence for Mg co-limitation at lower grain yields and P co-limitation at higher yields. We argue that critical concentrations of single nutrients, which are often applied in agronomy, should be replaced by nutrient ratios. In addition, links between plant P and Mg contents and root traits were found; high root number enhanced the P:N ratio, whilst steep root angle, indicating deep roots, increased the Mg:N ratio. The results have significant implications on the management and breeding targets of agriculturally grown wheat, which is one of the most important food crops worldwide.
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http://dx.doi.org/10.1038/s41598-021-88588-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8079383PMC
April 2021

Shoot and Root Traits Underlying Genotypic Variation in Early Vigor and Nutrient Accumulation in Spring Wheat Grown in High-Latitude Light Conditions.

Plants (Basel) 2021 Jan 18;10(1). Epub 2021 Jan 18.

Department of Crop Production Ecology, Swedish University of Agricultural Sciences, 75007 Uppsala, Sweden.

Plants with improved nutrient use efficiency are needed to maintain and enhance future crop plant production. The aim of this study was to explore candidate traits for pre-breeding to improve nutrient accumulation and early vigor of spring wheat grown at high latitudes. We quantified shoot and root traits together with nutrient accumulation in nine contrasting spring wheat genotypes grown in rhizoboxes for 20 days in a greenhouse. Whole-plant relative growth rate was here correlated with leaf area productivity and plant nitrogen productivity, but not leaf area ratio. Furthermore, the total leaf area was correlated with the accumulation of six macronutrients, and could be suggested as a candidate trait for the pre-breeding towards improved nutrient accumulation and early vigor in wheat to be grown in high-latitude environments. Depending on the nutrient of interest, different root system traits were identified as relevant for their accumulation. Accumulation of nitrogen, potassium, sulfur and calcium was correlated with lateral root length, whilst accumulation of phosphorus and magnesium was correlated with main root length. Therefore, special attention needs to be paid to specific root system traits in the breeding of wheat towards improved nutrient accumulation to counteract the suboptimal uptake of some nutrient elements.
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http://dx.doi.org/10.3390/plants10010174DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7831908PMC
January 2021

The Transcription Factor CDF3 Is Involved in Nitrogen Responses and Improves Nitrogen Use Efficiency in Tomato.

Front Plant Sci 2020 24;11:601558. Epub 2020 Nov 24.

Centro de Biotecnología y Genómica de Plantas, Universidad Politécnica de Madrid (UPM) - Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Madrid, Spain.

Nitrate is an essential macronutrient and a signal molecule that regulates the expression of multiple genes involved in plant growth and development. Here, we describe the participation of DNA binding with one finger (DOF) transcription factor CDF3 in nitrate responses and shows that gene is induced under nitrate starvation. Moreover, knockout mutant plants exhibit nitrate-dependent lateral and primary root modifications, whereas overexpression plants show increased biomass and enhanced root development under both nitrogen poor and rich conditions. Expression analyses of lines reveled that CDF3 regulates the expression of an important set of nitrate responsive genes including, , , , and nitrate transporters , , and as well as carbon assimilation genes like and in response to N availability. Consistently, metabolite profiling disclosed that the total amount of key N metabolites like glutamate, glutamine, and asparagine were higher in -overexpressing plants, but lower in in N limiting conditions. Moreover, overexpression of in tomato increased N accumulation and yield efficiency under both optimum and limiting N supply. These results highlight CDF3 as an important regulatory factor for the nitrate response, and its potential for improving N use efficiency in crops.
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http://dx.doi.org/10.3389/fpls.2020.601558DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7732579PMC
November 2020

Quantitative genetic architecture of adaptive phenology traits in the deciduous tree, Populus trichocarpa (Torr. and Gray).

Heredity (Edinb) 2020 12 8;125(6):449-458. Epub 2020 Sep 8.

Department of Plant Biology, Swedish University of Agricultural Sciences, Uppsala Biocentrum, Linnean Centre for Plant Biology, P.O. Box 7080, SE-750 07, Uppsala, Sweden.

In a warming climate, the ability to accurately predict and track shifting environmental conditions will be fundamental for plant survival. Environmental cues define the transitions between growth and dormancy as plants synchronise development with favourable environmental conditions, however these cues are predicted to change under future climate projections which may have profound impacts on tree survival and growth. Here, we use a quantitative genetic approach to estimate the genetic basis of spring and autumn phenology in Populus trichocarpa to determine this species capacity for climate adaptation. We measured bud burst, leaf coloration, and leaf senescence traits across two years (2017-2018) and combine these observations with measures of lifetime growth to determine how genetic correlations between phenology and growth may facilitate or constrain adaptation. Timing of transitions differed between years, although we found strong cross year genetic correlations in all traits, suggesting that genotypes respond in consistent ways to seasonal cues. Spring and autumn phenology were correlated with lifetime growth, where genotypes that burst leaves early and shed them late had the highest lifetime growth. We also identified substantial heritable variation in the timing of all phenological transitions (h = 0.5-0.8) and in lifetime growth (h = 0.8). The combination of additive variation and favourable genetic correlations in phenology traits suggests that populations of cultivated varieties of P. Trichocarpa may have the capability to adapt their phenology to climatic changes without negative impacts on growth.
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http://dx.doi.org/10.1038/s41437-020-00363-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7784687PMC
December 2020

Corrigendum: Multi-Dimensional Plant Element Stoichiometry-Looking Beyond Carbon, Nitrogen, and Phosphorus.

Front Plant Sci 2020 3;11:915. Epub 2020 Jul 3.

Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.

[This corrects the article DOI: 10.3389/fpls.2020.00023.].
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http://dx.doi.org/10.3389/fpls.2020.00915DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7355391PMC
July 2020

Multi-Dimensional Plant Element Stoichiometry-Looking Beyond Carbon, Nitrogen, and Phosphorus.

Front Plant Sci 2020 7;11:23. Epub 2020 Feb 7.

Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.

Nutrient elements are important for plant growth. Element stoichiometry considers the balance between different nutrients and how this balance is affected by the environment. So far, focus of plant stoichiometry has mainly been on the three elements carbon (C), nitrogen (N), and phosphorus (P), but many additional elements are essential for proper plant growth. Our overall aim is to test the scaling relations of various additional elements (K, Ca, Mg, S, Cu, Zn, Fe, Mn), by using ten data sets from a range of plant functional types and environmental conditions. To simultaneously handle more than one element, we define a stoichiometric niche volume as the volume of an abstract multidimensional shape in dimensions, with the sides of this shape defined by the plant properties in question, here their element concentrations. Thus, a stoichiometric niche volume is here defined as the product of element concentrations. The volumes of N and P ( ) are used as the basis, and we investigate how the volume of other elements ( ) scales with respect to with the intention to explore if the concentrations of other elements increase faster (scaling exponent > 1) or slower (<1) than the concentrations of N and P. For example, scaling exponents >1 suggest that favorable conditions for plant growth, i.e., environments rich in N and P, may require proportionally higher uptake of other essential elements than poor conditions. We show that the scaling exponent is rather insensitive to environmental conditions or plant species, and ranges from 0.900 to 2.479 (average 1.58) in nine out of ten data sets. For single elements, Mg has the smallest scaling exponent (0.031) and Mn the largest (2.147). Comparison between laboratory determined stoichiometric relations and field observations suggest that element uptake in field conditions often exceeds the minimal physiological requirements. The results provide evidence for the view that the scaling relations previously reported for N and P can be extended to other elements; and that N and P are the driving elements in plant stoichiometric relations. The stoichiometric niche volumes defined here could be used to predict plant performances in different environments.
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http://dx.doi.org/10.3389/fpls.2020.00023DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7020196PMC
February 2020

Genome Wide Associations of Growth, Phenology, and Plasticity Traits in Willow [ (L.)].

Front Plant Sci 2019 12;10:753. Epub 2019 Jun 12.

Department of Plant Biology, Uppsala BioCenter, Linnean Centre for Plant Biology, Swedish University of Agricultural Sciences, Uppsala, Sweden.

The short rotation biomass crop willow ( genera) has been of interest for bioenergy but recently also for biofuel production. For a faster development of new varieties molecular markers could be used as selection tool in an early stage of the breeding cycle. To identify markers associated with growth traits, genome-wide association mapping was conducted using a population of 291 accessions collected across Europe and Russia and a large set of genotyping-by-sequencing markers. The accessions were vegetatively propagated and planted in replicated field experiments, one in Southern Sweden and one in Central Sweden. Phenology data, including bud burst and leaf senescence, as well as different growth traits were collected and measured repeatedly between 2010 and 2017 at both field environments. A value of the plasticity for each accession was calculated for all traits that were measured the same year in both environments as the normalized accession value in one environment subtracted by the corresponding value in the other environment. Broad-sense accession heritabilities and narrow-sense chip heritabilities ranged from 0.68 to 0.95 and 0.45 to 0.99, respectively for phenology traits and from 0.56 to 0.85 and 0.24 to 0.97 for growth traits indicating a considerable genetic component for most traits. Population structure and kinship between accessions were taken into account in the association analyses. In total, 39 marker-trait associations were found where four were specifically connected to plasticity and interestingly one particular marker was associated to several different plasticity growth traits. Otherwise association consistency was poor, possibly due to accession by environment interactions which were demonstrated by the low structure adjusted accession correlations across environments (ranging from 0.40 to 0.58). However, one marker association with biomass fresh weight was repeatedly observed in the same environment over two harvest years. For some traits where several associations were found, the markers jointly explained over 20% of the accession variation. The result from this study using a population of unrelated accessions has given useful information about marker-trait associations especially highlighting marker-plasticity associations and genotype-by-environment interactions as important factors to take account of in future strategies of breeding.
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http://dx.doi.org/10.3389/fpls.2019.00753DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6582754PMC
June 2019

Mixture of Genotypes Promotes Root Colonization With Dark Septate Endophytes and Changes P Cycling in the Mycorrhizosphere.

Front Microbiol 2018 18;9:1012. Epub 2018 May 18.

Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.

The roots of spp. can be colonized by two types of mycorrhizal fungi (ectomycorrhizal and arbuscular) and furthermore by dark-septate endophytes. The fungal root colonization is affected by the plant genotype, soil properties and their interactions. However, the impact of host diversity accomplished by mixing different genotypes within the site on root-associated fungi and P-mobilization in the field is not known. It can be hypothesized that mixing of genotypes with strong eco-physiological differences changes the diversity and abundance of root-associated fungi and P-mobilization in the mycorrhizosphere based on different root characteristics. To test this hypothesis, we have studied the mixture of two fundamentally eco-physiologically different genotypes ( cv. 'Loden' and × cv. 'Tora') compared to plots with pure genotypes in a randomized block design in a field experiment in Northern Germany. We assessed the abundance of mycorrhizal colonization, fungal diversity, fine root density in the soil and activities of hydrolytic enzymes involved in P-mobilization in the mycorrhizosphere in autumn and following spring after three vegetation periods. Mycorrhizal and endophytic diversity was low under all treatments with being the dominating ectomyorrhizal fungal species, and and spp. being the most common endophytic fungi. Interspecific root competition increased richness and root colonization by endophytic fungi (four taxa in the mixture vs. one found in the pure host genotype cultures) more than by ectomycorrhizal fungi and increased the activities of hydrolytic soil enzymes involved in the P-mineralization (acid phosphatase and β-glucosidase) in mixed stands. The data suggest selective promotion of endophytic root colonization and changed competition for nutrients by mixture of genotypes.
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http://dx.doi.org/10.3389/fmicb.2018.01012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5968087PMC
May 2018

Altered Tuber Yield in Genetically Modified High-Amylose and Oil Potato Lines Is Associated With Changed Whole-Plant Nitrogen Economy.

Front Plant Sci 2018 15;9:342. Epub 2018 Mar 15.

Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.

Breeding for improved crop quality traits can affect non-target traits related to growth and resource use, and these effects may vary in different cultivation conditions (e. g., greenhouse vs. field). The objectives of this study are to investigate the growth and whole-plant nitrogen (N) economy of two genetically modified (GM) potato lines compared to their non-GM parental varieties and when grown in different cultivation conditions. A high-amylose GM potato line and its parent were grown under field and greenhouse conditions for one growing season in Sweden; and a GM oil potato line and its parent were grown in greenhouse conditions only. Tuber yield, above ground biomass, N uptake efficiency and other plant N economy traits were assessed. In both cultivation conditions, the GM lines produced between 1.5 and two times more tubers as compared with their parents. In the greenhouse, fresh tuber yield and N uptake efficiency were unaffected by the genetic modifications, but the GM-lines produced less tuber biomass per plant-internal N compared to their parents. In the field, the fresh tuber yield was 40% greater in the high-amylose line as compared with its parent; the greater fresh tuber yield in the high-amylose GM line was accomplished by higher water allocation to the harvested tubers, and associated with increased N recovery from soil (+20%), N uptake efficiency (+53%), tuber N content (+20%), and N accumulation (+120%) compared with the non-GM parent. The cultivation conditions influenced the yield and N economy. For example, the final fresh above-ground plant biomass and N pool were considerably higher in the greenhouse conditions, whilst the tuber yield was higher in the field conditions. In conclusion, the genetic modification inducing high accumulation of amylose in potato tubers affected several non-target traits related to plant N economy, and increased the plant N uptake and accumulation efficiency of the field-grown plants. Due to strongly increased plant N accumulation compared to the parental variety, the cultivation of the high-amylose line is expected to require higher N fertilization rates. However, starch productivity per unit land area or soil N still is expected to be higher in the high-amylose line.
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http://dx.doi.org/10.3389/fpls.2018.00342DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5862821PMC
March 2018

A transnational and holistic breeding approach is needed for sustainable wheat production in the Baltic Sea region.

Physiol Plant 2018 Dec 25;164(4):442-451. Epub 2018 Apr 25.

Department of Crop Production Ecology, SLU, Uppsala, Sweden.

The Baltic Sea is one of the largest brackish water bodies in the world. Eutrophication is a major concern in the Baltic Sea due to the leakage of nutrients to the sea with agriculture being the primary source. Wheat (Triticum aestivum L.) is the most widely grown crop in the countries surrounding the Baltic Sea and thus promoting sustainable agriculture practices for wheat cultivation will have a major impact on reducing pollution in the Baltic Sea. This approach requires identifying and addressing key challenges for sustainable wheat production in the region. Implementing new technologies for climate-friendly breeding and digital farming across all surrounding countries should promote sustainable intensification of agriculture in the region. In this review, we highlight major challenges for wheat cultivation in the Baltic Sea region and discuss various solutions integrating transnational collaboration for pre-breeding and technology sharing to accelerate development of low input wheat cultivars with improved host plant resistance to pathogen and enhanced adaptability to the changing climate.
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http://dx.doi.org/10.1111/ppl.12726DOI Listing
December 2018

Rice-duck co-culture for reducing negative impacts of biogas slurry application in rice production systems.

J Environ Manage 2018 May 26;213:142-150. Epub 2018 Feb 26.

Department of Crop Production Ecology, Swedish University of Agricultural Sciences, P.O. Box 7043, SE-750 07 Uppsala, Sweden. Electronic address:

Nitrogen (N) and phosphorus (P) losses are a potential limitation for the direct application of biogas slurry as a substitute for chemical fertilizer in irrigated rice production systems. The hypothesis was tested that a rice-duck co-culture promotes the rice N and P use efficiencies, reducing the losses of these nutrient elements through run-offs and enabling the use of biogas slurry as a substitute for chemical fertilizers. A field split-plot experiment was carried out to test the hypothesis. Our results showed that the direct application of biogas slurry was harmful for rice production. Compared with rice monoculture under chemical fertilization, biogas slurry application reduced N and P accumulation in grains, P use efficiency, and grain yield by 3.6%, 7.8%, 12.7%, and 14.8%, respectively, but increased the total N and P concentrations in the surface water 1.4- and 2.7-fold, respectively, on average on the eleventh day after fertilization. However, rice-duck co-culture compensated for the negative effects of biogas slurry on rice production. Under the biogas slurry application and in line with our hypothesis, the rice-duck co-culture significantly increased N and P accumulation and use efficiencies, as well as grain yield to levels similar to those acquired with chemical fertilization treatments. Meanwhile, total N and P concentrations were significantly lower for rice-duck co-culture than those of rice monoculture under biogas slurry application. Our results suggest that rice-duck co-culture can maintain rice yield and reduce the risks of N and P loss to local environments when utilizing biogas slurry as a substitute for chemical fertilizers.
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http://dx.doi.org/10.1016/j.jenvman.2018.02.077DOI Listing
May 2018

Genetics of phenotypic plasticity and biomass traits in hybrid willows across contrasting environments and years.

Ann Bot 2017 07;120(1):87-100

Swedish University of Agricultural Sciences, Department of Plant Biology, Uppsala BioCenter, Linnean Centre for Plant Biology, P.O. Box 7080, SE-750 07 Uppsala, Sweden.

Background And Aims: Phenotypic plasticity can affect the geographical distribution of taxa and greatly impact the productivity of crops across contrasting and variable environments. The main objectives of this study were to identify genotype-phenotype associations in key biomass and phenology traits and the strength of phenotypic plasticity of these traits in a short-rotation coppice willow population across multiple years and contrasting environments to facilitate marker-assisted selection for these traits.

Methods: A hybrid Salix viminalis  × ( S. viminalis × Salix schwerinii ) population with 463 individuals was clonally propagated and planted in three common garden experiments comprising one climatic contrast between Sweden and Italy and one water availability contrast in Italy. Several key phenotypic traits were measured and phenotypic plasticity was estimated as the trait value difference between experiments. Quantitative trait locus (QTL) mapping analyses were conducted using a dense linkage map and phenotypic effects of S. schwerinii haplotypes derived from detected QTL were assessed.

Key Results: Across the climatic contrast, clone predictor correlations for biomass traits were low and few common biomass QTL were detected. This indicates that the genetic regulation of biomass traits was sensitive to environmental variation. Biomass QTL were, however, frequently shared across years and across the water availability contrast. Phenology QTL were generally shared between all experiments. Substantial phenotypic plasticity was found among the hybrid offspring, that to a large extent had a genetic origin. Individuals carrying influential S. schwerinii haplotypes generally performed well in Sweden but less well in Italy in terms of biomass production.

Conclusions: The results indicate that specific genetic elements of S. schwerinii are more suited to Swedish conditions than to those of Italy. Therefore, selection should preferably be conducted separately for such environments in order to maximize biomass production in admixed S. viminalis × S. schwerinii populations.
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http://dx.doi.org/10.1093/aob/mcx029DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5737545PMC
July 2017

Two Genotypes Differ in Productivity and Nitrogen Economy When Grown in Monoculture and Mixture.

Front Plant Sci 2017 21;8:231. Epub 2017 Feb 21.

Department of Crop Production Ecology, Swedish University of Agricultural Sciences Uppsala, Sweden.

Individual plant species or genotypes often differ in their demand for nutrients; to compete in a community they must be able to acquire more nutrients (i.e., uptake efficiency) and/or use them more efficiently for biomass production than their competitors. These two mechanisms are often complementary, as there are inherent trade-offs between them. In a mixed-stand, species with contrasting nutrient use patterns interact and may use their resources to increase productivity in different ways. Under contrasting nutrient availabilities, the competitive advantages conferred by either strategy may also shift, so that the interaction between resource use strategy and resource availability ultimately determines the performance of individual genotypes in mixtures. The aim was to investigate growth and nitrogen (N) use efficiency of two willow () genotypes grown in monoculture and mixture in a fertilizer contrast. We explored the hypotheses that (1) the biomass production of at least one of the involved genotypes should be greater when grown in mixture as compared to the corresponding monoculture when nutrients are the most growth-limiting factor; and (2) the N economy of individual genotypes differs when grown in mixture compared to the corresponding monoculture. The genotypes 'Tora' ( ×) and 'Loden' (), with contrasting phenology and functional traits, were grown from cuttings in a growth container experiment under two nutrient fertilization treatments (high and low) in mono- and mixed-culture for 17 weeks. Under low nutrient level, 'Tora' showed a higher biomass production (aboveground biomass, leaf area productivity) and N uptake efficiency in mixture than in monoculture, whereas 'Loden' showed the opposite pattern. In addition, 'Loden' showed higher leaf N productivity but lower N uptake efficiency than 'Tora.' The results demonstrated that the specific functional trait combinations of individual genotypes affect their response to mixture as compared to monoculture. Plants grown in mixture as opposed to monoculture may thus increase biomass and vary in their response of N use efficiency traits. However, young plants were investigated here, and as we cannot predict mixture response in mature stands, our results need to be validated at field scale.
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http://dx.doi.org/10.3389/fpls.2017.00231DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5318404PMC
February 2017

Association mapping in L. (Salicaceae) - identification of candidate genes associated with growth and phenology.

Glob Change Biol Bioenergy 2016 May 29;8(3):670-685. Epub 2015 Jul 29.

Department of Plant Biology Uppsala BioCenter Swedish University of Agricultural Sciences and Linnean Center for Plant Biology P.O. Box 7043 750 07 Uppsala Sweden.

Willow species () are important as short-rotation biomass crops for bioenergy, which creates a demand for faster genetic improvement and breeding through deployment of molecular marker-assisted selection (MAS). To find markers associated with important adaptive traits, such as growth and phenology, for use in MAS, we genetically dissected the trait variation of a (L.) population of 323 accessions. The accessions were sampled throughout northern Europe and were established at two field sites in Pustnäs, Sweden, and at Woburn, UK, offering the opportunity to assess the impact of genotype-by-environment interactions (G × E) on trait-marker associations. Field measurements were recorded for growth and phenology traits. The accessions were genotyped using 1536 SNP markers developed from phenology candidate genes and from genes previously observed to be differentially expressed in contrasting environments. Association mapping between 1233 of these SNPs and the measured traits was performed taking into account population structure and threshold selection bias. At a false discovery rate (FDR) of 0.2, 29 SNPs were associated with bud burst, leaf senescence, number of shoots or shoot diameter. The percentage of accession variation (Radj2) explained by these associations ranged from 0.3% to 4.4%, suggesting that the studied traits are controlled by many loci of limited individual impact. Despite this, a SNP in the gene was repeatedly associated (FDR < 0.2) with bud burst. The rare homozygous genotype exhibited 0.4-1.0 lower bud burst scores than the other genotype classes on a five-grade scale. Consequently, this marker could be promising for use in MAS and the gene deserves further study. Otherwise, associations were less consistent across sites, likely due to their small Radj2 estimates and to considerable G × E interactions indicated by multivariate association analyses and modest trait accession correlations across sites (0.32-0.61).
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http://dx.doi.org/10.1111/gcbb.12280DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4973673PMC
May 2016

Editorial: Ecological Consequences of Biodiversity and Biotechnology in Agriculture and Forestry.

Front Plant Sci 2016 19;7:210. Epub 2016 Feb 19.

Department for Forest Botany and Tree Physiology, Büsgen-Institute, Georg-August-Universität Göttingen Göttingen, Germany.

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http://dx.doi.org/10.3389/fpls.2016.00210DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4760096PMC
February 2016

Erratum to: Genome-wide transcriptional and physiological responses to drought stress in leaves and roots of two willow genotypes.

BMC Plant Biol 2015 Dec 3;15:285. Epub 2015 Dec 3.

Department of Plant Biology, Uppsala BioCenter, Linnean Centre for Plant Biology, Swedish University of Agricultural Sciences, Uppsala, SE-750 07, Sweden.

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http://dx.doi.org/10.1186/s12870-015-0665-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4668637PMC
December 2015

Genome-wide transcriptional and physiological responses to drought stress in leaves and roots of two willow genotypes.

BMC Plant Biol 2015 Oct 12;15:244. Epub 2015 Oct 12.

Department of Plant Biology, Uppsala BioCenter, Linnean Centre for Plant Biology, Swedish University of Agricultural Sciences, SE-750 07, Uppsala, Sweden.

Background: Drought is a major environmental stress that can have severe impacts on plant productivity and survival. Understanding molecular mechanisms of drought responses is crucial in order to breed for drought adapted plant cultivars. The aim of the present study was to investigate phenotypic and transcriptional drought responses in two willow genotypes (520 and 592) originating from an experimental cross between S. viminalis × (S. viminalis × S. schwerinii). Willows are woody perennials in the Salicaceae plant family that are grown as bioenergy crops worldwide.

Methods: An experiment was conducted where plants were exposed to drought and different eco-physiological parameters were assessed. RNA-seq data was furthermore generated with the Illumina technology from root tips and leaves from plants grown in drought and well-watered (WW) conditions. The RNA-seq data was assembled de novo with the Trinity assembler to create a reference gene set to which the reads were mapped in order to obtain differentially expressed genes (DEGs) between the drought and WW conditions. To investigate molecular mechanisms involved in the drought response, GO enrichment analyses were conducted. Candidate genes with a putative function in the drought response were also identified.

Results: A total of 52,599 gene models were obtained and after filtering on gene expression (FPKM ≥ 1), 35,733 gene models remained, of which 24,421 contained open reading frames. A total of 5,112 unique DEGs were identified between drought and WW conditions, of which the majority were found in the root tips. Phenotypically, genotype 592 displayed less growth reduction in response to drought compared to genotype 520. At the transcriptional level, genotype 520 displayed a greater response in the leaves as more DEGs were found in genotype 520 compared to genotype 592. In contrast, the transcriptional responses in the root tips were rather similar between the two genotypes. A core set of candidate genes encoding proteins with a putative function in drought response was identified, for example MYBs and bZIPs as well as chlorophyll a/b binding proteins.

Discussion: We found substantial differences in drought responses between the genotypes, both at the phenotypic and transcriptional levels. In addition to the genotypic variation in several traits, we also found indications for genotypic variation in trait plasticity, which could play a role in drought adaptation. Furthermore, the two genotypes displayed overall similar transcriptional responses in the root tips, but more variation in the leaves. It is thus possible that the observed phenotypic differences could be a result of transcriptional differences mostly at the leaf level.

Conclusions: This study has contributed to a better general understanding of drought responses in woody plants, specifically in willows, and has implications for breeding research towards more drought adapted plants.
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http://dx.doi.org/10.1186/s12870-015-0630-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4604075PMC
October 2015

Contributions of a global network of tree diversity experiments to sustainable forest plantations.

Ambio 2016 Feb 12;45(1):29-41. Epub 2015 Aug 12.

Faculty of Biology, University of Freiburg, Schaenzlestrasse 1, 79104, Freiburg, Germany.

The area of forest plantations is increasing worldwide helping to meet timber demand and protect natural forests. However, with global change, monospecific plantations are increasingly vulnerable to abiotic and biotic disturbances. As an adaption measure we need to move to plantations that are more diverse in genotypes, species, and structure, with a design underpinned by science. TreeDivNet, a global network of tree diversity experiments, responds to this need by assessing the advantages and disadvantages of mixed species plantations. The network currently consists of 18 experiments, distributed over 36 sites and five ecoregions. With plantations 1-15 years old, TreeDivNet can already provide relevant data for forest policy and management. In this paper, we highlight some early results on the carbon sequestration and pest resistance potential of more diverse plantations. Finally, suggestions are made for new, innovative experiments in understudied regions to complement the existing network.
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http://dx.doi.org/10.1007/s13280-015-0685-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4709352PMC
February 2016

Trade-offs between seed output and life span - a quantitative comparison of traits between annual and perennial congeneric species.

New Phytol 2016 Jan 27;209(1):104-14. Epub 2015 Jul 27.

Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Uppsala, 75007, Sweden.

Perennial plants allocate more resources belowground, thus sustaining important ecosystem services. Hence, shifting from annual to perennial crops has been advocated towards a more sustainable agriculture. Nevertheless, wild perennial species have lower seed production than selected annuals, raising the questions of whether there is a fundamental trade-off between reproductive effort and life span, and whether such trade-off can be overcome through selection. In order to address these questions and to isolate life span from phylogenetic and environmental factors, we conducted a meta-analysis encompassing c. 3000 congeneric annual/perennial pairs from 28 genera. This meta-analysis is complemented with a minimalist model of long-term productivity in perennial species. Perennials allocate more resources belowground and less to seeds than congeneric annuals, independently of selection history. However, existing perennial wheat and rice could achieve yields similar to annuals if they survived three years and each year doubled their biomass, as other perennial grasses do. Selected perennial crops maintain the large belowground allocation of wild perennials, and thus can provide desired regulatory ecosystem services. To match the seed yield of annuals, biomass production of perennial grains must be increased to amounts attained by some perennial grasses - if this goal can be met, perennial crops can provide a more sustainable alternative to annuals.
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http://dx.doi.org/10.1111/nph.13574DOI Listing
January 2016

Genetic architecture of spring and autumn phenology in Salix.

BMC Plant Biol 2014 Jan 17;14:31. Epub 2014 Jan 17.

Department of Plant Biology, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, SE-750 07 Uppsala, Sweden.

Background: In woody plants from temperate regions, adaptation to the local climate results in annual cycles of growth and dormancy, and optimal regulation of these cycles are critical for growth, long-term survival, and competitive success. In this study we have investigated the genetic background to growth phenology in a Salix pedigree by assessing genetic and phenotypic variation in growth cessation, leaf senescence and bud burst in different years and environments. A previously constructed linkage map using the same pedigree and anchored to the annotated genome of P. trichocarpa was improved in target regions and used for QTL analysis of the traits. The major aims in this study were to map QTLs for phenology traits in Salix, and to identify candidate genes in QTL hot spots through comparative mapping with the closely related Populus trichocarpa.

Results: All traits varied significantly among genotypes and the broad-sense heritabilities ranged between 0.5 and 0.9, with the highest for leaf senescence. In total across experiment and years, 80 QTLs were detected. For individual traits, the QTLs explained together from 21.5 to 56.5% of the variation. Generally each individual QTL explained a low amount of the variation but three QTLs explained above 15% of the variation with one QTL for leaf senescence explaining 34% of the variation. The majority of the QTLs were recurrently identified across traits, years and environments. Two hotspots were identified on linkage group (LG) II and X where narrow QTLs for all traits co-localized.

Conclusions: This study provides the most detailed analysis of QTL detection for phenology in Salix conducted so far. Several hotspot regions were found where QTLs for different traits and QTLs for the same trait but identified during different years co-localised. Many QTLs co-localised with QTLs found in poplar for similar traits that could indicate common pathways for these traits in Salicaceae. This study is an important first step in identifying QTLs and candidate genes for phenology traits in Salix.
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http://dx.doi.org/10.1186/1471-2229-14-31DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3945485PMC
January 2014

Swedish spring wheat varieties with the rare high grain protein allele of NAM-B1 differ in leaf senescence and grain mineral content.

PLoS One 2013 21;8(3):e59704. Epub 2013 Mar 21.

Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.

Some Swedish spring wheat varieties have recently been shown to carry a rare wildtype (wt) allele of the gene NAM-B1, known to affect leaf senescence and nutrient retranslocation to the grain. The wt allele is believed to increase grain protein concentration and has attracted interest from breeders since it could contribute to higher grain quality and more nitrogen-efficient varieties. This study investigated whether Swedish varieties with the wt allele differ from varieties with one of the more common, non-functional alleles in order to examine the effect of the gene in a wide genetic background, and possibly explain why the allele has been retained in Swedish varieties. Forty varieties of spring wheat differing in NAM-B1 allele type were cultivated under controlled conditions. Senescence was monitored and grains were harvested and analyzed for mineral nutrient concentration. Varieties with the wt allele reached anthesis earlier and completed senescence faster than varieties with the non-functional allele. The wt varieties also had more ears, lighter grains and higher yields of P and K. Contrary to previous information on effects of the wt allele, our wt varieties did not have increased grain N concentration or grain N yield. In addition, temporal studies showed that straw length has decreased but grain N yield has remained unaffected over a century of Swedish spring wheat breeding. The faster development of wt varieties supports the hypothesis of NAM-B1 being preserved in Fennoscandia, with its short growing season, because of accelerated development conferred by the NAM-B1 wt allele. Although the possible effects of other gene actions were impossible to distinguish, the genetic resource of Fennoscandian spring wheats with the wt NAM-B1 allele is interesting to investigate further for breeding purposes.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0059704PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3605437PMC
January 2014

Autophagy mediates caloric restriction-induced lifespan extension in Arabidopsis.

Aging Cell 2013 Apr 28;12(2):327-9. Epub 2013 Feb 28.

Department of Plant Biology and Forest Genetics, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linnean Center for Plant Biology, PO Box 7080, Uppsala, SE-75007, Sweden.

Caloric restriction (CR) extends lifespan in various heterotrophic organisms ranging from yeasts to mammals, but whether a similar phenomenon occurs in plants remains unknown. Plants are autotrophs and use their photosynthetic machinery to convert light energy into the chemical energy of glucose and other organic compounds. As the rate of photosynthesis is proportional to the level of photosynthetically active radiation, the CR in plants can be modeled by lowering light intensity. Here, we report that low light intensity extends the lifespan in Arabidopsis through the mechanisms triggering autophagy, the major catabolic process that recycles damaged and potentially harmful cellular material. Knockout of autophagy-related genes results in the short lifespan and suppression of the lifespan-extending effect of the CR. Our data demonstrate that the autophagy-dependent mechanism of CR-induced lifespan extension is conserved between autotrophs and heterotrophs.
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http://dx.doi.org/10.1111/acel.12048DOI Listing
April 2013

Impact of ectomycorrhizal colonization and rust infection on the secondary metabolism of poplar (Populus trichocarpa x deltoides).

Tree Physiol 2012 Nov 12;32(11):1357-64. Epub 2012 Oct 12.

Soil Science, University of Rostock, Justus-von-Liebig-Weg 6, D-18059 Rostock, Germany.

Fungal colonization can significantly affect the secondary metabolism of the host plants. We tested the impact of a common below-ground symbiosis, i.e., ectomycorrhiza formation, on poplar leaf chemical components that are involved in the defence against a common disease, i.e., rust fungi, in N-deficient soil. A rust-susceptible poplar clone (Populus trichocarpa × deltoides 'Beaupré') was (a) non-associated with ectomycorrhizal fungus (EM) Hebeloma mesophaeum (Pers.) Quélet MÜN and non-infected with rust fungus Melampsora larici-populina Kleb. (isolate 98AG31), (b) associated with EM, (c) inoculated with rust fungus and (d) associated with EM and inoculated with rust fungus. Poplar leaves were analysed by photometric and mass spectrometric techniques (liquid chromatography-tandem mass spectrometry (LC-MS/MS), pyrolysis-field ionization mass spectrometry (Py-FIMS)). Both rust infection and mycorrhiza formation led to increased proportions of condensed tannins in relation to total phenolics (13% in the control, 18-19% in the fungal treatments). In contrast, salicylic acid concentration (6.8 µg g(-1) in the control) was higher only in the rust treatments (17.9 and 25.4 µg g(-1) with rust infection). The Py-FIMS analysis revealed that the rust-infected treatments were significantly separated from the non-rust-infected treatments on the basis of six flavonoids and one lipid. The relative abundance of these components, which have known functions in plant defence, was decreased after rust infection of non-mycorrhizal plants, but not in mycorrhizal plants. The results indicate that the ectomycorrhizal formation compensated the rust infection by a decrease in the flavonoid syntheses. The study provides new evidence for an interactive response of mycorrhizal colonization and infection with rust fungi in the metabolism of poplar.
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http://dx.doi.org/10.1093/treephys/tps093DOI Listing
November 2012

Plant stoichiometry at different scales: element concentration patterns reflect environment more than genotype.

New Phytol 2012 Jun 4;194(4):944-952. Epub 2012 Apr 4.

Department of Crop Production Ecology, Swedish University of Agricultural Sciences, PO Box 7043, SE-750 07 Uppsala, Sweden.

All plant species require at least 16 elements for their growth and survival but the relative requirements and the variability at different organizational scales is not well understood. We use a fertiliser experiment with six willow (Salix spp.) genotypes to evaluate a methodology based on Euclidian distances for stoichiometric analysis of the variability in leaf nutrient relations of twelve of those (C, N, P, K, Ca, Mg, Mn, S, Fe, Zn, B, Cu) plus Na and Al. Differences in availability of the elements in the environment was the major driver of variation. Variability between leaves within a plant or between individuals of the same genotype growing in close proximity was as large as variability between genotypes. Elements could be grouped by influence on growth: N, P, S and Mn concentrations follow each other and increase with growth rate; K, Ca and Mg uptake follow the increase in biomass; but uptake of Fe, B, Zn and Al seems to be limited. The position of Cu lies between the first two groups. Only for Na is there a difference in element concentrations between genotypes. The three groups of elements can be associated with different biochemical functions.
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http://dx.doi.org/10.1111/j.1469-8137.2012.04114.xDOI Listing
June 2012

Correspondence of ectomycorrhizal diversity and colonisation of willows (Salix spp.) grown in short rotation coppice on arable sites and adjacent natural stands.

Mycorrhiza 2012 Nov 14;22(8):603-13. Epub 2012 Mar 14.

Department of Microbiology, Institute of General and Molecular Biology, N. Copernicus University, Torun, Poland.

Willows (Salix spp.) are mycorrhizal tree species sometimes cultivated as short rotation coppice (SRC) on arable sites for energy purposes; they are also among the earliest plants colonising primary successional sites in natural stands. The objective of this study was to analyse the degree of colonisation and diversity of ectomycorrhizal (EM) communities on willows grown as SRC in arable soils and their adjacent natural or naturalized stands. Arable sites usually lack ectomycorrhizal host plants before the establishment of SRC, and adjacent natural or naturalized willow stands were hypothesized to be a leading source of ectomycorrhizal inoculum for the SRC. Three test sites including SRC stands (Salix viminalis, Salix dasyclados, and Salix schwerinii) and adjacent natural or naturalized (Salix caprea, Salix fragilis, and Salix × mollissima) stands in central Sweden were investigated on EM colonisation and morphotypes, and the fungal partners of 36 of the total 49 EM fungi morphotypes were identified using molecular tools. The frequency of mycorrhizas in the natural/naturalized stands was higher (two sites) or lower (one site) than in the corresponding cultivated stands. Correspondence analysis revealed that some EM taxa (e.g. Agaricales) were mostly associated with cultivated willows, while others (e.g. Thelephorales) were mostly found in natural/naturalized stands. In conclusion, we found strong effects of sites and willow genotype on EM fungi formation, but poor correspondence between the EM fungi abundance and diversity in SRC and their adjacent natural/naturalized stands. The underlying mechanism might be selective promotion of some EM fungi species by more effective spore dispersal.
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http://dx.doi.org/10.1007/s00572-012-0437-zDOI Listing
November 2012

Optimizing nitrogen economy under drought: increased leaf nitrogen is an acclimation to water stress in willow (Salix spp.).

Ann Bot 2011 Nov 6;108(7):1347-53. Epub 2011 Sep 6.

Department of Crop Production Ecology, POB 7043, Swedish University of Agricultural Sciences, Sweden.

Background And Aims: The major objective was to identify plant traits functionally important for optimization of shoot growth and nitrogen (N) economy under drought. Although increased leaf N content (area basis) has been observed in dry environments and theory predicts increased leaf N to be an acclimation to drought, experimental evidence for the prediction is rare.

Methods: A pedigree of 200 full-sibling hybrid willows was pot-grown in a glasshouse in three replicate blocks and exposed to two water regimes for 3 weeks. Drought conditions were simulated as repeated periods of water shortage. The total leaf mass and area, leaf area efficiency (shoot growth per unit leaf area, E(A)), area-based leaf N content (N(A)), total leaf N pool (N(L)) and leaf N efficiency (shoot growth per unit leaf N, E(N)) were assessed.

Key Results: In the water-stress treatment, shoot biomass growth was N limited in the genotypes with low N(L), but increasingly limited by other factors in the genotypes with greatest N(L). The N(A) was increased by drought, and drought-induced shift in N(A) varied between genotypes (significant G × E). Judged from the E(A)-N(A) relationship, optimal N(A) was 16 % higher in the water-stress compared with the well-watered treatment. Biomass allocation to leaves and shoots varied between treatments, but the treatment response of the leaf : shoot ratio was similar across all genotypes.

Conclusions: It is concluded that N-uptake efficiency and leaf N efficiency are important traits to improve growth under drought. Increased leaf N content (area basis) is an acclimation to optimize N economy under drought. The leaf N content is an interesting trait for breeding of willow bioenergy crops in a climate change future. In contrast, leaf biomass allocation is a less interesting breeding target to improve yield under drought.
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http://dx.doi.org/10.1093/aob/mcr227DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3197455PMC
November 2011

Genetic and environmental variation in spring and autumn phenology of biomass willows (Salix spp.): effects on shoot growth and nitrogen economy.

Authors:
Martin Weih

Tree Physiol 2009 Dec 29;29(12):1479-90. Epub 2009 Sep 29.

Department of Crop Production Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.

Six commercial willow (Salix spp.) varieties were examined to investigate the effects of genotype and environment on spring and autumn phenology and the relationships between phenology, shoot growth and leaf nitrogen (N) retranslocation. The willows were field-grown under different irrigation and fertilization in central Sweden. Two independent data sets of bud-burst, leaf unfolding duration, growth cessation and the timing of leaf abscission were assessed, and the biomass and leaf N data from the end of the first cutting cycle were used. Specific hypotheses were that (1) spring phenology has a greater effect on the shoot biomass production than autumn phenology; (2) later bud-burst is associated with more rapid leaf unfolding; (3) the timing of leaf abscission has a greater effect on the shoot biomass production than height growth cessation; and (4) later leaf fall is associated with poorer leaf N retranslocation. Bud-burst date varied by 19 and 39 days in the 2 years and leaf unfolding duration varied by 13 and 38 days. Growth cessation varied by 2.5 weeks and completion of leaf abscission (> 90% of leaves shed) by more than 3 weeks between the genotypes and treatments. Bud-burst date was inversely correlated with leaf unfolding duration (R(2) = 0.96). Significant effects of the duration of leafy period (bud-burst to leaf abscission) and bud-burst date on shoot growth were found. Delayed growth cessation and leaf abscission were generally associated with a greater biomass production, but especially the relationship between growth cessation and biomass was weak. The results show that the timing of bud-burst and leaf abscission is more important for willow biomass production than growth cessation. Delayed leaf abscission has a negative effect on leaf N retranslocation and increases the N losses. The results have implications for the breeding of perennial energy crops.
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http://dx.doi.org/10.1093/treephys/tpp081DOI Listing
December 2009

Mycorrhizas and biomass crops: opportunities for future sustainable development.

Trends Plant Sci 2009 Oct 10;14(10):542-9. Epub 2009 Sep 10.

Department of Biology, University of York, York, YO10 5YW, UK.

Central to soil health and plant productivity in natural ecosystems are in situ soil microbial communities, of which mycorrhizal fungi are an integral component, regulating nutrient transfer between plants and the surrounding soil via extensive mycelial networks. Such networks are supported by plant-derived carbon and are likely to be enhanced under coppiced biomass plantations, a forestry practice that has been highlighted recently as a viable means of providing an alternative source of energy to fossil fuels, with potentially favourable consequences for carbon mitigation. Here, we explore ways in which biomass forestry, in conjunction with mycorrhizal fungi, can offer a more holistic approach to addressing several topical environmental issues, including 'carbon-neutral' energy, ecologically sustainable land management and CO(2) sequestration.
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http://dx.doi.org/10.1016/j.tplants.2009.08.004DOI Listing
October 2009

Shoot biomass growth is related to the vertical leaf nitrogen gradient in Salix canopies.

Tree Physiol 2007 Nov;27(11):1551-9

Department of Crop Production Ecology, Swedish University of Agricultural Sciences, SE-750 07, Uppsala, Sweden.

Plant canopy optimization models predict that leaf nitrogen (N) distribution in the canopy will parallel the vertical light gradient, and numerous studies with many species have confirmed this prediction. Further, it is predicted that for a given canopy leaf area, a low vertical light extinction coefficient will promote rapid growth. Therefore, the ideal canopy of fast-growing plants should combine high leaf area index with a low light extinction coefficient; the latter being reflected in a flat vertical leaf N gradient throughout the canopy. Based on data from an experimental Salix stand (six varieties) grown on agricultural land in central Sweden, we tested the hypothesis that shoot growth is correlated with vertical leaf N gradient in canopies of hybrid willows bred for biomass production, which could have implications for Salix breeding. Tree improvement research requires screening of growth-related traits in large numbers of plants, but assessment of canopy leaf N gradients by chemical analysis is expensive, time-consuming and destructive. An alternative to analytical methods is to estimate leaf N gradients nondestructively with an optical chlorophyll meter (SPAD method). Here we provide a specific calibration for interpreting SPAD data measured in hybrid willows grown in biomass plantations on fertile agricultural land. Based on SPAD measurements, a significant and inverse relationship (r(2) = 0.88) was found between shoot biomass growth and vertical leaf N gradient across canopies of six Salix varieties.
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http://dx.doi.org/10.1093/treephys/27.11.1551DOI Listing
November 2007
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