Peter Ryser

Laurentian University, Biology, Faculty Member

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A starting guide to root ecology: strengthening ecological concepts and standardising root classification, sampling, processing and trait measurements

New Phytologist, 2021

SummaryIn the context of a recent massive increase in research on plant root functions and their ... more SummaryIn the context of a recent massive increase in research on plant root functions and their impact on the environment, root ecologists currently face many important challenges to keep on generating cutting‐edge, meaningful and integrated knowledge. Consideration of the below‐ground components in plant and ecosystem studies has been consistently called for in recent decades, but methodology is disparate and sometimes inappropriate. This handbook, based on the collective effort of a large team of experts, will improve trait comparisons across studies and integration of information across databases by providing standardised methods and controlled vocabularies. It is meant to be used not only as starting point by students and scientists who desire working on below‐ground ecosystems, but also by experts for consolidating and broadening their views on multiple aspects of root ecology. Beyond the classical compilation of measurement protocols, we have synthesised recommendations from ...

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Root porosity contributes to root trait space of wetland monocotyledons independently of economics traits

Plant and Soil, 2021

Aims Root aerenchyma, a key adaptive trait to anoxic soils has rarely been integrated into trait-... more Aims Root aerenchyma, a key adaptive trait to anoxic soils has rarely been integrated into trait-based plant ecology. This study aims to evaluate the relationship between root porosity and root economicsrelated traits among wetland plants, focusing on the effect of aerenchyma on root tissue density, a central trait in plant economics spectrum. Methods Root porosity, root tissue density with air-space included or excluded (RTD and RTDA), and other root economics-related traits were measured separately for basal and lateral roots of 16 garden-grown Ontario wetland monocots with contrasting root longevities. Results Interspeci c variation in root porosity was unrelated to root economics traits and did not differ between species with long-lived or short-lived roots. Consequently, RTDA better differentiated between species with contrasting root longevities than RTD did, consistently both for basal and lateral roots. Root dry matter content (RDMC) accurately predicted RTDA. A principal component analysis showed that in the root adaptive trait space of wetland plants, the rst dimension is de ned by economics-related traits, the second dimension by lateral root porosity and the ratio of lateral to basal root length, and the third dimension by basal root porosity. Conclusions Interspeci c variation in the aerenchyma content is independent of root economics: Wetland plants can construct economically conservative or acquisitive roots of any porosity. Consequently, to consistently express root functional relationships among wetland plant species, root tissue density should be expressed with RTDA, i.e., excluding the air space, or with the more easily measured RDMC.

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Root Suberin Plays Important Roles in Reducing Water Loss and Sodium Uptake in Arabidopsis thaliana

Metabolites, 2021

Suberin is a cell-wall-associated hetero-polymer deposited in specific plant tissues. The precise... more Suberin is a cell-wall-associated hetero-polymer deposited in specific plant tissues. The precise role of its composition and lamellae structure in protecting plants against abiotic stresses is unclear. In Arabidopsis thaliana, we tested the biochemical and physiological responses to water deficiency and NaCl treatment in mutants that are differentially affected in suberin composition and lamellae structure. Chronic drought stress increased suberin and suberin-associated waxes in wild-type plants. Suberin-deficient mutants were not more susceptible than the wild-type to the chronic drought stress imposed in this study. Nonetheless, the cyp86a1-1 cyp86b1-1 mutant, which had a severely altered suberin composition and lamellae structure, exhibited increased water loss through the root periderm. Cyp86a1-1 cyp86b1-1 also recorded lower relative water content in leaves. The abcg2-1 abcg6-1 abcg20-1 mutant, which has altered suberin composition and lamellae, was very sensitive to NaCl trea...

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Spring temperatures affect senescence and N uptake in autumn and N storage for winter in Rhynchospora alba (Cyperaceae)

Journal of Experimental Botany, 2019

Environmental and physiological factors underlying variation in timing of autumn senescence are n... more Environmental and physiological factors underlying variation in timing of autumn senescence are not well known. We investigated how the time of the onset of the growth in spring affects senescence and its functional consequences for nitrogen (N) uptake in autumn and storage of N for the winter, in a species that each year develops its bulbils for storage and overwintering anew. Rhynchospora alba was grown outdoors with two treatments, identical except for a 3 week difference in the start of growth in May. Leaf and root growth and senescence, and N uptake were recorded from August to November. By August, late-starting plants had caught up in size and total N content, but had smaller bulbils. They had a higher δ 13C, indicating a higher stomatal conductance during growth. Leaf and root senescence were delayed, extending 15N tracer uptake by 4 weeks. Nevertheless, after senescence, plants with an early start had 55% more N in their overwintering bulbils, due to earlier and more efficie...

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Influence of Gaps and Neighbouring Plants on Seedling Establishment in Limestone Grassland. Experimental Field Studies in Northern Switzerland

Journal of Vegetation Science, 1991

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Contrasting root overwintering strategies of perennial wetland monocots

Botany, 2018

Root turnover is an important contributor to ecosystem nutrient and carbon cycling, but seasonal ... more Root turnover is an important contributor to ecosystem nutrient and carbon cycling, but seasonal aspects of root mortality are not well known. This study tests the hypothesis that in strongly seasonal climates, such as in Northern Ontario, Canada, perennial wetland monocots fall into two distinct categories with respect to their root overwintering strategy: complete senescence or survival over the winter. Root survival in late winter and early spring was tested for a total of 26 species using vitality staining with tetrazolium chloride. Root survival in spring was either over 85% (18 species) or 0% (8 species). Lateral root survival was marginally lower than that of basal roots. In some species, low nutrient supply slightly increased root winter mortality, but did not change the seasonal pattern. We conclude that in a northern temperate climate, the overwintering strategies of roots of herbaceous monocots are binary: either avoidance or tolerance of the long unfavourable season, sim...

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Early Autumn Senescence in Red Maple (Acer rubrum L.) Is Associated with High Leaf Anthocyanin Content

Plants, 2015

Several theories exist about the role of anthocyanins in senescing leaves. To elucidate factors c... more Several theories exist about the role of anthocyanins in senescing leaves. To elucidate factors contributing to variation in autumn leaf anthocyanin contents among individual trees, we analysed anthocyanins and other leaf traits in 27 individuals of red maple (Acer rubrum L.) over two growing seasons in the context of timing of leaf senescence. Red maple usually turns bright red in the autumn, but there is considerable variation among the trees. Leaf autumn anthocyanin contents were consistent between the two years of investigation. Autumn anthocyanin content strongly correlated with degree of chlorophyll degradation mid to late September, early senescing leaves having the highest concentrations of anthocyanins. It also correlated positively with leaf summer chlorophyll content and dry matter content, and negatively with specific leaf area. Time of leaf senescence and anthocyanin contents correlated with soil pH and with canopy openness. We conclude that the importance of anthocyanins in protection of leaf processes during senescence depends on the time of senescence. Rather than prolonging the growing season by enabling a delayed senescence, autumn anthocyanins in red maple in Ontario are important when senescence happens early, possibly due to the higher irradiance and greater danger of oxidative damage early in the season.

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Regional distribution patterns of wetland monocots with different root turnover strategies are associated with local variation in soil temperature

New Phytologist

Chloroplast genomes of Lilium lancifolium, L. amabile, L. callosum, and L. philadelphicum: Molecular characterization and their use in phylogenetic analysis in the genus Lilium and other allied genera in the order Liliales

PloS one, 2017

Chloroplast (cp) genomes of Lilium amabile, L. callosum, L. lancifolium, and L. philadelphicum we... more Chloroplast (cp) genomes of Lilium amabile, L. callosum, L. lancifolium, and L. philadelphicum were fully sequenced. Using these four novel cp genome sequences and five other previously sequenced cp genomes, features of the cp genomes were characterized in detail among species in the genus Lilium and other related genera in the order Liliales. The lengths and nucleotide composition showed little variation. No structural variation was found among the cp genomes in Liliales. Gene contents were conserved among four newly sequenced cp genome in Lilium species, the only differences being in two pseudogenes. We identified 112 genes in 13 functional categories, 18 of which carried introns that were conserved among the species in Liliales. There were 16-21 SSR loci (>12 bp, >3 repeats) in the cp genomes in Lilium and the genomic locations of these loci were highly variable among the species. Average mutations were 15 SNPs per 1kb and 5 indels per 1kb, respectively, in the cp genomes o...

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Constraints of root response to waterlogging in Alisma triviale

Plant and Soil, Feb 1, 2011

To understand the economics of root aerenchyma formation in wetland plants, we investigated in de... more To understand the economics of root aerenchyma formation in wetland plants, we investigated in detail the response of Alisma triviale to waterlogging. We hypothesized costs being associated with development of a large root air space. In three outdoor pot experiments, seedlings (1 experiment) and mature plants (2 experiments) were grown under waterlogged and drained conditions for up to 2 months. Waterlogging promoted growth, and was associated with increased root porosity and decreased root density (fresh mass per volume). The increased formation of aerenchyma was associated with a higher root dry matter content for a given root density. Despite improved growth and earlier flowering, the waterlogged plants also showed signs of being constrained by the anoxic substrate, such as shallower roots, and a higher leaf dry matter content. The formation of aerenchyma was associated with costs, such as increased root dry matter content and reduced metaxylem vessel diameter. The faster growth of the seedlings under the waterlogged conditions, despite some signs of being stressed, was possibly a result of decreased requirements to allocate biomass below ground. In mature plants the increased aerenchyma allowed deeper root penetration, and ameliorated the effects of anoxia, reducing the differences in plant traits between the treatments.

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Using turf transplants to reintroduce native forest understory plants into smelter-disturbed forests

Restoration Ecology, 2015

Nutrient availability and limitation in traditionally mown and in abandoned limestone grasslands: a bioassay experiment

Management is necessary for the conservation of limestone grasslands. However, the traditional ma... more Management is necessary for the conservation of limestone grasslands. However, the traditional management of hay-making every year in July is no longer profitable for farmers. Hence many species-rich grasslands have become abandoned. The aim of this study is (a) to investigate the consequences of abandonment (as compared with annual mowing) on the availability of soil nutrients, and (b) to determine the type of nutrient limitation. The soil was taken from a long-term experimental site set up 22 years ago in northern Switzerland. The availability of soil N and P was assessed in a bioassay where soil from mown and unmown plots was supplied with different nutrient solutions or deionised water as control. Seedlings of Galium mollugo s.str. L. and Raphanus sativus ssp. oleiferus (DC) Metzg. were used as phytometer plants. Their growth in the control treatment was limited by N and P almost to the same extent, indicating that the availability of both elements was very low in this soil. P limited plant growth slightly more, but was overcome in the case of Raphanus by a high P content in the seeds. The N and P availability responded differently to management. The availability of N was slightly higher in soil from the abandoned plots, whereas the P availability did not differ significantly. Accumulation of nitrogen in the soil after abandonment did presumably not have any decisive effect on the vegetation because the amount was small and because the vegetation seemed primarily P-limited. The direct effect of mowing or abandonment on plants is therefore likely to be much more important for species composition than the minor changes in soil nutrients.

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Changes in the species composition and conservation value of limestone grasslands in Northern Switzerland after 22 years of contrasting managements

Perspectives in Plant Ecology, Evolution and Systematics, 2005

An experiment was established to assess the long-term effects of six different management types o... more An experiment was established to assess the long-term effects of six different management types on the species composition of dry limestone grasslands with the aim of finding an alternative to the traditional management (mowing annually in July) which is no longer economically viable. In addition to the traditional management (JU1), the following management types were applied experimentally for 22 years: mowing every 2 years in July (JU2), every 5 years (JU5), or not at all (ABN, abandonment), mowing annually in October (OCT), and controlled burning annually (CBR) at the end of winter. There were two study sites, Gra¨te and Gra¨tental, near Schaffhausen in N Switzerland, each with three replicate 5 m Â 10 m plots for every management. During the course of the experiment, the vegetation was recorded on 10 occasions, yielding 306 vegetation releve´s containing a total of 124 species. These data were analysed using correspondence analyses (CA). In addition, changes in the abundance of 16 plant species with high cover, high frequency or particular importance for nature conservation were examined in detail. The CA showed that the vegetation of the two study sites differed considerably, but that in both sites the various management types led to changes in floristic composition which were probably continuing even after 22 years. At the end of the experiment, on the Gra¨te site, species number in comparison to JU1 had declined in the following progressive order: OCT, JU2, JU5, CBR, ABN, where it was down to 70%. At the Gra¨tental site, species number showed no clear pattern, because of the immigration of 'new' species from the surrounding hedges and agricultural fields. Interestingly, Bromus erectus, the dominant species with a cover of 40-70% at the beginning, decreased to 5-30% under different managements, mainly because the regeneration of its tufts is affected by abandonment and particularly burning. The rhizomatous Brachypodium pinnatum showed the opposite pattern and increased from 5% to 60% in CBR. Trifolium medium as well as Salvia pratensis, Primula veris and other long-lived forbs of high conservation value tended to be favoured by OCT, CBR and/or ABN because they can store nutrients if they are not annually cut in July.

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Metal resistance in populations of red maple (< i> Acer rubrum</i> L.) and white birch (< i> Betula papyrifera</i> Marsh.) from a metal-contaminated region and …

Environmental Pollution, 2012

Metal resistance in populations of Acer rubrum and Betula papyrifera in the industrially contamin... more

Species richness and vegetation structure in a limestone grassland after 15 years management with six biomass removal regimes

Folia Geobotanica, 1995

Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears... more Each copy of any part of a JSTOR transmission must contain the same copyright notice that appears on the screen or printed page of such transmission. JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact

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Reliability of leaf relative water content (RWC) measurements after storage: consequences for in situ measurements

Botany, 2015

Relative water content (RWC) is widely used to describe plant water status, and is commonly measu... more Relative water content (RWC) is widely used to describe plant water status, and is commonly measured gravimetrically. The ephemeral nature of leaf fresh mass poses severe constraints for such measurements in fieldgrown plants. These constraints can be overcome by transporting the leaves in waterproof containers into the lab. However, even then, leaves lose water, and other changes may happen. The effects of a delay on the measurement of RWC have not been quantified so far. In this study, the influence of duration of storage up to 96 h and storage temperature on RWC and its components was investigated for four species. Alnus incana subsp. rugosa (Du Roi) R.T. Clausen, Impatiens capensis Meerb., and Scirpus microcarpus J.Presl & C.Presl leaves were stored in plastic bags, whereas those of Comptonia peregrina (L.) J.M.Coult. were stored in plastic vials. RWC remained within 5% of the initial value during 24 h cool storage, but after that, larger changes were observed. The effects of storage were species specific, being most pronounced in species poorly protected against desiccation, and under warm conditions. The effects of storage were not only limited to water loss, but also included cellular degradation. In general, storage at 10°C for 24 h enables measurement of RWC for field-grown plants with accuracy of a few percent, but care has to be taken with species vulnerable to desiccation, possibly requiring faster measurement and a cooler storage temperature.

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Positive interactions between plant species. I. Definition and examples from grassland ecosystems

Root survival of six cool-temperate wetland graminoids in autumn and early winter

Background: Timing of leaf senescence is an important ecological trait of species in cool-tempera... more Background: Timing of leaf senescence is an important ecological trait of species in cool-temperate climates. In contrast to above-ground biomass, not much is known about timing and extent of root mortality of herbaceous perennials at the end of the growing season.Aims: We undertook to assess patterns of end-of-season root mortality in species of temperate wetlands, investigate if the interspecific variation

Ifluence of gaps and neighbouring plants on seedling establishment in limestone grassland: Experimental field studies in northern Switzerland

Influence of seed bank and small mammals on the floristic composition of limestone grassland (Mesobrometum) in northern Switzerland

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