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Characterization of environmental stress responses during early development of Pringlea antiscorbutica in the field at Kerguelen
Abstract
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Early development of Kerguelen cabbage (Pringlea antiscorbutica) was studied in the Kerguelen archipelago, its natural habitat, and under laboratory conditions. Polyamines, which are involved in developmental processes and responses to stress in several plant species, were used as markers of physiological status of P. antiscorbutica seedlings.
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Analysis under laboratory conditions of responses to low water availability and to salinity enabled identification of major environmental constraints restricting seedling development in the subantarctic region.
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Salt stress was found to modify polyamine distribution between seedling organs, in controlled experiments and in the field, thus indicating that polyamine responses to salt stress were functional in the field at Kerguelen. By contrast, exposure to low water availability induced different polyamine responses in controlled experiments and in the field.
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The present work thus shows that, under certain conditions, polyamine concentrations can be used as a marker of specific stress responses of seedlings in the field. Discrepancies are discussed in terms of growth conditions in the laboratory and of combined stresses in natural habitats.
Supplementary resources (5)
Data
February 2004
... Des études sur le stress salin de plusieurs espèces végétales de la région subantarctique réparties depuis la côte jusqu'aux fellfields ont montré que ces plantes pouvaient être définies comme des glycophytes tolérant le stress salin (Smith 1978;Hennion and Bouchereau 1998;Hummel et al. 2004). ...
... Furthermore, sodium at high concentration can reduce stomata density and then alter photosynthesis (Orsini et al. 2011). In the sub-Antarctic region, studies of salt stress have been performed on several plant species some of which are spread from the coast up to fellfields, concluding that such plants could be defined as glycophytes tolerant of salt stress (Smith 1978;Hennion and Bouchereau 1998;Hummel et al. 2004). For L. kerguelensis, higher sodium concentrations in soil may add to other abiotic stresses in their habitats and increasetheir sensitivity to other osmotic stresses such as drought (Jamshidi Goharrizi et al. 2020) . ...
... In contrast, under warmer and drier climates, L. kerguelensis might experience a decrease in its growing season due to more frequent and/or intense drought in summer and winter as observed in alpine tundra (Ernakovich et al. 2014). Regeneration might be challenged as breaking dormancy will be harder under warmer and drier conditions and drought might easily damage seedlings as wilting of seedlings was already observed in summer in this species as well as in Pringlea antiscorbutica (Hummel et al. 2004). Furthermore, the results from our several approaches suggest that L. kerguelensis cushion necrosis may be accelerated in the driest and most saline environments. ...
The adaptive capacity of plants to climate change is defined as the ability of a species or population to cope with new environmental conditions and persist in surviving and reproducing. The Kerguelen Islands, in the sub-Antarctic region, harbour the long-lived endemic species, Lyallia kerguelensis Hook.f. (Montiaceae). The plant's distribution is restricted to the Island fellfields, regarded as a form of tundra ecosystem of rock with cold climate and strong winds. The plant might seem ill-equipped to face drastic climate change. Its strict endemism, relatively scarce distribution, cushion form and the occurrence of necrosis led to questioning its adaptive capacity. We hypothesized that the pool of variability (of morphology, transcriptome and soil rhizomicrobiome) of L. kerguelensis across contrasted environments might provide insights into its adaptation to harsh environments and its possible response to rapid climate change. In addition, we used data from long-term monitoring of the fate of populations and their morphological dynamics. L. kerguelensis’ morphology reveals allometry and responses to soil water content and wind intensity. Its transcriptome is region-specific with differential expression of genes related to abiotic or biotic stress responses. The microbiome of the Kerguelen Islands’ fellfield soils is specific and varies in relation to the soil nutrient content, and the rhizomicrobiome shows a similar variation while its composition is under the influence of the plant. Necrosis might be drought stress damages strongly related to fast drying and warming climate and might be worsened by salt stress and a shift in rhizomicrobiome composition. Finally, L. kerguelensis growth is very slow and population-specific and its life span is estimated at least several decades. Under current climate change trends in the Kerguelen Islands, L. kerguelensis may have the capacity to cope and change to adjust to environmental variation to a certain extent.
... Desiccation-tolerant mosses (Rensing et al., 2008) and Antarctic mosses (Pizarro et al., 2019) are examples of bryophyte life under extreme or subextreme conditions. Among vascular plants, Arctic, Antarctic and sub-Antarctic plants (Hummel et al., 2004;Cerfonteyn et al., 2011;Lee et al., 2013;Byun et al., 2015;Cho et al., 2018;Clemente-Moreno et al., 2020), alpine plants (Streb et al., 2003;Zhao et al., 2012;Munné-Bosch et al., 2016), ice plants (Oh et al., 2015), resurrection plants (Bartels & Salamini, 2001;Farrant & Moore, 2011;VanBuren et al., 2017), mangrove plants (Ball, 1988), xerophytes (Guo et al., 2010), cryophytes (Zhao et al., 2012), halophytes (Bose et al., 2014;Zeng et al., 2015), and metallophytes (Suryawanshi et al., 2016;Briskine et al., 2017) are considered to be extremophiles (Oh et al., 2012;Nawaz et al., 2017). ...
... The genome of Eutrema parvulum (formerly Thellungiella parvula) shows particular variations of gene copy numbers and tandem duplications in relation to stress tolerance functioning and regulation (Dassanayake et al., 2011;Oh et al., 2012). Genome comparison of E. salsugineum with Arabidopsis has shown an enrichment in the 'response to stimulus' gene ontology category, in particular in the In the sub-Antarctic environment, these indigenous plants are exposed to cold and windy conditions under a wide range of habitats from coastal areas to mountains (Hummel et al., 2004;Cerfonteyn et al., 2011). Image was taken by Dr Françoise Hennion within the framework of the Institut Polaire Français Paul-Emile Victor (research programme no. ...
... The physico-chemical conditions of extreme life, in terms of temperature, water potential, salinity, and ionic strength, impose drastic constraints on cell functioning (Oh et al., 2012;Polle & Chen, 2015) that lead to adjustments or perturbations of metabolic processes in the different compartments of the cell (Streb et al., 2003;Hummel et al., 2004;Paramonova et al., 2004;Ottow et al., 2005;Ellouzi et al., 2014;Challabathula et al., 2018). A number of these metabolic adjustments or perturbations generate regulatory signals that can be sensed and transduced into adaptive and protective responses (Slesak et al., 2003;Baena-González & Sheen, 2008;Schwarzländer & Finkemeier, 2013;Broeckx et al., 2016;Chan et al., 2016). ...
Plant life relies on complex arrays of environmental stress sensing and signalling mechanisms. Extremophile plants develop and grow in harsh environments with extremes of cold, heat, drought, desiccation or salinity, which have resulted in original adaptations. In accordance with their polyphyletic origins, extremophile plants likely possess core mechanisms of plant abiotic stress signalling. However, novel properties or regulations may have emerged in the context of extremophile adaptations. Comparative omics of extremophile genetic models, like Arabidopsis lyrata, Craterostigma plantagineum, Eutrema salsugineum, Physcomitrella patens, reveal diverse strategies of sensing and signalling that lead to general improvement of abiotic stress responses. Current research points out to putative differences of sensing and emphasises significant modifications of regulatory mechanisms, at the level of secondary messengers (Ca2+, phospholipids, reactive oxygen species), signal transduction (intracellular sensors, protein-kinases, transcription factors, ubiquitin-mediated proteolysis) or signalling crosstalk. Involvement of hormone signalling, especially ABA signalling, cell homeostasis surveillance and epigenetics mechanisms also shows that large-scale gene regulation, whole-plant integration, and probably stress memory are important features of adaptation to extreme conditions. This evolutionary and functional plasticity of signalling systems in extremophile plants may have important implications for plant biotechnology, crop improvement and ecological risk assessment under conditions of climate change.
... Th e authors reported that the increase in Put levels hinges also on the plant tissue in rice treated with KCl, NaCl or PEG: in roots it was detected for the salt-resistant cultivar, whereas in shoots -for salt-sensitive. Similarly, Hummel et al. (2004a) showed that the major eff ect, even after long-term exposure of Pringlea antiscorbutica seedlings to salinity and osmotic stress was the modification of PA distribution between roots and shoots. Higher PA content in roots was assumed to be a developmental response to stress and their accumulation in roots facilitated reinitiation of root growth. ...
... He et al. (2002) reported that the enhanced activity of SAMDC in spinach leaves, accompanied with an increase in Spd amounts in chloroplasts, are important for cold acclimation of photosynthetic apparatus. Hummel et al. (2004a) studied Kerguelen cabbage (Pringlea antiscorbutica, known to tolerate exposure to freezing temperature) seedling response to adverse conditions. Total PA pools and agmatine content in control plants were found to be higher in seedlings grown in the fi eld, where the mean temperature was lower than in controlled conditions. ...
This book describes the significance of amino acids and their derivatives in plant stress adaptation/tolerance, and presents biotechnological strategies for the manipulation of amino acids and their major derivatives to improve abiotic and abiotic stress tolerance in crop plants. Chapter 1 presents a general introduction on the role of amino acids and their derivatives in plant stress response. The succeeding chapters focus on amino acids and peptides (chapters 2-6), and amines and brassinosteroids (chapters 7-16), and their role in plant stress adaptation. A brief discussion of the prospects for further research (chapter 17) is included. This publication is suitable for scholars and researchers exploring sustainable strategies for crop improvement and abiotic stress tolerance.
... Les effets de ces modifications du climat sont analysés au niveau de certaines espèces autochtones, telles que le chou de Kerguelen Pringlea antiscorbutica, chez qui l'on a observé une mortalité importante des plantules lors des sécheresses estivales récentes. Les feuilles de P. antiscorbutica présentent des caractéristiques physiologiques incompatibles avec la tolérance à la sécheresse (Dorne & Bligny, 1993) et des expériences in situ ont montré que l'implantation des plantules est très restreinte dans les sites pauvres en eau, le stress hydrique affectant particulièrement le développement racinaire (Hummel et al., 2004). La plante âgée de quelques semaines manifeste bien une résistante certaine aux stress salins et aux cycles de gel-dégel, peutêtre aidée en cela par sa richesse en osmolytes (Aubert et al., 1999a,b), mais à l'inverse, la plasticité physiologique des plantules à l'égard des stress osmotiques est beaucoup plus faible (Hennion & Bouchereau, 1998;Hummel et al., 2004). ...
... Les feuilles de P. antiscorbutica présentent des caractéristiques physiologiques incompatibles avec la tolérance à la sécheresse (Dorne & Bligny, 1993) et des expériences in situ ont montré que l'implantation des plantules est très restreinte dans les sites pauvres en eau, le stress hydrique affectant particulièrement le développement racinaire (Hummel et al., 2004). La plante âgée de quelques semaines manifeste bien une résistante certaine aux stress salins et aux cycles de gel-dégel, peutêtre aidée en cela par sa richesse en osmolytes (Aubert et al., 1999a,b), mais à l'inverse, la plasticité physiologique des plantules à l'égard des stress osmotiques est beaucoup plus faible (Hennion & Bouchereau, 1998;Hummel et al., 2004). Par ailleurs, le développement de P. antiscorbutica est optimal en conditions froides, au contraire des plantes tempérées (Hennion & Martin-Tanguy, 2000), et la sensibilité du développement aux températures élevées apparaît dès les premiers jours suivant la germination (Dufeu et al., 2003). ...
Biological invasions, in connection with climate changes, are amongst the most significant threats to biodiversity worldwide. Even in antarctic and subantarctic regions, alien species arrived since the end of the 18th century. Most of these introductions are obviously associated with human activities and ship landings. Otherwise, as predicted by many global circulation models, rates of warming are expected to be stronger at
higher latitudes. Our study on the Kerguelen Islands confirms this trend and demonstrates that the effects of warming (+ 1.3°C since the mid 1960s) and summer droughts on plants and invertebrates are now visible. With climate change occurring rapidly, both the numbers of introductions and the success of colonisation by alien species are likely to increase, with as consequence subsequent impacts on the entire ecosystem.
... oban under saline condition (Mutlu and Bozcuk 2007 ) . A marked increase was noted in free Spd and Spm, soluble conjugated and insoluble bound Put, Spd and Spm contents in the roots of cucumber ( Cucumis sativus L) cultivar Changchun mici (comparatively tolerant to high salinity) than Jinchun No. 2 under short-term salt stress (Duan et al. 2008 ) . Hummel et al. ( 2004 ) observed the reduction in polyamines measured in shoots and partially in roots during long term exposure of Pringlea antiscorbutica seedlings to severe salinity (300 mM NaCl). Only spermine content was increased in roots after salt stress. The authors concluded that major effect of saline stress was the modi fi cation of polyamine distr ...
... The authors concluded that major effect of saline stress was the modi fi cation of polyamine distribution between roots and shoots. Higher Spm content in roots was a developmental response to stress and its accumulation in roots facilitated reinitiation of root growth (Hummel et al. 2004 ) . In general one possible mechanism is assumed which explain the participation of endogenous polyamines (primarily spermine) in plant salt tolerance. ...
Abiotic and biotic stresses cause alterations in the normal physiological processes of all plants, including the economically important crops. Plant damage and decrease in their productivity take place most often due to naturally occurring unfavorable factors of the environment (natural stress factors). These include extreme tempera-tures; water de fi cit or abundance; increased soil salinity; high solar irradiance; early autumn or late spring ground frosts; pathogens, etc. Along with these factors, plants are imposed to a large scale of new stressors related to human activity (anthropo-genic stress factors) including, toxic pollutants such as pesticides, noxious gasses (SO 2 , NO, NO 2 , NO x , O 3 and photochemical smog); photooxidants; soil acidi fi cation and mineral de fi cit due to acid rains; overdoses of fertilizers; heavy metals; intensi fi ed UV-B irradiation, etc. (Fig. 13.1). All these stresses cause an increased production of reactive oxygen species (ROS) in plants that alter their normal physio-logical functions, decrease the biosynthetic capacity of plant organisms, and cause damages which may lead to plant death (Mittler 2002 ; Ahmad et al. 2008 ; Gill and Tuteja 2010b ; Potters et al. 2010) . 13.1.1 Reactive Oxygen Species Independently of the type of stress (natural or anthropogenic), the accumulation of ROS is an undeniably established fact. Currently, overproduction of more than ten
... Specifically, fellfield plants such as the dominant, keystone species Azorella selago (Apiaceae) (Chapuis et al. 2004;le Roux et al. 2005), and species on well-drained soils (e.g. Aceana magellanica (Rosaceae) or Pringlea antiscorbutica (Brassicaceae): Chapuis et al. 2004;Hummel et al. 2004), or with shallow root systems (e.g. Ranunculus spp. ...
... At lower altitudes, where soils are moister and more organic, longer dry spells may also affect plant and invertebrate communities, particularly since lowland peat moisture content has already declined significantly between 1966 and 1991 (Chown and Smith 1993). Less frequent rainfall will result in higher soil salinity (wind-blown salt-spray will accumulate for longer; Huntley 1971), which can be lethal even for salt-tolerant species like Crassula moschata (Crassulaceae) (Berjak 1979; see also Hummel et al. 2004). Furthermore, two of the most important decomposers, the kelp fly Paractora dreuxi (Diptera: Helcomyzidae) (littoral zone) and the flightless moth Pringleophaga marioni (Lepidoptera: Tineidae) (mire habitats), are predicted to be negatively affected due to their larvae's sensitivity to desiccation (Klok and Chown 1997;Klok and Chown 2001). ...
The ecological consequences of climate change are determined by many climate parameters, not just by the commonly investigated
changes in mean temperature and rainfall. More comprehensive studies, including analyses of climate variability, extremes
and aggregate changes in the climate system, can improve the understanding of the nature, and therefore possible consequences,
of recent changes in climate. Here climate trends on the sub-Antarctic Marion Island are documented (between 1949 and 2003)
in more detail than previously. Significant trends in biologically-relevant, and previously unexplored, parameters were observed,
and the potential ecological consequences of these changes discussed. For example, the decline in precipitation experienced
on the island comprises a trend for longer dry spells punctuated by fewer and smaller precipitation events. This more detailed
understanding of the island’s drying trends enables more accurate predictions about its impacts, including, for example, particularly
severe effects on plant species growing in soils with poor water-holding capacity. Therefore, in addition to changes in average
conditions, more inclusive climate analyses should also examine trends in climatic variability and extremes, for individual
climate parameters as well as for the climate system as a whole.
... Polyamines or transgenic plants developed to express genes involved in the biosynthesis of polyamines. Since polyamines are regulated by various abiotic environmental stimuli, their cellular functions are: mineral nutrient deficiencies, metal toxicity (Alcázar et al., 2006;Choudhary et al., 2012), salinity, high and low temperatures (Hummel et al., 2004), drought (Alcázar et al., 2010), hypoxia (Moschou et al., 2008), infiltration (Osmotic) and oxidative factors (Gill and Tuteja, 2010). In addition to regulating the titer in response to external stimuli, polyamines also modify ion channels (Takahashi and Kakehi, 2010), stimulate the synthesis of specific proteins, stimulate the assembly of 30S ribosomal subunits and stimulate the formation of Ile-tRNAs (Igarashi and Kashiwagi, 2000). ...
Plants often face incompatible growing environments like drought, salinity, cold, frost,
and elevated temperatures that affect plant growth and development leading to low
yield and, in worse circumstances, plant death. The arsenal of versatile compounds for
plant consumption and structure is called metabolites, which allows them to develop
strategies to stop enemies, fight pathogens, replace their competitors and go beyond
environmental restraints. These elements are formed under particular abiotic stresses
like flooding, heat, drought, cold, etc., and biotic stress such as a pathogenic attack,
thus associated with survival strategy of plants. Stress responses of plants are vigorous
and include multifaceted crosstalk between different levels of regulation, including
regulation of metabolism and expression of genes for morphological and physiological
adaptation. To date, many of these compounds and their biosynthetic pathways have
been found in the plant kingdom. Metabolites like amino acids, phenolics, hormones,
polyamines, compatible solutes, antioxidants, pathogen related proteins (PR proteins),
etc. are crucial for growth, stress tolerance, and plant defense. This review focuses on
promising metabolites involved in stress tolerance under severe conditions and events
signaling the mediation of stress-induced metabolic changes are presented.
... Furthermore, sodium at high concentration can reduce stomata density and then alter photosynthesis (Orsini et al. 2011). In the sub-Antarctic region, studies of salt stress have been performed on several plant species some of which are spread from the coast up to fellfields, concluding that such plants could be defined as glycophytes tolerant of salt stress (Smith 1978;Hennion and Bouchereau 1998;Hummel et al. 2004). For L. kerguelensis plants, higher concentration in soil may add to other abiotic stresses in their habitats and increase their sensitivity to other osmotic stresses such as drought as was found in other plants (Jamshidi Goharrizi et al. 2020). ...
In recent decades, climate change has been faster in various parts of the world. Within species, to counter rapid climate changes shift of geographical area, individuals’ plastic responses or populations’ genetic adaptation might occur. The sub-Antarctic islands are subject to one of the most rapid climate changes on earth, with already visible impacts on native vegetation. Such might be the case of Lyallia kerguelensis a cushion plant strictly endemic to the Kerguelen Islands. In L. kerguelensis, necrotic parts were observed in cushions these last decades and possibly related to water stress. We analysed morphological variability of L. kerguelensis, including necrosis extent, across 19 populations spanning a wide range of environments across the Kerguelen Islands. Inter-population variations in the cushion surface area, shape and compactness were well explained by topography, degree of wind exposure, slope aspect, proportions of coarse sand and bare soil, and geographical distance between populations. All these variables are related to wind intensity and water availability. Moreover, in cushions with less than 10% necrosis in surface area, necrosis extent was positively correlated to soil sodium. Sodium availability might reduce the plant’s capacity for osmotic adjustment in face of other abiotic stresses, such as water stress. We conclude that cushion morphology may have the capacity to adjust to environmental variation, including aspects of climate change, but that cushion necrosis may be accelerated in the driest and most saline environments.
... There were relatively few significant correlations of individual compounds (amines or quercetins) with morphological traits (except for quercetins with the number of leaves) ( Table 4, Figures S3 and S4). Whatsoever, our study demonstrated that amine or quercetin compositions are related to both environmental conditions and traits in nature within species, a topic rarely addressed for amines [41] and never yet for quercetins [39]. ...
Plants produce a high diversity of metabolites which help them sustain environmental stresses and are involved in local adaptation. However, shaped by both the genome and the environment, the patterns of variation of the metabolome in nature are difficult to decipher. Few studies have explored the relative parts of geographical region versus environment or phenotype in metabolomic variability within species and none have discussed a possible effect of the region on the correlations between metabolites and environments or phenotypes. In three sub-Antarctic Ranunculus species, we examined the role of region in metabolite differences and in the relationship between individual compounds and environmental conditions or phenotypic traits. Populations of three Ranunculus species were sampled across similar environmental gradients in two distinct geographical regions in îles Kerguelen. Two metabolite classes were studied, amines (quantified by high-performance liquid chromatography and fluorescence spectrophotometry) and flavonols (quantified by ultra-high-performance liquid chromatography with triple quadrupole mass spectrometry). Depending on regions, the same environment or the same trait may be related to different metabolites, suggesting metabolite redundancy within species. In several cases, a given metabolite showed different or even opposite relations with the same environmental condition or the same trait across the two regions, suggesting metabolite versatility within species. Our results suggest that metabolites may be functionally redundant and versatile within species, both in their response to environments and in their relation with the phenotype. These findings open new perspectives for understanding evolutionary responses of plants to environmental changes.
... The authors noted that these cultivars are drought-sensitive and suggested that microsome-and thylakoid-associated PAs might be adequate markers of plant stress tolerance. Hummel et al. (2004) showed that after long term exposure of Pringlea antiscorbutica seedlings to osmotic stress the major effect was a redistribution of PA between roots and shoots. Moreover, higher PA content in roots was assumed to be a developmental response to stress and PA accumulation in roots facilitated root growth reinitiation. ...
This review highlights the recent advances concerning the role of polyamines and brassinosteroids in stress tolerance of plants with a special accent on drought. Alterations of the endogenous polyamine and brassinosteroid levels and their function in alleviation of drought stress are discussed. Possibilities for application of exogenous polyamines and brassinosteroids to lessen the stress injuries and to increase drought tolerance are also summarized. Genetic and molecular approaches for improving plant tolerance to drought via modification of polyamine levels and involvement of brassinosteroids in signal transduction pathways under stress are presented. Interaction of polyamines and brassinosteroids with phytohormones and osmolytes under drought stress is reviewed. We describe also the recent investigations in Bulgaria and Egypt concerning the modulation of plant reactions to drought stress by application of polyamines and brassinosteroids.
... These studies did not aim to identify persistent responses to community neighbourhood but sampled plants in situ which might show a particularly strong signal of reversible plasticity (which is very high in metabolites – Schweitzer et al. 2008 ). Among metabolites, amines are particularly interesting as these compounds are set at an interface between stress and developmental response in plants (Hummel et al. 2004). Therefore, amines are well suited to integrate growth and stress responses to different neighbourhoods . ...
* Global change triggers rapid alterations in the composition and diversity of plant communities which may change ecosystem functioning. Do changes in community diversity also change traits persistently, that is does coexistence with numerous or functionally or phylogenetically distinct species trigger, in a given focal species, trait shifts that persist? * We studied the grass Dactylis glomerata. Dactylis was grown in experimental plots with different species compositions for 5 years, sampled, cloned and grown in a common garden. We studied amines, regulators integrating growth responses of organisms to their environment. * We found that the mean levels and variances of most amines depended on the diversity of the source community, notably the species richness and the phylogenetic and functional distinctness from Dactylis, unbiased by species identity or biomass shifts. * Synthesis. Our results suggest that different levels of ambient diversity can, within a few years, select for different genotypes which have different compositions of growth regulators. Our study also suggests that a plant species can evolve in response to the diversity or distinctness of the surrounding plant community. Evolutionary changes of plant phenotypes might mediate an impact of past biological diversity on present ecosystem functioning
... Mature P. antiscorbutica plants show some salt tolerance with characteristics such as high levels of proline in all organs and proline accumulation in the cell cytoplasm in response to salt concentration in the surrounding medium Bouchereau 1998, Aubert et al. 1999a,b). In contrast, in field microenvironments as under laboratory experiments, water and salt stresses were shown to result in a drastic reduction of root growth and high mortality of seedlings, suggesting that seedling establishment of P. antiscorbutica may be restricted by climate change (Hummel et al. 2004b). ...
[extract] Antarctic ecosystems represent one extreme of the continuum of environmental conditions across the planet. To our eyes, the environment appears harsh but, even though terrestrial biological diversity is restricted, a wide range of life is present and, locally, thrives. In the Antarctic, unusually, environments exist in which physical characteristics are dominant and overcome biological considerations. These are at the extreme ends of the ranges of many characteristics (temperature, snow, ice and solar radiation) found across environments globally. However, the Antarctic is also a large continent, comparable in area to continental Europe, and further surrounded by the cold Southern Ocean, within which lie a ring of subantarctic islands. Together, these islands and the continent give a natural environmental gradient with which to study the biological impacts of climate variables.
Antarctica is also a focus for studies of responses to regional and global change (eg Bergstrom and Chown 1999, Convey 2001, 2003, Robinson et al. 2003). Some of the fastest changing regions on earth (air temperatures along the western Antarctic Peninsula and Scotia Arc) are found here (King and Haranzogo 1998, Skvarca et al. 1998, Smith 2002, Quayle et al. 2002, 2003). Evaluations of change in this area are expected to provide a vital ‘early warning system’ for change consequences worldwide (Convey et al. 2003a, b). This chapter addresses an area central to our ability to understand and evaluate biotic responses to climate change predictions – that of organism physiology.
... These studies did not aim to identify persistent responses to community neighbourhood but sampled plants in situ which might show a particularly strong signal of reversible plasticity (which is very high in metabolites - Schweitzer et al. 2008). Among metabolites, amines are particularly interesting as these compounds are set at an interface between stress and developmental response in plants (Hummel et al. 2004). Therefore, amines are well suited to integrate growth and stress responses to different neighbourhoods. ...
... The fact that endemic species have higher levels of phenotypic integration and are restricted to certain combinations of environmental conditions may have important implications given climate change trends in the sub-Antarctic (Bergstrom & Chown, 1999;Frenot et al., 2006). High sensitivity to desiccating conditions has already been reported for several endemic species and implies a limited ability to cope with certain environmental changes (Chapuis et al., 2004;Hummel et al., 2004). Moreover, a recent study has shown that a relatively short period of rapid warming has led to large changes in the distribution of species and community organization on Marion Island. ...
Aim. Why are some species geographically restricted? Ecological explanations suggest that endemic species may have restricted distributions because limited phenotypic variability results in narrow niches. However, studying variability of traits independently may not fully explain the interactions within and between complex phenotypes and environments. Here, we hypothesize that endemic species are restricted to a narrow range of habitats due to strong phenotypic integration (i.e. strong correlations among traits), strong environmental integration (i.e. strong correlations among the environments occupied) and strong correlations among trait–environment combinations.
Location. Kerguelen Islands, sub-Antarctic.
Methods. We measured flowering phenology, multiple morphological characters, and species distribution along three abiotic environmental gradients (elevation, soil moisture and soil salinity) in 14 plant species whose distributions range from strictly endemic to cosmopolitan.
Results. We found that for individual species trait means and variances were independent of endemism, but that endemics occupied higher and less variable microhabitats. However, phenotypic integration, environmental integration along the three gradients, and the strength of trait–environment correlations all increased with the level of species endemism.
Main conclusions. Higher levels of integration within and between phenotypes and environments are associated with more restricted geographical ranges in the species studied. In endemic species phenotypic integration may explain range contraction during the taxon cycle and reduce the ability to adapt to novel microhabitats formed as a result of environmental change.
... ADC is known to respond to abiotic stresses in plants but is not usually accumulated ( Bouchereau et al. 1999a, Hennion and Martin-Tanguy 2000, Kasinathan and Wingler 2004. Previous work on P. antiscorbutica seedling development strongly suggested ADC to be the major pathway for PA biosynthesis in Pringlea and had shown larger variations in Agm than other PAs in relation to environmental conditions ( Hummel et al. 2002, Hummel et al. 2004a, 2004b. This work expands the finding of Agm accumulation in P. antiscorbutica to various populations from different sites or geographical origins. ...
Although polyamine (PA) metabolism in plants responds to abiotic stresses, few studies have investigated this response in plants under natural conditions. Using high-performance liquid chromatography, we studied the amine composition of the subantarctic crucifer Pringlea antiscorbutica R. Br. both in the field (Crozet and Kerguelen Islands) and under controlled temperatures in the laboratory. Plants collected from different sites showed a large variability of amine composition and contents. The aliphatic and acetylated amine composition of leaves allowed to statistically identify two groups. The first group, composed of Kerguelen coastal plants, was characterized by high levels of acetylspermidine and acetylspermine, showing the presence in P. antiscorbutica of this uncommon regulation pathway. PA acetylation may be induced in P. antiscorbutica under conditions of low water availability. The second group, composed of plants from Kerguelen altitude sites and plants from Crozet sites, showed high levels of free spermidine (Spd). In these plants, the ratio Spd/putrescine did not positively correlate with plant size as was found in developmental studies, suggesting that free Spd may be devoted to other aims, such as cold tolerance. Some differences between Crozet and Kerguelen plant responses suggested the possibility that different regulations of amine metabolism could take place in plants from these two islands. Agmatine accumulation pattern was diverse and suggested this amine to be sensitive to combinations of environmental factors. Studies on amine variation patterns in P. antiscorbutica provide insights into the roles of rarely reported amines, such as acetylated amines, in plant metabolic adaptation to abiotic stresses.
... Previous studies have focused on the physiological adaptation of the Kerguelen cabbage to the windy and cold subantarctic climate (e.g. Hennion and Bouchereau 1998; Aubert et al. 1999; Hummel et al. 2004a). Very little is known about its mating system, although this information would be crucial for understanding the current evolution of this species. ...
The reproductive biology of Pringlea antiscorbutica R. Br. (Brassicaceae), an endemic species from the southern Indian Ocean islands, is investigated here. Controlled crosses were performed between plants grown in a common garden on the Kerguelen Islands. Searching for potential insect pollinators, we investigated the flying ability of all insects known from the Kerguelen Islands. We showed evidence for self-compatibility, low pollen limitation in the absence of a biotic pollen vector and slight selfing depression in P. antiscorbutica. The insects present on the islands are mostly wingless and are not likely to be efficient pollinators of this species. Since P. antiscorbutica shows morphological adaptations to insect pollination despite the absence of pollinators in its present range, we conclude that this species recently evolved from insect pollination to wind and/or autonomous pollination.
Microclimate is the most appropriate measure of climate affecting species. Understanding microclimate variation is essential
for predicting effects of climate change on species. This study examined (1) variation in microclimate temperatures associated
with Azorella selago Hook. (Apiaceae) across Marion Island, (2) differences between microclimate temperature and meteorological station temperatures,
and (3) effect of A. selago on microclimate temperatures. Microclimate temperatures were shown to vary significantly with altitude and island side. The
microclimate associated with A. selago was also more extreme than meteorological station temperature ranges suggest. A. selago was shown to ameliorate temperature conditions compared to those on the ground. Given the biotic differences that have been
documented between the sides of Marion Island, this finding argues strongly for improved understanding of spatial variability
in Marion Island’s climate. Such understanding is particularly critical given the rapid rate of climate change currently being
experienced by the island.
Premise of the study:
While plants show lineage-specific differences in metabolite composition, plant metabolites are also known to vary in response to the environment. The extent to which these different determinants of metabolite composition are mutually independent and recognizable is unknown. Moreover, the extent to which the metabolome can reconcile evolutionary constraint with the needs of the plant for rapid environmental response is unknown. We investigated these questions in plant species representing different phylogenetic lineages and growing in different subantarctic island environments. We studied their amines-metabolites involved in plant response to environmental conditions.
Methods:
Nine species were sampled under high salinity, water saturation, and altitude on the Kerguelen Islands. Their profiles of free aromatic, aliphatic, and acetyl-conjugated amines were determined by HPLC. We related amine composition to species and environment using generalized discriminant analyses.
Key results:
Amine composition differed significantly between species within the same environment, and the differences reflected phylogenetic positions. Moreover, across all species, amine metabolism differed between environments, and different lineages occupied different absolute positions in amine/environment space. Interestingly, all species had the same relative shifts in amine composition between environments.
Conclusion:
Our results indicate a similar response of amine composition to abiotic environments in distantly related angiosperms, suggesting environmental flexibility of species is maintained despite major differences in amine composition among lineages. These results aid understanding of how in nature the plant metabolome integrates ecology and evolution, thus providing primordial information on adaptive mechanisms of plant metabolism to climate change.
Polyamines have been demonstrated to play an important role in adventitious root formation and development in plants. Here, we present a detailed analysis of influence of exogenously added polyamines on adventitious root development and its relationship to cold tolerance in Virginia pine (Pinus virginia Mill.). Our results demonstrated that polyamines putrescine (Put), spermidine (Spd), and spermine (Spm) at 0.001 mM improve rooting frequency and promote root elongation. Put, Spd, and Spm at 0.01-1 mM decrease rooting frequency and reduce root elongation root elongation. Measurements of diamine oxidase (DAO, EC 1.4.3.6) and polyamine oxidase (PAO, EC 1.4.3.4) activities showed that higher DAO and PAO enzyme activities were obtained when high concentrations of polyamines were applied and when plantlets were treated for 5-7 week at 4 degrees C and 16 degrees C. Survival rate of plantlets increased with the treatment of polyamines at low temperature. Polyamines increased mitotic index of cells in root tips of regenerated plantlet cultured on medium containing 0.001 microM Put, Spd, or Spm, but did not increase mitotic index in tissues of needle tips of the same plantlets. These results demonstrated that polyamines promote root elongation and growth by increasing root cell division in regenerated Virginia pine plantlets.
Wild velvet-grass (Hocus lanatus) collected from a natural population along a drought gradient, previously demonstrated as genetically homogeneous, was studied for phenotypic plasticity and acclimation mechanisms to water deficits. A three months greenhouse experiment was designed with plants submitted to nine levels of water availability, three months being the usual length of summer drought in field conditions. Aboveground biomass, total soluble proteins, free proline, free polyamines, leaf morphology, stomatal and hair characteristics, and net photosynthetic rates were analysed, and their significance discussed. Moderate drought did not damage the velvet-grass, and the plants grew better than without water limitation. Water stress-typical responses were shown as time and severity dependent in all the measured parameters. Lowest water availability treatments induced significative increase in free proline and soluble protein contents, as well as reductions in leaf size and aboveground biomass. Spermidine contents rose significatively in the most severe water stress. Furthermore, velvet-grass acclimated progressively to long-term water limitation.
The effect of salinity stress on the activity of arginine decarboxylase (ADC, EC 4.1.1.19), the first enzyme in biosynthesis of polyamines (PA) from arginine, as well as its transcript level has been compared in salt-sensitive (M-1-48) and salt-tolerant (Pokkali) rice cultivars. Treatment of 72 h grown seedlings either with increasing concentrations of NaCl or with 150 mM NaCl for different time periods, showed a gradual increase of activity in Pokkali. In M-1-48 an immediate increase followed by sharp decrease was observed on prolonged treatment beyond 6 h or above 150 mM NaCl. To generate a DNA probe for ADC, the polymerase chain reaction was used with oat genomic DNA and sequence-specific primers. A region of oat genomic DNA containing a coding sequence for 166 amino acids of the C-terminal part of the ADC enzyme was amplified and called OAD1. Southern analysis of EcoRI- or BamHI-cut genomic DNAs from different cultivars of rice with OAD1 as the probe revealed strong hybridization with one DNA fragment of rice and restriction fragment length polymorphism (RFLP) was noticed. Northern analysis of total RNA of rice with OAD1 as the probe revealed hybridization with a transcript of similar size to the ADC transcript in oat. While in Pokkali, at least a 20-fold accumulation of OAD1 homologous transcript was detected after treatment with 200 mM NaCl, only a seven-fold increase in transcript level was found in M-1-48 after 150 mM NaCl treatment. Results suggest that in the salt-tolerant rice cultivar Pokkali, ADC enzyme activity increases and its transcript also accumulates during the prolonged salinity stress, this mechanism is absent in the salt-sensitive rice cultivar M-1-48 where a prolonged period of salinity stress down-regulates both ADC activity and its transcript level.
This paper presents the first results from a 7-year monitoring of Pringlea plants established naturally from seed at Kerguelen at two sites with different microenvironmental characteristics. The field
growth and reproductive traits of Pringlea are reported for the first time. Pringlea plants grow much faster than was previously believed, attaining around 50 cm diameter in 4 years. The growth pause in winter
is short. Pringlea first flowers mainly in its 3rd or 4th year of growth and, as such, this species can be described as an early-flowering perennial.
Inter-individual variability for all growth and reproductive parameters was generally higher than inter-site variability.
These biological traits are compared to other subantarctic phanerogams and are discussed in terms of adaptation to subantarctic
climate and ecological distribution of Pringlea antiscorbutica.
Pringlea antiscorbutica R. Br., a subantarctic endemic cruciferous species, is endangered in its natural sites by several ecological changes. This
species is tolerant to salinity and a permanent cold temperature on Kerguelen and Crozet Islands. We attempted the investigation
of regulating mechanisms of osmotic adjustment in this species. 13C NMR analyses of water-soluble compounds from leaves collected from the field revealed glucose and proline to be the main
accumulated organic solutes. Colorimetric determinations in these samples showed that proline and soluble carbohydrates were
present at remarkably high levels. When young plants were cultivated in growth chambers they showed a good resistance to cold
and medium resistance to saline conditions. High levels of soluble carbohydrates were present in all situations. Proline was
accumulated in response to a saline and a cold treatment. The quantitative variations of the pool of proline in response to
saline treatments were rapid and important. The adaptive value of these responses of organic solutes in the tolerance of Pringlea antiscorbutica to various stresses is discussed.
Seeds of six endemic species and two circumpolar species were collected from several sites on Kerguelen and tested for germination
between 5 and 25°C on thermogradient bars. Pringlea antiscorbutica and Colobanthus kerguelensis had a near 100% viability with an initial germination temperature of ca. 24°C. Colobanthus attained nearly 100% viability from 5 to 25°C whereas Pringlea germination declined markedly below 20°C. In Poa kerguelensis and P. cookii germination was poor and varied between sites. The three Ranunculus spp. showed various degrees of dormancy. In Lyallia kerguelensis, although the seed appeared mature, a variety of treatments could only partly release an apparently deep dormancy. These
data are discussed with respect to field observations on reproduction from seed.
Morphological descriptions of the seeds of eight phanerogamic species are provided together with observations on the dispersal
of the seeds and the habitats of parent plants. These are discussed in relation to long-distance dispersal and proposals are
made for future research.
Root development is under the control of hormonal, metabolic, and environmental cues that can act on genetically-controlled developmental programmes and thus affect the plasticity of root architecture. These processes involve not only the five `classical' plant hormones, but also other growth regulators, such as polyamines. The present review emphasises the importance of polyamines in the different aspects of root development: primary root growth and lateral and adventitious root formation. Free (agmatine, putrescine, spermidine, spermine), conjugated (such as hydroxycinnamate conjugates) and macromolecule-bound polyamines are reported to be present in root systems. Modifications of their endogenous levels by inhibitor treatment, by mutation, by gene manipulation, or by exogenous treatment can have drastic effects on root development and subsequent architecture. These effects may be related to the involvement of polyamines in the control of cell division and differentiation, which plays an important role in the root apex and during lateral and adventitious root formation. The exact mechanisms of action remain to be elucidated, but accumulating evidence in plant and animal cells supports the idea that, besides biophysical effects on membranes and nucleic acids, polyamines interact with protein kinases and transcription factors and are thus involved in signal transduction pathways. The high flexibility of polyamine metabolism in response to environmental stress and the metabolic link between polyamine and ethylene synthesis strongly suggest that polyamines may play a role in environmentally-induced plasticity of root development. Moreover, polyamines may be implicated in the establishment of biotic interactions between roots and rhizospheric micro-organisms.
The possible involvement of polyamines (PAs) in the chilling tolerance of cucumber (Cucumis sativus L. cv Jinchun No. 3 and cv Suyo) was investigated. Plants with the first expanded leaves were exposed to 3 degrees C or 15 degrees C in the dark for 24 h (chilling), and then transferred to 28 degrees C/22 degrees C under a 12-h photoperiod for another 24 h (rewarming). Chilling-tolerant cv Jinchun No. 3 showed a marked increase of free spermidine (Spd) in leaves, once during chilling and again during rewarming. Putrescine increased significantly during rewarming, but the increase of spermine was slight. Any of these PAs did not increase in chilling-sensitive cv Suyo during either period. PA-biosynthetic enzyme activities appear to mediate these differences between cultivars. Pretreatment of Spd to cv Suyo prevented chill-induced increases in the contents of hydrogen peroxide in leaves and activities of NADPH oxidases and NADPH-dependent superoxide generation in microsomes and alleviated chilling injury. Pretreatment of methylglyoxal-bis-(guanylhydrazone), a PA biosynthesis inhibitor, to chilled cv Jinchun No. 3 prevented Spd increase and enhanced microsomal NADPH oxidase activity and chilling injury. The results suggest that Spd plays important roles in chilling tolerance of cucumber, probably through prevention of chill-induced activation of NADPH oxidases in microsomes.
Plant responses to salt and water stress have much in common. Salinity reduces the ability of plants to take up water, and this quickly causes reductions in growth rate, along with a suite of metabolic changes identical to those caused by water stress. The initial reduction in shoot growth is probably due to hormonal signals generated by the roots. There may be salt-specific effects that later have an impact on growth; if excessive amounts of salt enter the plant, salt will eventually rise to toxic levels in the older transpiring leaves, causing premature senescence, and reduce the photosynthetic leaf area of the plant to a level that cannot sustain growth. These effects take time to develop. Salt-tolerant plants differ from salt-sensitive ones in having a low rate of Na+ and Cl-- transport to leaves, and the ability to compartmentalize these ions in vacuoles to prevent their build-up in cytoplasm or cell walls and thus avoid salt toxicity. In order to understand the processes that give rise to tolerance of salt, as distinct from tolerance of osmotic stress, and to identify genes that control the transport of salt across membranes, it is important to avoid treatments that induce cell plasmolysis, and to design experiments that distinguish between tolerance of salt and tolerance of water stress.
The possible involvement of polyamines in the chilling tolerance of spinach (Spinacia oleracea L.) was investigated focusing on photosynthesis. During chilling at 8/5C (day/night) for 6 d, S-adenosylmethionine decarboxylase (SAMDC) activity increased significantly in leaves in parallel with the increase in putrescine and spermidine (Spd) content in leaves and chloroplasts. Treatment of leaves with methylglyoxal-bis(guanylhydrazone) (MGBG), an SAMDC inhibitor, resulted in the deterioration of plant growth and photosynthesis under chilling conditions, which was reversed by the concomitant treatment with Spd through the roots. Plants treated with MGBG showed lower photochemical efficiency of PSII than either the control or plants treated with MGBG plus Spd during chilling and even after transfer to warm conditions, suggesting an increase of photoinhibition due to low Spd in chloroplasts. Indeed, MGBG-treated plants had much lower activities of thylakoid electron transport and enzymes in carbon metabolism as well as higher degrees of lipid peroxidation of thylakoid membranes compared to the control. These results indicate that the enhanced activity of SAMDC with a consequential rise of Spd in chloroplasts is crucial for the cold acclimation of the photosynthetic apparatus in spinach leaves.
Polyamine involvement in root development at low temperature was studied in seedlings of Pringlea antiscorbutica R. Br. This unique endemic cruciferous species from the subantarctic zone is subjected to strong environmental constraints
and shows high polyamine contents. In the present study, free polyamine levels were modified by inhibitors of polyamine biosynthesis
(d‐arginine, difluoromethylornithine, cyclohexylammonium, and methylglyoxal‐bis‐guanylhydrazone) and variations of the endogenous pools were compared to changes in root growth. The arginine decarboxylase
pathway, rather than that of ornithine decarboxylase, seemed to play a major role in polyamine synthesis in Pringlea antiscorbutica seedlings. Root, but not shoot, phenotypes were greatly affected by these treatments, which modified polyamine endogenous
levels according to their expected effects. A positive correlation was found between agmatine level and growth rate of the
primary root. Spermidine and spermine contents also showed positive correlations with primary root growth whereas the putrescine
level showed neutral or negative effects on this trait. Free polyamines were therefore found to be differentially involved
in the phenotypic plasticity of root architecture. A comparison of developmental effects and physiological concentrations
suggested that agmatine and spermine in particular may play a significant role in the control of root development.
The possible involvement of polyamines (PAs) in the chilling tolerance of cucumber (Cucumis sativus L. cv Jinchun No. 3 and cv Suyo) was investigated. Plants with the first expanded leaves were exposed to 3°C or 15°C in the dark for 24 h (chilling), and then transferred to 28°C/22°C under a 12-h photoperiod for another 24 h (rewarming). Chilling-tolerant cv Jinchun No. 3 showed a marked increase of free spermidine (Spd) in leaves, once during chilling and again during rewarming. Putrescine increased significantly during rewarming, but the increase of spermine was slight. Any of these PAs did not increase in chilling-sensitive cv Suyo during either period. PA-biosynthetic enzyme activities appear to mediate these differences between cultivars. Pretreatment of Spd to cv Suyo prevented chill-induced increases in the contents of hydrogen peroxide in leaves and activities of NADPH oxidases and NADPH-dependent superoxide generation in microsomes and alleviated chilling injury. Pretreatment of methylglyoxal-bis-(guanylhydrazone), a PA biosynthesis inhibitor, to chilled cv Jinchun No. 3 prevented Spd increase and enhanced microsomal NADPH oxidase activity and chilling injury. The results suggest that Spd plays important roles in chilling tolerance of cucumber, probably through prevention of chill-induced activation of NADPH oxidases in microsomes.
Silver sagebrush (Artemisia cana Pursh), a common shrub on Northern Mixed Prairie in Canada, is an excellent species to consider for ecological restoration. On the Canadian Prairies, freezing temperatures can occur during April and early May, months when most silver sagebrush seedlings emerge. Decreasing temperatures in autumn or exposure to freezing temperatures through winter may also be lethal to seedlings of this long-lived shrub. The purpose of this study was to characterize freezing tolerance in silver sagebrush seedlings because low temperatures may reduce establishment. Seedlings were grown from 1 week to 1 full growing season, exposed to freezing temperatures under controlled conditions, and lethal temperatures for 50 and 95% mortality $({\rm LT}_{50}\ \text{and}\ {\rm LT}_{95})$ were determined. Averaged across 1- to 6-week-old seedlings, LT50 and ${\rm LT}_{95}$ were -7.7 and -11.1°C, respectively. Changes in mortality with temperature variations were more gradual in younger than older seedlings, and mean ${\rm LT}_{95}$ was 2.8°C lower in 1- and 2-week than 4- and 6-week-old seedlings. Within age groups, death after freezing was greater in non-acclimated than acclimated seedlings. Virtually no non-acclimated seedlings survived -14°C, while mortality of acclimated seedlings was nearly nil in most cases. Only 6.9% (SE = 5.5) of seedlings grown under field conditions died in November after exposure to -39°C. Freezing tolerance of field-grown seedlings remained high over winter; seedling mortality after exposure to -39 and -45°C averaged 5.6% (SE = 4.1) in March. No seedlings survived temperatures lower than -15°C in April, and predicted LT50 and ${\rm LT}_{95}$ averaged -15.6 and -19.3°C, respectively. Increased mortality after freezing in April indicates seedlings de-acclimated as temperatures rose and day length increased in spring. Since the potential of developing freezing tolerance is greater in older than younger seedlings, silver sagebrush seedlings that germinate early in growing season may survive the winter better than those germinating later. Under normal circumstances, temperatures on the Canadian Prairies should not threaten survival of silver sagebrush seedlings during their first winter.
Rice (Oryza sativa L.) frequently confronts chilling injury at seedling stage when it is grown in early spring in temperate and subtropical areas. Understanding the physiological and genetic bases of chilling resistance should benefit our improvement of tolerance of rice seedlings to the stress. Previous study revealed that an accumulation of abscisic acid (ABA) or polyamines in rice seedlings responding to low temperature may be correlated with the chilling resistance of seedlings. The objective of this study, using rice seedlings with various genetic backgrounds, was to explore the relationships among the capacity of accumulation in ABA, putrescine, and chilling tolerance. Changes in ABA and putrescine levels in shoots and roots of seedlings after chilling treatment (5°C) were measured and compared among 11 rice cultivars ranging from chilling-tolerant to sensitive. On exposure of seedlings to chilling, ABA and putrescine accumulated rapidly in both shoots and roots of chilling-tolerant cultivars. Changes in ABA levels were closely correlated with chilling tolerance of the tested cultivars (r = 0.96 in shoots and 0.92 in roots). Changes of putrescine levels in shoots were also positively correlated with the cultivar resistance to chilling (r = 0.95). Furthermore, among the tested cultivar, there was also a high correlation between the relative changes of ABA and putrescine in shoots. Our results suggest chilling-induced changes in ABA and putrescine levels may be used as physiological markers for chilling tolerance of rice seedlings
The leaves, stems and roots of the subantarctic endemic species from Kerguelen Lyallia kerguelensis showed different patterns of amine accumulation. The leaves contained the highest free amine, stems the intermediate and roots the lowest content. Leaves accumulated massively agmatine and tyramine, whereas stems contained high levels of octopamine and spermidine. A high content of an amine which was co-chromatographed with homospermidine was observed in leaves and stems. Conjugated amines did not accumulate to any significant extent in stems and roots, whereas they were detected in high amounts in
leaves.
Proline is one of the major solutes accumulated upon salt stress in leaves, stem and roots of the subantarctic Brassicaceae Pringlea antiscorbutica R. Br. (Kerguelen cabbage). Using in vivo13C-NMR techniques, it was possible for the first time to visualize the subcellular compartmentation of proline between cytoplasmic and vacuolar compartments in Pringlea leaves. We observed that this osmolyte accumulated at a 2–3 times higher concentration in the cytoplasm than in the vacuole.
Pringlea antiscorbutica R. Br., an endemic crucifer from the Kerguelen Archipelago in the subantarctic, has been previously shown to be unable to acclimatize to 25°C when transferred after several months cultivation under cold conditions. Furthermore, the polyamine composition was greatly modified in such high-temperature-treated plants. The development of seedlings of this species was investigated under a regime mimicking the subantarctic summer thermoperiod (5/10°C night/day) and a regime with high temperatures (22/25°C night/day). In parallel, the associated changes in polyamine composition that occurred during the first 6 days of seedling life were determined. Marked acceleration of seedling growth and intense cotyledon greening were observed at day 4 in 5/10°C-grown seedlings but not in 22/25°C-grown seedlings. Seedlings grown at high temperature accumulated agmatine and putrescine, whereas cold-cultivated seedlings maintained high levels of spermidine. Cold-cultivated seedlings accumulated the uncommon long-chain polyamines norspermidine and homospermidine. These seedlings also accumulated free 1,3-diaminopropane, cadaverine, N1-acetylspermidine, N1-acetylspermine and bound polyamines, whereas seedlings under high temperature accumulated N1-acetylputrescine. Aromatic amine metabolism also appeared to be very responsive to temperature: seedlings under a cold regime accumulated free dopamine and bound phenylethylamine and tyramine, whereas seedlings grown at high temperature accumulated free tyramine. The possible relationships between the observed amine patterns and seedling growth under low and high temperature are discussed.
The subantarctic Brassicaceae Pringlea antiscorbutica R. Br. (Kerguelen cabbage) was used as a model to study the physiological adaptations of higher plants to the subantarctic environment. 13C-nuclear magnetic resonance permitted, in combination with biochemical methods, the identification and quantification of the major solutes in leaves, stem and roots. As characterized in many Brassicaceae, proline was a major solute in all organs of the plants, and its accumulation was mainly controlled by salt stress rather than temperature. Glucose was the major soluble sugar in the leaves, whilst sucrose and starch accumulated in stems and roots. Over a period of 1 year we found strong correlations between (i) glucose content in leaves and irradiance, and (ii) starch content in non-photosynthetic organs and air temperature. The pattern of carbohydrate accumulation indirectly indicated that photosynthetis was sustained throughout the year, even during cold days when the temperature remained near 0 °C. This is consistent with the direct gas exchange measurements showing that photosynthetic capacity is mainly influenced by irradiance and weakly by temperature. Taken together, these characteristics demonstrated that the growth and development cycle occurs without a period of dormancy.
Changes of ABA levels in chilled rice (Oryza sativa L.) seedlings of two varieties were determined. On exposure to chilling, ABA concentration rapidly increased in the chilling-tolerant cultivar (cv. Tainung 67, TNG.67) but not in the chilling-sensitive cultivar (cv. Taichung Native 1, TN.1). Both detached shoots and roots of TNG.67 seedlings showed a significant ABA increase after exposure to chilling. TN.1 seedlings could not accumulate ABA under low temperature but well-watered status. Exogenous application of the ABA biosynthetic inhibitor, fluridone, reduced ABA accumulation, as well as survival ratio of chilled TNG.67 seedlings. Electrolyte leakage and leaf conductance were also increased by the inhibitor and the effects could be reversed by exogenously applied ABA. ABA concentrations in xylem sap of TNG.67 seedlings increased within 4 h after chilling, and this was temporally coincident with the reduction of leaf conductance. The roles of endogenous ABA in the tolerance of rice seedlings to chilling on a whole plant basis are discussed and suggested.
Different polyamine and aromatic amine compositions and contents were observed in the leaves and the roots of plants from the subantarctic crucifer Pringlea antiscorbutica growing in the field and collected during the austral summer in Kerguelen and those grown under controlled conditions mimicking the thermoperiod and photoperiod conditions in summer in Kerguelen. In controlled conditions, the plants grew more slowly than in the field and did not flower. In roots, this was associated with an increase of agmatine (Agm). In contrast, acetylated putrescine (Put) disappeared while dopamine (Dop) and tryptamine (Try) were strongly reduced. In leaves, cultivation under controlled conditions led to an accumulation of Agm, acetylated Put, tyramine (Tyr) and Try. A complete depletion of acetylated spermidine (Spd) and spermine (Spm) and a strong decrease of Dop occurred. Cultivation of plants at constant 25°C was lethal after a few weeks. Before the external symptoms of heat challenge became acute, leaves and roots showed a different amine content and composition. In roots, and to a lesser extent in leaves, heat treatment was associated with an apparent impairment in the ability to accumulate Agm, acetylated Put and Try. Strong increases in Put, Spd and Tyr and accumulation of hydroxycinnamoyl amines as feruloylputrescine, feruloylspermidine and feruloyltyramine were observed in leaves. Aminoguanidine, a potent and specific inhibitor of diamine oxidase activities, caused phenotypic alterations and changes in amine composition and content in roots and leaves of Pringlea plants similar to those observed under the heat treatment. Our results highlight possible roles of amine catabolism, acetylated polyamines and hydroxycinnamoyl amines in plant responses to external conditions.
The Kerguelen cabbage, Pringlea antiscorbutica, is an endemic species restricted to some Subantarctic Islands, Up to now, all long term acclimatation assays of Kerguelen cabbage in the temperate zones remained unsuccessful. In the field, the Pringlea leaf relative water content (RWC) never decreased below 83%. At the same time the leaf diffusion resistance (LDR) remained low since the water flux was not limited in the plant as in these islands the soil water content is permanently high. Severe water deprivation was necessary to induce stomatal closure with excised leaves. In parallel in vitro experiments, irreversible damage to photosynthesis and respiration were observed in leaf slices under osmotic stress. These results sustain the hypothesis that Kerguelen cabbage can not support water deprivation and is probably specifically adapted to the subantarctic climate.
The McDonald Islands (53°03′S, 72°36′E) are situated in the southern Indian Ocean, approximately 43 km west of Heard Island. These sub-Antarctic islands comprise
McDonald Island itself, measuring ca.1 × 2 km, and two much smaller rocky outcrops, Flat Island and Meyer Rock. Five species
of vascular plant occur on the islands. Only four species of moss were found, no hepatics, and eight species of lichen, together
with algal and fungal species. Phanerogamic vegetation, comprising grassland and cushion-carpet herbfield, covers about one-third
of the main island. Elsewhere, vegetation is absent or restricted to cryptogamic species. The distribution and occurrence
of vegetation are strongly influenced by salt deposition, exposure to wind, substrate stability and biotic influences, particularly
the very large assemblages of sea birds. The species-depauperate McDonald Islands are unique and have suffered negligible
human impact. A management plan has been prepared; its implementation will be assisted by the information in this paper. The
islands' protection will be further enhanced by an affirmative final decision on the current proposal for World Heritage Listing
of Heard and the McDonald Islands.
A review is presented of the recent developments in the metabolism andfunction of polyamines in plants. Polyamines appear to be involved in a widerange of plant processes so their exact role is not completely understood. Inthis review, the metabolic pathways involved in polyamine biosynthesis anddegradation are explained, along with the transport and conjugation of thesecompounds. The methodologies involved in the analysis of polyamine functionusing metabolic inhibitors and genetic and molecular approaches are described.The occurrence and distribution of polyamine-derived alkaloids are also dealtwith. The direction of future research in the study of plant polyamines isindicated.
In order to precise the relative importance of ionic and osmotic components of salt stress on modification of free polyamine level, seedling of two rice cultivars (I Kong Pao (IKP): salt-sensitive and Pokkali: salt-resistant) were exposed to isoosmotic concentrations of NaCl, KCl (50 and 100 mM) or polyethylene glycol (PEG 6000, 16 and 26%) for a maximal period of 12 h in daylight conditions. Both ion and polyamine concentrations were already modified after 3 h of exposure to ionic stresses. At the shoot level, this response occurred independently of any change in the plant water status. Conversely, exposure to 26% PEG during 12 h induced a strong decrease in shoot osmotic potential and water content but had only a limited impact on endogenous free polyamine level. It was thus suggested that the ionic component by itself might trigger short-term polyamine accumulation. This effect might be attributed to monovalent ions, although K+ and Na+ accumulation had different effects on polyamine content. Putrescine may assume differential role in non-photosynthetic organs versus photosynthetic ones since it accumulated to high amounts in the roots of the salt-resistant cultivar Pokkali comparatively to salt-sensitive cultivar IKP, while an opposite trend was recorded in the shoots. Tyramine was also present at higher concentrations in the roots of Pokkali; its level clearly increased in response to ionic stresses while cadaverine level increased in water stress conditions only. No clear relationship was observed between the mean level of salinity resistance and the endogenous concentrations of spermidine or spermine.
The effects of putrescine on germination and seedling growth of Atropa belladonna plants under the influence of NaCl were studied. Rate of germination, seedling growth, endogenous putrescine and alkaloids content decreased when seeds were subjected to salt stress. Presoaking seeds in 10−2 mM putrescine and treatment with NaCl reduced the net accumulation of sodium and chloride ions in different organs of the plant. Thus, presoaking seeds in 10−2 mM putrescine can alleviate the adverse effect of NaCl during germination and early seedling growth of A. belladonna and increase alkaloids as well as endogenous putrescine.
We have investigated the role of abscisic acid (ABA) in the regulation of polyamine biosynthesis in rice (Oryza sativa L.) seedlings exposed to chilling (5°C). In a chilling-tolerant cultivar (cv. Tainung 67, TNG.67), levels of free putrescine and activity of arginine decarboxylase (ADC, EC 4.1.1.19) in both shoots and roots, and levels of free spermidine/spermine and activity of S-adenosylmethionine decarboxylase (SAMDC, EC 4.1.1.50) in shoots increased after exposure to chilling. In a chilling-sensitive cultivar (cv. Taichung Native 1, TN.1), level of free putrescine and activity of ADC in shoots increased slightly after exposure to chilling while those in roots decreased. Activity of ornithine decarboxylase (ODC, EC 4.1.1.17) in both cultivars remained unchanged after exposure to chilling. α-Difluoromethylarginine (DFMA), an irreversible inhibitor of ADC, but not α-difluoromethylornithine (DFMO), an irreversible inhibitor of ODC, at 0.5 mM inhibited free putrescine accumulation in chilled TNG.67 and resulted in a decrease in chilling tolerance; a decrease in survival and an increase in electrolyte leakage. The effects of DFMA were partially reversed by the addition of 0.5 mM putrescine. In TNG.67, chilling induced an increase of free ABA levels first, then ADC activity and finally free putrescine levels. Fluridone, an inhibitor of ABA synthesis, at 0.5 mM inhibited the increase of free ABA levels, ADC activity and free putrescine levels in chilled TNG.67, and resulted in a less tolerance of TNG.67 to chilling; these effects could be reversed by the pre-chilling treatment of 10 μM ABA. Application of 10 μM ABA for 48 h before chilling not only rendered TN.1 tolerant to chilling but also induced a change of polyamine pattern to be similar to chilled TNG.67. It seems that, for the materials used in this study, one of strategies of rice seedlings to resist chilling stress is to raise ABA levels and, in turn, one of ABA's functions is to enhance the ADC-mediated putrescine synthesis.
Seminal rice (Oryza sativa L. cv. Taichung Native 1) roots were grown in vitro to investigate the relationships among polyamine biosynthesis, root growth and chilling tolerance. At 25°C, the level of free putrescine and the activities of arginine decarboxylase (ADC; EC 4.1.1.19) and ornithine decarboxylase (ODC; EC 4.1.1.17) increased as growth progressed while the levels of free spermidine/spermine and the activity of S-adenosylmethionine decarboxylase (SAMDC, EC 4.1.1.50) decreased. Exogenously applied putrescine, ranging from 0.01 to 1 mM, enhanced the elongation of roots grown at 25°C whereas application of spermidine or spermine inhibited root elongation. α-Difluoromethylarginine (DFMA) at 5 μM or α-difluoromethylornithine (DFMO) at 10 μM inhibited the increase in root length and the levels of free putrescine at 25°C; these effects were reversed by the addition of 1 mM putrescine. Roots exposed to 5°C ceased growth and lost their re-growth ability after 9 days of chilling. The level of free putrescine and the activity of ADC in chilled roots increased with a peak at day 3 and then decreased to a plateau after 9 days. The levels of free spermidine and spermine increased after 9 days. When putrescine was applied at concentrations greater than 0.1 mM, chilled roots partially recovered their re-growth ability. Contrary to DFMO (10 μM), DFMA (5 μM) inhibited both the chilling-induced free putrescine increase and the re-growth ability of chilled roots, and these effects were reversed by 1 mM putrescine. These results suggest that polyamines are related to growth of rice roots cultured in vitro. The relationships between putrescine and chilling tolerance is discussed.
Several studies in arid ecosystems have demonstrated that seedling establishment and survival were greater underneath the canopies of shrubs than in the open spaces between shrubs. These results led to the formulation of the hypothesis that seedling recruitment and survival were dependent on the shelter provided by shrub species (nurse-plant hypothesis). Seedling emergence and survival beneath and between the canopies of selected perennial shrub species were investigated at five localities in the Strandveld Succulent Karoo, each dominated by a different shrub species. Seedling emergence and survival were also examined at three localities dominated by annual species. In general, species richness and seedling densities were significantly higher in open areas than underneath shrubs, while seedling survival percentages did not differ significantly between microsites. Therefore, no evidence could be found to support the hypothesis that seedling recruitment and survival were facilitated by the presence of shrub species. Although most species will be able to establish in the absence of shrubs, the presence of woody species may have other advantages when restoring vegetation in mined areas.
Lettuce seeds from nine cultivars were germinated under control and saline (150 mM NaCl) conditions. The effect of salt stress on germination, growth, ethylene production, respiration rate and polyamine levels was investigated. Salinity delayed germination and reduced the growth of all studied cultivars, but only significantly reduced final germination percentage in Inverna and Baby Star cultivars, while the other seven cultivars reached 100% germination under saline conditions. Respiration rate and ethylene production increased with salinity in all the nine lettuce cultivars. Moreover, cultivars that had a higher increase in ethylene production under salt stress showed the lowest reduction in fresh weight. The presence of salt reduced putrescine (Put) level, while spermidine (Spd) and spermine (Spm) increased. The effects of salinity on ethylene production and polyamine metabolism are discussed in relation to salinity tolerance of lettuce seedlings. The possible role of ethylene and polyamines as physiological markers for salinity tolerance in lettuce seedlings is also discussed.
In this review, we will try to summarize some recent data concerning the changes in polyamine metabolism (biosynthesis, catabolism and regulation) in higher plants subjected to a wide array of environmental stress conditions and to describe and discuss some of the new advances concerning the different proposed mechanisms of polyamine action implicated in plant response to environmental challenges. All the data support the view that putrescine and derived polyamines (spermidine, spermine, long-chained polyamides) may have several functions during environmental challenges. In several systems (except during hypoxia, and chilling tolerance of wheat and rice) an induction of polyamines (spermidine, spermine) not putrescine accumulation, may confer a stress tolerance. In several cases stress tolerance is associated with the production of conjugated and bound polyamines and stimulation of polyamine oxidation. In several environmental challenges (osmotic-stress, salinity, hypoxia, environmental pollutants) recent results indicate that both arginine decarboxylase and ornithine decarboxylase are required for the synthesis of putrescine and polyamines (spermidine and spermine). Under osmotic and salt-stresses a production of cadaverine is observed in plants. A new study demonstrates that under salt-stress putrescine catabolism (via diamine oxidase) can contribute to proline (a compatible osmolyte) accumulation.
After dispersal, seeds can germinate and establish as seedlings, persist as seeds, or die. Knowledge of these three seed fates is crucial for understanding the abundance and distribution of plant populations and ultimately, community composition and diversity. Few studies, however, have simultaneously measured these fates, while also examining the factors causing mortality. The goal of this research was to simultaneously quantify the three seed fates and factors causing death (predation and fungal disease) for four species found in prairies in western Oregon, USA. The most common seed fate for the four study species was death (44-80%). Fungal disease, which has seldom been quantified in natural ecosystems, generally caused less than 10% mortality for each of the four species. Vertebrate predation substantially reduced seed numbers only for Bromus carinatus (21%). Of the unmeasured mortality factors, indirect evidence showed invertebrate predation was a cause of death for seeds of only one species, Prunella vulgaris. In addition, competitive pressures caused seedling death for only the two grass species, Bromus carinatus and Cynosurus echinatus. Survival as established seedlings was generally much more common than survival as persistent seed, with the exception of Daucus carota, in which 14% of the sown seeds persisted the first year.
Previous work from our lab identified mutants, Mgr3 and Mgr9, of tobacco (Nicotiana tabacum) that produced unusual elongated green outgrowths from placentae in vivo. Similarly appearing stigmatoid growths were described developing from some in vitro cultures of excised placentae of tobacco (Hicks and McHughen, 1974, 1977). Here we report a developmental analysis and comparison of the unusual stigmatoid outgrowths seen in in vitro cultures of wild-type and mutant placentae, as well as the green outgrowths seen in vivo in the mutants. The growths produced by wild-type and mutant placental cultures in vitro, and the growths produced by the mutants in vivo, are identified as abnormal stigmas and styles. Wild-type in vitro placental cultures also produce outgrowths identified as homologs of whole carpels. Carpel fusion is not required for differentiation of stigma, style, transmitting tract, vascular traces, ovary, and ovules in these structures. The type and extent of stigmatoid growth production depends upon the age of the explant at excision and culture initiation. Before ovule primordium initiation, few growths are seen in culture; for a short window of time afterward, the primordia are competent to give rise to stigmatoid and carpelloid growths when cultured. After commitment to ovule development occurs, the primordia produce only ovules when cultured. The behavior of the mutant placental cultures is dimorphic. Explants from early stages behave similarly to wild-type when cultured, but differences between wild-type and the mutant behaviors in culture arise at the time when the stigmatoid growths begin to appear in vivo in the mutants. These results imply that ovule primordia pass through stages of distinct sequential restrictions of fate, first to growth as gynoecia, and then second to growth as ovules. The mutant strains described here perturb the commitment to differentiation as ovules.
We isolated an Arabidopsis thaliana mutant line carrying an insertion of the En-1 transposable element at the ADC2 locus. The insertion causes a knockout of the arginine decarboxylase 2 gene. We demonstrated that ADC2 is the gene responsible for induction of the polyamine biosynthetic pathway by osmotic stress. No induction of ADC activity by the osmolite sorbitol could be observed in the homozygous mutant, indicating a predominant role of ADC2 in stress response. ADC activity is reduced in the mutant by 44% under non-stressed conditions and the mutant shows no obvious phenotype. This is the first report of a genetically mapped mutation in the polyamine biosynthetic pathway in plants.
Drought rhizogenesis is an adaptive strategy that occurs during progressive drought stress and is characterized in the Brassicaceae and related families by the formation of short, tuberized, hairless roots. These roots are capable of withstanding a prolonged drought period and give rise to a new functional root system upon rehydration. The kinetics of drought rhizogenesis during progressive water shortage was analyzed in the Arabidopsis thaliana wild-type ecotypes Landsberg erecta and Columbia. In both genotypes, this response started from a similar threshold of soil humidity (about 2%). The intensity of drought rhizogenesis was compared in various A. thaliana hormonal mutants. The wild-type lines and most of the mutants achieved a similiar drought rhizogenetic index (DRI), defined as the maximum number of short roots produced per mg of root biomass, after progressive drought stress. However, this DRI was dramatically reduced in the abscisic acid (ABA)-deficient aba, ABA-insensitive abi1-1, and auxin-resistant axr1-3 mutants. These data indicate that endogenous ABA and auxin play a promotive role in drought rhizogenesis. The DRI was highly increased in the gibberellin (GA) biosynthetic mutant ga5, suggesting that some GAs might also participate in this process. The possible role and identity of the GA species involved is discussed in view of the unaltered DRI values of the ga2, ga3, and ga4 mutants. The present analysis also allowed further discrimination among the various ABA-insensitive (abi1 versus abi2 and abi3) and auxin-resistant (axr1 versus aux1) mutants tested. In particular, drought rhizogenesis is the first physiological response shown to be differentially affected by the abi1-1 and abi2-1 mutations.
The development of proplastids or etioplasts to chloroplast is visualized by the accumulation of chlorophyll in leaves of higher plants. The biosynthesis of chlorophyll includes a light-dependent reduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide). This light-dependent step is catalysed by the nucleus-encoded NADPH:Pchlide oxidoreductase (POR, EC 1.6.99.1). POR is active within plastids and therefore has to be translocated over the plastid envelope membranes. The import of chloroplast proteins seems to follow a general import pathway using translocons at the outer and inner envelope membrane. POR cross-linking to Toc75, one of the major translocon components at the outer envelope membrane, indicates its use of the general import pathway. However, since variations exist within the so-called general import pathway one has to consider previous data suggesting a novel totally Pchlide-dependent import pathway of one POR isoform, PORA. The suggested Pchlide dependency of POR import is discussed since recent observations contradict this idea. In the stroma the POR transit peptide is cleaved off and the mature POR protein is targeted to the plastid inner membranes. The correct and stable association of POR to the membrane requires the cofactor NADPH. Functional activity of POR calls for formation of an NADPH-Pchlide-POR complex, a formation that probably takes place after the membrane association and is dependent on a phosphorylation reaction.
Effects of sugars and several growth regulators on the chilling injury of rice seedling
- Tajima K
- Kabaki N
- Tajima K
- Kabaki N
Correlation of reduced chilling injury with increased Spd and Spm levels in zucchini squash
- Kramer
- Fg
- Yang
- Cy
Kramer FG, Yang CY. 1989. Correlation of reduced chilling injury with increased Spd and Spm levels in zucchini squash. Physiologia Plantarum 76: 479 – 484.
Climate change in Kerguelen Islands and colonization of recently deglaciated areas by Poa kerguelensis and Poa annua
- Y Frenot
- Jc Gloaguen
- Trehen
Frenot Y, Gloaguen JC, Trehen P. 1997. Climate change in Kerguelen Islands and colonization of recently deglaciated areas by Poa kerguelensis and Poa annua. In: Battaglia B, Valencia J, Walton DWH, eds. Antarctic communities: species, structure and survival. Cambridge, UK: Cambridge University Press, 358 – 366.