Phenotypic and yield responses of common bean (Phaseolus vulgaris l.) varieties to different soil moisture levels.

BACKGROUND: Morphological plasticity is one of the capacities of plants to modify their morphological appearance in response to external stimuli. A plant's morphology and physiology are constantly tuned to its variable surroundings by complex interactions between environmental stimuli and internal signals. In most of plant species,, such phenotypic and physiological expression varies among different varieties based on their levels of particular environmental stress conditions. However, the morphological and yield responses of common bean varieties to different environmental conditions are not well known. The purpose of the study was to evaluate morphological and yield response of common bean to soil moisture stress and to investigate the morphological mechanism by which common bean varieties tolerate fluctuations in moisture stress. METHODS: A pot experiment was carried out to investigate the effects of different moisture levels on the phenotypic and yield responses of common bean varieties. A factorial combination of five common bean varieties (Hirna, kufanzik, Awash-1, Ado, and Chercher) and three moisture levels (control, waterlogging stress, and moisture deficit stress) was used in three replications. Moisture stress treatments were started 20 days after planting, at the trifoliate growth stage. To evaluate the response of each variety, morphological and yield data were collected at week intervals. MAIN RESULTS: The results indicated that moisture levels and varieties had a significant influence on all growth parameters. Crop phenology was significantly influenced by the interaction effect of moisture level and variety. Exposing Hirna variety to moisture stress led to extended flowering and pod setting by 23 and 24 days, respectively, compared to the other treatments. The results showed that the phenotypic responses to moisture deficit and waterlogging stress varied between varieties. Waterlogging stress had a stronger reduction effect on the fresh weight, dry weight and leaf area of common bean varieties than moisture deficit and the control. Pods per plant, seeds per plant, grain yield per plant, and harvest index were significantly influenced by the varieties, moisture stress levels and their interaction. Except for Chercher and Hirna. However, varieties Ado, kufanzik and Awasha-1 did not show significant differences on the time of flower initiation due to moisture level. Biomass and growth in leaf fresh weight, leaf dry weight, leaf area, leaf number and plant height were significantly influenced by moisture level. When moisture deficit and waterlogging stress occurred, Ado and Awash-1 were more responsive to moisture stress than Hirna, Chercher, and Kufanzik. CONCLUSION: Hence, Hirna and Kufanzik varieties were found to be tolerant because they produced higher yields than the Chercher, Awash-1, and Ado varieties.

Transcriptional responses to salinity-induced changes in cell wall morphology of the euryhaline diatom Pleurosira laevis.

Diatoms are unicellular algae with morphologically diverse silica cell walls, which are called frustules. The mechanism of frustule morphogenesis has attracted attention in biology and nanomaterials engineering. However, the genetic regulation of the morphology remains unclear. We therefore used transcriptome sequencing to search for genes involved in frustule morphology in the centric diatom Pleurosira laevis, which exhibits morphological plasticity between flat and domed valve faces in salinity 2 and 7, respectively. We observed differential expression of transposable elements (TEs) and transporters, likely due to osmotic response. Up-regulation of mechanosensitive ion channels and down-regulation of Ca2+-ATPases in cells with flat valves suggested that cytosolic Ca2+ levels were changed between the morphologies. Calcium signaling could be a mechanism for detecting osmotic pressure changes and triggering morphological shifts. We also observed an up-regulation of ARPC1 and annexin, involved in the regulation of actin filament dynamics known to affect frustule morphology, as well as the up-regulation of genes encoding frustule-related proteins such as BacSETs and frustulin. Taken together, we propose a model in which salinity-induced morphogenetic changes are driven by upstream responses, such as the regulation of cytosolic Ca2+ levels, and downstream responses, such as Ca2+-dependent regulation of actin dynamics and frustule-related proteins. This study highlights the sensitivity of euryhaline diatoms to environmental salinity and the role of active cellular processes in controlling gross valve morphology under different osmotic pressures.

Normal skeletal pattern formation in chick limb bud with a mesenchymal hole is mediated by adjustment of cellular properties along the anterior-posterior axis in the limb bud.

The chick limb bud has plasticity to reconstruct a normal skeletal pattern after a part of mesenchymal mass is excised to make a hole in its early stage of development. To understand the details of hole closure and re-establishment of normal limb axes to reconstruct a normal limb skeleton, we focused on cellular and molecular changes during hole repair and limb restoration. We excised a cube-shaped mass of mesenchymal cells from the medial region of chick hindlimb bud (stage 23) and observed the following morphogenesis. The hole had closed by 15 â€‹h after excision, followed by restoration of the limb bud morphology, and the cartilage pattern was largely restored by 48 â€‹h. Lineage analysis of the mesenchymal cells showed that cells at the anterior and posterior margins of the hole were adjoined at the hole closure site, whereas cells at the proximal and distal margins were not. To investigate cell polarity during hole repair, we analyzed intracellular positioning of the Golgi apparatus relative to the nuclei. We found that the Golgi apparatus tended to be directed toward the hole among cells at the anterior and posterior margins but not among cells at identical positions in normal limb buds or cells at the proximal and distal hole margins. In the manipulated limb buds, the frequency of cell proliferation was maintained compared with the control side. Tbx3 expression, which was usually restricted to anterior and posterior margins of the limb bud, was temporarily expanded medially and then reverted to a normal pattern as limb reconstruction proceeded, with Tbx3 negative cells reappearing in the medial regions of the limb buds. Thus, mesenchymal hole closure and limb reconstruction are mainly mediated by cells at the anterior and posterior hole margins. These results suggest that adjustment of cellular properties along the anteroposterior axis is crucial to restore limb damage and reconstruct normal skeletal patterns.

On the use of antibiotics in plasticity research: Gastropod shells unveil a tale of caution.

Through phenotypic plasticity, individual genotypes can produce multiple phenotypes dependent on the environment. In the modern world, anthropogenic influences such as man-made pharmaceuticals are increasingly prevalent. They might alter observable patterns of plasticity and distort our conclusions regarding the adaptive potential of natural populations. Antibiotics are nowadays nearly ubiquitous in aquatic environments and prophylactic antibiotic use is also becoming more common to optimize animal survival and reproductive output in artificial settings. In the well-studied plasticity model system Physella acuta, prophylactic erythromycin treatment acts against gram-positive bacteria and thereby reduces mortality. Here, we study its consequences for inducible defence formation in the same species. In a 2 × 2 split-clutch design, we reared 635 P. acuta in either the presence or absence of this antibiotic, followed by 28-day exposure to either high or low predation risk as perceived through conspecific alarm cues. Under antibiotic treatment, risk-induced increases in shell thickness, a well-known plastic response in this model system, were larger and consistently detectable. Antibiotic treatment reduced shell thickness in low-risk individuals, suggesting that in controls, undiscovered pathogen infection increased shell thickness under low risk. Family variation in risk-induced plasticity was low, but the large variation in responses to antibiotics among families suggests different pathogen susceptibility between genotypes. Lastly, individuals that developed thicker shells had reduced total mass, which highlights resource trade-offs. Antibiotics thus have the potential to uncover a larger extent of plasticity, but might counterintuitively distort plasticity estimates for natural populations where pathogens are a part of natural ecology.

Phylogenomic analysis of pseudocryptic diversity reveals the new genus Deltalsia (Rhodomelaceae, Rhodophyta).

Molecular analyses, in combination with morphological studies, provide invaluable tools for delineating red algal taxa. However, molecular datasets are incomplete and taxonomic revisions are often required once additional species or populations are sequenced. The small red alga Conferva parasitica was described from the British Isles in 1762 and then reported from other parts of Europe. Conferva parasitica was traditionally included in the genus Pterosiphonia (type species P. cloiophylla in Schmitz and Falkenberg 1897), based on its morphological characters, and later transferred to Symphyocladia and finally to Symphyocladiella using molecular data from an Iberian specimen. However, although morphological differences have been observed between specimens of Symphyocladiella parasitica from northern and southern Europe they have yet to be investigated in a phylogenetic context. In this study, we collected specimens from both regions, studied their morphology and analyzed rbcL and cox1 DNA sequences. We determined the phylogenetic position of a British specimen using a phylogenomic approach based on mitochondrial and plastid genomes. Northern and southern European populations attributed to S. parasitica represent different species. Symphyocladiella arecina sp. nov. is proposed for specimens from southern Europe, but British specimens were resolved as a distant sister lineage to the morphologically distinctive Amplisiphonia, so we propose the new genus Deltalsia for this species. Our study highlights the relevance of using materials collected close to the type localities for taxonomic reassessments, and showcases the utility of genome-based phylogenies for resolving classification issues in the red algae.

Astroglial Regulation of Magnocellular Neuroendocrine Cell Activities in the Supraoptic Nucleus.

Studies on the interactions between astrocytes and neurons in the hypothalamo-neurohypophysial system have significantly facilitated our understanding of the regulation of neural activities. This has been exemplified in the interactions between astrocytes and magnocellular neuroendocrine cells (MNCs) in the supraoptic nucleus (SON), specifically during osmotic stimulation and lactation. In response to changes in neurochemical environment in the SON, astrocytic morphology and functions change significantly, which further modulates MNC activity and the secretion of vasopressin and oxytocin. In osmotic regulation, short-term dehydration or water overload causes transient retraction or expansion of astrocytic processes, which increases or decreases the activity of SON neurons, respectively. Prolonged osmotic stimulation causes adaptive change in astrocytic plasticity in the SON, which allows osmosensory neurons to reserve osmosensitivity at new levels. During lactation, changes in neurochemical environment cause retraction of astrocytic processes around oxytocin neurons, which increases MNC's ability to secrete oxytocin. During suckling by a baby/pup, astrocytic processes in the mother/dams exhibit alternative retraction and expansion around oxytocin neurons, which mirrors intermittently synchronized activation of oxytocin neurons and the post-excitation inhibition, respectively. The morphological and functional plasticities of astrocytes depend on a series of cellular events involving glial fibrillary acidic protein, aquaporin 4, volume regulated anion channels, transporters and other astrocytic functional molecules. This review further explores mechanisms underlying astroglial regulation of the neuroendocrine neuronal activities in acute processes based on the knowledge from studies on the SON.

Filamentous growth is a general feature of Candida auris clinical isolates.

A striking feature of pathogenic Candida species is morphological plasticity that facilitates environmental adaptation and host infection. Candida auris is an emerging multidrug-resistant fungal pathogen first described in Japan in 2009. In this study, we demonstrate that clinical isolates of C. auris have multiple colony and cellular morphologies including the yeast, filamentous, aggregated, and elongated forms. This phenotypic diversity has been observed in eight clinical isolates of C. auris representing four major genetic clades, suggesting that it could be a general characteristic. We further demonstrate that different cell types of C. auris exhibit distinct antifungal resistance and virulence properties in a Galleria mellonella infection model. Our findings imply that morphological diversity is an important biological feature of C. auris and could be a contributor to its emergence and rapid prevalence worldwide. LAY SUMMARY: Candida auris is an emerging multidrug-resistant fungal pathogen. Morphological analyses indicate that filamentation is a general feature of clinical isolates of C. auris. This ability is associated with antifungal resistance and virulence.

Mechanisms of the Morphological Plasticity Induced by Phytohormones and the Environment in Plants.

Plants adapt to environmental changes by regulating their development and growth. As an important interface between plants and their environment, leaf morphogenesis varies between species, populations, or even shows plasticity within individuals. Leaf growth is dependent on many environmental factors, such as light, temperature, and submergence. Phytohormones play key functions in leaf development and can act as molecular regulatory elements in response to environmental signals. In this review, we discuss the current knowledge on the effects of different environmental factors and phytohormone pathways on morphological plasticity and intend to summarize the advances in leaf development. In addition, we detail the molecular mechanisms of heterophylly, the representative of leaf plasticity, providing novel insights into phytohormones and the environmental adaptation in plants.

Strength and size of phosphorus-rich patches determine the foraging strategy of Neyraudia reynaudiana.

BACKGROUND: Under natural conditions, soil nutrients are heterogeneously distributed, and plants have developed adaptation strategies to efficiently forage patchily distributed nutrient. Most previous studies examined either patch strength or patch size separately and focused mainly on root morphological plasticity (increased root proliferation in nutrient-rich patch), thus the effects of both patch strength and size on morphological and physiological plasticity are not well understood. In this study, we examined the foraging strategy of Neyraudia reynaudiana (Kunth) Keng ex Hithc, a pioneer grass colonizing degraded sites, with respect to patch strength and size in heterogeneously distributed phosphorus (P), and how foraging patchily distributed P affects total plant biomass production. Plants were grown in sand-culture pots divided into ½, », 1/6 compartments and full size and supplied with 0 + 0/30, 0 + 7.5/30 and 7.5 + 0/30 mg P/kg dry soil as KH2PO4 or 0 + 15/15, 0 + 18.5/ 18.5, 7.5 + 15/15 mg kg - 1 in the homogenous treatment. The first amount was the P concentration in the central region, and that the second amount was the P concentration in the outer parts of the pot. RESULTS: After 3 months of growth under experimental conditions, significantly (p < 0.05) high root elongation, root surface area, root volume and average root diameter was observed in large patches with high patch strength. Roots absorbed significantly more P in P-replete than P-deficient patches. Whole plant biomass production was significantly higher in larger patches with high patch strength than small patches and homogeneous P distribution. CONCLUSION: The result demonstrates that root morphological and physiological plasticity are important adaptive strategies for foraging patchily distributed P and the former is largely determined by patch strength and size. The results also establish that foraging patchily distributed P resulted in increased total plant biomass production compared to homogeneous P distribution.

Sex-specific strategies of phosphorus (P) acquisition in Populus cathayana as affected by soil P availability and distribution.

Soil phosphorus (P) availability and its distribution influence plant growth and productivity, but how they affect the growth dynamics and sex-specific P acquisition strategies of dioecious plant species is poorly understood. In this study, the impact of soil P availability and its distribution on dioecious Populus cathayana was characterized. P. cathayana males and females were grown under three levels of P supply, and with homogeneous or heterogeneous P distribution. Females had a greater total root length, specific root length (SRL), biomass and foliar P concentration under high P supply. Under P deficiency, males had a smaller root system than females but a greater exudation of soil acid phosphatase, and a higher colonization rate and arbuscular mycorrhizal hyphal biomass, suggesting a better capacity to mine P and a stronger association with arbuscular mycorrhizal fungi to forage P. Heterogeneous P distribution enhanced growth and root length density (RLD) in females. Female root proliferation in P-rich patches was related to increased foliar P assimilation. Localized P application for increasing P availability did not enhance the biomass accumulation and the morphological plasticity of roots in males, but it raised hyphal biomass. The findings herein indicate that sex-specific strategies in P acquisition relate to root morphology, root exudation and mycorrhizal symbioses, and they may contribute to sex-specific resource utilization patterns and niche segregation.

Terminal Arbors of Callosal Axons Undergo Plastic Changes in Early-Amputated Rats.

Sensory information is processed in specific brain regions, and shared between the cerebral hemispheres by axons that cross the midline through the corpus callosum. However, sensory deprivation usually causes sensory losses and/or functional changes. This is the case of people who suffered limb amputation and show changes of body map organization within the somatosensory cortex (S1) of the deafferented cerebral hemisphere (contralateral to the amputated limb), as well as in the afferented hemisphere (ipsilateral to the amputated limb). Although several studies have approached these functional changes, the possible finer morphological alterations, such as those occurring in callosal axons, still remain unknown. The present work combined histochemistry, single-axon tracing and 3D microscopy to analyze the fine morphological changes that occur in callosal axons of the forepaw representation in early amputated rats. We showed that the forepaw representation in S1 was reduced in the deafferented hemisphere and expanded in the afferented side. Accordingly, after amputation, callosal axons originating from the deafferented cortex undergo an expansion of their terminal arbors with increased number of terminal boutons within the homotopic representation at the afferented cerebral hemisphere. Similar microscale structural changes may underpin the macroscale morphological and functional phenomena that characterize limb amputation in humans.

Height-related variations of leaf traits reflect strategies for maintaining photosynthetic and hydraulic homeostasis in mature and old Pinus densiflora trees.

Because tree size and age co-vary, it is difficult to separate their effects on growth and physiological function. To infer causes for age-related height-growth decline, we compared various leaf traits between mature (ca. 100 years) and old (ca. 300 years) trees of Pinus densiflora, having similar heights (ca. 30 m) and growing in the same stand. For many leaf traits, mature and old trees showed similar height-related trends reflecting acclimation to height-related hydraulic limitation for maintaining photosynthetic and hydraulic homeostasis. Photosynthetic capacity was constant within crowns of both age-classes, though 4.9-5.4 µmol CO2 m-2 s-1 lower for old than for mature trees. Biochemical acclimation of photosynthesis, allocating more nitrogen to treetop leaves, was observed only for mature trees. Leaf turgor loss point was also constant within crowns of both age-classes with no significant effect of age on leaf hydraulic traits. In mature trees, leaf capacitance increased, while bulk tissue elastic modulus decreased with height, whereas opposite height-related trends were observed for old trees. For both age-classes, leaf mass per area (LMA), transfusion-tissue area, and xylem area all increased with height, but LMA was ca. 30 g m-2 greater for old than for mature trees. In old trees, mesophyll area decreased with height, suggesting anatomical acclimation to height may negatively affect photosynthetic capacity. We inferred that old trees rely more on morphological than biochemical acclimation and that such post-maturational shift in resource allocation could underlie height-growth decline of P. densiflora after reproductive maturity.

Total Non-Consumptive Effects of Fish on Pelobates fuscus and Hyla orientalis Tadpoles in Pond Enclosure Experiments.

Most research on non-consumptive predator effects on amphibian larvae has been conducted in laboratory or mesocosm designs. Here, Pelobates fuscus and Hyla orientalis tadpoles were separately exposed to non-lethal (free-moving, but with tied mouthparts) common carp Cyprinus carpio for one week in enclosures placed in a pond densely stocked with fish. Tadpoles exposed to nonlethal fish did not differ in mortality, body mass, or, except for deeper tail fin depth in P. fuscus, morphological plasticity from controls kept in a fishless pond. Hyla orientalis tadpoles recovered from the fish treatment were subsequently enclosed until metamorphosis in either the pond with fish or the fishless pond. Metamorphs from the pond containing fish were heavier, and did not differ in survivorship or development time from their counterparts initially kept in the fish treatment and then transferred to the fishless pond or from controls kept the entire time under fish-free conditions. The lack of apparent metamorphic costs is consistent with previous experiments on anuran larvae, but the morphological defenses induced (or their absence) are not. In the fish-dominated pond, carp indirectly affected tadpole developmental responses by generating turbidity, through adverse impacts on submerged vegetation and predatory insects, and by increasing food resource (unicellular algae) levels. While the present study does not question the validity of laboratory and mesocosm experiments on the costs of non-consumptive predator effects on amphibian larvae, their outcomes cannot easily be extrapolated to ecologically complex natural habitats.

Integrative Approach for the Reliable Detection and Specific Identification of the Microsporidium Loma morhua in Atlantic Cod (Gadus morhua).

Microsporidia are fungal parasites that infect diverse invertebrate and vertebrate hosts. Finfish aquaculture supports epizootics due to high host density and the high biotic potential of these parasites. Reliable methods for parasite detection and identification are a necessary precursor to empirical assessment of strategies to mitigate the effects of these pathogens during aquaculture. We developed an integrative approach to detect and identify Loma morhua infecting Atlantic cod. We show that the spleen is more reliable than the commonly presumed gills as best organ for parasite detection in spite of substantial morphological plasticity in xenoma complexes. We developed rDNA primers with 100% sensitivity in detecting L. morhua and with utility in distinguishing some congeneric Loma species. ITS sequencing is necessary to distinguish L. morhua from other congeneric microsporidia due to intraspecific nucleotide variation. 64% of L. morhua ITS variants from Atlantic cod have a 9-nucleotide motif that distinguishes it from Loma spp. infecting non-Gadus hosts. The remaining 36% of ITS variants from Atlantic cod are distinguished from currently represented Loma spp., particularly those infecting Gadus hosts, based on a 14-nucleotide motif. This research approach is amenable to developing templates in support of reliable detection and identification of other microsporidian parasites in fishes.

Morphometric and molecular characterisation of Tenuiproboscis keralensis n. sp. infecting marine and brackish water fishes from the south-west coast of India with a note on morphological plasticity.

A new species of acanthocephalan infecting marine and brackish water fishes from the south-west coast of India is described. The parasite belongs to the genus Tenuiproboscis, and the fish hosts include Lutjanus argentimaculatus, L. ehrenbergii, Siganus javus, Epinephelus malabaricus, E. coioides, Scatophagus argus, Parascolopsis aspinosa, Caranx ignobilis, Gerres filamentosus and Lates calcarifer. The parasite inhabits mid- and hindgut regions and is characterised by an elongated, cylindrical, bulbous and posteriorly tapering metasoma and a claviform proboscis having 14-15 rows of 14-15 hooks each. Females larger than males, measured 3898.16-10,318.00 µm (6430.00 ± 1417.30) in length and 458.93-1435.68 µm (929.81 ± 250.39) in width. Males measured 3234.89-8644.20 µm (5729.50 ± 1176.60) in length and 388.30-1584.61 µm (795.88 ± 184.12) in width. Parasites recovered from different host species showed morphological/morphometric variations. However, principal component analysis (PCA) revealed significant overlapping of characters indicating their similarities. Proboscis profiling based on variations in size and position of hooks also yielded similar results. Further, in molecular phylogenetic analysis, parasites from different fish hosts formed a monophyletic clade with strong bootstrap support, again indicating their conspecific nature. These morphological/morphometric variations can be ascribed to differences in host species. Morphology and morphometrics in combination with PCA, proboscis profiling and molecular analysis suggest the present acanthocephalan parasite is different from other described species of Tenuiproboscis. Hence, it is considered as a new species and named T. keralensis n. sp. Prevalence, intensity and abundance of the parasite in different hosts are also discussed.

The bladed Bangiales (Rhodophyta) of the South Eastern Pacific: Molecular species delimitation reveals extensive diversity.

A molecular taxonomic study of the bladed Bangiales of the South Eastern Pacific (coast of Chile) was undertaken based on sequence data of the mitochondrial COI and chloroplast rbcL for 193 specimens collected from Arica (18°S) in the north to South Patagonia (53°S) in the south. The results revealed for the first time that four genera, Porphyra, Pyropia, Fuscifolium and Wildemania were present in the region. Species delimitation was determined based on a combination of a General Mixed Yule Coalescence model (GMYC) and Automatic Barcode Gap Discovery (ABGD) coupled with detection of monophyly in tree reconstruction. The overall incongruence between the species delimitation methods within each gene was 29%. The GMYC method led to over-splitting groups, whereas the ABGD method had a tendency to lump groups. Taking a conservative approach to the number of putative species, at least 18 were recognized and, with the exception of the recently described Pyropia orbicularis, all were new to the Chilean flora. Porphyra and Pyropia were the most diverse genera with eight 'species' each, whereas only a 'single' species each was found for Fuscifolium and Wildemania. There was also evidence of recently diverging groups: Wildemania sp. was distinct but very closely related to W. amplissima from the Northern Hemisphere and raises questions in relation to such disjunct distributions. Pyropia orbicularis was very closely related to two other species, making species delimitation very difficult but provides evidence of an incipient speciation. The difference between the 'species' discovered and those previously reported for the region is discussed in relation to the difficulty of distinguishing species based on morphological identification.

Are inter- and intraspecific variations of sapling crown traits consistent with a strategy promoting light capture in tropical moist forest?

Background and Aims Morphological variation in light-foraging strategies potentially plays important roles in efficient light utilization and carbon assimilation in spatially and temporally heterogeneous environments such as tropical moist forest understorey. By considering a suite of morphological traits at various hierarchical scales, we examined the functional significance of crown shape diversity and plasticity in response to canopy openness. Methods We conducted a field comparative study in French Guiana among tree saplings of 14 co-occurring species differing in light-niche optimum and breadth. Each leaf, axis or crown functional trait was characterized by a median value and a degree of plasticity expressed under contrasting light regimes. Key Results We found divergent patterns between shade-tolerant and heliophilic species on the one hand and between shade and sun plants on the other. Across species, multiple regression analysis showed that relative crown depth was positively correlated with leaf lifespan and not correlated with crown vertical growth rate. Within species displaying a reduction in crown depth in the shade, we observed that crown depth was limited by reduced crown vertical growth rate and not by accelerated leaf or branch shedding. In addition, the study provides contrasting examples of morphological multilevel plastic responses, which allow the maintenance of efficient foliage and enable effective whole-plant light capture in shaded conditions under a moderate vertical light gradient. Conclusions This result suggests that plastic adjustment of relative crown depth does not reflect a strategy maximizing light capture efficiency. Integrating and scaling-up leaf-level dynamics to shoot- and crown-level helps to interpret in functional and adaptive terms inter- and intraspecific patterns of crown traits and to better understand the mechanism of shade tolerance.

Latitudinal and longitudinal clines of phenotypic plasticity in the invasive herb Solidago canadensis in China.

Phenotypic plasticity is thought to be important for plants in variable environments. The climatic variability hypothesis poses that populations at higher latitudes, due to the stronger variation in temperature, there should be more plastic in response to temperature than populations at lower latitudes. Similarly, populations at locations with stronger precipitation fluctuations should be more plastic in response to water availability than populations at locations with less variable precipitation. We sampled seven and nine populations of Solidago canadensis, a North American native that is invasive in China, along a latitudinal (temperature variability) and a longitudinal (precipitation variability) gradient, respectively, in China, and grew them under two temperature treatments and two water-availability treatments, respectively. Among the four traits with significant variation in plasticity among populations in response to temperature, plasticity of leaf length-to-width ratio was significantly positively correlated with latitude and temperature seasonality of the populations. In addition, root/shoot ratio and water-use efficiency showed significant variation in plasticity among populations in response to water availability, and plasticities of these two traits were significantly negatively correlated with longitude and positively correlated with precipitation seasonality. The observed geographic clines in plasticity suggest that phenotypic plasticity of S. canadensis may have evolved rapidly in regions with different climatic conditions, and this may have contributed to the spread of this invasive species.

Growth and nutrients accumulation potentials of giant reed (Arundo donax L.) in different habitats in Egypt.

Arundo donax L. has a high biomass production and a tendency toward community dominance in many habitats and thereby a tolerance to a wide range of environmental conditions. Therefore, the present study investigated the potentiality of A. donax to accumulate nutrients and trace metals in its biomass. Six main habitats (Nile Bank, Drain Bank, Canal Bank, Field Edges, Railways and Roadsides) were recognized. At each habitat, six quadrats (each 1 m(2)), distributed equally in two sites, were selected for growth measurements (e.g., density, shoot height, diameter, leaf area and biomass), plant and soil analyses. Plants from Nile, Canal and Drain Banks had the highest values of most growth measurements, while those from Railways and Roadsides had the lowest. Canal Bank plants accumulated the highest concentrations of P, Cu and Pb in their leaves; Zn in the stem; and Mg, Cd and Fe in the rhizome. The bioaccumulation factor (BF) of A. donax, for Cd, Fe, Mn and Zn, was greater than 1, while the translocation factor (TF) of most trace metals was less than unity in most habitats. In conclusion, A. donax showed morphological plasticity in response to habitat heterogeneity, and its growth was most vigorous in the riparian habitats. The high BF, as well as the significant positive correlations between trace metals, especially Cd, in soil and plant, renders A. donax a powerful phytoremediator.

Synaptopodin regulates spine plasticity: mediation by calcium stores.

The role of synaptopodin (SP), an actin-binding protein residing in dendritic spines, in synaptic plasticity was studied in dissociated cultures of hippocampus taken from control and SP knock-out (SPKO) mice. Unlike controls, SPKO cultures were unable to express changes in network activity or morphological plasticity after intense activation of their NMDA receptors. SPKO neurons were transfected with SP-GFP, such that the only SP resident in these neurons is the fluorescent species. The localization and intensity of the transfected SP were similar to that of the native one. Because less than half of the spines in the transfected neurons contained SP, comparisons were made between SP-containing (SP(+)) and SP lacking (SP(-)) spines in the same dendritic segments. Synaptic plasticity was induced either in the entire network by facilitation of the activation of the NMDA receptor, or specifically by local flash photolysis of caged glutamate. After activation, spines that were endowed with SP puncta were much more likely to expand than SP(-) spines. The spine expansion was suppressed by thapsigargin, which disables calcium stores. The mechanism through which SP may promote plasticity is indicated by the observations that STIM-1, the sensor of calcium concentration in stores, and Orai-1, the calcium-induced calcium entry channel, are colocalized with SP, in the same dendritic spines. The structural basis of SP is likely to be the spine apparatus, found in control but not in SPKO cells. These results indicate that SP has an essential, calcium store-related role in regulating synaptic plasticity in cultured hippocampal neurons.