Plant Phytoliths Research Articles

Phytolith characterization of culturally salient plant species of the Pacific Northwest of North America

Palaeoecological and archaeological studies often use soil phytoliths to gain insight into past vegetation changes and the long-term use of plants by people, particularly domesticated cultivars. However, to make accurate interpretations and analyses using plant phytoliths, regionally-specific reference collections are warranted. There is ample research documenting phytolith morphotypes observed in grass species worldwide (due to their high phytolith production), and of dicots in tropical regions, but there is dearth of phytolith references for dicot species in temperate regions like the Pacific Northwest of North America. This study aims to fill part of this gap by documenting phytolith morphotypes observed in 60 culturally important plant foods, medicines, and textiles, all predominantly dicot species. Phytoliths are classified by abundance in specific plant parts (e.g., stem, leaf, flower) and the findings are compared to closely related species studied elsewhere. Results indicate that many of the dicot plant species in the Pacific Northwest produce more phytoliths than closely related species worldwide, likely due to differing environmental factors which affect phytolith production in plants. These findings could be useful in palaeoecological contexts to assess vegetation changes or identify dicot-dominated ecosystems, like Indigenous cultivated and managed forests and other perennial fruit tree/shrub dominated landscapes. Additionally, three of the species studied here showed possible diagnostic phytoliths but further confirmation is warranted. Future studies should consider localized environmental patterns affecting phytolith production, and therefore, our understanding of phytolith taxonomy and deposition/taphonomy.

Woody plant phytolith morphology and representation in surface sediments across the Northern Territory, Australia

Phytoliths are a good tool for investigating vegetation change in northern Australia. However, there is a lack of phytolith reference material across the Australian continent, particularly for woody plants. The development of reference material from woody plants is critical to understand regional patterns of phytolith production and preservation. This study analyses phytolith material from 40 woody plants to examine morphological and anatomical variation in phytolith production among Australian plant families. This is paired with phytolith assemblages from nine surface sediment samples to assess the representation and preservation of woody plant phytolith morphotypes. All woody plant species examined produce identifiable phytolith morphotypes, but most morphotypes cannot be differentiated between woody eudicots, monocots, and conifers. However, some woody plant morphotypes do have good potential for taxonomic or anatomical discrimination of plant groups. The analysis of surface sediment phytolith assemblages reveals that not all woody plant morphotypes preserve equally in surface sediments, potentially restricting their ability for taxonomic discrimination. Finally, the relevance of phytolith morphotypes for palaeoecological reconstruction is discussed.

Elemental composition of grass phytoliths: Environmental control and effect on dissolution

Plant phytoliths, which represent the main pool of silica (Si) in the form of hydrous Si oxide, are capable of providing valuable information on different aspect of environmental issues including paleo-environmental reconstruction and agricultural sustainability. Phytoliths may have different chemical composition, which, in turn, affects their preservation in soils ad impacts terrestrial cycle of the occluded elements including micro-nutrients and environmental toxicants. Yet, in contrast to sizable work devoted to phytoliths formation, dissolution and physico-chemical properties, the mechanisms that control total (major and trace) elemental composition and the impact that various elements exert on phytolith reactivity and preservation in soils remains poorly known. In order to fil this gap in knowledge, here we combined two different approaches – analytical trace element geochemistry and experimental physical chemistry. First, we assessed full elemental composition of phytoliths from different plants via measuring major and trace elements in 9 samples of grasses collected in northern Eurasia during different seasons, 18 grasses from Siberian regions, and 4 typical Si-concentrating plants (horsetail, larch, elm and tree fern). We further assessed the dissolution rates of phytoliths exhibiting drastically different concentrations of trace metals.In the European grasses, the variations of phytolith chemical composition among species were highly superior to the variations across vegetative season. Compared to European samples, Siberian grass phytoliths were impoverished in Ca and Sr, exhibited similar concentrations of Li, B, Na, Mg, K, V, Zn, Ni, Mo, As, Ba, and U, and were strongly enriched (x 100–1000) in lithogenic elements (trivalent and tetravalent hydrolysates), P, Mn, Fe and divalent metals. Overall, the variations in elemental composition between different species of the same region were lower compared to variations of the same species from distant regions.The main factors controlling phytoliths elemental composition are the far-range atmospheric (dust) transfer, climatic conditions (humidity), and, in a lesser degree, local lithology and anthropogenic pollution. Despite significant, up to 3 orders of magnitude, difference in TE composition of grass and other plant phytoliths, the dissolution rates of grass phytoliths measured in this study were similar, within the experimental uncertainty, to those of other plants studied in former works. Therefore, elemental composition of phytoliths has relatively minor impact on their preservation in soils.

Production of phytoliths in woody plants of the Atlantic Forest in islands of the Paraná River, Brazil

The analysis of phytoliths is a recent addition to the geosciences and has found applications in various fields over the last few decades, including palaeoenvironmental studies in fluvial environments. As a developing field, it is essential to carry out studies aimed at creating a modern reference collection that fills an information gap on the production of phytoliths by plants in this environment. These studies are essential to increase the reliability and accuracy of phytolith research in reconstructing past vegetation patterns and compositions. This study is the first with the aim of creating a pioneer collection of phytoliths in fluvial environments of the Upper Paraná River, addressing woody eudicotyledon species of greater representation on the Três Ilhas (Three Islands) Archipelago. The phytoliths were extracted from the leaves of 51 species from the botanical collection of the Nupélia herbarium (HNUP) using the dry ashing extraction method. The analysis found that 21 plant families established on the site have some kind of silica accumulation and 34 species are producers of phytoliths with an identifiable shape and size (<5um). It was confirmed the Moraceae family produces Acute bulbosus (with ramifications), both considered diagnostic at family level. Confirming the current literature on the subject, redundancy of the spheroid ornate and spheroid psilate morphotypes was observed in woody plants. Although no new morphotypes were found, the information will contribute to studies on the evolution of fluvial geoforms.

The phytolith carbon sequestration in terrestrial ecosystems: the underestimated potential of bamboo forest

BackgroundTerrestrial ecosystems contain significant carbon storage, vital to the global carbon cycle and climate change. Alterations in human production activities and environmental factors affect the stability of carbon storage in soil. Carbon sequestration in plant phytoliths offers a sustainable method for long-term carbon stabilization. Carbon occluded in phytoliths (PhytOC) is a kind of carbon that can be stable and not decomposed for a long time, so it is crucial to conduct more in-depth research on it.ResultsWe undertook a meta-analysis on PhytOC across global terrestrial ecosystems, analyzing 60 articles, encapsulating 534 observations. We observed notable differences in phytolith and PhytOC contents across various ecosystems. Bamboo forest ecosystems exhibited the highest vegetation phytolith and PhytOC content, while soil phytolith content was most prominent in bamboo forests and PhytOC content in croplands. Human activities, such as grassland grazing, had a lesser impact on soil PhytOC transport than actions like cutting and tillage in croplands and forests. Our study separated bamboo ecosystems, analyzing their PhytOC content and revealing an underestimation of their carbon sink capacity.ConclusionsNotwithstanding our findings, phytoliths’ intricate environmental interactions warrant further exploration, crucial for refining ecosystem management and accurately estimating PhytOC stocks. This deepened understanding lays the foundation for studying phytoliths and the carbon sink dynamics.

Production of phytolith and PhytOC and distribution of extractable Si Pools in aerobic rice as influenced by different Si sources.

Phytoliths are composed of 66 to 91% SiO2 and 1 to 6% organic carbon (C) known as phytolith occluded carbon (PhytOC). PhytOC is critical for long-term C storage in the agroecosystem. A field experiment was carried out to investigate the effect of three different sources of exogenous Si, i.e., diatomaceous earth (DE), silicic acid (SA) and rice husk biochar (RHB) on 1) plant phytolith, C content in phytolith and PhytOC content in different rice organs; 2) relationship between plant phytolith, C content in phytolith, PhytOC content, and soil properties (soil physicochemical properties and readily soluble silicon pools). Different Si sources produced significantly higher phytolith, PhytOC content, and readily soluble Si pools (CCSi, AASi, and ASi) than the control (RDF), with treatment receiving 4t RHB ha-1 outperforming the other treatments. Phytolith and PhytOC production were found to be significantly correlated to soil organic carbon (OC), available nitrogen (N) and potassium (K), 0.01 M CaCl2 extractable Si (CCSi) and amorphous Si (ASi) content in the soil. Redundancy analysis showed that treatments receiving 4t RHB ha-1 have a stronger relationship with the CCSi and ASi which majorly contributed to the higher phytolith and PhytOC production. Thus, practices such as Si fertilizers and RHB application have a high potential for phytolith production and PhytOC sequestration, a critical mechanism of the global biogeochemical C sink.

Phytoliths in modern plants from Amazonia and the Neotropics at large: II. Enhancement of eudicotyledon reference collections

Phytolith studies of Neotropical vegetation history and its human influences require large modern reference collections from diverse woody and herbaceous plants. In order to further enlarge our reference collection, we analyzed phytoliths from 435 species of eudicotyledons from 84 families and 361 genera of mainly lowland Amazonian forest taxa along with other Neotropical plants. Our analysis revealed new morphologies from the silicification of bark in arboreal taxa that don't produce diagnostic vegetative phytoliths, as well as distinctive-looking phytoliths from leaves of previously unstudied trees. Several of the phytolith types uncovered here occur as unknowns in our earlier Amazonian terrestrial soil research. No morphotypes were revealed that overlapped with diagnostic phytoliths documented previously in other families and genera. Our reference collection now totals approximately 1540 Neotropical eudicotyledon species. For the Amazonian forest below 1000m it includes 80% of eudicotyledon families often with half or more of their genera and many of the most commonly occurring trees. A significant number of herbaceous and arboreal/woody taxa can be identified at the family, genus, and possibly species level for study of Neotropical vegetational and forest history. Phytolith and palynological investigations are excellent complements to each other.

Microbiomorphs of the soddy solodic planosol and buried organic-accumulative quasi-clay soil of West Siberia

The purpose of the study. Reconstruction of the conditions of solodic soils formation in the forest-steppe zone using soil characteristics and microbiomorphic analysis. Location and time of the study. The study was conducted in the forest-steppe zone (Kulunda, Novosibirsk region, Russia) where in the birch grove a pedocomplex consisting of a surface turf soddy soil and a buried soil. Soil samples were collected in 2014. Methods. Phytolith and some other microbiomorphs morphology, composition and relative abundance were analysed and their soil profile changes accessed. Results. Several peaks of the maximum accumulation of phytoliths were found in the microbiomorphic profile of the soddy solodic planosol. The largest number of phytoliths was found in the eluvial horizon. Phytoliths of steppe gramineous plants and elongated forms of dicotyledonous grasses (forbs, legumes, etc.) accounted for a significant proportion. Diatoms were present throughout the entire soil profile; sponge spicules were rare. Conclusion. At the first stage of its formation the buried soil went through the steppe stage of development (predominance of steppe grasses), followed by overgrowing of the steppe soil with meadow-forest vegetation at the current stage (increased share of forest and meadow grasses). The presence of diatomic shells is typical for soils experiencing recurrent (seasonal) flooding of the birch groves: a lot of snow usually accumulates there, and after the snowmelt water stays for a long time in summer. During wet years, when the groundwater level rises and merges with the surface waters, the phytolith forms characteristic of reeds, sponge spicules, and other indicators of increased moisture increased. Thus, the microbiomorphic composition of the buried organo-accumulative soil reflected its formation.

Chemical status of zinc in plant phytoliths: Impact of burning and (paleo)environmental implications

Phytoliths are microscopic structures made of amorphous opal (opal-A), an amorphous hydrated silica, dispersed within plant tissues and persisting after the decay of the plant. Silicon is known to alleviate metal toxicity in plants, but the role of phytoliths in metal sequestration and detoxification is unclear. Dry ashing, the most common protocol for phytolith extraction, was previously shown to lead to sequestration of metals by the phytoliths; however, the mechanisms of this process remained elusive. The purpose of this study was to evaluate whether the association between metals and phytoliths results from dry ashing or pre-exists in plant tissues. Thus, we compared phytoliths extracted by dry ashing at 700 °C and plant leaves before and after dry ashing. A combination of ICP-MS, XRD, SEM-EDX and Zn-K-edge EXAFS spectroscopy was used to assess elemental concentrations, morphology and crystallography of silica, and chemical status of Zn. Results demonstrated a phase transition from amorphous opal (opal-A) to opal-CT and α-cristobalite, and the sequestration of metal in phytoliths during dry ashing. For Zn, Mn and Pb, a linear relationship was found between the concentration in phytoliths and in leaves. In the phytoliths, Zn was sequestered in silica in tetrahedral configuration. We hypothesize that this association results form a solid-state reaction during ashing, involving a redistribution of Zn from the organic material to the silica, possibly promoted by the release of structural water from amorphous opal throughout the heating procedure. This study improves our understanding of the impact of high temperature treatments on plant biomass and phytoliths. It suggests that Zn toxicity alleviation in plants by silicon does not rely on its sequestration by phytoliths. In natural settings, wild fire events and biomass burning may lead to metal sequestration in low-soluble form, which should be considered in modeling of biogeochemical cycles and in paleoenvironmental studies.

Phytolith-occluded carbon in leaves of Dendrocalamus Ronganensis influenced by drought during growing season.

Being an important carbon (C) sink, phytolith-occluded carbon (PhytOC) has been investigated in various soil-plant systems. However, the effects of environmental factors (i.e., drought) on phytoliths, including altered deposition in plant tissues, morphological variation, and amounts of carbon occluded within phytoliths, are less studied. In this study, we analyzed the monthly variations of phytolith production and PhytOC in the leaves of Dendrocalamus ronganensis grown on a karst mountain in southwestern China during a drought year. This study thus sought to understand the effects of drought on phytolith formation, morphological variations and carbon sequestration within phytoliths in plants. Our results showed that the phytolith assemblages and PhytOC between new and old leaves differed significantly and varied with plant growth stages. The average PhytOC values of old leaves and tip leaves were 3.2% and 2.2%, respectively. In particular, both PhytOC and proportions of ELONGATE, BULLIFORM FLABELLATE, and STOMA phytoliths in tip leaves significantly decreased from September to January the following year because of drought effects. This study suggests that PhytOC in plants varies between phytolith morphotypes and is significantly affected by plant growth stage and hydrologic conditions. This indicates that we can improve the efficiency of phytolith carbon sequestration in plants by improving the soil water conditions required for plant growth.

Electron probe microanalysis of the elemental composition of phytoliths from woody bamboo species.

Electron probe microanalysis (EPMA) is promising for accurately determining elemental components in micro-areas of individual phytolith particles, interpreting compositional features and formation mechanisms of phytoliths in plants, identifying archeological and sedimental phytolith. However, the EPMA method of analyzing mounted slide phytoliths has not well been defined. In this study, we attempted different EPMA methods to determine the elemental compositions of phytoliths in mounted slides. Direct analysis of carbon (DAC) with other elements in phytolith could obtain abnormally high total values and carbon values. The method of carbon excluded in measuring elements (non-carbon analysis (NCA)) was feasible to obtain elemental compositions in phytolith. The NCA method was conducive to obtain the factual elemental compositions of an individual phytolith (morphotype) when the carbon content of phytolith was relatively low. The EPMA results of phytoliths from 20 bamboo species (three genera) showed that phytolith was dominantly composed of SiO2 but also included low contents of diverse other elements. The EPMA of phytoliths can provide the elemental composition of micro-areas of an individual phytolith particle. The elemental compositions of phytolith varied with their morphotypes, the genera and ecotype of bamboos. The EPMA of elemental compositions in phytoliths is a potential tool to study the formation mechanism of phytoliths, plant taxonomical identification, archaeological and paleoenvironmental reconstruction.

Phytoliths from Woody Plants: A Review

Phytoliths are efficient proxies in archaeology, plant taxonomy, palaeoenvironment, and palaeoecology reconstruction, the research of which has been developing rapidly in recent years. Phytolith morphology is the basis of phytolith research. The morphological identification and classification of grass phytoliths are clear and detailed enough for application. However, the morphology of phytoliths from woody plants is ambiguous and unsystematic because of the relatively rare research on modern phytoliths and consequently seldom used in archaeology and palaeoenvironment reconstruction. This paper summarizes and concludes the research of woody phytolith morphology in the past decades. Previous studies show that palms and conifers produce some diagnostic phytoliths for identification and classification. There is progress in micromorphology, morphometry, and taxonomic identification of palms and conifers phytoliths. The phytolith morphology of broad-leaved trees is summarized according to produced parts of phytoliths in plants. The potential of further classification for broad-leaved phytoliths was discussed.

Foliar element distributions in Guadua bamboo, a major forest dominant in southwestern Amazonia

Silica is the best-known component filling the spaces that form phytoliths in many plants, but phytoliths may also contain other elements. We used scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX) to map element distributions in the leaves of Guadua bamboo, which is a successful competitor in southwestern Amazonian forests. We emphasize immobile elements that can be mineralized (silicon and calcium) as well as potassium, an abundant mobile nutrient with many vital functions. We discovered high silicon (Si) content with little or no calcium (Ca) or potassium (K) in bulliform cells, bilobate shaped short cells and stomata, all of which can form phytoliths, and moderately high Si content in the bundle sheet, prickle tips and papillae. K often surrounded Si-loaded cells, Si and K had overlapping distributions in the intercostal areas near vein margins, and Ca showed abundant spotted distribution in the intercostal areas. The dark inside content of the costal zones of some samples in light microscopy showed no mineralization but prominently contained sulfur. Adjacent fusoid cells showed different Si, K and Ca combinations, which may suggest potentially variable functions of these cells. Widespread Si deposition strengthens Guadua bamboo leaves and may help it to outcompete tree species during periods of drought.

Phytolith records from 15 continuously growing Bambusa emeiensis leaves and its climatic significance

In order to explore the effect of silica accumulation on the modern bamboo phytoliths, 15 consecutive bamboo leaves of Bambusa emeiensis were employed for observation of different leaf-age phytolith types and their link to the climatic environment. Phytoliths for anatomical terms are divided into six groups: short cells, long cells, bulliform cells, hair cells, silicified tissues and stomata. Short cells make a great contribution to the total percentage of phytoliths counted under the microscope. The effect of silica accumulation on the phytolith morphology of Bambusa emeiensis leaf is limited, and it can not prevent the phytolith records of the climatic information of the growth environment of Bambusa emeiensis. Three phytolith assemblage zones respond very clearly to the three major climatic stages varying from warm-humid to warm-dry and cool-dry conditions. Correlation analysis among phytolith indices and climatic factors at different time levels indicate that the warmth index (Iw) has a highly significant correlation with the 10-day mean temperature, and aridity index (S/F) has a significant correlation with 10-day total evaporation, respectively, which is in good accordance with the average maturity time (10 days or so) of a new leaf. This study reveal that the leaf phytoliths of Bambusa emeiensis can sensitively respond to the living temperature and evaporation corresponding to the growth and maturity of a new leaf. Our results will provide valuable evidence for the climatic significance of modern plant phytoliths and shed the insight into the plant ecophysiological response to the global change in the future.

Allophanes, a significant soil pool of silicon for plants

While in tropical soils recycling of plant phytoliths has been shown to represent a major pool of Si available for plants, the main Si pools available for plants in temperate soils are still poorly constrained. We characterised the various Si pools of temperate forested and cultivated soils in France by selecting seven paired sites (adjacent wheat and forest plots) for four soil groups: Luvisols, Albeluvisols, calcaric and hypereutric Cambisols. We showed that CaCl2-extracted Si (bioavailable) is mostly controlled by pH and allophanes (short-range ordered aluminosilicates) but not by phytoliths. Cultivation, by decreasing the soil organic carbon content increases the allophane content and the SiCaCl2 concentration. Our work highlights the importance of allophanes as the missing link between the soil solution and the clay minerals that could explain the reported correlation between the clay mineral content and bioavailable Si.

The representativeness of the dental calculus dietary record: insights from Ta\xef chimpanzee faecal phytoliths

In recent years, new applications of microremain dietary analysis using dental calculus as a source of dietary data on ancient human subsistence and behaviours have accelerated. The dental calculus of contemporary human and non-human populations with known diets have been used as reference datasets, including the chimpanzees of Taï National Park (Côte d'Ivoire), but explaining the preservation mechanism involved is challenged by our incomplete knowledge of the microremain content within the diets of these reference populations and our rudimentary information on microremain incorporation into dental calculus. Here, we analyse phytoliths in faecal samples to assess to what extent plant phytoliths of a diet are reflected in the dental calculus as well as in the egested faeces. In this study, we identify and document the faecal phytolith assemblages as an indicator of plant consumption in two Western chimpanzees of the Taï National Park (Côte d'Ivoire) before (wet season), during (dry season) and after (dry season) a dust-rich period. Moreover, observational dietary records of these two individuals were compiled to improve the interpretability of this dental calculus phytolith dataset. The faecal phytolith assemblages vary significantly across samples in terms of abundance and diversity. The most common phytolith morphotypes were eudicot plates, single-cell and multi-cell tracheids, monocot rugulose and echinate spheroids and, to a lesser extent, unspecified thick and thin elongates. High loads of grit and other micro-remains (e.g. diatoms) are found during the dry period. Using observational dietary records as a starting point and our faecal results as a terminus, we consider how dental calculus can accumulate phytoliths. Our findings enable identification of the phytolith morphotypes that are under-represented in dental calculus, which is highly informative for future dental calculus research strategies.

Phytolith morphotypes of woody plants and their preservation in soil in the warm temperate humid zones of China

Studies of the morphotypes, production and preservation of phytoliths in soils provide a theoretical basis for paleovegetation reconstruction. However, there is a lack of systematic studies of the phytoliths of woody plants in the warm temperate humid zones, which greatly limits the application of phytoliths in paleovegetation reconstruction in this environmental context. In this study we analyzed the phytoliths of 211 plant samples (81 leaf samples, 73 branch samples, 57 bark samples) and 30 topsoil samples from the warm temperate humid zones of China. The results demonstrate that while most of the leaf samples contained phytoliths, only a few of the branch and bark samples did so. In terms of phytolith concentration, the sample types were ordered as follows: bark samples > leaf samples > branch samples. In this study the phytoliths in woody plants were classified into10 categories and 22 sub-categories, and the results of detrended correspondence analysis (DCA) showed that elongate dentate and blocky morphotypes were closely associated with Picea; elongate cavate and margin-cuneiform morphotypes were closely associated with Larix; acute bulbosus and hair base morphotypes were associated with Morus, Broussonetia and Diospyros; and elongate psilate, elongate attenuate, and sclereid morphotypes were associated with Quercus, but these types are not unique to Quercus. The topsoil woody phytolith assemblages contained four types of broad-leaved phytolith (tabular, tabular sinuate, sclereid, epidermal phytolith), and three types of coniferous phytolith (blocky, elongate dentate, elongate tabular). The ratio of the total of broad-leaved phytoliths to the sum of broad-leaved phytoliths and coniferous phytoliths is useful for discriminating broad-leaved forest from coniferous forest. Overall, the results confirm the usefulness of phytoliths as indicators of woody plants in the warm temperature humid region in China, and they demonstrate the potential of woody phytolith assemblages for paleovegetation reconstruction.

Herbivore effect in the assemblages of phytoliths incorporated to soils from cow dung

Phytoliths represent an important fraction of soil's components and they are incorporated through different agents. One of the sources of phytoliths to soils and sediments is dung. In particular, in agroecosystems, the incorporation of phytoliths from dung may be of importance, since pastures (grasses) belong to one of the highest producer families. The main objective of this work was to compare the content and state of phytoliths in rumen and dung samples from cows in relation to the phytoliths produced in the forage plants eaten. Secondly, we analyzed if phytolith assemblages differed between dung collected in different pastures in Pampean region, Argentina. Phytoliths from rumen and dung samples from five fistulated cows were compared with the main forage species eaten (Festuca arundinacea). Also, dung of three different pastures (two naturals and one controlled) were compared. Phytoliths of plants and dung were extracted by a calcination technique, while rumen samples were treated with hydrogen peroxide. In rumen and dung samples, the morphologies derived from Festuca arundinacea plants had different stages of degradation: the acute bulbosus and the papillate were the most degraded, while the rondels remained with little wear. A high percentage of phytoliths remained unidentified, probably due to their degradation state. Through phytolith morphometric analysis, it was possible to identify that the principal organ eaten by cows was the inflorescence. The dung belonging from different pastures was differentiated by their phytolith content, although the unidentified morphotypes predominated. Dung allow the incorporation of new morphologies and a high amount of degraded phytoliths to soils, modifying its permanent stock of phytoliths.

Biochemical responses of wheat to silicon application under salinity

AbstractBackground: Salinity is one of the main threats that can cause crop yield losses by limiting plant growth. Several important cultivated crops including wheat exhibit sensitivity to salt stress by severe yield reductions. Approaches to improve salt resistance are critical for improved food production in the future.Aims: Silicon (Si) is well known for its role as quasi‐essential element to enhance growth and development of monocot food crops, especially under a variety of abiotic and biotic stress conditions. However, the mechanism of Si‐induced stress resistance is still not fully understood. Here, we investigate the biochemical basis of Si‐induced salt resistance of wheat.Methods: Effect of Si treatment on wheat plants under salt stress was measured by biochemical studies of photosynthetic pigments, ions, oxidative stress indicators, enzymatic and non‐enzymatic antioxidant systems, phytohormones along with expression of two Si‐transport genes.Results: Our results suggest that Si‐induced salt resistance of wheat involves a signaling cascade that triggers the biochemical defense responses. Salinity induces production of the stress hormone abscisic acid that upregulates the expression of Si‐influx transporter gene TaLsi1 and Si‐efflux transporter gene TaLsi2, in the presence of soluble Si in cytosol, and this triggers jasmonate‐mediated activation of both enzymatic and non‐enzymatic antioxidant systems along with osmolyte production. Moreover, peculiar stoichiometric changes in photosynthetic pigments after Si application, as signatures of shaded condition, also lead us to the hypothesis that insoluble Si phytoliths in plants may aid a physical defense response by creating a “mechanically shielded leaf microenvironment” against a variety of abiotic and biotic stress conditions.Conclusion: This study demonstrates that Si activates biochemical defense responses against salt stress in wheat plants.

Phytoliths in modern plants from amazonia and the neotropics at large: Implications for vegetation history reconstruction

Phytolith analysis is increasingly being applied in studies of Neotropical forest history and associated pre-Columbian human influences, especially in the Amazon Basin. In order to enlarge modern reference collections that are integral to these efforts, we analyzed phytoliths from 360 species of mainly eudicotyledons from 80 different families and 10 Arecaceae species. Many are native to Amazonia and have not been studied previously. Production and morphological characteristics of the phytoliths were assessed along with their survivability in ancient soils and sediments. Our analysis affirmed the validity of family- and genus-level diagnostic phytoliths from arboreal and other woody growth taxa uncovered in previous research. It also revealed new diagnostic phytoliths from both well- and little-studied families of importance in the Amazonian forest, and affirmed the utility of other types such as spheroids and sclereids for documenting arboreal/woody growth more generally in paleoecological research. Although where pollen is recovered it will continue to document a greater number of arboreal/woody species, phytoliths can identify a diversity of those taxa in the Amazonian and Neotropical forest at large--including when pollen does not-- with family, genus, and possibly even species-level diagnostics.