Search

Phytolith have been recognized as an important soil bioavailable Si source for plants, as well as a sink of C and heavy metals in soils. Though the impacts of fire and heat on phytolith sequestration of some nutrients (phosphorus, potassium) and heavy metals have been addressed, little attention has been paid to fire's effects on phytolith carbon sequestration. In this study, the carbon and dissolved Si content of phytoliths extracted from 6 common grass species and their burned ashes, as well as phytoliths collected from different areas (burned, transitional, and unburned) of a pine forest, were compared to characterize the effects of open fire on phytolith carbon content, solubility, and carbon sequestration. The carbon content and Si dissolution of ashed phytoliths varied between plant species, and differed with phytoliths from modern plants. The topsoil phytoliths had increased carbon content, and generally decreased solubility across the gradient of unburned, transitional, and burned pine forest. We therefore conclude that open fire can cause changes in phytolith related carbon content and solubility, as well as its preservation in soils. This study provides new perspective on the effects of open fire on phytolith carbon sequestration and its estimation. [ABSTRACT FROM AUTHOR]

Abstract Phytolith have been recognized as an important soil bioavailable Si source for plants, as well as a sink of C and heavy metals in soils. Though the impacts of fire and heat on phytolith sequestration of some nutrients (phosphorus, potassium) and heavy metals have been addressed, little attention has been paid to fire’s effects on phytolith carbon sequestration. In this study, the carbon and dissolved Si content of phytoliths extracted from 6 common grass species and their burned ashes, as well as phytoliths collected from different areas (burned, transitional, and unburned) of a pine forest, were compared to characterize the effects of open fire on phytolith carbon content, solubility, and carbon sequestration. The carbon content and Si dissolution of ashed phytoliths varied between plant species, and differed with phytoliths from modern plants. The topsoil phytoliths had increased carbon content, and generally decreased solubility across the gradient of unburned, transitional, and burned pine forest. We therefore conclude that open fire can cause changes in phytolith related carbon content and solubility, as well as its preservation in soils. This study provides new perspective on the effects of open fire on phytolith carbon sequestration and its estimation.

In the context of global climate change, one central interest is an improved understanding of the global carbon cycle. A large number of studies have investigated carbon cycling and associated elements, mainly nitrogen and phosphorus. However, as an essential element for diatom growth, Si has been largely ignored. Si is the second most abundant element and is widely distributed on Earth. The chemical weathering of silicates on land and photosynthesis of diatoms in the ocean play an important role in atmospheric CO2 levels at various timescales. Diatoms are the primary producers in the ocean and account for as much as 40% of the annual ocean carbon fixation, which have an absolute requirement for Si to form siliceous cells. The main mechanism underlying ocean carbon sinks is a "biological pump." The biological pump is driven by the biological Si pump to a large extent. Therefore, the biogeochemical process of Si has become one of the key research issues for global environmental change.Based on previous studies, the regulation and influence of the Si biogeochemical cycle on the carbon cycle are discussed in this review. The coupling effect and mechanism of the Si and carbon cycles in shellfish culture ecosystems were analyzed and the key research questions were explored. Chemical weathering of silicates and the cycling of their products form the basis of Si biogeochemistry. CO2 is consumed during weathering reactions. Therefore, silicate weathering on land represents an important sink for atmospheric CO2. Furthermore, at the geological timescale, primary silicate mineral weathering is the source of secondary silicate. Terrestrial plants absorb soluble silica through their root system during growth. Amorphous silica deposited in plant tissue after maturity is called phytolith. Phytoliths have excellent geochemical stability and occlude a certain amount of organic carbon during the formation process. The organic carbon occluded within phytolith is called phytolith-occluded carbon (PhytOC) and is buried in the soil. PhytOC is released into the soil with phytolith and may be preserved in soils for several thousands of years. As a consequence, PhytOC in terrestrial ecosystems could be significant potential carbon sinks globally due to the refractory phytolith. Primarily through river input, the dissolved silicate (DSi) is transported into the coastal ocean (approximately 84% of DSi input to the oceans). As the major primary producer, diatoms absorb DSi during growth and account for a large fraction of the total carbon fixation in the modern oceans. DSi is converted into biogenic silica via biological processes, is transported to the deep ocean, and is finally buried into sediments with organic carbon in the marine ecosystem. Thus, by controlling the contribution of diatoms to the total primary production, DSi can affect the carbon cycle in oceans. The carbon pump is driven by the Si pump.Mariculture has developed quickly in recent decades. Shellfish, which are dominated by filter-feeding species, are the main mariculture species. The filter-feeding shellfish consume particulate organic carbon as phytoplankton and use dissolved inorganic carbon to build their shell during growth. Filter-feeding shellfish are an import fishery carbon sink. As one of the important feed sources of filter-feeding shellfish, diatoms form fishery carbon sinks in coastal shellfish culture areas. Silicate is an essential salt for diatom growth. Consequently, the carbon sink of filter-feeding shellfish culture is connected with DSi through diatoms. Si could play an important role in driving the formation of carbon sinks in filter-feeding shellfish culture. Hence, it is necessary to consider all processes and coupling effects in the study of the Si biogeochemical cycle. It is important to understand its role in the carbon sinks of shellfish culture.Nowadays, in many systems, human perturbation has resulted in a decline in the ratio of Si: N to 1:1 or less, with severe impacts on the quality and structure of aquatic ecosystems. DSi limitation has been reported in many studies, in both coastal and marine waters. DSi limitation causes shifts from diatoms to non-siliceous algae and is supposedly related to the decreasing export of carbon. A shift from diatoms to other species would enhance the recycling of organic matter in the upper water column because diatoms are very effective in carbon sequestration. DSi limitation has also appeared in some aquaculture bays in China, such as Jiaozhou Bay and Laizhou Bay, in spring. Regarding future directions, it is suggested that more research be conducted on Si biogeochemistry in shellfish culture systems and coupling with the carbon cycle. The subsequent results could evaluate the role of Si in the carbon sink of filter-feeding shellfish culture. Future studies are expected to provide ideas for alleviating Si deficiency in the aquaculture bay and exploring the expansion path in shellfish farming.

Nickel (Ni) is extremely toxic to plants at high concentrations. Phytoliths have the potential to sequester the heavy metals absorbed by plants and act as a detoxification mechanism for the plant. The authors of the present study aimed to evaluate the effects of Ni on the growth and phytolith yield of grasses in two artificially contaminated soils. Two experiments separated by soil types (Typic Quartzipsamment and Rhodic Hapludox) were conducted in a completely randomized design in a 2 × 4 factorial scheme with three replications. The factors were two species of grass (Urochloa decumbens and Megathyrsus maximus) and three concentrations of Ni (20, 40, and 120 mg kg−1) and control treatment. The grasses were influenced by the increase in Ni rates in the soils. Ni exerted a micronutrient function with the addition of 30 mg kg−1 of Ni in soils, but this concentration caused toxicity in grasses. Such a level is lower than the limits imposed by the Brazilian environmental legislation. Higher Ni availability in Typic Quartzipsamment promoted Ni toxicity, with reduced growth and increased phytolith yield in the shoot, increased Ni in the shoot, and Ni occlusion in phytoliths by grasses, in comparison with Rhodic Hapludox. The yield and Ni capture in phytoliths by grasses in Ni-contaminated soils are related to the genetic and physiological differences between grasses and Ni availability in soils. Ni capture by phytoliths indicates that it may be one of the detoxification mechanisms of Urochloa decumbens to Ni contamination, providing additional tolerance. Megathyrsus maximus may be a future grass for the phytoremediation technique in Ni-contaminated soils. [ABSTRACT FROM AUTHOR]

BACKGROUND: The micro/nano silicon-carbon deposit in Fengcheng City, Jiangxi Province, is the first sedimentary deposit mineralized by phytoliths in the world. According to the research carried out here, micro/nano silicon-carbon ore may have been formed by the long-term accumulation and consolidation of phytoliths. In terms of distribution range, genetic type and resource type, the micro/nano silicon-carbon deposit has many new features. Therefore, considering the particularity of the deposit, it is of great significance to carry out research, especially chronological research. Moreover, Re-Os isotope system of organic-enriched sedimentary rocks has been applied to directly dating deposition ages or stratigraphic boundary age, which has made many achievements in chronological research. However, most of the studies focus on marine sediments samples, while lacustrine sediments samples are rarely affected by many factors, such as provenance, geological processes, and terrigenous clastic materials. OBJECTIVES: To accurately determine the mineralization age of the natural micro/nano silicon-carbon deposit. METHODS: Re-Os isotope testing was used to date the phytolith rock samples (lacustrine sediment samples) in the lower section of the Shilukeng Formation in the mining area. Isotope ratios were determined by NTIMS, and GBW04477 (JCBY) was used as the reference material. RESULTS: The Re-Os isotope age of the samples is 43.1±3.7Ma (n=7, MSWD=6.2) which directly defines the diagenetic mineralization age of phytolith rock of the deposit. The high 187Re/188Os value of the samples is closely related to the sedimentary environment and the origin of biological sedimentation. The high initial 187Os/188Os ratio may be related to tectonic movement events, high Os content and migration rate of adjacent strata. The study shows that Re and Os isotopes are adsorbed and sealed in phytolith with organic carbon in the process of enrichment. Owing to the phytolith’s stable silica structure, high temperature resistance and corrosion resistance, the Re-Os isotope system has a good sealing property in it. Protected by the special structure, the organic carbon in phytolith mainly exists in the tiny cavity of phytolith, and the organic carbon has not been exchanged with the outside world due to its storage, which provides favorable conditions for dating. Moreover, the large amount of phytolith in the samples also provides favorable conditions for the enrichment of Re and Os isotopes. CONCLUSIONS: The results of this study provide for the determination of sedimentary age about lacustrine sediments samples by the Re-Os isotope analysis. It is important to strengthen research about the study of Re-Os enrichment mechanism by micro/nano silicon-carbon ore samples. [ABSTRACT FROM AUTHOR]

Silicon (Si) is abundant in the lithosphere, and previous studies have confirmed that silicon plays an important role in plant growth. Higher plants absorb soluble silicon from soil through roots which is deposited in plant tissues mainly in the form of phytoliths. Based on previous studies, the research progress in silicon and phytoliths in the structural protection, enhancement on photosynthesis and transpiration of plants and plant growth and stress resistance was reviewed. Meanwhile, gaps in phytolith research, including phytolith morphology and function, impact of diverse environmental factors coupling with phytoliths, phytolith characteristics at different stages of plant development and phytoliths in regional vegetation are identified. The paper intends to promote the wider application of phytolith research findings and provides reference for further research on phytoliths.

The moisture, ash, and silicon content, as well as the phytolith morphotype and concentration in the tissue-cultured, seed-cultured, and grafted seedling leaves of Dendrocalamus brandisii were determined to investigate the differences in silicon uptake and phytolith morphology in the leaves from different rearing methods. The results showed that ash, silicon content, and phytolith concentration were higher in the mature leaves. Tissue-cultured seedlings had a significantly higher moisture content than grafted seedlings. Ash and silicon demonstrated the same order of grafted seedlings > tissue-cultured seedlings > seed-cultured seedlings. The highest phytolith concentration was found in tissue-cultured seedlings. The phytolith morphotypes in D. brandisii seedling leaves raised by different methods were identical and grouped into eight morphotypes. The phytolith assemblage was characterized by a high frequency of bilobate and saddle, accounting for more than 60%, whereas the morphotypes of elongate, blocky, flabellate, and circular phytoliths accounted for the smallest proportion, normally all below 4.5%. The phytolith size demonstrated an increasing trend in the maturing leaves. The sizes of bilobate, saddle, and acute phytoliths expanded the fastest in tissue-cultured seedling leaves, implying rapid growth of the cell in tissue-cultured seedlings. Accordingly, the tissue-cultured seedlings contained more silicon and phytoliths of larger sizes, which could be a better choice of stock supply for establishing large-scale plantations. If the stock of the seed-cultured and grafted seedlings is to be used, silicon fertilizer application is an optimal option to boost seedling growth. [ABSTRACT FROM AUTHOR]

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 4 t 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 4 t 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. [ABSTRACT FROM AUTHOR]

Summary: Phytoliths, microscopic deposits of hydrated silica within plants, play a myriad of functional roles in extant tracheophytes – yet their evolutionary origins and the original selective pressures leading to their deposition remain poorly understood. To gain new insights into the ancestral condition of tracheophyte phytolith production and function, phytolith content was intensively assayed in a basal, morphologically conserved tracheophyte: the foxtail clubmoss Lycopodiella alopecuroides.Wet ashing was employed to perform phytolith extractions from every major anatomical region of L. alopecuroides. Phytolith occurrence was recorded, alongside abundance, morphometric information, and morphological descriptions.Phytoliths were recovered exclusively from the microphylls, which were apicodistally silicified into multiphytolith aggregates. Phytolith aggregates were larger and more numerous in anatomical regions engaging in greater evapotranspirational activity.The tissue distribution of L. alopecuroides phytoliths is inconsistent with the expectations of proposed adaptive hypotheses of phytolith evolutionary origin. Instead, it is hypothesized that phytoliths may have arisen incidentally in the L. alopecuroides‐like ancestral plant, polymerizing from intraplant silicon accumulations arising via bulk flow and 'leaky' cellular micronutrient channels. This basal, nonadaptive phytolith formation model would provide the evolutionary 'raw material' for later modification into the useful, adaptative, phytolith deposits seen in later‐diverging plant clades. [ABSTRACT FROM AUTHOR]

The middle and lower Huai River Valley, located between the Yangtze and Yellow Rivers, was a key transitional zone for the northward spread of rice and southward migration of millet agriculture in central-eastern China during the Holocene. Knowing when millets spread here, how they were combined with rice in mixed farming, the reasons for their spread, and the temporal variation of cropping patterns is of crucial significance to the development of our understanding of ancient adaptation strategies adopted by human societies in response to climatic and cultural changes. Focusing on crops, phytolith analyses of the soil samples, in tandem with radiocarbon dating from the Wanbei site, reveal evidence of a multicropping pattern of combining rice (Oryza sative), broomcorn millet (Panicum miliaceum), and foxtail millet (Setaria italica) during the Dawenkou culture period between 5720 and 4426 cal. BP in the middle and lower Huai River Valley, China. The data show that rice was always the principal crop of the pattern, and that domesticated rice was developed during the early and middle Dawenkou culture periods. However, its domestication rate became lower during the late Dawenkou culture period. Broomcorn millet and foxtail millet with domesticated traits appeared only in lower proportions of the total produced throughout the period. The proportions of rice and foxtail millet increased slightly, while the proportions of broomcorn millet decreased over time. Finally, the formation of the multicropping pattern at Wanbei may have been primarily influenced by both the warm and wet climatic environment and the cultural exchange and communication between the Haidai region and the middle and lower Huai River Valley during the Dawenkou culture period. The findings in this paper may not only contribute to mapping the spatiotemporal route for the northward expansion of rice agriculture and southward spread of millet agriculture, but also assist in understanding the human adaptation strategies employed in eastern China during the Holocene. [ABSTRACT FROM AUTHOR]

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 4 t 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 4 t 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.

Organic carbon occluded in phytoliths is extremely stable and plays important roles in long-term preservation of soil and stable carbon sequestration in terrestrial ecosystems. To clarify the effects of land-use changes on the accumulation of soil phytolith-occluded organic carbon (PhytOC), the typical six land-use types of forest, open forest, shrub, grassland, corn field and abandoned farmland in Southwest China were used to study the associations of soil PhytOC accumulation with land-use change. The present results showed that land-use changes significantly affected soil PhytOC accumulation and its proportion to TSOC (total soil organic carbon). Compared to vegetation coverage, vegetation productivity increased soil PhytOC accumulation more effectively. The content and reserves of soil PhytOC in the open forest all ranked highest among the six land uses studied. Forest thinning not only substantially increased soil stable organic carbon sequestration but also obviously increased the TSOC pool. When land use changed from forest to grassland, there were obvious releases or run off of soil organic carbon, but the stability of the soil organic C pool improved obviously. After the corn field was abandoned, the PhytOC pool did not vary obviously. Soil pH was the important factor influencing the soil PhytOC pool, and acidic soils were made against PhytOC accumulation in soils. Soil PhytOC accumulation was significantly affected by soil C, N and P nutrition contents and stoichiometric ratios. Significant negative effects of bulk density on PhytOC accumulation in soils were observed. The present results are of great significance in land use regulation for increasing the soil carbon sink of terrestrial ecosystems.

Nickel (Ni) is extremely toxic to plants at high concentrations. Phytoliths have the potential to sequester the heavy metals absorbed by plants and act as a detoxification mechanism for the plant. The authors of the present study aimed to evaluate the effects of Ni on the growth and phytolith yield of grasses in two artificially contaminated soils. Two experiments separated by soil types (Typic Quartzipsamment and Rhodic Hapludox) were conducted in a completely randomized design in a 2 × 4 factorial scheme with three replications. The factors were two species of grass (Urochloa decumbens and Megathyrsus maximus) and three concentrations of Ni (20, 40, and 120 mg kg−1) and control treatment. The grasses were influenced by the increase in Ni rates in the soils. Ni exerted a micronutrient function with the addition of 30 mg kg−1 of Ni in soils, but this concentration caused toxicity in grasses. Such a level is lower than the limits imposed by the Brazilian environmental legislation. Higher Ni availability in Typic Quartzipsamment promoted Ni toxicity, with reduced growth and increased phytolith yield in the shoot, increased Ni in the shoot, and Ni occlusion in phytoliths by grasses, in comparison with Rhodic Hapludox. The yield and Ni capture in phytoliths by grasses in Ni-contaminated soils are related to the genetic and physiological differences between grasses and Ni availability in soils. Ni capture by phytoliths indicates that it may be one of the detoxification mechanisms of Urochloa decumbens to Ni contamination, providing additional tolerance. Megathyrsus maximus may be a future grass for the phytoremediation technique in Ni-contaminated soils.

The study of macroscopic, microscopic, and biomolecular remains recovered from coprolites can provide a wide range of information on past human and animal behavior and environments. In earlier studies, research tended to focus on one or two proxies, but multiproxy approaches combining data from all remains within coprolites are becoming more common. Multiproxy analyses have demonstrated value for strengthening our understanding of the past and reducing equifinality. Here we present a sequential biomolecular, macrofossil, and microfossil extraction protocol that separates all different coprolite components and is intended as a best-practice guideline for coprolite analysis. We demonstrate the effectiveness of this method by applying it to an assemblage of coprolites from the Paisley Caves, Oregon, USA. By combining a wide range of proxies, this study provides important information on the taxonomy and behavior of organisms in the past as well as the paleoecological context of behavior.

The accumulation of phytolith-occluded carbon (PhytOC) in Moso bamboo could be a novel long-term carbon sequestration strategy. The objective of this study was to investigate the effects of temperature change and different fertilization on PhytOC accumulation. The pot experiment was established with different fertilization (including control (CK), nitrogen fertilizers (N), silicon fertilizers (Si), and a combination of nitrogen and silicon (NSi)) under high- and low-temperature. Despite the different fertilization, the PhytOC accumulation of the high-temperature group increases by 45.3% on average compared with the low-temperature group, suggesting higher temperature is greatly beneficial to the PhytOC accumulation. Fertilization significantly increases the accumulation of PhytOC (increased by 80.7% and 48.4% on average for the low- and high-temperature group, respectively) compared with CK. However, the N treatment increased both Moso bamboo biomass and PhytOC accumulation. The difference in the accumulation of PhytOC in Si and NSi was insignificant, indicating the combination of N and Si didn't bring extra benefit to PhytOC accumulation compared to Si fertilizer alone. These results indicated the application of nitrogen fertilizer is a practical and effective method for enhancing long-term carbon sequestration for Moso bamboo. Based on our study, we conclude that global warming poses a positive effect on promoting the long-term carbon sequestration of Moso bamboo. [ABSTRACT FROM AUTHOR]

Abstract 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.

The accumulation of metal(loid)s in phytoliths can physically immobilize the toxic materials and reduce toxicity in plant bodies and soil. Spider brake (Pteris multifida) is a well-known As hyperaccumulator that also harbors phytolith. However, As accumulation in phytoliths has not yet been studied with P. multifida. Soil water content is considered the main factor influencing phytolith accumulation. In this study, the As concentration in the phytoliths of P. multifida was compared with that in common reed (Phragmites australis) phytoliths with various soil water content. The range of As concentration in the phytoliths of P. multifida was 414.70–1610.74 mg kg−1, and the range for P. australis phytoliths was 41.67–126.54 mg kg−1. In P. multifida, higher soil water content increased As accumulation in the phytolith but did not affect the phytolith content in the plant. In P. australis, the higher soil water content increased phytolith content in the plant but decreased As concentration in phytoliths. This study suggests that P. multifida has higher As content in phytoliths than P. australis, and this accumulation can be affected by soil water content. The current findings provide how As encapsulated in phytolith and detoxified in different plants and conditions. [ABSTRACT FROM AUTHOR]

Crop cultivation has great potential to result in a phytolith carbon sink and can play important roles in the long-term stable carbon sequestration of terrestrial ecosystems. Buckwheat, an important multigrain crop with a very long cultivation history, is widely planted around the world. The phytolith carbon sink potential of buckwheat planting is still limited in the in-depth understanding of biogeochemical carbon sequestration in croplands. In order to estimate the phytolith carbon sink potential of buckwheat planting, in the present study, six species including 17 populations of Fagopyrum plants were selected as study materials. Firstly, their phytoliths were extracted using the wet oxidation method; then, the phytolith-occluded organic carbon (PhytOC) contents were determined using the spectrophotometry method; finally, the phytolith carbon sink potential of buckwheat planting was estimated. Results showed the following: 1) The PhytOC content range of the six Fagopyrum species studied was 0.006%~0.038%, which was significantly lower than that of rice, wheat, sugarcane, and some cereal and oil crops. There were significant differences in total silicon, phytolith, and PhytOC content of Fagopyrum plants among the different species, different organs (root, stem, and leaf), and different living forms (annual, partly perennial, and completely perennial). There were significant positive relationships between PhytOC and phytolith content and between phytolith and total silicon content. 2) The average phytolith carbon sequestration rate of Fagopyrum esculentum and Fagopyrum tataricum planting was 2.62 × 10-3 and 1.17 × 10-3 t CO2 hm-2·a-1, respectively, being approximately equal to that of terrestrial shrub vegetation. 3) The global total amount of phytolith carbon sequestration of buckwheat planting reached 5,102.09 t CO2 in 2018, and the Chinese total amount of phytolith carbon sequestration of buckwheat cultivation was 624.79 t CO2 in 2020. The phytolith carbon sink of buckwheat planting had significant potential for playing obvious roles in the carbon cycle. The present results are of great significance in crop phytolith studies and provide important references for phytolith carbon sink potential estimation of farmland ecosystems. [ABSTRACT FROM AUTHOR]

Research has generally outlined that the Neolithic East Asian farmers expanded into Southeast Asia, leading to substantial social and cultural transformations. However, the associated archaeobotanical evidence until now has been insufficient to clarify the exact timing, dispersal route, and farming package of the emergence of agriculture in Mainland Southeast Asia. To clarify these issues, the micro-plant remains of phytolith and starch from three Neolithic sites in Ha Long Bay were extracted and analyzed. This study validates the earliest evidence of co-cropping in northern Vietnam, involving the cultivation of rice together with foxtail millet at 4000 years BP or slightly earlier. Moreover, the results indicate that at least two patterns of subsistence strategy were practiced simultaneously during the initial farming phase in the region. The Trang Kenh people, a regional variant of the Phung Nguyen cultural group often have been seen as the first farmers in northern Vietnam, and they mainly practiced a cereal-based subsistence strategy with more vital cultural characteristics of southern China origin. Meanwhile, the Ha Long people, mainly composed of indigenous hunter-gatherer descendants, continued to utilize a wide range of their preferred plant resources such as taros, yams, and acorns, while they absorbed and incorporated new elements such as millet and rice into their food system. This study provides solid information to understand the diverse economic systems among different cultural groups in Vietnam. [ABSTRACT FROM AUTHOR]

Silicon (Si) is considered a beneficial element in plant nutrition, but its importance on ecosystems goes far beyond that. Various forms of silicon are found in soils, of which the phytogenic pool plays a decisive role due to its good availability. This Si returns to the soil through the decomposition of plant residues, where they then participate in the further cycle as biogenic amorphous silica (bASi) or so-called phytoliths. These have a high affinity for water, so that the water holding capacity and water availability of soils can be increased even by small amounts of ASi. Agricultural land is a considerable global dust source, and dust samples from arable land have shown in cloud formation experiments a several times higher ice nucleation activity than pure mineral dust. Here, particle sizes in the particulate matter fractions (PM) are important, which can travel long distances and reach high altitudes in the atmosphere. Based on this, the research question was whether phytoliths could be detected in PM samples from wind erosion events, what are the main particle sizes of phytoliths and whether an initial quantification was possible.Measurements of PM concentrations were carried out at a wind erosion measuring field in the province La Pampa, Argentina. PM were sampled during five erosion events with Environmental Dust Monitors (EDM). After counting and classifying all particles with diameters between 0.3 and 32 µm in the EDMs, they are collected on filters. The filters were analyzed by Scanning Electron Microscopy and Energy Dispersive X-Ray analysis (SEM-EDX) to investigate single or ensembles of particles regarding composition and possible origins.The analyses showed up to 8.3 per cent being phytoliths in the emitted dust and up to 25 per cent of organic origin. Particles of organic origin are mostly in the coarse dust fraction, whereas phytoliths are predominately transported in the finer dust fractions. Since phytoliths are both an important source of Si as a plant nutrient and are also involved in soil C fixation, their losses from arable land via dust emissions should be considered and its specific influence on atmospheric processes should be studied in detail in the future.

Phytolith is widely known as a silica structure in numerous silicon (Si) accumulator plants, e.g., rice, and it contains various nutrients and other beneficial elements. When rice straw is returned to paddy fields, the silica structure of phytolith can be dissolved, thereby releasing its occluded nutrients. While the intrinsic characteristics and dissolution properties of phytoliths under the effect of solution chemistry have been intensively studied, the effect of gas phases, especially CO2, on phytolith stability and the implications for nutrient release are not fully known. Here, dissolution properties of phytolith ashes obtained from dry ashing of rice straw at 400, 600 and 800 °C were investigated by quantifying Si release together with other nutrients under two atmospheric conditions, i.e., without and with CO2 support (aeration). In a time span of 6 days, the releases of nutrients (K, P, Ca, Mg) showed high dependence on the overall dissolution of the phytolith ashes. CO2 significantly reduced the dissolution rate of the phytolith ashes but increased the release rates of cationic as well as anionic nutrients. The aeration of CO2 shifted the carbonate equilibrium (H2CO3, HCO3− and CO32−) towards H2CO3, reducing solution pH, thereby decreasing the dissolution rate of phytoliths. Following this, intensification of H+ exchange promoted nutrient releases from the phytolith ashes. This indicates contrasted responses of phytoliths and their occluded nutrients to CO2, and provides a better insight on the fate of soil phytoliths and the tendency of nutrient budgets from rice straw phytoliths in soils. [ABSTRACT FROM AUTHOR]

Carbon (C) occluded in phytoliths is stable and an important source of long-term C storage into the agroecosystems. As a silicon (Si) accumulator crop, rice produces a large amount of phytolith occluded carbon (PhytOC) and which plays a crucial role in the coupled biogeochemical cycle of C and Si. In this study, we sampled above ground biomass from 22 intensively cultivated rice ecosystems to evaluate the rate of C sequestration through phytoliths. Depending on the rice varieties there exist a great variability in PhytOC content (0.12–0.26%) across the rice ecosystems. The collected samples were further classified into three groups: viz., long (>140 days), medium (125–140 days) and short duration ( 0.05) whereas, the PhytOC content found to be significant (p 140 days) varieties showed 69.7% and 164.0% higher PhytOC sequestration flux over medium and short-duration varieties, respectively. Our results suggest that the Indian rice ecosystems sequester 0.95 Tg CO2 yr−1 through Phytoliths, which is equivalent to the 15.5% of PhytOC sink in the global rice field. Considering the PhytOC flux of relatively higher PhytOC accumulating long duration varieties, the annual PhytOC sink rate in the Indian rice ecosystems can be increased to ∼4 folds over the current rate. It was revealed that the selection of higher PhytOC accumulating long duration varieties can enhance the phytolith C sequestration.

Dental microwear texture (DMT) analysis is used to differentiate abrasive dental wear patterns in many species fed different diets. Because DMT parameters all describe the same surface, they are expected to correlate with each other distinctively. Here, we explore the data range of, and correlations between, DMT parameters to increase the understanding of how this group of proxies records wear within and across species. The analysis was based on subsets of previously published DMT analyses in guinea pigs, sheep, and rabbits fed either a natural whole plant diet (lucerne, grass, bamboo) or pelleted diets with or without added quartz abrasives (guinea pigs and rabbits: up to 45 days, sheep: 17 months). The normalized DMT parameter range (P4: 0.69 ± 0.25; M2: 0.83 ± 0.16) and correlation coefficients (P4: 0.50 ± 0.31; M2: 0.63 ± 0.31) increased along the tooth row in guinea pigs, suggesting that strong correlations may be partially explained by data range. A comparison between sheep and guinea pigs revealed a higher DMT data range in sheep (0.93 ± 0.16; guinea pigs: 0.47 ± 0.29), but this did not translate into more substantial correlation coefficients (sheep: 0.35 ± 0.28; guinea pigs: 0.55 ± 0.32). Adding rabbits to an interspecies comparison of low abrasive dental wear (pelleted lucerne diet), the softer enamel of the hypselodont species showed a smaller data range for DMT parameters (guinea pigs 0.49 ± 0.32, rabbit 0.19 ± 0.18, sheep 0.78 ± 0.22) but again slightly higher correlations coefficients compared to the hypsodont teeth (guinea pigs 0.55 ± 0.31, rabbits 0.56 ± 0.30, sheep 0.42 ± 0.27). The findings suggest that the softer enamel of fast-replaced ever-growing hypselodont cheek teeth shows a greater inherent wear trace consistency, whereas the harder enamel of permanent and non-replaced enamel of hypsodont ruminant teeth records less coherent wear patterns. Because consistent diets were used across taxa, this effect cannot be ascribed to the random overwriting of individual wear traces on the more durable hypsodont teeth. This matches literature reports on reduced DMT pattern consistency on harder materials; possibly, individual wear events become more random in nature on harder material. Given the species-specific differences in enamel characteristics, the findings suggest a certain species-specificity of DMT patterns.

The diet of prehistoric humans in the Qijia period (4,400–3,500 BP) was significantly changed by the advent of dry agriculture and food globalization. However, it is yet to be proven whether wild plants were exploited despite the cultivation of millet, and whether wheat crops, cattle, and sheep originating from southwestern Asia were adopted into the regional human diet. This study presents stable isotope, starch grain, and phytolith analyses of 24 human teeth from the Lajia site in Qinghai, which is a representative Qijia culture settlement site. The carbon and nitrogen isotope results show that the subjects primarily ate C4 plants and had a high protein diet. Starch grain and phytolith results showed that the inhabitants consumed broomcorn millet (Panicum miliaceum), foxtail millet (Setaria italica), Triticeae, tubers and roots, along with other Pooideae and Poaceae plants. This data proves that although broomcorn and foxtail millet formed the mainstay of the Qijia diet, it also included a wide range of plants, such as the tribe Triticeae, tubers and roots, which would have been foraged rather than grown. Compared with the other three contemporaneous sites in Northern China, the proportion of millet starches was highest at the Lajia site, while the type and proportion of foraged plants were the lowest. This was probably because of the arid environment in the region, which could not have supported sufficient plant resources for foraging, which in turn might have led to enhanced millet cultivation and/or a greater reliance on hunting. No wheat or barley traces were found in human teeth in Lajia, and the high proportion of nitrogen was possibly related to the consumption of sheep because sheep bones were found in a zooarchaeological study. This study enhances our understanding of the subsistence strategies present in Qijia culture and of prehistoric food globalization, which is of pivotal significance for a deeper understanding of interactions between east and west Asia during the Neolithic and Bronze ages.

The middle and lower Huai River Valley, located between the Yangtze and Yellow Rivers, was a key transitional zone for the northward spread of rice and southward migration of millet agriculture in central-eastern China during the Holocene. Knowing when millets spread here, how they were combined with rice in mixed farming, the reasons for their spread, and the temporal variation of cropping patterns is of crucial significance to the development of our understanding of ancient adaptation strategies adopted by human societies in response to climatic and cultural changes. Focusing on crops, phytolith analyses of the soil samples, in tandem with radiocarbon dating from the Wanbei site, reveal evidence of a multicropping pattern of combining rice (Oryza sative), broomcorn millet (Panicum miliaceum), and foxtail millet (Setaria italica) during the Dawenkou culture period between 5720 and 4426 cal. BP in the middle and lower Huai River Valley, China. The data show that rice was always the principal crop of the pattern, and that domesticated rice was developed during the early and middle Dawenkou culture periods. However, its domestication rate became lower during the late Dawenkou culture period. Broomcorn millet and foxtail millet with domesticated traits appeared only in lower proportions of the total produced throughout the period. The proportions of rice and foxtail millet increased slightly, while the proportions of broomcorn millet decreased over time. Finally, the formation of the multicropping pattern at Wanbei may have been primarily influenced by both the warm and wet climatic environment and the cultural exchange and communication between the Haidai region and the middle and lower Huai River Valley during the Dawenkou culture period. The findings in this paper may not only contribute to mapping the spatiotemporal route for the northward expansion of rice agriculture and southward spread of millet agriculture, but also assist in understanding the human adaptation strategies employed in eastern China during the Holocene.

Despite decades of investigation, consensus has yet to be reached on when and where wheat replaced millet as the primary crop in the core regions of early Imperial China. Previous studies have suggested that wheat cultivation likely became widespread prior to or during the Han Dynasty (202 BC–AD 220). Here, we tested this hypothesis by applying archeobotanical tools to plant remains found in five pottery model granaries (cang) entombed in a newly excavated late Western Han burial at the Longzaocun cemetery in the Guanzhong Basin. This analysis allowed us to explore the extent of wheat expansion and agricultural strategies in the heartland of early dynastic China. Macro- and micro-botanical evidence shows that the Longzaocun residents consumed two kinds of crops: foxtail and common millet. Combining these findings with previous studies, we argue that millet-based multi-crop farming dominated the regional agricultural system during the Western Han Dynasty (202 BC-AD 8) and analyze the political and cultural motivations for the Han people's usage on millet crops from the burial concepts and fiscal systems. Echoing previous studies, we argue that millets remained the most valuable subsistence food for inhabitants of the Loess Basins in the Han core, and that wheat was not cultivated on a large scale in this area during the Western Han Dynasty. [ABSTRACT FROM AUTHOR]

Neolithic rice remains were recovered from a mixed rice–millet farming area in China outside the original centers of rice farming. Whether the rice remains were the result of local cultivation or obtained through trade remains unclear. Rice paddy fields are direct evidence of local cultivation. In this study, phytolith samples from the Zhangwangzhuang site were analyzed. The discriminant function distinguished 17 of 30 samples in the suspected paddy field area as rice paddy fields with an average probability of 74%; The proportion of rice bulliform phytoliths with ≥9 scales indicated that rice (Oryza sativa) was still being domesticated and, moreover, six η-type phytoliths from broomcorn millet (Panicum miliaceum) were identified. These results suggested that the suspected paddy field at Zhangwangzhuang might be the earliest rice paddy field (ca. 6000 cal. BP) in northern China and that mixed farming was practiced here since the early Yangshao period. This study adopted discriminant analysis methods to discover ancient rice paddy fields, observed rice paddy fields outside the core rice origin area, and provided the earliest evidence regarding the development of mixed rice–millet farming in the upper Huai River region. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Mainland Southeast Asia experienced a long, sustained period of foraging economy before rice and millet farming spread into this area prior to 4,000 years BP. Although hundreds of individuals from dense cemeteries are found in several hunter-gatherer sites in Guangxi, Southern China, and Northern Vietnam, dating from the early to middle Holocene (ca. 9,000–4,500 years BP), so far, little has been known about food sources in these pre-farming contexts. In particular, plant food resources have been unclear, although they likely were crucial to supporting rather large populations of hunter-gatherers in this region. To investigate this issue, micro plant remains, including starches and phytoliths, were recovered from stone tools excavated at the Cai Beo site in Ha Long Bay of coastal Northeastern Vietnam, and those findings revealed new understanding of the ancient diet. Examinations of those residues indicated that the hunter-gatherers at Cai Beo as early as 7,000–6,000 years BP exploited a broad spectrum of plants, such as taros, yams, acorns, palms, and more. This study exemplifies how maritime hunter-gatherers interfaced with the local plants and generated population growth from about 7,000 to 4,500 years BP. The results help us to conceptualize the early exploitation, management, and potential cultivation of subtropical and tropical plants over the broad geography of Asia and the Pacific before the arrival of rice and millet farming. In particular, the result validates the significance of roots and tubers in the ancient subsistence economy of Southeast Asia. Moreover, from the archaeological context of 4,500 to 4,000 years BP, the rice discovered in this study represents one of the earliest known in Mainland Southeast Asia.

Despite decades of investigation, consensus has yet to be reached on when and where wheat replaced millet as the primary crop in the core regions of early Imperial China. Previous studies have suggested that wheat cultivation likely became widespread prior to or during the Han Dynasty (202 BC–AD 220). Here, we tested this hypothesis by applying archeobotanical tools to plant remains found in five pottery model granaries (cang) entombed in a newly excavated late Western Han burial at the Longzaocun cemetery in the Guanzhong Basin. This analysis allowed us to explore the extent of wheat expansion and agricultural strategies in the heartland of early dynastic China. Macro- and micro-botanical evidence shows that the Longzaocun residents consumed two kinds of crops: foxtail and common millet. Combining these findings with previous studies, we argue that millet-based multi-crop farming dominated the regional agricultural system during the Western Han Dynasty (202 BC-AD 8) and analyze the political and cultural motivations for the Han people’s usage on millet crops from the burial concepts and fiscal systems. Echoing previous studies, we argue that millets remained the most valuable subsistence food for inhabitants of the Loess Basins in the Han core, and that wheat was not cultivated on a large scale in this area during the Western Han Dynasty.

The Zang-Yi Corridor is of pivotal significance for the interactions between northwest China, southwest China, and mainland Southeast Asia. It has been hypothesized that the formation of mixed farming in this region and its surrounding areas was based on multiple waves of crop dispersal, with foxtail millet and broomcorn millet arriving first from northwest China around 5,300 cal. BP and rice from middle Yangtze valley after 4,700 cal. BP. Based on the systematic sampling and direct dating conducted at the Guijiabao site, Sichuan Province, this study demonstrates that by no later than 5,000 cal. BP, mixed farming had already emerged in the south part of Zang-Yi corridor, which was much earlier than expected before. With this new evidence, it is argued that the transformation into farming in Southwest China was based on the dispersal of a crop package comprising foxtail millet, broomcorn millet, and rice instead of different waves of introduction. A further comparison of all archaeobotanical data in this region revealed that crop patterns varied significantly between different sites because of their diverse environmental conditions.

Open science is an integral part of all scientific research, but the extent of open science practices in phytolith research is unknown. Phytolith analysis examines silica bodies that are initially formed within and between plant cells during the life of the plant but become deposited in sediments once the plant dies. The use of phytoliths in archaeobotanical and palaeoecological studies has been increasing in recent years resulting in an upsurge in publications. The aims of this article are to assess open science practices in phytolith research by reviewing data and metadata sharing, and open access, in a sample of journal articles containing primary phytolith data from 16 prominent archaeological and palaeoecological journals (341 articles). This study builds on similar studies conducted for zooarchaeology (Kansa et al. 2020) and macrobotanical remains (Lodwick 2019). This study shows that 53% of papers shared data in any format but only 4% of papers contained reusable data, 74% included some pictures of phytolith morphotypes for identification purposes, 69% had a fully described method, 47% used the International code for phytolith nomenclature (ICPN 1.0) and only 13% of articles were open access. Steps forward are then proposed, including planning for open projects, making more articles openly accessible and implementing the FAIR data principles, to use as a starting point for discussions in the wider phytolith and archaeological communities to develop guidelines for greater integration of open science practices. [ABSTRACT FROM AUTHOR]

Open science is an integral part of all scientific research, but the extent of open science practices in phytolith research is unknown. Phytolith analysis examines silica bodies that are initially formed within and between plant cells during the life of the plant but become deposited in sediments once the plant dies. The use of phytoliths in archaeobotanical and palaeoecological studies has been increasing in recent years resulting in an upsurge in publications. The aims of this article are to assess open science practices in phytolith research by reviewing data and metadata sharing, and open access, in a sample of journal articles containing primary phytolith data from 16 prominent archaeological and palaeoecological journals (341 articles). This study builds on similar studies conducted for zooarchaeology (Kansa 'et al'. 2020) and macro-botanical remains (Lodwick 2019). This study shows that 53% of papers shared data in any format but only 4% of papers contained reusable data, 74% included some pictures of phytolith morphotypes for identification purposes, 69% had a fully described method, 47% used the International code for phytolith nomenclature (ICPN 1.0) and only 13% of articles were open access. Steps forward are then proposed, including planning for open projects, making more articles openly accessible and implementing the FAIR data principles, to use as a starting point for discussions in the wider phytolith and archaeological communities to develop guidelines for greater integration of open science practices.

Paleoclimate reconstitution for the state of São Paulo results from past and ongoing research efforts in palynology, anthracology, and stable isotope studies. In cases such as southern São Paulo, however, researchers are required to extrapolate data from the states of Paraná, Santa Catarina, and Rio Grande do Sul for comparisons. Phytoliths and seeds were collected from sediments retrieved from excavation units D18 and G6 at the Abrigo de Itapeva [Itapeva Shelter] archeological site and analyzed. Seed results indicate that Ocotea (Lauraceae) is present in the initial levels, whereas Syagrus romanzoffiana predominates at all other stratigraphic levels. The former is a species of Atlantic Forest that occurs in Araucaria Forests; the latter is a palm species found in southeastern and southern Brazil. Phytoliths analysis reveals a change from a drier climate with grassland vegetation to a woody forest in the later periods of shelter occupation. As such, grassland and forest vegetation types occur from base stratigraphic levels up to level seven, dating from 5,510 cal BP to 730 cal BP. Conversely, from level seven up to the surface levels, dated from 730 cal BP to 560 cal BP, we see species linked to Araucaria Forest proliferation which may indicate the presence of Jê groups in the study area, thus corroborating studies on the possible anthropization of São Paulo forests from 1,000 BP.

Many plants, including grasses and some important human food sources, accumulate, and precipitate silica in their cells to form opaline phytoliths. These phytoliths contain small amounts of organic matter (OM) that are trapped during the process of silicification. Previous work has suggested that plant silica is associated with compounds such as proteins, lipids, lignin, and carbohydrate complexes. It is not known whether these compounds are cellular components passively encapsulated as the cell silicifies, polymers actively involved in the precipitation process or random compounds assimilated by the plant and discarded into a "glass wastebasket." Here, we used Raman spectroscopy to map the distribution of OM in phytoliths, and to analyze individual phytoliths isolated from Sorghum bicolor plants grown under different laboratory treatments. Using mapping, we showed that OM in phytoliths is distributed throughout the silica and is not related to dark spots visible in light microscopy, previously assumed to be the repository for phytolith OM. The Raman spectra exhibited common bands indicative of C-H stretching modes of general OM, and further more diagnostic bands consistent with carbohydrates, lignins, and other OM. These Raman spectra exhibited variability of spectral signatures and of relative intensities between sample treatments indicating that differing growth conditions altered the phytolith carbon. This may have strong implications for understanding the mechanism of phytolith formation, and for use of phytolith carbon isotope values in dating or paleoclimate reconstruction.

Identifying when agricultural expansion has occurred and how it altered the landscape is critical for understanding human social survival strategies as well as current ecological diversity. In the present study, phytolith records of three profiles from the Baodun site area were dated to the period from 7,500 to 2,500 aBP by optically stimulated luminescence and 14C dating, providing the first evidence that the Asian cultivated rice (Oryza sativa) progenitor was distributed in the Chengdu Plain as early as 7,500 aBP. The percentage of rice bulliform with ≥9 scales and the concentration of rice phytoliths sharply increased by approximately 4,200 aBP, suggesting that rice cultivation occupied a dominant position in survival strategy no later than approximately 4,200 aBP, which might be driven by climate deterioration in eastern China. The results further showed that the proportion of Bambusoideae phytoliths increased synchronously with the increase in the proportion of rice phytoliths, suggesting that the vegetation structure near the site was changed intentionally as a consequence of increasing rice agricultural activity since 4,200 aBP. The present study contributes to a deeper understanding of the distribution of wild rice and rice farming throughout the Baodun culture in the Chengdu Plain, and it also provides a glimpse of how humans intentionally changed the vegetation landscape on a local scale.

The accumulation of metal(loid)s in phytoliths can physically immobilize the toxic materials and reduce toxicity in plant bodies and soil. Spider brake (Pteris multifida) is a well-known As hyperaccumulator that also harbors phytolith. However, As accumulation in phytoliths has not yet been studied with P. multifida. Soil water content is considered the main factor influencing phytolith accumulation. In this study, the As concentration in the phytoliths of P. multifida was compared with that in common reed (Phragmites australis) phytoliths with various soil water content. The range of As concentration in the phytoliths of P. multifida was 414.70–1610.74 mg kg−1, and the range for P. australis phytoliths was 41.67–126.54 mg kg−1. In P. multifida, higher soil water content increased As accumulation in the phytolith but did not affect the phytolith content in the plant. In P. australis, the higher soil water content increased phytolith content in the plant but decreased As concentration in phytoliths. This study suggests that P. multifida has higher As content in phytoliths than P. australis, and this accumulation can be affected by soil water content. The current findings provide how As encapsulated in phytolith and detoxified in different plants and conditions.

Five improved Erianthus arundinaceus clones were studied for variations in phytoliths present in leaves. Phytoliths were extracted by acid digestion and the morphology was studied by light microscopy. Phytoliths belonging to three classes viz., Eupanicoid, Festucoid and Chloridoid were identified in the samples. Variations in type and shape were observed among the clones studied. The results indicate that phytolith characteristics may be an important and reliable trait for clonal characterization in improved Erianthus clones and also there is a possibility of using this trait as a tool for the identification of species, hybrids and their parentage in sugarcane and their related genera.

Abstract Silicon (Si) is beneficial to plants since it increases photosynthetic efficiency, and alleviates biotic and abiotic stresses. In the most highly weathered and desilicated soils, plant phytoliths make up the reservoir of bioavailable Si. The regular removal of crop residues, however, substantially decreases this pool. Si supply may therefore be required to sustain continuous cropping. Available Si fertilizers are costly and usually poor in soluble Si. Biochar produced from the pyrolysis of phytolith‐rich biomass is thus a promising alternative Si source for plants. Taking into account the challenges of increasing food demand and environmental concerns, we evaluate the global potential of biochar produced from major crop residues and manures in terms of phytogenic Si (PhSi) supply. Crop residues contribute to 80% of the global production of biomass dry matter (8,201 Tg/year) of which 3,137 Tg/year are potentially available after pyrolysis, giving a potential application rate of 1.7 T ha−1 year−1 for highly weathered soils in the tropics. The potential PhSi supply from crop biochar amounts to 102 Tg Si/year. On its own, rice straws produce 57.7 Tg PhSi/year, accounting for 56.6% of the potential annual PhSi production. The Si release from crop biochar depends on inter altere feedstock type, pyrolysis temperature, soil pH, and buffer capacity. Furthermore, the amplitude of plant Si uptake and mineralomass depends on plant species, soil properties, and processes. These factors interact and can exert a decisive influence on the effectiveness of phytolithic biochar in releasing Si into highly weathered soils. We conclude that the use of phytolithic biochar as a Si fertilizer offers undeniable potential to mitigate desilication and to enhance Si ecological services due to soil weathering and biomass removal. This potential must be explored, as well as the conditions for using biochar in the field.

Background The fern Dicranopteris linearis is a hyperaccumulator of rare earth elements (REEs), aluminium (Al) and silicon (Si). However, the physiological mechanisms of tissue-level tolerance of high concentrations of REE and Al, and possible interactions with Si, are currently incompletely known. Methods A particle-induced X-ray emission (μPIXE) microprobe with the Maia detector, scanning electron microscopy with energy-dispersive spectroscopy and chemical speciation modelling were used to decipher the localization and biochemistry of REEs, Al and Si in D. linearis during uptake, translocation and sequestration processes. Results In the roots >80 % of REEs and Al were in apoplastic fractions, among which the REEs were most significantly co-localized with Si and phosphorus (P) in the epidermis. In the xylem sap, REEs were nearly 100 % present as REEH3SiO42+, without significant differences between the REEs, while 24–45 % of Al was present as Al-citrate and only 1.7–16 % Al was present as AlH3SiO42+. In the pinnules, REEs were mainly concentrated in necrotic lesions and in the epidermis, and REEs and Al were possibly co-deposited within phytoliths (SiO2). Different REEs had similar spatial localizations in the epidermis and exodermis of roots, the necrosis, veins and epidermis of pinnae of D. linearis. Conclusions We posit that Si plays a critical role in REE and Al tolerance within the root apoplast, transport within the vascular bundle and sequestration within the blade of D. linearis. [ABSTRACT FROM AUTHOR]

Neolithic rice remains were recovered from a mixed rice–millet farming area in China outside the original centers of rice farming. Whether the rice remains were the result of local cultivation or obtained through trade remains unclear. Rice paddy fields are direct evidence of local cultivation. In this study, phytolith samples from the Zhangwangzhuang site were analyzed. The discriminant function distinguished 17 of 30 samples in the suspected paddy field area as rice paddy fields with an average probability of 74%; The proportion of rice bulliform phytoliths with ≥9 scales indicated that rice (Oryza sativa) was still being domesticated and, moreover, six η-type phytoliths from broomcorn millet (Panicum miliaceum) were identified. These results suggested that the suspected paddy field at Zhangwangzhuang might be the earliest rice paddy field (ca. 6000 cal. BP) in northern China and that mixed farming was practiced here since the early Yangshao period. This study adopted discriminant analysis methods to discover ancient rice paddy fields, observed rice paddy fields outside the core rice origin area, and provided the earliest evidence regarding the development of mixed rice–millet farming in the upper Huai River region.

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.