The continental bio-cycling of silicon (Si) plays a key role in global Si cycle and as such partly controls global carbon (C) budget through nutrition of marine and terrestrial biota, accumulation of phytolith-occluded organic carbon (PhytOC) and weathering of silicate minerals. Despite the key role of elemental composition of phytoliths on their solubility in soils, the impact of plant cultivar and organ on the elemental composition of phytoliths in Si high-accumulator plants, such as rice (Oryza sativa) is not yet fully understood. Here we show that rice cultivar significantly impacts the elemental composition of phytoliths (Si, Al, Fe and C) in different organs of the shoot system (grains, sheath, leaf and stem). The amount of occluded OC within phytoliths is affected by contents of Si, Al and Fe in plants, while independent of the element composition of phytoliths. Our data document, for different cultivars, higher bio-available Si release from phytoliths of leaves and sheaths, which are characterized by higher enrichment with Al and Fe (i.e., lower Si/Al and Si/Fe ratios), compared to grains and stems. We indicate that phytolith solubility in soils may be controlled by rice cultivar and type of organs. Our results highlight that the role of the morphology, the hydration rate and the chemical composition in the solubility of phytoliths and the kinetic release of Si in soil solution needs to be studied further. This is central to a better understanding of the impact of soil amendment with different plant organs and cultivars on soil OC stock and on the delivery of dissolved Si as we show that sheath and leaf rice organs are both characterized by higher content of OC occluded in phytolith and higher phytolith solubility compared to grains and stems. Our study shows the importance of studying the impact of the agro-management on the evolution of sinks and sources of Si and C in soils used for Si-high accumulator plants.

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Impact of rice cultivar and organ on elemental composition of phytoliths and the release of bio-available silicon.

https://cyberleninka.org/article/n/1302921.pdf

Plant biostimulants: Definition, concept, main categories and regulation

Impact of rice cultivar and organ on elemental composition of phytoliths and the release of bio-available silicon

Mechanisms of silicon-mediated alleviation of heavy metal toxicity in plants: A review

Zinc (Zn) still represents an important health problem in developing countries, caused mainly by inadequate dietary intake. A large consumption of cereal-based foods with small concentrations and low bioavailability of Zn is the major reason behind this problem. Modern cultivars of cereals have inherently very small concentrations of Zn and cannot meet the human need for Zn. Today, up to 50% of wheat-cultivated soil globally is considered poor in bioavailable Zn. Agricultural strategies that are used to improve the nutritional value of crop plants are known as biofortification strategies. They include genetic biofortification, which is based on classical plant breeding and genetic engineering for larger nutrient concentrations, and greater agronomic biofortification, which is based on optimized fertilizer applications. This review focuses on agronomic biofortification with Zn, which has proved to be very effective for wheat and also other cereal crops including rice. Molecular and genetic research into Zn uptake, transport and grain deposition in cereals are critically important for identifying ‘bottlenecks’ in the biofortification of food crops with Zn. Transgenic plants with large Zn concentrations in seeds are often tested under controlled laboratory or glasshouse conditions with sufficient available Zn in the growth medium for the entire growth period. However, they might not always show the same performance under ‘real-world’ conditions with limited chemical availability of Zn and various stress factors such as drought. What purpose can an upgraded transport and storage system serve if the amount of goods to be transported and stored is limited anyway? Given the fact that the Zn concentrations required to achieve a measurable impact on human health are well above those required to avoid any loss of yield from Zn deficiency, providing crop plants with sufficient Zn through the soil and foliar fertilizer strategy under field conditions is critically important for biofortification efforts.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/ejss.12437

Agronomic biofortification of cereals with zinc: a review

Plant impact on the coupled terrestrial biogeochemical cycles of silicon and carbon: Implications for biogeochemical carbon sequestration

Carbon (C) bio-sequestration within the phytoliths of plants, a mechanism of long-term biogeochemical C sequestration, may play a major role in the global C cycle and climate change In this study, we explored the potential of C bio-sequestration within phytoliths produced in cultivated rice (Oryza sativa), a well known silicon accumulator The rice phytolith extraction was undertaken with microwave digestion procedures and the determination of occluded C in phytoliths was based on dissolution methods of phytolith-Si Chemical analysis indicates that the phytolith-occluded C (PhytOC) contents of the different organs (leaf, stem, sheath and grains) on a dry weight basis in 5 rice cultivars range from 04 mg g−1 to 28 mg g−1, and the C content of phytoliths from grains is much lower than that of leaf, stem and sheath The data also show that the PhytOC content of rice depends on both the content of phytoliths and the efficiency of C occlusion within phytoliths during rice growth The biogeochemical C sequestration flux of phytoliths in 5 rice cultivars is approximately 003–013 Mg of carbon dioxide (CO2) equivalents (Mg-e-CO2) ha−1 year−1 From 1950 to 2010, about 237 × 108 Mg of CO2 equivalents might have been sequestrated within the rice phytoliths in China Assuming a maximum phytoliths C bio-sequestration flux of 013 Mg-e-CO2 ha−1 year−1, the global annual potential rate of CO2 sequestrated in rice phytoliths would approximately be 194 × 107 Mg Therefore rice crops may play a significant role in long-term C sequestration through the formation of PhytOC

Occluded C in rice phytoliths: implications to biogeochemical carbon sequestration

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.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcbb.12635

Zimin Li

Papers

Impact of rice cultivar and organ on elemental composition of phytoliths and the release of bio-available silicon.

Impact of rice cultivar and organ on elemental composition of phytoliths and the release of bio-available silicon

Plant impact on the coupled terrestrial biogeochemical cycles of silicon and carbon: Implications for biogeochemical carbon sequestration

Occluded C in rice phytoliths: implications to biogeochemical carbon sequestration

Phytolith‐rich biochar: a potential Si fertilizer in desilicated soils