Silicon, the silver bullet for mitigating biotic and abiotic stress, and improving grain quality, in rice?

Abstract

Environmental and Experimental Botany • Si nutrition is central mitigating abiotic and biotic stress in rice • Structural Si maintains yield through shoot strength and defends the plant from insect attack • Structural Si protects against, UV, water-stress, Na, Fe, Mn and Al toxicity and lodging • Si competes with As for uptake and Cd is bound to Si both in cell walls and phytoliths • Recycling straw phytolith Si is central to sustainable rice farming Abstract _____________________________________________________________________________________________ Adequate silicon fertilization greatly boosts rice yield and mitigates biotic and abiotic stress, and improves grain quality through lowering the content of cadmium and inorganic arsenic. This review on silicon dynamics in rice considers recent advances in our understanding of the role of silicon in rice, and the challenges of maintaining adequate silicon fertility within rice paddy systems. Silicon is increasingly considered as an element required for optimal plant performance, particularly in rice. Plants can survive with very low silicon under laboratory/glasshouse conditions, but this is highly artificial and, thus, silicon can be considered as essential for proper plant function in its environment. Silicon is incorporated into structural components of rice cell walls were it increases cell and tissue rigidity in the plant. Structural silicon provides physical protection to plants against microbial infection and insect attack as well as reducing the quality of the tissue to the predating organisms. The abiotic benefits are due to silicon's effect on overall organ strength. This helps protect against lodging, drought stress, high temperature (through efficient maintenance of transpiration), and photosynthesis by protecting against high UV. Furthermore, silicon also protects the plant from saline stress and against a range of toxic metal stresses (arsenic, cadmium, chromium, copper, nickel and zinc). Added to this, silicon application decreases grain concentrations of various human carcinogens, in particular arsenic, antimony and cadmium. As rice is efficient at stripping bioavailable silicon from the soil, recycling of silicon rich

Mitigation of cadmium and arsenic in rice grain by applying different silicon fertilizers in contaminated fields

“…The field experiment is necessary to confirm the effects of Si fertilizers on heavy metal mitigation, especially in the paddy fields contaminated with multiple elements. Silicon fertilizers such as Si-calcium fertilizer and Si-potash fertilizer have been extensively applied in rice fields for increasing productivity (Ma et al 2001;Meharg and Meharg 2015).…”

Managing Water and Soils to Achieve Adaptation and Reduce Methane Emissions and Arsenic Contamination in Asian Rice Production

“…The authors conclude that amending soils with FH, RSA, or RHA might enable smallholder rice farmers to increase plant-available silicon, while not causing higher levels of methane emissions [204]. Although silicon is not considered an essential element, it has been shown to reduce biotic and abiotic stresses, including arsenic uptake and toxicity [205][206][207][208][209][210][211][212][213][214].…”

Impact of 60 Years of Intensive Rice Cropping on Clay Minerals in Soils Due to Si Exportation

“…Recent works (see references included in [18]) show that for rice cultivation, the form "composted rice straw" appears to be a more efficient silica source than all other forms of vegetable compost, although technically the straw is rich in silica, less it is digestible for cattle or sheep and more difficult it is composting. Another interesting source of silica may be, after conditioning the rice in the flourmill, the recovery and return to the field of the cuticles of the grain.…”

“…Thus, the effect of Si deficiency on rice growth and of different methods of fertilization has been investigated (e.g. see synthesis by [18,19]. However, the impact of rice crops on the mineralogy of silicate minerals of soil has not been thoroughly investigated because it is assumed that soils contain large amounts of Si so that this is not a limiting factor [25].…”

“…Comparison with contents of Ca (0.1 to 0.6%), S (0.1 to 1.5%), N (0.5 to 6%), P (0.15 to 0.5%) and K (0.8 to 8%) showed that Si in plants could be present in an equivalent amount, or even larger than several macronutrients [17]. Si accumulated in the plant maintains the structure of the stem, prevents lodging, organizes aerial architecture for better perception of light, protects against herbivore attacks, limits aluminium and manganese toxicity, increases resistance to salt and heating stresses and contributes positively to yield by limiting intrusion of problematic toxic elements such as arsenic, antimony or cadmium [18]. Grasses have high phytolith contents and some wetland plant species, such as rice and phragmites, are typical Si-accumulators where Si content amounts to 10-15% [17,19].…”