Effects of exogenous salicylic acid on alleviation of arsenic-induced oxidative damages in rice

Salicylic acid (SA) is a phenolic phytohormone that plays a vital role in plant development and mediates plant responses to plenty of adversity including arsenic (As) stress. The effects of exogenous addition of SA on As tolerance and As accumulation were assessed in two cultivars of rice (Oryza sativa L.) Nipponbare and Zhongzao 39, hydroponically grown with Kimura B nutrient solution under arsenite [As (III)] and dimethylarsonic acid (DMA) exposure. In the second ex-periment, the influence of soaking seed with SA on As uptake and As damages was investigated in rice (cv. Nipponbare) exposed to As (III) and DMA. The results showed that exogenous addition of SA sig- nificantly decreased the concentrations of hydrogen peroxide (H2O2) and malondialdehyde (MDA) in both As (III)- and DMA-stressed rice, indicating that SA alleviates As-induced oxidative damages in rice. SA increased the activity of antioxidant enzymes and, moreover, increased the relative amount of glutathione (GSH) and ascorbate (ASA) by accelerating the GSH- ASA circle system. Exogenous addition of SA significantly decreased the As concentration in both roots and shoots of rice under As(III) stress by influ- encing the expression of genes encoding As transporters, viz. OsLsi1, OsLsi2. The addition of SA significantly decreased the As content in shoots under DMA stress, which may be related to the expression of OsPTR7 involved in shoot xylem unloading. This finding may foster a novel perspec- tive for reducing As accumulation in rice grains

Organic manure stimulates biological activity and barley growth in soil subject to secondary salinization

A pot experiment was performed to compare the impact of organic manure on soil enzymatic activity, respiration rate and the growth of two barley cultivars (Hordeum vulgare L.) differing in their salt tolerance under a simulated salinized environment. A plastic pot with a hole (2 cm in diameter) in the center of bottom was filled with an anthropogenic (paddy) soil and placed in a porcelain container containing NaCl solution (3.0 g L-1) such that a secondary salinization process was simulated via upward capillary water movement along the soil profile. A treatment with neither organic manure nor simulated soil salinization was taken as a control (CK1). The organic manure was applied either inside or outside rhizobag made of nylon cloth (40 mu m of pore size). The soil was treated with: 20 g kg(-1) rice straw (RS), 20 g kg(-1) pig manure (PM), or 10 g kg(-1) rice straw plus 10 g kg(-1) pig manure (RS + PM). No organic manure was added in an additional control treatment (CK2). The results indicated that the placement of organic manure both inside and outside rihzobags significantly increased the activity of urease, alkaline phosphatase and dehydrogenase, as well as respiration rate in both rhizosphere and bulk soils. Also, nutrient uptake by barley plants was enhanced in the treatments with organic manure amended either inside or outside rhizobags. The activity of these enzymes along with the respiration rate was higher in rhizosphere than in non-rhizosphere when organic manure was supplied inside rhizobags, while the opposite was found in the case of manure incorporated outside rhizobags. Among all the treatments, RS + PM treatment had most significant stimulating effects on enzymatic and microbial activity and shoot dry weight of barley, followed by PM and RS. Moreover, more significant stimulating effects on both enzyme activity and plant growth were achieved in the treatments with manure amended inside rhizobags than outside rhizobags. The results of the present study confirmed the view that incorporation of organic manure especially into soil-root zones is an effective low-input agro-technological approach to enhancing soil fertility and minimizing phytotoxicity induced by secondary salinization

Silicon fertilization influences microbial assemblages in rice roots and decreases arsenic concentration in grain: A five-season in-situ remediation field study

Microbial mechanism of in-situ remediation of arsenic (As) in As-contaminated paddy fields by silicon (Si) fertilization has been rarely reported, especially under continuous rice cultivation and Si applications. In this study, two Si fertilizers were applied for three phases in five consecutive rice seasons to investigate the longlasting impacts on in-situ remediation of As, and the underpinning microbial mechanism of root-associated compartments (bulk soil, rhizosphere and endosphere) was explored using the last double-cropping rice. Repeated application of Si fertilizers as base manure had a long-lasting effect on reducing As concentrations in rice grains. Application of Si fertilizer at an adequate amount resulted in an extended in-situ remediation effect from endosphere to rhizosphere. The microbial diversity and richness in rhizosphere soil and endosphere were significantly impacted by Si fertilization, the effects depending on application doses and prolonged seasons. Si fertilization can immobilize As in the root or rhizosphere, and Fe concentrations and the As-and Fe-transforming microorganisms (i.e. Geobacteraceae) are the determinants of As uptake in rice. We recommend more extensive supplementation of Si fertilizer at a higher rate to decrease grain As concentration for in-situ remediation. This study sheds light on the microbial-mediated mechanism underlying Si fertilization effect on decreased As uptake in paddy fields

Silicon Reduces Aluminum-Induced Suberization by Inhibiting the Uptake and Transport of Aluminum in Rice Roots and Consequently Promotes Root Growth

Silicon (Si) can alleviate aluminum (Al) toxicity in rice (Oryza sativa L.), but the mechanisms underlying this beneficial effect have not been elucidated, especially under long-term Al stress. Here, the effects of Al and Si on the suberization and development of rice roots were investigated. The results show that, as the Al exposure time increased, the roots accumulated more Al, and Al enhanced the deposition of suberin in roots, both of which ultimately inhibited root growth and nutrient absorption. However, Si restricted the apoplastic and symplastic pathways of Al in roots by inhibiting the uptake and transport of Al, thereby reducing the accumulation of Al in roots. Meanwhile, the Si-induced drop in Al concentration reduced the suberization of roots caused by Al through down-regulating the expression of genes related to suberin synthesis and then promoted the development of roots (such as longer and more adventitious roots and lateral roots). Moreover, Si also increased nutrient uptake by Al-stressed roots and thence promoted the growth of rice. Overall, these results indicate that Si reduced Al-induced suberization of roots by inhibiting the uptake and transport of Al in roots, thereby amending root growth and ultimately alleviating Al stress in rice. Our study further clarified the toxicity mechanism of Al in rice and the role of Si in reducing Al content and restoring root development under Al stress

Effects of calcined phosphogypsum replacement on hydration and properties of calcium sulfoaluminate cement at different curing temperatures

The present research aims to understand the cement hydration and microstructure formation mechanism of calcined phosphogypsum (CPG) supplemented calcium sulfoaluminate (CSA) pastes cured under hot-weather temperatures and to ensure the appropriate application and effective service of CSA cement-based materials, as well as to address the problem of overstocking of CPG. The effects of CPG dosage on the heat of hydration, electrical resistivity, hydration products, and bound water content of CSA cement pastes were investigated at curing temperatures of 20 °C, 35 °C, and 50 °C. Hydration kinetics was studied to elucidate the hydration mechanism, and thermodynamic modelling was performed to predict the phase assemblages. The results show that the incorporation of CPG facilitated the formation of ettringite and significantly reduced the transformation of ettringite to monosulfate, and these phenomena were enhanced with an increase in the CPG. The addition of CPG at elevated curing temperature (35 °C and 50 °C) significantly improved the compressive strength of CSA cement pastes. The growth rate and nucleation rate predicted by the BNG model for the CSA cement pastes cured at 50 °C were substantially higher compared to those at 20 °C.This is a manuscript of the article Published as Liao, Yishun, Jiawen Chen, Jinxin Yao, Kejin Wang, Haoran Huang, Guoxi Jiang, Shengwen Tang, and Yibing Zuo. "Effects of calcined phosphogypsum replacement on hydration and properties of calcium sulfoaluminate cement at different curing temperatures." Journal of Sustainable Cement-Based Materials (2024): 1-13. doi: https://doi.org/10.1080/21650373.2024.2314517.Copyright © The Authors. CC BY-NC. Posted with Permission