Cadmium uptake reduction in paddy rice with a combination of water management, soil application of calcium magnesium phosphate and foliar spraying of Si/Se

A field experiment with 24 different treatments was carried out to study the effects of a combination of water management (WM), soil application of calcium magnesium phosphate (CMP), and foliar spraying of Si/Se on Cd uptake by paddy rice (Teyou 524). The water management modes included W₁ (conventional water management) and W₂ (flooding during the whole growth period). The application of CMP included P₁ (1800 kg·hm^-2) and P₂ (3000 kg·hm^-2). The leaf spraying regulations included LS (2.0 mmol·L^-1 Na₂SiO₃), LX (25 μmol·L^-1 Na₂SeO₃), and LSX (1.0 mmol·L^-1 Na₂SiO₃ and 12.5 μmol·L^-1 Na₂SeO₃). The results indicated that, compared to the control (W₁), flooding and CMP reduced soil exchangeable Cd by 10.3, 21.5, 32.2, 27.6 and 36.9% under conditions of W₂, P₁, P₂, W₂P₁ and W₂P₂, respectively; but the grain yield was reduced under W₂ condition. Some individual treatments, including W₂, P₁, P₂, LS, LX, and LSX, could reduce Cd concentration in the grain by 23.1-60.3%; but the combined regulations could reduce grain Cd concentrations up to 79.5%. Only the combined mode of CMP and leaf spraying of Si/Se could control grain Cd concentration below the Chinese National Food Safety Standard (0.2 mg·kg^-1). Combined modes of fertilizer application (W₂ and CMP) and foliar spraying (Si/Se), including W₂P₂LS, W₂P₂LX, W₂P₂LSX, were the most effective in reducing the Cd transport coefficients of both root-to-straw (RS) and straw-to-seed (SS). Considering Cd concentration in grain, treatments W₂P₂LS and W₂P₂LSX were the most effective ones, which could reduce Cd concentrations to 0.090 mg·kg^-1 and 0.089 mg·kg^-1 in grain, respectively. These results demonstrated that combined manipulation of the root zone (W₂ and CMP) and foliar spraying (Si/Se) can effectively reduce grain Cd concentrations in rice.

Response of rice and bacterial community to phosphorus-containing materials in soil-plant ecosystem of rare earth mining area

The effects of phosphate rock (PR), bone charcoal (BC), single superphosphate (SSP) and calcium magnesium phosphate (CMP) on rice growth and bacterial community structure in mining area of heavy and light rare earth elements(REEs) were studied by pot experiment, field experiments were conducted with CMP and BC as restorative materials. The pot experiment showed that BC, SSP and CMP improved dry weight of rice (especially grains) in two places by 84.23%, 116.97%, 81.83%, 1630.77%, 1817.95% and 902.56% respectively; and reduced REE content of rice (especially roots) in two places by 28.19%, 81.67%, 90.58%, 67.87%, 81.72% and 94.81%; PR had little effect on dry weight and REE content of rice in both places, but reduces Bacillusabundance in both places, while BC significantly improved the abundance of Perlucidibaca and Bacillus; CMP had little effect on bacterial community, two-year field experiments showed that dry weight of rice grain treated with BC was 100% and 43.0% higher than that treated with CK and CMP, and the content of REEs was 91.8% and 16.8% lower than that with CK and CMP. The results of pot and field experiments both show BC is the most potential material for restoring soil-plant ecosystem in REE mining area.

Magnesium substitution in the structure of orthopedic nanoparticles: A comparison between amorphous magnesium phosphates, calcium magnesium phosphates, and hydroxyapatites

As biocompatible materials, magnesium phosphates have received a lot of attention for orthopedic applications. During the last decade multiple studies have shown advantages for magnesium phosphate such as lack of cytotoxicity, biocompatibility, strong mechanical properties, and high biodegradability. The present study investigates the role of Mg(+2) and Ca(+2) ions in the structure of magnesium phosphate and calcium phosphate nanoparticles. To directly compare the effect of Mg(+2) and Ca(+2) ions on structure of nanoparticles and their biological behavior, three groups of nanoparticles including amorphous magnesium phosphates (AMPs) which release Mg(+2), calcium magnesium phosphates (CMPs) which release Mg(+2) and Ca(+2), and hydroxyapatites (HAs) which release Ca(+2) were studied. SEM, TEM, XRD, and FTIR were used to evaluate the morphology, crystallinity, and chemical properties of the particles. AMP particles were homogeneous nanospheres, whereas CMPs were combinations of heterogeneous nanorods and nanospheres, and HAs which contained heterogeneous nanosphere particles. Cell compatibility was monitored in all groups to determine the cytotoxicity effect of particles on studied MC3T3-E1 preosteoblasts. AMPs showed significantly higher attachment rate than the HAs after 1 day and both AMPs and CMPs showed significantly higher proliferation rate when compared to HAs after 7days. Gene expression level of osteoblastic markers ALP, COL I, OCN, OPN, RUNX2 were monitored and they were normalized to GAPDH housekeeping gene. Beta actin expression level was monitored as the second housekeeping gene to confirm the accuracy of results. In general, AMPs and CMPs showed higher expression level of osteoblastic genes after 7 days which can further confirm the stimulating role of Mg(+2) and Ca(+2) ions in increasing the proliferation rate, differentiation, and mineralization of MC3T3-E1 preosteoblasts.