Search

Biochar is beneficial to soil phosphorus (P) availability and crop growth, but the effects vary greatly across different soil types. We investigated the effects of rice straw biochar (4% of total mass) and P application (0, 30, and 90 kg P·hm -2 ) on soil P availability, phosphomonoesterase activity, and soybean P uptake by using lateritic red soil (pH 4.91) and cinnamon soil (pH 7.24) as test materials. The results showed that biochar application at different P levels significantly increased available P and total P in both soils. Biochar application with 30 kg P·hm -2 increased soil available P with maxima at 192.6% and 237.1% in lateritic red soil and cinnamon soil, respectively. Biochar application with 30 kg P·hm -2 in lateritic red soil significantly increased the activity of alkaline phosphomonoesterase by 78.9%, decreased the content of active organic P by 39.3%, and subsequently stimulated soybean P absorption and growth. Biochar amendment significantly reduced active organic P content in cinnamon soil, but did not affect soil phosphomonoesterase activity and plant growth. The content of active organic P was significantly negatively correlated with soil available P content. In summary, the effect of biochar on soil P availability varied across different soil types (lateritic red soil > cinnamon soil) and P levels (better at 30 kg P·hm -2 ). Our results could provide scientific basis for a promising application of biochar in reducing the amount of P fertilizer and increasing soybean P uptake, especially in lateritic red soil.

Objective: To determine the expression of kidney aquaporin-2 (AQP2) and urine AQP2 excretion in chronic heart failure (CHF) rats and investigate effects of perindopril on the expression and excretion of AQP2., Methods: Sixty rats were randomized into three groups: control group, CHF group, CHF + Perindopril group. According to left ventricular myocardial infarction size, CHF group and perindopril group were further divided into heart failure subgroup (LVMI ≥ 20%) and cardiac functional compensation subgroup (LVMI < 20%), respectively. Blood and urine samples were collected from the rats for measuring serum Na(+), urine volume and urine osmolality. The concentration of plasma arginine vasopressin (p-AVP) was detected by radioimmunoassay (RIA). Immunohistochemistry, semi-quantitative real time-polymerase chain reaction (RT-PCR) and Western blot were performed for measurement of kidney inner medullary AQP2. The concentration of Urine AQP2 was measured by indirect enzyme-linked immunosorbent assay (indirect ELISA)., Results: Immunohistochemistry, RT-PCR, Western blot examinations revealed increased quantity of the inner kidney medullary AQP2 expression (0.2013 ± 0.0417), AQP2 mRNA (0.98 ± 0.33) and AQP2 protein expression (0.94 ± 0.21) in heart failure subgroup (n = 13) compared to control group (n = 20, 0.1518 ± 0.0214, 0.58 ± 0.51, 0.51 ± 0.46), which could be significantly by perindopril (n = 13, 0.0712 ± 0.0218, 0.76 ± 0.45, 0.82 ± 0.49, all P < 0.05 vs. heart failure subgroup). The concentration of plasma arginine AVP [(19.72 ± 3.91) ng/ml] and Urine AQP2 [(82.52 ± 11.77) ng/L] were significantly higher in heart failure subgroup than in control group [n = 20, (51.67 ± 12.58) ng/L, (6.94 ± 3.10) ng/ml] (P < 0.05), which were significantly reduced by perindopril [n = 13, (15.65 ± 4.10) ng/L, (71.65 ± 9.21) ng/ml]., Conclusion: Increased expression of the kidney inner medullary AQP2 and the excretion of urine AQP2 in chronic heart failure rats could be reduced by perindopril.