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Nitrogen fertilization degrades soil aggregation by increasing ammonium ions and decreasing biological binding agents on a Vertisol after 12 years

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Pedosphere 2022年第4期32卷 629-636页

作者： Zichun GUO Wei LI Mahbub UL ISLAM Yuekai WANG Zhongbin ZHANG Xinhua PENG State Key Laboratory of Soil and Sustainable Agriculture Institute of Soil ScienceChinese Academy of SciencesNanjing 210008China Crop Research Institute Anhui Academy of Agricultural SciencesHefei 230031China University of Chinese Academy of Sciences Beijing 10049China Bangladesh Agricultural Research Institute Gazipur 1701Bangladesh

Degraded soil aggregation arising from nitrogen(N)fertilization has been reported in many studies;however,the mechanisms have not yet been *** the impact of N fertilization on soil aggregation would help to improve soil structure and sustain high crop *** objective of this study was to determine the impact of long-term N fertilization on soil aggregation and its association with binding and dispersing agents.A 12-year(2008–2019)N fertilization field experiment on a Vertisol was performed,covering a wide range of N application rates(0,360,450,540,630,and 720 kg ha-1 year-1)and including straw management(straw return and straw removal)in a wheat(Triticum aestivum L.)-maize(Zea mays L.)cropping *** samples of 0–20 cm depth were collected from 12 field treatments with 3 replications in *** aggregate stability(mean weight diameter(MWD))and contents of soil organic carbon(SOC),glomalin-related soil protein(GRSP),microbial biomass carbon(MBC),and mineral N(NH4+and NO3-)were ***-term N fertilization under straw removal conditions reduced soil MWD by 12%–18%at N rates from 0 to 720 kg ha-1 compared to that under straw return(Paggregating agents(SOC,GRSP,and MBC)(P0.05);consequently,it improved soil ***,our results indicate that long-term N fertilization may degrade soil aggregation because of the increases in monovalent ions(H+and NH4+)and the decrease in MBC during soil acidification,especially when the applied N dose exceeded 360 kg ha-1 *** finding can minimize the negative structural impacts on Vertisol.

关键词： aggregating agents aggregate stability long-term nitrogen fertilization soil structure straw incorporation

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Effects of 5-Hydroxytraptamine on Aggregation,Release Reaction and Mobilization of Cytosolic Free Calcium Concentration in Rabbit Normal and Washed Single Platelets

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哈尔滨医科大学学报 1993年第5期 378-379页

作者：李柏岩,白颖,Makoto Katori,Masataka Majima,李文汉 Department of Pharmacology Department of Neurology The Harbin First Hospital Department of Pharmaeology.School of Medicine Kitasato University Kitasato 1-15-1 Sagamihara Kanagawa228 Japan Department of Pharmaeology.School of Medicine Kitasato University Kitasato 1-15-1 Sagamihara Kanagawa228 Japan Department of Pharmacology

In rabbit platelet rich plasma （PRP）, 5-hydroxytraptamine （5-HT,0.03～3μmol/L） induced decrease in light transmission （DLT） dose-de pendently with centralization, as revealed by electron microscopy. However, 5-HT did not induced platelet aggregation and release reaction. 5-HT-induced DLT was inhibited by methysergide （0.3～30μmol/L）, indomethacin （0.3～10μmol/L） and PGE1（0.01～0.3μmol/L） in a dose-dependent manner, but not EGTA（0.3～3mmol/L）. Collagen（Coll）, arachidonic acid （AA）, adenosine diphosphate （ADP） and a stable thromboxane A2 analoge（STA2） also induced DLT before aggregation by themselves, which was also inhibited by PGE1, but not inhibited by EGTA except for Coll However,Coll-, AA-, STA2-and ADP-induced DLT were reduced by pretreatment of PRP with 5-HT dose-depen-dently. The duration of DLT by Coll and AA were decreased from 151.4±5.93 sec and 15（?）38±0.60sec to 45.44±4.04 sec and 9.00±1.25 sec respectively (（?）±s（?） P<0.01), but not by ADP and STA2, 3μmol/L of ADP-and 0.3μmol/L of STA2-induced aggregation which was not accompanied with release reaction were enhanced by 5-HT pretreatment, but in those （Coil 5μg/ml, AA 100～200μmol/L and STA21～3 μmol/L） with release reaction, the amount of adenosine triphosphate（ATP）were suppressed significantly （P<0.001） by 5-HT pretreatment without the effect on the magnitude of aggregation, The mobilization of cytosolic free calcium concentration ([Ca2+]i) was observed after 5-HT treatment in single washed platelet, the results indicated that the basic level of [Ca2+] i was 64.78±3.24nmol/L and this level was increased dose-dependently and significantly at 30 sec after administration of 5-HT and the time of peak value of [Ca2+] i was at 90～100 *** similar time courses of suppression of ATP released during aggregation, in cases of Coll（5μg/ml）, AA （200μmol/L） and STA2（3μmol/L）, by 5-HT were also found in the present experiment.

关键词： 5-hydroxytraptamine (serotonin, 5-HT) aggregating agents Aggregation Release reaction Cytosolic free calcium concentration([Ca2+]i) Rabbit washed single platelet

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