To understand the dynamics of added nitrogen (N) in alpine meadow and the role of alpine plants and soil microorganisms in the retention of deposited N, the fate of 15 N labeled nitrate and ammonium salts was...To understand the dynamics of added nitrogen (N) in alpine meadow and the role of alpine plants and soil microorganisms in the retention of deposited N, the fate of 15 N labeled nitrate and ammonium salts was determined in an alpine meadow for two months. Two weeks after 15 N application, total recovery of 15 N from NO - 3_ 15 N was 73.5% while it was 78% from NH + 4_ 15 N. More 15 N was recovered in plants than in soil organic matter or in microbial biomass, irrespective of forms of N added. After one month, 70.6% of added NO - 3_ 15 N and 57.4% of NH + 4_ 15 N were recovered in soils and plants. 15 N recovered in soil organic matter decreased greatly while that recovered in plants varied little, irrespective of the form N. Compared with the results of two weeks after 15 N application, more NO - 3_ 15 N than NH + 4_ 15 N was recovered in microbial biomass. Total recovery was 58.4% (six weeks) and 67% (eight weeks) from NO - 3_ 15 N, and 43.1% and 49% from NH + 4_ 15 N, respectively. Both plants and soil microorganism recovered more NO - 3_ 15 N than NH + 4_ 15 N. But plants recovered more 15 N than soil microorganisms. During the whole experiment plants retained more NO - 3_N and 15 N than soil microorganisms while 15 N recovered in inorganic N pool did not exceed 1% due to lower amount of inorganic N. This indicates that plants play more important roles in the retention of deposited N although microbial biomass can be an important sink for deposited N in early days after N application.展开更多
Cucumber ( Cucumis sativus L.) LHC_Ⅱ complex, which consists of only one subunit (27 kD), was isolated and purified. 2_D crystallization was performed by batch method. The crystal is 0.7 μm×1.0 μm, and diff...Cucumber ( Cucumis sativus L.) LHC_Ⅱ complex, which consists of only one subunit (27 kD), was isolated and purified. 2_D crystallization was performed by batch method. The crystal is 0.7 μm×1.0 μm, and diffracts to 30 ?. The projection map of the negatively stained two_dimensional crystal of LHC_Ⅱ complex shows that the crystal has p3 symmetry, lattice constant 15.4 nm×15.4 nm, which is different from the LHC_Ⅱ of spinach (Spinacia oleracea L.) and pea (Pisum satium L.). A continuous tomographic tilt series, containing 12 projections from the two_dimensional crystal was subjected to 3_D reconstruction. The 3_D model represents that LHC_Ⅱ complex consists of 6 monomers. These trimer and dimer interactions build up the six member ring.展开更多
In addition to six known flavonoids quercitrin, hyperoside, avicularin, rutin, quercetin and kaemferol, a new flavonol glycoside named 6″_O_acetyl quercetin 3_O_β_ D _alloside (1) was isolated from the aerial par...In addition to six known flavonoids quercitrin, hyperoside, avicularin, rutin, quercetin and kaemferol, a new flavonol glycoside named 6″_O_acetyl quercetin 3_O_β_ D _alloside (1) was isolated from the aerial parts of Hypericum perforatum L. The structures were determined on the basis of spectroscopic methods (UV, IR, FAB_MS, 1H_NMR and 13 C NMR). Antifungal assay of all compounds showed that metabolite 1, quercitrin and quercetin were inhibitory to the growth of phytopathogenic fungus Helminthosporium sativum Pamel King et Bakke with minimum inhibitory concentrations (MICs) of 25, 50 and 50 μg/mL, respectively. Moreover, glycoside 1 and quercitrin were also shown to be able to inhibit the growth of Fusarium graminearum Schw. with MIC of 100 μg/mL. The MICs of ketoconazole used as control against the test fungi were 0.5 μg/mL in our assay.展开更多
文摘To understand the dynamics of added nitrogen (N) in alpine meadow and the role of alpine plants and soil microorganisms in the retention of deposited N, the fate of 15 N labeled nitrate and ammonium salts was determined in an alpine meadow for two months. Two weeks after 15 N application, total recovery of 15 N from NO - 3_ 15 N was 73.5% while it was 78% from NH + 4_ 15 N. More 15 N was recovered in plants than in soil organic matter or in microbial biomass, irrespective of forms of N added. After one month, 70.6% of added NO - 3_ 15 N and 57.4% of NH + 4_ 15 N were recovered in soils and plants. 15 N recovered in soil organic matter decreased greatly while that recovered in plants varied little, irrespective of the form N. Compared with the results of two weeks after 15 N application, more NO - 3_ 15 N than NH + 4_ 15 N was recovered in microbial biomass. Total recovery was 58.4% (six weeks) and 67% (eight weeks) from NO - 3_ 15 N, and 43.1% and 49% from NH + 4_ 15 N, respectively. Both plants and soil microorganism recovered more NO - 3_ 15 N than NH + 4_ 15 N. But plants recovered more 15 N than soil microorganisms. During the whole experiment plants retained more NO - 3_N and 15 N than soil microorganisms while 15 N recovered in inorganic N pool did not exceed 1% due to lower amount of inorganic N. This indicates that plants play more important roles in the retention of deposited N although microbial biomass can be an important sink for deposited N in early days after N application.
文摘Cucumber ( Cucumis sativus L.) LHC_Ⅱ complex, which consists of only one subunit (27 kD), was isolated and purified. 2_D crystallization was performed by batch method. The crystal is 0.7 μm×1.0 μm, and diffracts to 30 ?. The projection map of the negatively stained two_dimensional crystal of LHC_Ⅱ complex shows that the crystal has p3 symmetry, lattice constant 15.4 nm×15.4 nm, which is different from the LHC_Ⅱ of spinach (Spinacia oleracea L.) and pea (Pisum satium L.). A continuous tomographic tilt series, containing 12 projections from the two_dimensional crystal was subjected to 3_D reconstruction. The 3_D model represents that LHC_Ⅱ complex consists of 6 monomers. These trimer and dimer interactions build up the six member ring.
文摘In addition to six known flavonoids quercitrin, hyperoside, avicularin, rutin, quercetin and kaemferol, a new flavonol glycoside named 6″_O_acetyl quercetin 3_O_β_ D _alloside (1) was isolated from the aerial parts of Hypericum perforatum L. The structures were determined on the basis of spectroscopic methods (UV, IR, FAB_MS, 1H_NMR and 13 C NMR). Antifungal assay of all compounds showed that metabolite 1, quercitrin and quercetin were inhibitory to the growth of phytopathogenic fungus Helminthosporium sativum Pamel King et Bakke with minimum inhibitory concentrations (MICs) of 25, 50 and 50 μg/mL, respectively. Moreover, glycoside 1 and quercitrin were also shown to be able to inhibit the growth of Fusarium graminearum Schw. with MIC of 100 μg/mL. The MICs of ketoconazole used as control against the test fungi were 0.5 μg/mL in our assay.
