小麦穗发芽抑制剂的筛选

以5种植物为材料提取穗发芽抑制物质,并进行了小麦穗发芽抑制效应试验。结果表明,提取物中均含有发芽抑制物质,其中,M3是对小麦籽粒发芽抑制效果显著、作用迅速而持久的天然抑制物质,对种子发芽抑制率达到85%以上,且抑制效果不存在与小麦品种间的互作。     

抑制剂和激活剂对梨星毛虫中肠蛋白酶活性的影响

旨在研究不同抑制剂和激活剂对梨星毛虫Illiberis pruni中肠蛋白酶活性的影响。利用生化技术分别测定梨星毛虫幼虫不同龄期的4种中肠蛋白酶（总蛋白酶、强碱性胰蛋白酶、弱碱性胰蛋白酶和胰凝乳蛋白酶）活性,进而在最适龄期（4龄幼虫）测定蛋白酶激活剂（EDTA,MgCl₂,EGTA,CaCl₂）和抑制剂（PMSF,TPCK,STI,TLCK,IAA,DTT）对梨星毛虫中肠蛋白酶活性的影响。结果表明：梨星毛虫幼虫中肠总蛋白酶、强碱性胰蛋白酶、弱碱性胰蛋白酶、胰凝乳蛋白酶均在4龄具有最高酶活性。所有试剂均对总蛋白酶有激活作用;5 mmol/L CaCl₂对强碱性胰蛋白酶抑制作用最高;对弱碱性胰蛋白酶有抑制作用的仅有5 mmol/L DTT;对胰凝乳蛋白酶抑制效果最佳的为10 mmol/L EGTA。所筛选的对梨星毛虫主要中肠蛋白酶具有抑制作用的抑制剂,对以昆虫中肠蛋白酶为靶标的绿色害虫防控技术的开发具有参考价值。     

Pollination-induced oxidative stress in floral organs of Cymbidium pendulum (Roxb.) Sw. and Cymbidium aloifolium (L.) Sw. (Orchidaceae): A biochemical investigation

A perusal of literature showed that a little is known about the metabolic changes related to senescence in orchid flowers. It was observed that unpollinated flowers of Cymbidium pendulum (Roxb.) Sw. remained fresh for 20 days and senesced within 8 days after pollination (DAP), while that of Cymbidium aloifolium (L.) Sw. took 18 days when unpollinated but showed senescence in 7 DAP. A higher level of electrolyte leakage was recorded in all the floral organs of pollinated flowers in both the species. There was a concomitant increase in levels of malondialdehyde (MDA) and hydrogen peroxide (H₂O₂); indicators of oxidative damage, in all the organs for both the species. Ascorbic acid, on the other hand, decreased significantly. Higher amount of electrolyte leakage, MDA and H₂O₂ content were recorded in C. pendulum as compared of the other species while the ascorbic acid, on the other hand, was observed to be decreased and this decrease was more in C. pendulum than C. aloifolium suggesting a higher oxidative damage to the floral organs in the former species than the latter. TIBA, i.e. tri-iodobenzoic acid (an auxin inhibitor; 0.25 μM) and silver nitrate (ethylene inhibitor; 0.25 μM) application to pollinated flowers partially prevented the elevation of oxidative damage and consequently senescence suggesting the involvement of these hormones in governing these changes in orchid flowers. Comparatively, AgNO₃ was more effective than TIBA in delaying senescence.     

长期定位监测钾肥施用效果研究

缺钾是水稻土的主要障碍因子之一,合理增施钾肥,既能促进水稻的营养代谢,又能大幅度提高水稻产量。为此本文利用5 a施肥定位监测资料,研究了钾肥在水稻土上的施用效果。结果表明:施用有机肥增施钾肥一般可增产6%左右,不施有机肥增施钾肥一般可增产4.9%左右。增施农肥及氮、磷、钾肥配合使用,才能保证水稻高产稳产。     

Effect of cycloheximide on N2O and NO3– production in a forest and an agricultural soil

The present work aims at evaluating the effect of cycloheximide at concentrations of between 0.5 and 5mgg^–1 on N₂O and NO₃ ^– production in two slightly alkaline soils, sampled from deciduous woodland and arable cultivation. In the first experiment, peptone was used as the “inducing substrate” for heterotrophic activity, and soil was incubated with cycloheximide (at different concentrations) and/or acetylene (1mll^–1) to block induced eukaryotic protein synthesis and ammonia monooxygenase activity, respectively. Peptone addition stimulated N₂O and NO₃ ^– production significantly in woodland soil, whereas arable soil showed no significant N₂O emissions and low NO₃ ^– production. Low cycloheximide concentrations drastically reduced N₂O emissions in woodland soil, suggesting a potential role of fungi in N₂O emissions. However, acetylene was equally effective in blocking N₂O emissions and part of NO₃ ^– production, so that a possible role of ammonia monooxygenase in an organic-inorganic pathway of N nitrification in fungal metabolism can be hypothesized. A second experiment was carried out on the woodland soil to check if low cycloheximide concentrations had non-target biocidal effects on soil microorganisms. Attention was focused on the range of concentrations which had reduced N₂O emission in the woodland soil. The results suggested that at concentrations of cycloheximide between 0.5 and 2mgg^–1 any biocidal effect on microbial biomass was negligible in the first 48h; therefore only selective inhibition of protein synthesis could be expected. The whole nitrifier population seemed to be particularly sensitive to cycloheximide concentrations higher than 2.5mgg^–1. Received: 4 July 1997     

Progress in association of RSK2 with malignancies and its inhibitors

Ribosomal S6 kinase 2 (RSK2) is a member of the p90^Rsk, which belongs to Ser/Thr kinase family. It is a downstream molecule of Ras/MAPK cascade and regulates a variety of cellular processes. RSK2 plays a key role in the cell proliferation, survival and transformation. Furthermore, the aberrant up-regulation of RSK2 was observed in different malignancies. We here briefly review the structure and function of RSK2, the relationship between RSK2 and tumor, and the existing RSK2 inhibitors.     

Nitrous oxide production in grassland soils: assessing the contribution of nitrifier denitrification

Nitrifier denitrification is the reduction of NO₂⁻ to N₂ by nitrifiers. It leads to the production of the greenhouse gas nitrous oxide (N₂O) as an intermediate and possible end product. It is not known how important nitrifier denitrification is for the production of N₂O in soils. We explored N₂O production by nitrifier denitrification in relation to other N₂O producing processes such as nitrification and denitrification under different soil conditions. The influence of aeration of the soil, different N sources, and pH were tested in four experiments. To differentiate between sources of N₂O, an incubation method with inhibitors was used [Biol. Fertil. Soils 22 (1996) 331]. Sets of four incubations included controls without addition of inhibitors, incubations with addition of small concentrations of C₂H₂ (0.01-0.1 kPa), large concentrations of O₂ (100 kPa), or a combination of C₂H₂ and O₂. The results indicate that the availability of NO₂⁻ stimulated the apparent N₂O production by nitrifier denitrification. A decreasing O₂ content increased the total N₂O production, but decreased N₂O production by nitrifier denitrification. No significant effect of pH could be found. The study revealed problems concerning the use of the inhibitors C₂H₂ and O₂. Almost one-third of all incubations with inhibitors produced more N₂O than the controls. Possible reasons for the problems are discussed. The inhibitors C₂H₂ and O₂ need to be tested thoroughly for their effects on different N₂O producing processes before further application.     

Contributions from different microbial processes to N2O emission from soil under different moisture regimes

Nitrous oxide emissions from a sandy-loam textured soil wetted to matric potentials of either-1.0 or-0.1 kPa were determined in laboratory experiments in which the soil was incubated in air (control), air plus 10 Pa C₂H₂ (to inhibit nitrification), 100 kPa O₂ (to suppress denitrification), 10 kPa C₂H₂ (to inhibit N₂O reduction to N₂ in denitrification) or following autoclaving. The total N₂O production, consumption and net N₂O emission from the soils together with the contributions to N₂O emission from different processes of N₂O production were estimated. The rate of N₂O production was significantly greater in the wetter soil (282 pmol N₂O g^-1 soil h^-1) than in the drier soil (192 pmol N₂O g^-1 soil h^-1), but because N₂O consumption by denitrifiers was also greater in the wetter soil, the net N₂O emissions from the wetter and the drier soils did not differ significantly. Non-biological sources made no significant contribution to N₂O emission under either moisture regime and biological processes other than denitrification and nitrification made only a small contribution (1% of the total N₂O production) in the wetter soil. Denitrifying nitrifiers were the predominant source of N₂O emitted from the drier soil and other (non-nitrifying) denitrifiers were the predominant source of N₂O emitted from the wetter soil.     

抑制物对草菇生长的影响

为了解决草菇低产问题,参考同是草腐菌的双孢蘑菇文献,对造成草菇低产因素之一的抑制物采用液体培养,并逐步排除。有目的地将培养料分为A、B、C 3组,经过一个栽培周期后,将3组培养料制备成提取液,并将提取液分为T1、T2、T3、T4处理,分别接草菇菌种,观察生长情况和记录生物质量。结果显示:各组以20 g/L的T1、T2、T3处理均不抑制草菇的生长,各组不处理的提取液(T4)均抑制草菇生长,其中BT4和CT4有未知物生长,各组的生物量均以T3处理的最高;将不同质量浓度梯度的(100、250、500 g/L)CT1处理提取液加到液体培养基中,均不抑制草菇的生长,生物量随着质量浓度的增大而增大;将1 000 g/L CT1和CT2处理加到液体培养基中,均不抑制草菇的生长,生物量以CT1处理的最高;进一步对BT4和CT4的未知物进行分子检测,得到肉座菌属和烟曲霉。说明界定在本栽培环境中影响草菇生长或产量的抑制物为肉座菌属和烟曲霉。