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1.
对5个无核葡萄品种的试验表明,不同培养方式对离体胚发育的影响是很明显的,其中4个品种胚发育率液体培养高于固体培养,‘京早晶’在液体培养中胚发育率高达73.7%,是目前国内外胚发育率最高的报道;液体培养比固体培养胚的发育程度高,发育整齐,无畸形胚,易成苗. 相似文献
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A disease causing the decline of papaya (Carica papaya) plants was noticed in the Jordan Valley in 1982. The disease caused severe yellowing of the upper leaves and dieback of the apex. The disease was not transmissible mechanically and continued efforts to associate viruses and viroids have so far been unsuccessful. Epidemiological observations suggested that the disease is airborne and probably caused by a mollicute. In order to test this hypothesis, plots were covered by an insect-proof net and with white nets providing 15, 30 and 50% shade. The 30%, 50% and insect-proof nettings provided complete protection, and the 15% netting reduced disease incidence to <2%, compared with>37% in the uncovered control plot. Spraying plants at weekly intervals with a commercial whitewash solution was also found to be effective in reducing disease incidence. The advantages of using a range of netting field treatments as a simple means for obtaining information on the epidemiological nature of a new disease are described. 相似文献
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石灰性土壤的电超滤(EUF)特性主要是浸提时因需控制电流而必须大大降低电压。在一定范围内,降压程度与土壤 CaCO_3%有密切关系。控流限额愈低,电压需成比例地下降,但土壤EUF-值减小不多。电流控制在一定值时,离子的解吸总量亦为定值。控流主要控制了各石灰性土壤解吸/溶解份额特大的 Ca+Mg 量近于定值,对于含量小的其他养分离子则并无多大影响,仍可区辨各土壤间的差别。通过冬小麦盆栽试验和有关化学测试法等方面的相关研究,表明采用国际通用的5g 土样和控电流方法测定 EUF-K 和-P 等有效养分,对于石灰性土壤也是可行的,但其EUF-(Ca+Mg)值则毫无植物营养有效性的意义。土壤 EUF 值只是一种指数,并非真正的解吸离子量。石灰性土壤 EUF-K 值因浸提时降压控流而略低,80℃时5min 内解吸的钾不一定是非交换性钾。由于 Ca-P 和 CaCO_3在高温高电压时浸出较多,故石灰性土壤 EUF-P 和-(Ca+Mg)的80℃值/20℃值之比,与酸性土壤或非石灰性土壤相比要大得多。 相似文献
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SUMMARY: Aoshio is hypoxic milky blue-green seawater observed in some eutrophic bays. Previous studies have shown that colloidal sulfur causes the coloration and that the source of aoshio water is attributed to coastal anoxic bottom water. Occurrences of aoshio have been reported in limited areas of coastal seawater, although hypoxic transparent water seems rather universal. Promotion in auto-oxidation of sulfide by metal ions in seawater was investigated to explain the occurrences of aoshio. Artificial seawater containing 10 μM metal ion was assayed for the sulfide oxidation rate. The velocity constant which represents the oxidation rate within the initial 30 min and the amount of reacted sulfide in 2 h were determined by oxygen monitoring and sulfide quantification, respectively. Fe2+ and Cu2+ enhanced the initial 30 min reaction. Fe2+ , Fe3+ and Ni2+ increased the amount of reacted sulfide in 2 h, forming whitish turbid water. Seawater from a suspected source of aoshio water was also assayed for the auto-oxidation rate of sulfide. The oxidation rate in water from 12 m depth was 13–19 times higher than the artificial seawater without an addition of heavy metal ions. More than 15% of the oxidation rate in 12 m deep seawater was explained by dissolved iron in the seawater. 相似文献
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Big bluestem (Andropogon gerardii Vitman) and little bluestem [Schizachyrium scoparium (Michaux) Nash.] are native to the North America and are important forage grasses and ornamental grasses. Both grasses are proposed as ideal biomass producers for cellulosic ethanol production. To apply genetic transformation, which is an important tool for incorporating desirable agronomic traits into plants to both species, however requires an efficient and reproducible regeneration protocol. We used mature caryopses from big and little bluestem as explants and tested the effect of various combinations of 2, 4-dichlorophenoxyacetic acid (2, 4-D) (1, 2, 3, 4 or 5 mg l−1) and kinetin (KT) (0, 0.1 or 0.2 mg l−1) on embryogenic callus induction with LS as the basal medium. The highest percentage of embryogenic calli induction occurred on medium containing 2, 4-D alone at 2 mg l−1 for ‘Bison’ and on medium containing 4 mg l−1 2, 4-D alone for ‘Bonilla’ big bluestem. For little bluestem, the highest percentage of embryogenic callus induction occurred on medium containing 3 mg l−1 2, 4-D plus 0.1 mg l−1 kinetin, suggesting that addition of KT is beneficial. Shoot regeneration took place on LS basal medium without any plant growth regulator for both species, although the addition of KT increased both regeneration frequency and the number of shoots produced per callus. Rooting of shoots reaching about 2 cm long occurred readily with or without α-naphthaleneacetic acid (NAA). Rooted plantlets were all successfully established in the soil. 相似文献
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中国学术文献总库(CNKI)的主要功能和使用技巧 总被引:3,自引:1,他引:2
结合在线咨询服务和用户培训中积累的经验,就升级后新版的CNKI的主要功能和使用技巧进行了整理和总结. 相似文献
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从师生自身反馈角度,结合成立于2003年的中国地质大学工程学院土木工程试验班的具体情况,针对其本硕贯通式的培养教学计划,提出了包括增加专业软件学习、互动式外语教学、高低阶力学课程合并、压缩人文社科类课程等具体改进建议。 相似文献