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91.
中国矮生刺黄瓜品系特性的研究初报 总被引:5,自引:0,他引:5
本文利用由中国蔓生刺黄瓜自然突变产生的矮生型黄瓜为材料,通过多低自交选育及性状观察,初步了解该矮生黄瓜植物学性状除具有自封顶、植株矮化性状外,与蔓生型黄瓜无明显差异。在生物学方面,该矮生黄瓜具有早熟、雌花节率高、结果集中、生长期短等特性。通过对中国矮生刺黄瓜与不同品种蔓生黄瓜杂交后代的观察、分析,初步认为黄瓜植株高度是由单基因体系和多基因体系共同作用决定的。 相似文献
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Modelling land use strategies to optimise crop production and protection of ecologically important weed species 总被引:1,自引:0,他引:1
There is a need to develop farming systems that enable both a satisfactory level of crop production and suitable environmental conditions for natural species. Wildlife‐friendly cropping techniques, such as a reduced amount of applied herbicide or a lower crop density, might be adopted in order to maintain populations of weed species of biological interest. An alternative might be to adopt an intensive cropping system in a part of the field and spare the other part as set‐aside or field margins, available for the natural development of plant species. The objective of this study was to present a method to compare two strategies for maintaining a desirable level of abundance of a given species of interest in agricultural areas, specifically (i) a strategy based on a wildlife‐friendly cropping system in a large cultivated area and (ii) a strategy based on a more intensive cropping system in a reduced area of cultivation, i.e. with land‐sparing. The principle is to calculate the ratio of crop production obtained with strategy (i) to the production obtained with strategy (ii) for a given target density of natural species. We show that the value of this ratio, and thus the relative performance of the two strategies, depends on the density of the weed species that can be maintained in an uncultivated ecological area. The method is applied in case studies of two plant species with contrasting ecology and conservation goals. The numerical results show that the strategy based on a wildlife‐friendly cropping system is more profitable in most situations. 相似文献
94.
国土资源信息是国民经济信息中不可或缺的、重要的土地信息资源,在国家经济和社会发展中具有重要的公益性、战略性和基础性作用。文章就加强国土资源信息化建设的必要性进行了分析,并提出了具体的发展措施,以促进土地管理科学化进程,提高土地可持续发展利用。 相似文献
95.
Lorena Caro-Corrales Jose Caro-Corrales Angel Valdez-Ortiz Jose Lopez-Valenzuela Hector Lopez-Moreno Daniel Coronado-Velazquez Emilio Hernandez-Ortiz Jose Rendon-Maldonado 《Journal of insect science (Online)》2015,15(1)
The Mexican fruit fly, Anastrepha ludens Loew (Diptera: Tephritidae), is one of the most harmful pests of mango causing direct damage by oviposition on the fruit pulp. Mango for export is subjected to hydrothermal treatment as a quarantine method for the control of this pest, but exposure to heat for long periods of time reduces considerably the quality and shelf-life of treated fruit. The aim of this work was to study morphological changes of third-instar larvae and adults of A. ludens after in vitro exposure to high temperature at sublethal times. A heating block system was used to expose larvae at 46.1°C for 19.6 and 12.9 min, producing 94.6 and 70% mortality, respectively. Treated larvae were processed for optical microscopy. A fraction of surviving treated larvae was separated into containers with artificial diet to allow development into adults. Adult sexual organs were dissected and processed for transmission electron microscopy analysis. Results showed that 94.6% of the treated larvae died at 46.1°C for 19.6 min and none of the surviving larvae eclosed to adulthood, as they developed as malformed puparia. For the in vitro treatment at 46.1°C during 12.9 min, 70% of the treated larvae died and only 3.75% reached the adult stage, but ultrastructural damage in the male testes and in the female ovaries was observed. Additionally, 11.1% of the adult flies from the in vitro treatment also showed wing malformation and were incapable of flying. The analysis showed that surviving flies were unable to reproduce. 相似文献
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建设社会主义新农村是我国政府的重要任务,而新农村建设的关键任务之一是推进具有信息化特征的现代农业。在农村地区信息化背景下,研究驱动农村用户采纳移动信息服务的主要因素。根据使用移动信息服务的内部动机和外部动机,主要研究娱乐、信息、社会互动、长期在线和方便性等5个因素并建立了模型。根据实证数据验证了模型,最后得到了一些重要结论,反映了农村地区在移动信息服务采纳中的现状,可为电信部门推广农村业务提供帮助。 相似文献
99.
Induction of meiotic gynogenesis in bagrid catfish (Pseudobagrus ussuriensis) with homologous sperm and its confirmation for female homogamety 下载免费PDF全文
Zheng‐Jun Pan Chuan‐Kun Zhu Hui Wang Guo‐Liang Chang Huai‐Yu Ding Xiao‐Gang Qiang Xiang‐Sheng Yu 《Aquaculture Research》2017,48(11):5659-5665
The bagrid catfish, Pseudobagrus ussuriensis, exhibits significant sexual dimorphism in growth rate and body size with males growing faster than females. Therefore, an all‐male culture can dramatically increase the output and profitability of fishery products. According to the monosex breeding route, super‐male individuals’ acquirement by XY male sex reversal and artificial gynogenesis is the key step. An effective protocol to induce meiotic gynogenesis using homologous sperms has been developed in this study. The most effective UV irradiation for sperm genetic inactivation was found to be at a distance of 20 cm with 66 μW/cm2 light intensity for 25 min. Optimal treatment for cold shock was 5 min post‐fertilization at 0‐4°C for 30 min, which gave the best survival rate of 13.65 ± 2.87%. The sex ratio in the meiotic gynogens showed a significant female‐biased deviation (p < .05); thirty meiogynogens and their parents were further analysed using a male‐specific AFLP marker, of which only the male parent produced a male‐specific DNA band of 412 bp. These results indicated the female homogametic XX/XY sex determination system in P. ussuriensis. The optimization of a protocol for the successful induction of meiogynogenesis in the bagrid catfish lays the basis for all‐male production and is useful in ascertaining the genetic sex determination system in this promising aquaculture species. 相似文献
100.