排序方式: 共有53条查询结果,搜索用时 15 毫秒
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为探寻黄淮海平原井灌区冬小麦适宜的调亏灌溉控制指标,通过3季(2015-2017年)不同灌水下限与灌水定额(30、60、90、120和180mm)2因素组合试验,研究调亏灌溉对冬小麦产量及作物水分利用效率的影响。灌水下限分别为:轻旱(LD),冬小麦苗期至返青期、拔节期、抽穗期和灌浆成熟期田间持水量分别为田间持水量(field capacity,FC)的50%、55%、60%和50%;中旱(MD),冬小麦苗期至返青期、拔节期、抽穗期和灌浆成熟期田间持水量分别为田间持水量的40%、50%、55%和45%。研究结果表明,随灌水定额的增加,产量呈先增加后下降趋势,水分利用效率呈下降趋势。90mm灌水定额下,随灌水下限的增加,冬小麦产量呈增加趋势。基于CRITIC赋权的TOPSIS法构建冬小麦综合效益多目标优化模型获得的结果与产量和作物水分利用效率分析法获得的结论具有一致性,均表明LD60处理最优。综合考虑,为实现本地区冬小麦稳产与水资源高效利用的双重目标,冬小麦适宜采用轻旱胁迫下灌水定额为60mm的调亏灌溉控制指标。本结论可为黄淮海平原井灌区冬小麦的管理提供科学依据。 相似文献
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大巴山北坡不同海拨6个土壤类型中,粘粒矿物以2:1型为主,1:1型高岭石很少。硅铝率在3.06~4.34之间,硅铝铁率在2.38~3.23之间。随海拨升高,蛭石及水云母在矿物中所占比重下降,绿泥石逐渐成为主要矿物。亚高山草甸土及山地暗棕壤以绿泥石为主,水云母次之,伴少量蒙脱石;棕色石灰土、山地棕壤、山地黄棕壤以水云母及蛭石为主,伴有蒙脱石及高岭石,其矿物组合各有特点;黄褐土以水云母,蒙脱石为主,伴有蛭石及高岭石。 相似文献
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辣椒自南美洲引进中国后,形成了十分丰富的辣椒品种并成为中国栽培面积最大的蔬菜作物和调味品。而当前由于单一品种的大面积推广,使大量农家品种丢失,某些种质资源也随之遗失。通过综述辣椒种质资源的现状,提出了一套较为完善的辣椒种质资源遗传多样性的保护体系。同时,从遗传关系、生物化学、细胞学等方面对辣椒种质资源利用研究进展进行了综述,指出通过保护和合理的利用,辣椒种质资源的数量就会不断地扩大,进而供人类持续的利用。 相似文献
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苜蓿多糖对小鼠淋巴细胞增殖和NK细胞活性影响的研究 总被引:1,自引:1,他引:0
为了探讨苜蓿多糖对小鼠免疫功能的影响,从苜蓿中提取苜蓿多糖,通过体外苜蓿多糖对淋巴细胞增殖和NK细胞活性影响的研究,初步确定其免疫调节活性。采用MTT法,检测苜蓿多糖对正常Balb/c小鼠体外脾淋巴细胞增殖的影响和NK细胞对K562细胞杀伤活性的影响。结果表明:苜蓿多糖可以单一激活促进小鼠脾淋巴细胞的增殖,可以协同ConA刺激T细胞增殖,或协同LPS刺激B细胞增殖,提示苜蓿多糖能够调节机体的细胞免疫和体液免疫功能;苜蓿多糖可以显著地增强NK细胞对K562靶细胞的杀伤活性,提示苜蓿多糖能显著地增强机体非特异性免疫功能。因此,说明苜蓿多糖具有很好的免疫调节效果。 相似文献
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Chuanbo Guo Yushun Chen Rodolphe E. Gozlan Zhongjie Li Thomas Mehner Sovan Lek Craig P. Paukert 《Fish and Fisheries》2019,20(5):857-869
Understanding drivers of freshwater fish assemblages is critically important for biodiversity conservation strategies, especially in rapidly developing countries, which often have environmental protections lagging behind economic development. The influences of natural and human factors in structuring fish assemblages and their relative contributions are likely to change given the increasing magnitude of human activities. To discriminate natural and human drivers of fish diversity and assemblage patterns in developing countries with rapid socio‐economic development, a dataset of 908 freshwater fish species and 13 metrics including three categories of both natural (i.e., biogeographic) and human drivers (i.e., economic growth, inland fisheries) in China were analysed with machine learning algorithms (i.e., self‐organizing map, random forest). Here, we found that biogeographic drivers explained 21.8% of the observed fish assemblage patterns in China and remained stronger predictors when compared to human drivers (i.e., 15.6%, respectively). Freshwater fish species richness was positively correlated to rainfall, air temperature, surface water area and inland fisheries production but negatively correlated with urbanization. In addition, the strong structuring effects of climatic variables on Chinese fish richness patterns suggested that the fish assemblages could be particularly vulnerable to climate change. Our results showed that natural biogeographic factors still dominate in driving freshwater fish assemblage patterns despite increased human disturbances on aquatic ecosystems in a rapidly developing country. These findings consequently suggested that we should consider both natural (e.g., climate) and human (e.g., urbanization, inland fisheries) factors when establishing aquatic conservation strategies and priorities for developing countries that are experiencing rapid socio‐economic changes. 相似文献
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为了研究新疆乌苏地区棉花黄萎病菌的致病型和群体间的变异性,从该地区不同棉株上分离8株病原菌,通过对病原菌的菌落培养形态、菌丝和孢子的显微结构、对寄主的致病性、ITS序列的克隆、菌株间的系统进化及营养亲和性分析等方面进行了研究。结果表明:分离的病原菌均属于非落叶型棉花黄萎病菌(Verticillium dahliae),为大丽轮枝菌;系统进化树显示8株菌在系统进化上属于2个不同的进化方式;8株黄萎病菌在相同的寄主上致病性存在差,Vd-1菌株致病力最强,Vd-34致病力最弱;不同致病力的菌株之间的营养亲和性分为2个营养亲和群(VCGs)。新疆乌苏地区棉花黄萎病的致病菌是大丽轮枝菌,病原菌在进化上差异显著。 相似文献