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21.
于2017—2018年和2018—2019年,在西北中部旱作雨养农业区以冬小麦‘康庄974’为试验材料,设秸秆带状覆盖(SM)、地膜覆盖(PM)和无覆盖对照(CK)共3个栽培处理,分析不同覆盖方式对小麦灌浆期土壤水分和温度及抗氧化能力的影响,探讨花后干物质积累量和粒重形成的关系。结果表明,随生育期推进,花后旗叶相对含水量(RWC)逐渐降低,丙二醛(MDA)含量逐渐升高,且PM较SM降、升幅度明显。与CK相比,覆盖显著提高花后旗叶抗氧化酶活性,增加渗透调节物质含量;开花时间越长,SM抗氧化酶活性升高的幅度越大,而PM主要提高花后7 d旗叶抗氧化能力。SM和PM的粒重分别较CK增加14.3%和19.1%(P<0.05)。相关分析表明,土壤水分(SW)是影响旗叶生理活性的关键因子,提高SW,有利于增加RWC(r=0.84**),从而提高旗叶抗氧化能力,其中RWC和抗坏血酸酶(ASA)活性呈极显著正相关关系(r=0.82**);ASA活性和脯氨酸(Pro)含量呈极显著正相关关系(r=0.94**),和MDA含量呈极显著负相... 相似文献
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通过对黄土高原腹地甘肃合水MJY全新世土壤剖面磁化率、全铁、TOC、Rb、Sr和Rb/Sr等气候代用指标的测定分析,揭示了与全新世环境变化相对应的成壤过程,并在此基础上,阐明黄土高原中部地区环境资源变化对人类活动的影响。认为全新世早期,黄土高原中部地区气候比较温和干燥,风尘堆积速率降低,地表植被以草本为主,并有一定的生物风化成壤作用,土壤发育表现为边沉积边成壤;全新世中期,气候温暖湿润,地表植被发育,生物风化成壤作用大于风尘堆积作用,随着沉积和成壤的继续,土壤层深厚,形成古土壤层(S0);全新世晚期,气候开始恶化,干旱少雨,植被退化,沙尘暴频繁发生,风尘堆积作用大于风化成壤作用,土壤退化形成的现代黄土层(L0)覆盖了土壤(S0)使之成为埋藏古土壤。在寺洼文化时期(3250—2520 a B.P.),由于气候干旱使环境资源恶化,土壤退化严重,土地资源利用方式和文化形态从原始的农耕文化转向游牧类型文化。 相似文献
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Desiccation and cracking behaviour of clay layer from slurry state under wetting-drying cycles 总被引:3,自引:0,他引:3
Laboratory tests were conducted to investigate the effect of wetting-drying (W-D) cycles on the initiation and evolution of cracks in clay layer. Four identical slurry specimens were prepared and subjected to five subsequent W-D cycles. The water evaporation, surface cracks evolution and structure evolution during the W-D cycles were monitored. The effect of W-D cycles on the geometric characteristics of crack patterns was analyzed by image processing. The results show that the desiccation and cracking behaviour was significantly affected by the applied W-D cycles: the measured cracking water content θc, surface crack ratio Rsc and final thickness hf of the specimen increased significantly in the first three W-D cycles and then tended to reach equilibrium; the formed crack patterns after the second W-D cycle were more irregular than that after the first W-D cycle; the increase of surface cracks was accompanied by the decrease of pore volume shrinkage during drying. In addition, it was found that the applied W-D cycles resulted in significant rearrangement of specimen structure: the initially homogeneous and non-aggregated structure was converted to a clear aggregated-structure with obvious inter-aggregate pores after the second W-D cycle; the specimen volume generally increased with increasing cycles due to the aggregation and increased porosity. The image analysis results show that the geometric characteristics of crack pattern were significantly influenced by the W-D cycles, but this influence was reduced after the third cycle. This is consistent with the observations over the experiment, and indicates that the image processing can be used for quantitatively analyzing the W-D cycle dependence of clay desiccation cracking behaviour. 相似文献
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赵昌普 《拖拉机与农用运输车》2009,36(6):1-5
论述了在内燃机缸内速度测量、喷雾粒子粒度测量及燃烧过程温度和组分浓度测量中常用的激光诊断技术和测试方法,并对其工作原理、适用范围与场合、优缺点等进行了比较和分析。相位多谱勒粒子测速(PDPA)技术比较适合于单点速度、粒子尺寸及其分布的测量;粒子图像测速(PIV)技术适合于缸内二维平面速度场的测量;激光全息术是分析喷雾特性的有效途径和测量喷雾液滴尺寸的标准方法;平面激光诱导荧光(PLIF)法已成为喷雾、燃烧过程组分浓度及火焰结构研究的重要工具。 相似文献
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霍山石斛类原球茎诱导及其发育过程研究 总被引:4,自引:0,他引:4
以霍山石斛试管苗带节茎段为材料, 诱导产生类原球茎, 并研究类原球茎发育过程。结果表
明, 霍山石斛类原球茎诱导的适宜培养基为Knudson + 2, 4-D 0.1 mg·L - 1 + KT 0.05 mg·L - 1 , 诱导率为25.50%。以固体静置、固液双层静置、液体静置、液体振荡4种不同培养方式进行增殖培养, 其中液体振荡培养方式更适于类原球茎快速增殖。类原球茎通过胚状体发生途径形成, 类似于合子胚的发育, 即经历原胚、心形胚、鱼雷形胚和子叶胚, 最后发育为成熟胚。类原球茎发育进程大致可分为类原球茎形成期、类原球茎肥大期、茎叶分化期、茎叶形成期以及茎叶伸长期等阶段。 相似文献
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Successful development and adoption of transgenic cassava (Manihot esculenta Crantz) varieties in Africa depend on in vitro regeneration of landraces because of their agronomic value and amenability to genetic modification. The study investigated somatic embryogenesis from axillary bud and immature leaf-lobe explant and regeneration via shoot organogenesis in five cassava landraces. Landraces exhibited significant (P < 0.05) differences in frequencies of primary somatic embryo production, number of embryos per explant, and frequency of secondary embryos. The frequency of primary somatic embryogenesis ranged from 7.8 to 14.5%, whereas the number of embryos per explant varied from 5.3 to 10.6. However, only frequency of primary somatic embryos and number of embryos per explant showed significant (P < 0.05) differences when immature leaf lobe was used as explant. The frequency of primary somatic embryogenesis ranged from 42.7 to 49.2%, whereas number of embryos per immature leaf-lobe explant varied from 9.5 to 15.2 per explant. Secondary embryogenesis was cultivar-independent in the case of immature leaf-lobe explant. Cyclic and green (mature) embryogenesis showed no significant (P < 0.05) landrace differences in both axillary bud and immature leaf-lobe explants. Shoot regeneration from cotyledon of somatic embryos had significant (P < 0.05) landrace differences. The mean shoot-bud formation frequency of axillary bud and immature leaf-lobe explants was 51.4% and 37.2%, respectively. Root formation was efficient, with greater than 70% of shoots forming root in all landraces. Similarly, landrace differences were detected for the survival of acclimatized regenerated plants, with a mean of 94.7% for both explants. In conclusion, somatic embryos were produced from immature leaf and axillary bud explants of the landraces and the embryos were converted to plantlets via shoot organogenesis. 相似文献