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1.
Leaf senescence is often caused by water deficit and the chimeric gene PSA612-1PT is an auto-regulated gene delaying leaf senescence. Using in vitro leaf discs culture system, the changes of contents of chlorophylls, carotenoids, soluble protein and thiobarbituric acid reactive substance （TBARS） and antioxidant enzymes activities were investigated during leaf senescence of PSA612-1PT modified gerbera induced by osmotic stress compared with the control plant （wild type）. Leaf discs were incubated in 20%, 40% （w/v） polyethylene glycol （PEG） 6 000 nutrient solution for 20 h under continuous light [ 130 μmol/（m^2·s）]. The results showed that the contents of chlorophylls, carotenoids and soluble protein were decreased by osmotic stress with the decrease being more pronounced at 40% PEG, but that, at the same PEG concentration the decrease in the transgenic plants was significantly lower than that in the control plant. The activities of superoxide dismutase （SOD）, catalases （CAT）, ascorbate peroxidase （APX）, guaiacol peroxidase （GPX） and dehydroascorbate reductase （DHAR） were stimulated by PEG treatment. However, the increases were higher in PSA612-IPT transgenic plants than in the control plants, particularly at 40% PEG treatment. Lipid peroxidation （TBARS content） was increased by PEG treatment with the increase being much lower in transgenic plant than in the control plant. It could be concluded that the increases in the activities ofantioxidant enzymes including SOD, CAT, APX, GPX and DHAR were responsible for the delay of leaf senescence induced by osmotic stress. 相似文献
2.
以小麦幼胚愈伤组织为外植体,研究继代培养时间、外源激素及叶片大小对小麦试管苗叶片愈伤组织诱导和再生的影响。结果表明：继代培养1～6个月的胚性愈伤组织,有较高的再生苗频率;当生长素浓度为2,4-D2mg／L＋NAA1mg／L、叶片高度为4cm时,小麦试管苗叶片愈伤组织的诱导率最高,从而建立了小麦试管苗叶片愈伤组织诱导和再生的培养体系。 相似文献
3.
本文系统地介绍了双子叶植物叶结构分类术语。这不仅有利于术语规范化，而且有利于国内外同行交流。 相似文献
4.
利用扫描电镜技术、叶片离析法和石蜡切片法研究了假鹰爪属Desmos 4种植物和皂帽花属Dasy-maschalon 3种植物叶片的形态结构。结果表明：假鹰爪属植物叶片近轴面表皮具大型球状含晶簇细胞和不含晶簇的表皮细胞两种类型，远轴面表皮细胞均具一较小的晶簇；叶肉组织明显分化为栅栏组织细胞和海绵组织细胞，油细胞分布于第2层的栅栏组织和海绵组织内，单位毫米叶宽油细胞数为4～6个；主脉维管组织被薄壁细胞分隔成束状。皂帽花属植物叶片近轴面表皮细胞形状相同，均具一晶簇，远轴面表皮细胞的晶簇和近轴面表皮细胞的晶簇相似；靠近上、下表皮的叶肉组织均分化为栅栏组织细胞，在两层栅栏组织细胞之间分化为一至几层海绵组织细胞，油细胞分布于海绵组织内，单位毫米叶宽油细胞数为2～3个；主脉维管组织形成连续的环状。由此可见两属叶的结构具有明显的差异，因而支持假鹰爪属和皂帽花属为两个独立属的观点。 相似文献
5.
浅析《最后一片叶子》的文体特征 总被引：1，自引：0，他引：1
陈燕 《安徽广播电视大学学报》2010,(4):89-92
从叙述视角、修辞手法和会话三个方面对欧.亨利的著名短篇小说《最后一片叶子》进行文体分析,以期对作品的主题思想和美学价值有更深刻的了解。 相似文献
6.
Studies were initiated for two consecutive years to find out the effect of time of transplanting and seedlings hill^-l on the productivity of rice in Dera Ismail Khan district of North West Frontier Province （NWFP）, Pakistan. The experiment was laid out in a randomized complete block design with split plot arrangements. Main plots consisted of four transplanting dates viz. 20th and 27th of June and 4th and 1 lth of July while sub-plots contained 1, 2, 3 or 4 seedlings hill^-1. Among transplanting dates, June 20th planted crop gave highest paddy yield and net return with I seedling hill^-1. It explains that the use of more seedlings hill^-1 not only adds to cost but is also a mere wastage of natural resources. Based on research findings, we conclude that the use of I seedling hill^-1 is most appropriate for timely sowing otherwise 4 seedlings hill^-1 should be used to compensate for the yield gap in late transplanted rice. 相似文献
7.
《大学英语》课本选编了欧.亨利和毛姆的两个短篇小说,对之进行比较研究也是一种深化的阅读。《最后一片叶子》与《患难之交》两篇文章中不同的人性主题相互交应,相似的叙述结构与不同的叙述模式显现出文艺审美倾向的差异。一俗一雅两篇小说间的平行研究揭示出英美文学发展的特点和叙事视角运用的一般规律。 相似文献
8.
Fu-min Wang Jing-feng Huang Qi-fa Zhou Xiu-zhen Wang 《Journal of Zhejiang University. Science. B》2008,9(12):953-963
The objectives of the study were to select suitable wavebands for rice leaf area index (LAI) estimation using the data acquired over a whole growing season, and to test the efficiency of the selected wavebands by comparing them with feature positions of rice canopy spectra. In this study, the field experiment in 2002 growing season was conducted at the experimental farm of Zhejiang University, Hangzhou, China. Measurements of hyperspectral reflectance (350-2500 nm) and corresponding LAI were made for a paddy rice canopy throughout the growing season. And three methods were employed to identify the optimal wavebands for paddy rice LAI estimation: correlation coefficient-based method, vegetation index-based method, and stepwise regression method. This research selected 15 wavebands in the region of 350-2500 nm, which appeared to be the optimal wavebands for the paddy rice LAI estimation. Of the selected wavebands, the most frequently occurring wavebands were centered around 554, 675, 723, and 1633 nm. They were followed by 444, 524, 576, 594, 804, 849, 974, 1074, 1219, 1510, and 2194 nm. Most of them made physical sense and had their counterparts in spectral known feature positions, which indicates the promising potential of the 15 selected wavebands for the retrieval of paddy rice LAI. 相似文献
9.
2001年/2002年在云南冬春香料烟主产区保山的罗明片和柯街片进行密度种植试验和气候考察.揭示出本区冬春香料烟生产季最高最低气温、平均气温和土温时空变化特点及差异气候特征;其中,冬季温度变化关键期(12月/1月)大部时段土温旬均值高于气温O.5℃～3.0℃,最低气温极值为3.0℃～3.4℃,随时空而异.研究表明,密度对烟叶产量和质量的影响以及株高迅速生长的天数随气候类型的不同而异;冬季热量水平低是生产优质冬春香料烟的制约因素;影响冬春香料烟生长发育和烟叶品质的温度因素因地域而异;光温差积影响烟叶总糖含量,10 cm土温影响烟叶烟碱含量;适宜种植密度行株距为40cm×12cm,单株风干烟茎重达28.44g～31.33g/株、风干烟叶重达82.99g～91.41g/株、产量为1 729.1kg～1 903.8kg/hn2.此外,建立了株高-温度关系模型,模型通式:y'=c0 n∑i=1ci·xi.在此基础上,提出在主产区实现优质香料烟生产的对策建议. 相似文献
10.
在扫描电镜下,比较观察了冷杉属全世界36种2变种的叶角质层内表面的结构特征,根据叶角
质层内表面胞间凸缘特征的显著差异,将冷杉属植物归为4类:(1)直且发达的单凸缘;(2)双凸缘;
(3)不发达的单凸缘;(4)弯曲且发达的单凸缘。并发现这四种凸缘类型在冷杉属中的分布格局与该
类植物的地理分布具有相关性。根据所观察的结果和前人的属下分类系统以及化石资料,认为北美西部是现代冷杉属植物的一个多样性中心。 相似文献