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981.
982.
The mechanism of light-inhibited ethylene production in excised rice (Oryza sativa L.) and tobacco (Nicotiana tabacum L.) leaves was examined. In segments of rice leaves light substantially inhibited the endogenous ethylene production, but when CO2 was added into the incubation flask, the rate of endogenous ethylene production in the light increased markedly, to a level which was even higher than that produced in the dark. Carbon dioxide, however, had no appreciable effect of leaf segments incubated in the dark. The endogenous level of 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene, was not significantly affected by lightdark or CO2 treatment, indicating that dark treatment or CO2exerted its effect by promoting the conversion of ACC to ethylene. This conclusion was supported by the observations that the rate of conversion of exogenously applied ACC to ethylene was similarly inhibited by light, and this inhibition was relieved in the presence of CO2. Similar results were obtained with tobacco leaf discs. The concentrations of CO2 giving half-maximal activity was about 0.06%, which was only slightly above the ambient level of 0.03%. The modulation of ACC conversion to ethylene by CO2 or light in detached leaves of both rice and tobacco was rapid and fully reversible, indicating that CO2 regulates the activity, but not the synthesis, of the enzyme converting ACC to ethylene. Our results indicate that light inhibition of ethylene production in detached leaves is mediated through the internal level of CO2, which directly modulates the activity of the enzyme converting ACC to ethylene.Abbreviation ACC
1-aminocyclopropane-1-carboxylic acid
Recipient of a Republic of China National Science Council Fellowship 相似文献
983.
桑萎缩病的类菌原体病原物及其超微病变特征 总被引:4,自引:0,他引:4
对感染桑萎缩病的桑叶及嫩梢进行超薄切片的电镜观察发现,其韧皮部组织,筛管及伴胞内有多型性类菌原体。菌体为圆形及椭圆形,大小约为50~160nm,双层膜,厚度约为8~10nm,内含物中具有核质样的纤维状物质,而在健株叶梢中未观察到任何病原体.随着病害的发展,可观察到细胞成份的降解。第一,在感病植株叶肉细胞内存在部分细胞核的降解、核膜破裂或核质流失甚至核仁分散消失。第二,叶绿体内有不同程度的淀粉粒和嗜锇颗粒累积,部分叶绿体外膜破裂,基质流失,基粒降解。第三,线粒体及粗面内质网在数量上有所增加,部分线粒体嵴已降解。 相似文献
984.
Summary Organoboronic acids may be used as solubilizing agents for glucose in organic solvents for the enzymatic condensation of glucose. Glucose in organic solvents was condensed to -glucobioses by -glucosidase in the presence of organoboronic acids. Organoboronic acids appear to be a good solubilizing agents without any disturbing effect on the enzyme reaction. 相似文献
985.
商平 《Acta Botanica Sinica》1987,(2)
本文报道了阜新盆地含煤地层中的植物化石和植物群特征,对植物化石在垂直方向上的变化规律进行了讨论。 相似文献
986.
A search was made for the lymphoid cell type(s) which are the source of immune RNA (I-RNA) capable of transferring tumor-specific cell-mediated cytotoxicity (CMC). Hartley guinea pigs were immunized with syngeneic murine fibrosarcomas (BP-10 or BP-11) induced by 3,4-benzo(a)pyrene in C3H/HeJ mice, and the I-RNA was extracted individually from their spleens, lymph nodes, and peritoneal exudate (PE) cells. All three I-RNA preparations were able to convert normal C3H/HeJ mouse lymphocytes to effector cells significantly cytolytic to the specific syngeneic mouse tumor in vitro. Furthermore, lymphocytes and macrophages were purified from the spleens, lymph nodes, and PE cells of tumor-immunized guinea pigs. I-RNA was extracted from these purified cell populations and also from the pooled guinea pig lymphoid tissues. Normal C3H/HeJ lymphocytes were incubated with each type of I-RNA and tested in vitro for CMC against the specific tumor cells. Significant CMC against BP-10 targets was observed with mouse lymphocytes incubated with I-RNA extracted from pooled lymphoid tissues of BP-10 tumor-immunized guinea pigs. There was a reduced but still significant CMC when mouse lymphocytes were incubated with I-RNA extracted from purified guinea pig lymphocytes, whereas there was a markedly increased CMC when the I-RNA was extracted from purified guinea pig macrophages. As indicated by sucrose density gradient analysis, the lesser effectiveness of lymphocyte I-RNA was not due to RNA degradation resulting from lymphocyte purification or I-RNA extraction. Treatment of all types of I-RNA with RNase abrogated the transfer of CMC, whereas treatment of I-RNA with DNase or pronase did not. RNA extracted from the lymphoid tissues of guinea pigs immunized with complete Freund's adjuvant without tumor was ineffective. Mouse lymphocytes incubated with BP-10 macrophage I-RNA destroyed BP-10 but not BP-11 tumor cells, whereas lymphocytes incubated with BP-11 macrophage I-RNA killed BP-11 but not BP-10 tumor cells, thus indicating tumor specificity of the immunity transferred by macrophage I-RNA. Our results suggest that macrophages are the principal source of I-RNA capable of transferring tumor-specific CMC. 相似文献
987.
Yilun Shang 《PloS one》2015,10(3)
Large-scale time-evolving networks have been generated by many natural and technological applications, posing challenges for computation and modeling. Thus, it is of theoretical and practical significance to probe mathematical tools tailored for evolving networks. In this paper, on top of the dynamic Estrada index, we study the dynamic Laplacian Estrada index and the dynamic normalized Laplacian Estrada index of evolving graphs. Using linear algebra techniques, we established general upper and lower bounds for these graph-spectrum-based invariants through a couple of intuitive graph-theoretic measures, including the number of vertices or edges. Synthetic random evolving small-world networks are employed to show the relevance of the proposed dynamic Estrada indices. It is found that neither the static snapshot graphs nor the aggregated graph can approximate the evolving graph itself, indicating the fundamental difference between the static and dynamic Estrada indices. 相似文献
988.
989.
Jian-Li Shang Hui Guo Zai-Shun Li Biao Ren Zheng-Ming Li Huan-qin Dai Li-Xin Zhang Jian-Guo Wang 《Bioorganic & medicinal chemistry letters》2013,23(3):724-727
A total of 29 novel sulfenamide compounds were synthesized, spectroscopically characterized and evaluated in vitro for antimicrobial activity against various infectious pathogens. Compounds 1b and 2c exhibited potent inhibition against clinical Methicillin-resistant Staphylococcus aureus (MRSA) strains with minimum inhibitory concentration (MIC) values of 1.56 μg/mL. 相似文献
990.
Xiaoying Liu Li Tian Yu Shang Jiusheng Jiang Jilin Zhang Jiayi Wei Dongxin Liu Wengang Fang Xinyue Zhao Hao Yu Yuhua Chen Deshu Shang 《Neurochemical research》2019,44(4):905-916
Neurochemical Research - Neuroinflammation is an important part of the development of neurodegenerative diseases such as Alzheimer’s disease (AD), Parkinson’s and amyotrophic lateral... 相似文献