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511.
Growth and reproduction of Scytosiphon lomentaria (Fucophyceae) in relation to temperature in two populations from Denmark 总被引:1,自引:0,他引:1
Two strains of Scytosiphon lomentaria from Denmark have been grown under long-day conditions on a temperature-gradient plate. The material from north-west Jutland (strain No. 46) has a reduced prostrate system (a few-celled lump) whereas the other material from the Sound (strain No. S41) has a well-developed crust. This difference plays a significant role in growth and reproductive patterns. Strain No. 46 rapidly produces a great number of cylindrical macrothalli. Within a four-week experimental period, formation of swarmers from plurilocular sporangia on the macrothalli takes place and results in a maximum dry weight of 32.9 mg at 18.2°C.
Swarmers from the macrothalli of strain S41 always develop into knot-filamentous or crust-shaped thalli. The development of the macrothalli, therefore, takes a longer time than in strain 46 and the maximum dry weight is only 16.5 mg at 16°C even within an experimental period of six weeks. The reproductive pattern is more complex than in strain 46. The crusts produce unilocular sporangia at temperatures between 16°C and 23.8°C, and function, therefore, as the reproductive system during the summer as macrothalli disappear at temperatures above 18°C both in nature and in culture. Formation of plurilocular sporangia on macrothalli starts when they are from 6–9 weeks old at temperatures between 11°C and 18°C.
The temperature range for growth in the two strains also differs: Strain 46 grows from 7.3–24.4°C while strain S41 grows at least from 4–5.1°C to an upper limit of 27.1°C, but lower limit has not been determined precisely in the present experiment. These results indicate that temperature ecotypes exist, even within a limited geographic area. 相似文献
Swarmers from the macrothalli of strain S41 always develop into knot-filamentous or crust-shaped thalli. The development of the macrothalli, therefore, takes a longer time than in strain 46 and the maximum dry weight is only 16.5 mg at 16°C even within an experimental period of six weeks. The reproductive pattern is more complex than in strain 46. The crusts produce unilocular sporangia at temperatures between 16°C and 23.8°C, and function, therefore, as the reproductive system during the summer as macrothalli disappear at temperatures above 18°C both in nature and in culture. Formation of plurilocular sporangia on macrothalli starts when they are from 6–9 weeks old at temperatures between 11°C and 18°C.
The temperature range for growth in the two strains also differs: Strain 46 grows from 7.3–24.4°C while strain S41 grows at least from 4–5.1°C to an upper limit of 27.1°C, but lower limit has not been determined precisely in the present experiment. These results indicate that temperature ecotypes exist, even within a limited geographic area. 相似文献
512.
Are Kristiansen Kjell M. Vårum Hans Grasdalen 《Biochimica et Biophysica Acta (BBA)/General Subjects》1998,1425(1):137-150
This paper considers the non-productive (inhibitory) binding of chitosans to lysozyme from chicken egg white. Chitosans are linear, binary heteropolysaccharides consisting of 2-acetamido-2-deoxy-β-d-glucose (GlcNAc; A-unit) and 2-amino-2-deoxy-β-d-glucose (GlcN, D-unit). The active site cleft of lysozyme can bind six consecutive sugar residues in subsites named A–F, and specific binding of chitosan sequences to lysozyme occurs with A-units in subsite C. Chitosans with different fractions of A-units (FA) induced nearly identical changes in the 1H NMR spectrum of lysozyme upon binding, and the concentration of bound lysozyme could be determined. The data were analysed using a modified version of the McGhee and von Hippel model for binding of large ligands to one-dimensional homogeneous lattices. The average value of the dissociation constant for different sequences that may bind to lysozyme (KaveD) was estimated, as well as the number of chitosan units covered by lysozyme upon binding. KaveD decreased with increasing FA-values at pH* 3 and 4.5, while the opposite was true at pH* 5.5. Contributions from different hexamer sequences to KaveD of the chitosans were considered, and the data revealed interesting features with respect to binding of lysozyme to partially N-acetylated chitosans. The relevance of the present data with respect to understanding lysozyme degradation kinetics of chitosans is discussed. 相似文献