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991.
992.
The haploid phase (myxamoebae-swarm cells) of the myxomycete Physarum flavicomum grew readily in chemically defined liquid media. The minimal medium contained salts, glucose, biotin, thiamine, hematin, glycine, l-arginine and l-methionine. Cell yields of 1.4x107 cells/ml were obtained in this medium in aerobic shake culture. These cells consumed about 35 μliters of oxygen/mg protein·hr in the minimal medium. The morphology of cells maintained in this medium appeared to be “normal”. l-valine replaced either glycine or l-methionine in the minimal medium but the growth rates and cell yields were reduced. Growth rates increased in media containing four, seven, or fourteen amino acids. 相似文献
993.
994.
A laboratory colony of 50 adults ofAltica carduorum Guérin-Méneville was established at South Dakota State University. Beetles reared in this colony had an average preoviposition period of 7 days when exposed to a regular cycle of 16 hr of light (24°C) and 8 hr of darkness (12.7°C). The laboratory reared females, whose longevity averaged 100 days, laid an average of 259.3±9.7 eggs. High temperatures and/or low RH are limiting factors to beetle survival. In the field eggs were laid throughout June on the underside of leaves along the edges of the veins. Adults fed throughout the summer and then over-wintered in the soil. Some of these beetles emerged the following spring and laid viable eggs. Factors limiting establishment in South Dakota, however, were high temperatures, low humidities, and the predators,Lebia viridis Say andHarpalus pennsylvanicus Degeer.A. carduorum originates from the Swiss Rhône valley where there is a relatively “continental” climate, but is limited to special habitats where comparatively high humidity occurs. South Dakota climate is characterized by cold winters, and hot, dry summers, therefore establishment would be most difficult. 相似文献
995.
996.
997.
998.
Excised primary roots of Phaseolus vulgaris L. were treated with canavanine and the effect on arginine utilization was studied. Arginine utilization was observed to be depressed to a low level by canavanine (1.8 × 10?4M) in rapidly dividing and growing tissues. In addition, canavanine inhibited arginine utilization to a lesser degree in root sections composed of mature and non-dividing tissues. This demonstrated that canavanine inhibition is not limited to those tissues where active DNA synthesis occurs. Canavanine was observed to inhibit the onset of mitosis in primary roots as evidenced by a significant reduction of the frequency of mitotic figures. In addition, this amino acid was found to affect the course of mitosis once it was initiated by altering the relative frequency of mitotic stages, decreasing the percentage of prophase figures and increasing the percentage observed in the telophase. An influence on the rate of spiralization and despiralization of the chromosomes is suggested. The effects on mitosis are probably related to growth-inhibitory and toxic effects of canavanine. The possible function of canavine as an allelopathic substance is hypothesized. 相似文献
999.
1000.