Incompatibility Between the Dimorphic Flowers of Collomia grandiflora, a Cleistogamous Species     

Lord EM  Eckard KJ 《Science (New York, N.Y.)》1984,223(4637):695-696

The cleistogamous species Collomia grandiflora produces dimorphic cross-incompatible flowers on a single plant. The open or chasmogamous flower has smaller, flask-shaped stigmatic papillae, larger pollen grains, longer styles, and faster pollen tube growth rates down the style than the closed or cleistogamous flower. In intermorph crosses, pollen tube growth rates are greatly decreased and fertilization does not occur.  相似文献   

Renewed Interest in Food Irradiation: FDA ponders approval as proponents push it as an alternative to pesticides     

Sun M 《Science (New York, N.Y.)》1984,223(4637):667-668

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The Fifth Generation: Taking Stock: The Japanese computer project is approaching its third birthday; meanwhile, the American programs are finally getting organized     

Waldrop MM 《Science (New York, N.Y.)》1984,226(4678):1061-1063

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Groundwater contamination     

Bredehoeft JD  Usselman TM 《Science (New York, N.Y.)》1984,224(4655):1292

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Newton: in the presence of the creator     

Mahoney MS 《Science (New York, N.Y.)》1984,226(4670):39-40

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Do bacteria-sized marine eukaryotes consume significant bacterial production?     

Fuhrman JA  McManus GB 《Science (New York, N.Y.)》1984,224(4654):1257-1260

Up to 60 percent of the total marine primary production (or about one-fourth of the total global carbon dioxide fixation) passes through the free-living bacterioplankton. Grazing by bacteriovores is probably the predominant fate of the bacteria, although data are scarce. Evidence is presented that previously uncharacterized, small eukaryotes that are able to pass even 0.6-micrometer filters may be responsible for a large fraction (more than 50 percent) of the total grazing in coastal waters. These organisms have not yet been observed microscopically.  相似文献   

Dormancy of micropropagated sour cherry plantlets     

Borkowska B 《Tree physiology》1986,1(3):303-307

Micropropagation of fruit trees results in the early onset of dormancy in the young plantlets. Prechilling of shoot cultures of sour cherry cvs Schattenmorelle and North Star at 4 degrees C for 6-8 weeks prolonged shoot extension of the plantlets but longer cold treatments adversely affected shoot growth and survival. Chilling of cultures had no affect on rhizogenesis. No significant influence of ABA, GA(3) or ABA + GA(3) was observed on root development. Gibberellic acid A(3) did not stimulate extension of the shoots, but when supplied together with ABA, it significantly decreased both shoot extension and the number of actively growing apices of plantlets of cv Schattenmorelle. The combined hormonal treatment had no effect on plantlets of the North Star cv.  相似文献   

Validation of liquid chromatographic method for assay of calcitriol and alfacalcidol in capsule formulations     

B C Flann  B A Lodge 《Journal of the Association of Official Analytical Chemists》1986,69(6):1026-1030

The validation of a liquid chromatographic procedure suitable for the determination of calcitriol and alfacalcidol in their respective formulations labeled to contain at least 0.25 micrograms drug per unit is described. The capsule content is diluted and chromatographed in 15-20 min on silica columns (5 micron) with a mobile phase of hexane-tetrahydrofuran-methylene dichloride-isopropanol (72 + 12 + 12 + 4, v/v) with detection at 254 nm. The calibration curve is linear. Recoveries of "spikes" averaged 101% with a standard deviation of 2%. Precision was better than 1.5%.  相似文献   

Venus: detailed mapping of maxwell montes region     

Alexandrov YN  Crymov AA  Kotelnikov VA  Petrov GM  Rzhiga ON  Sidorenko AI  Sinilo VP  Zakharov AI  Akim EL  Basilevski AT  Kadnichanski SA  Tjuflin YS 《Science (New York, N.Y.)》1986,231(4743):1271-1273

From October 1983 to July 1984, the north hemisphere of Venus, from latitude 30 degrees to latitude 90 degrees , was mapped by means of the radar imagers and altimeters of the spacecraft Venera 15 and Venera 16. This report presents the results of the radar mapping of the Maxwell Montes region, one of the most interesting features of Venus' surface. A radar mosaic map and contour map have been compiled.  相似文献   

Research Coterie Meets At NAS to Assess Budget: NAS assembles 400 representatives academe, industry, and government to discuss priorities for science     

Crawford M 《Science (New York, N.Y.)》1986,231(4743):1239

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