Floras and oxygen     

VAN Valen L 《Science (New York, N.Y.)》1979,205(4412):1302

  相似文献   

Carotenoids function in photoperiodic induction of diapause in a predacious mite     

VAN Zon AQ  Overmeer WP  Veerman A 《Science (New York, N.Y.)》1981,213(4512):1131-1133

Predacious mites fed for two generations solely on the eggs of wild-type spider mites responded normally to short day lengths by entering diapause. However, predacious mites fedfor two generations on eggs of albino spider mites, which are completely devoid of carotenoids, did not respond to short-day photoperiods. Apparently carotenoids are essential for photoperiodic induction; possibly a carotenoid or carotenoid derivative functions as the photopigment concerned in photoperiodic light reception in these mites.  相似文献   

A.J. Kluyver,microbiologist     

VAN NIEL CB 《Science (New York, N.Y.)》1956,124(3216):308

  相似文献   

Photosynthesis-associated gene families: differences in response to tissue-specific and environmental factors     

Simpson J  VAN Montagu M  Herrera-Estrella L 《Science (New York, N.Y.)》1986,233(4759):34-38

The endogenous small subunit of the ribulose-1,5-bisphosphate carboxylase gene rbcS and the light-harvesting chlorophyll a/b-binding protein gene (LHCP) of pea are expressed in a light-inducible manner and are active mainly in green chloroplast-containing tissue. Chimeric genes under control of the 5'-flanking sequences of the rbcS ss3.6 or LHCP AB80 genes from pea were used to study the factors relating to the issue-specific and lightinducible expression of these nuclear-encoded genes in transgenic tobacco plants. The results show that plastid development plays a crucial role in the activation of expression of these chimeric genes. Particular members of each of the above gene families respond differently to tissue-specific and environmental factors. Furthermore, the light-inducible expression directed by the 5'-flanking sequence of ss3.6 rbcSgene is not exclusively mediated by phytochrome, but probably is controlledin large part by another photoreceptor.  相似文献   

Terminal cretaceous extinctions in the hell creek area, montana: compatible with catastrophic extinction     

Smit J  VAN DER Kaars S 《Science (New York, N.Y.)》1984,223(4641):1177-1179

Inaccurate stratigraphic correlations in the Hell Creek area, Montana, have led to the assumption that transitional vertebrate faunas (Bug Creek Anthills) exist in the latest Cretaceous, refuting a catastrophic turnover at the Cretaceous-Tertiary boundary. Establishment of the transitional faunas in Paleocene channels that cut down through the Cretaceous-Tertiary boundary renders the terrestrial faunal record compatible with the marine record and with catastrophic extinction.  相似文献   

转PEPC基因水稻接种固氮菌的效应   总被引：1，自引：1，他引：1  

严建民  闫春玲  林敏  张保明  陈炳松  焦德茂 《江苏农业学报》2003,19(2):65-69

利用~(15)N-同位素技术研究转PEPC基因水稻及无PEPC基因水稻在接种不同固氮菌后的光合特性、产量性状和固氮能力的变化。结果表明:接种水稻联合固氮工程菌处理与未接种固氮菌处理相比,转PEPC基因水稻的PEPC活性、PS Ⅱ光化学效率(Fv/Fm)、净光合速率均明显提高,生物学产量和经济产量也相应增加了38.08％和26.86％;与无PEPC基因水稻相比,转PEPC基因水稻能明显提高水稻联合固氮工程菌的固氮效率。这种水稻光合与固氮相互促进的机理值得深入研究。  相似文献   

PHYSIOLOGY OF THE AMINO ACIDS     

VAN Slyke DD 《Science (New York, N.Y.)》1942,95(2463):259-263

We have followed the amino acids from their entrance into the alimentary tract in the form of food proteins through the successive steps of digestion, absorption into the blood stream and passage from the blood stream into the tissues, where they are concentrated by some unknown mechanism to many times their concentration in the blood plasma. We have seen something of the way in which certain of the amino acids can be transformed into one another in the body or synthesized from ammonia and keto acids. However, we have had to admit that our bodies can form in such ways only about half of the different amino acids that are required, and that the other half must be made for us by plants, bacteria or other organisms which have greater synthetic powers than we. And finally we have seen something of the manifold fates of the amino acids after they have entered our tissues; how they may be destroyed and their nitrogenous parts turned into urea in the liver before it is possible to put them to their more specialized uses, how their carbon fractions can be used to form glucose, how they may sacrifice themselves to protect us from toxic products, how they can serve as source material for certain vitamins, hormones and other compounds with physiological functions still to be identified, and how finally those amino acids which are not deflected to these various fates may enter into the proteins of the tissues and become for a time parts of our living structures.  相似文献   

Oceanic Residence Times of Dissolved Beryllium and Aluminum Deduced from Cosmogenic Tracers 10Be and 26Al     

Yokoyama Y  Guichard F  Reyss JL  VAN NH 《Science (New York, N.Y.)》1978,201(4360):1016-1017

The residence times of the soluble fractions of beryllium and aluminum in seawater are estimated to be 1500 years or more. These residence times are estimated from a comparison of the annual deposition rates of cosmogenic beryllium-10 and aluminum-26 with the concentrations of beryllium-10 and aluminum-26 in seawater estimated from the specific activities of these radionuclides in an authigenic mineral assembly such as a manganese nodule. These residence times are greater by an order of magnitude than the mean residence times of beryllium and aluminum estimated from the geochemical balance.  相似文献   

A NORTHERN MICHIGAN BASELEVEL     

VAN Hise CR 《Science (New York, N.Y.)》1896,4(86):217-220

  相似文献   

THE GEOLOGY OF ORE DEPOSITS. II     

VAN Hise CR 《Science (New York, N.Y.)》1901,14(360):785-793

  相似文献