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961.
Initial organic products of assimilation of [N]ammonium and [N]nitrate by tobacco cells cultured on different sources of nitrogen 下载免费PDF全文
Glutamine is the first major organic product of assimilation of 13NH4+ by tobacco (Nicotiana tabacum L. cv. Xanthi) cells cultured on nitrate, urea, or ammonium succinate as the sole source of nitrogen, and of 13NO3− by tobacco cells cultured on nitrate. The percentage of organic 13N in glutamate, and subsequently, alanine, increases with increasing periods of assimilation. 13NO3−, used for the first time in a study of assimilation of nitrogen, was purified by new preparative techniques. During pulse-chase experiments, there is a decrease in the percentage of 13N in glutamine, and a concomitant increase in the percentage of 13N in glutamate and alanine. Methionine sulfoximine inhibits the incorporation of 13N from 13NH4+ into glutamine more extensively than it inhibits the incorporation of 13N into glutamate, with cells grown on any of the three sources of nitrogen. Azaserine inhibits glutamate synthesis extensively when 13NH4+ is fed to cells cultured on nitrate. These results indicate that the major route for assimilation of 13NH4+ is the glutamine synthetase-glutamate synthase pathway, and that glutamate dehydrogenase also plays a role, but a minor one. Methionine sulfoximine inhibits the incorporation of 13N from 13NO3− into glutamate more strongly than it inhibits the incorporation of 13N into glutamine, suggesting that the assimilation of 13NH4+ derived from 13NO3− may be mediated solely by the glutamine synthetase-glutamate synthase pathway. 相似文献
962.
Cytokinins in tRNA Obtained from Spinacia oleracea L. Leaves and Isolated Chloroplasts 总被引:4,自引:4,他引:0
Cytokinin-active ribonucleosides have been isolated from tRNA of whole spinach (Spinacia oleracea L.) leaves and isolated spinach chloroplasts. The tRNA from spinach leaf blades contained: 6-(4-hydroxy-3-methyl-2-butenylamino)-9-β-d-ribofuranosylpurine (cis and trans isomers), 6-(3-methyl-2-butenylamino)-9-β-d-ribofuranosylpurine, and 6-(4-hydroxy-3-methyl-2-butenylamino)-2-methylthio-9-β-d -ribofuranosylpurine (cis and trans isomers). A method for isolation of large amounts of intact chloroplasts was developed and subsequently used for the isolation of chloroplast tRNA. The chloroplast tRNA contained 6-(3-methyl-2-butenylamino)-9-β-d-ribofuranosylpurine and 6-(4-hydroxy-3-methyl-2-butenylamino)-2-methylthio-9-β-d -ribofuranosylpurine (the cis isomer only). The structures of these compounds were assigned on the basis of their chromatographic properties and mass spectra of trimethylsilyl derivatives which were identical with those of the corresponding synthetic compounds. The results of this study indicate that ribosylzeatin was present in spinach leaf tRNA, but absent from the purified chloroplast tRNA preparation. 相似文献
963.
The metabolism of 14CO2 in the cool temperate saltmarsh grass Spartina townsendii was investigated in plants grown in their natural habitats at two temperatures. Both in the spring at 10°C and in the late summer at 25°C radioactivity was initially incorporated into the organic acids malate and aspartate and then transferred to 3-phosphoglycerate in the manner characteristic of the C4 pathway of photosynthesis. Metabolism was not disrupted at the lower temperature as in some C4 plants. Radioactivity was transferred more slowly from malate into alanine, glycine and serine at 10°C, but sugars were labelled equally at both temperatures. 相似文献
964.
Summary Cells of the scutellum of immature embryos ofSorghum bicolor plated onto an agar medium containing 2,4-D give rise to shoots and embryo-like structures and to some callus. Some of the embryo-like structures later develop into typical sorghum embryos complete with scutellum, coleoptile and coleorhiza. The results of anatomical studies of the development of these secondary growth forms by light and scanning electron microscopy suggest that shoots and embryo-like structures can arise directly from cells of the primary scutellum without an intervening callus phase. In some cases it appears that the scutellum of the secondary embryos arises by folding of the scutellum of the sexual embryo and does not arisede novo. In other cases the structures arise from single cells. No evidence was found to indicate that organized structures arose from proliferating callus cells. The unorganized callus which arises initially is not capable of growth through continuous subculture; it produces a purple-black pigment and rapidly becomes necrotic. The significance of these observations is discussed in relation to present views on morphogenesis in cereal cell cultures and their implications forin vitro cell genetics.Abbreviations used in the text 2,4-D
2,4-dichlorophenoxyacetic acid
- MS
Murashige and Skoog 相似文献
965.
966.
Thomas R. Defler 《Primates; journal of primatology》1978,19(1):153-167
This paper analyzes allogrooming (social grooming) data collected from two large, fully integrated and long established social
groups of macaques (one of pigtail macaques and one of bonnet macaques). The data demonstrates a species and sex difference
for total allogrooming given with females of both species giving more grooming than the males and with pigtails as a species
giving more grooming than bonnets. Also, pigtail females gave more allogrooming to clan members than to nonclan members, but
this was not true for pigtail males, bonnet males, and bonnet females. Allogrooming given and allogrooming received by age
class for both species showed development of a sexual dichotomy at three to four years. The analysis characterized some of
the social structures extant in two closely related species of macaque, particularly the somewhat different use of allogrooming
in pigtail females as opposed to the other three categories of animals. Social implications with relation to macaque societies
are discussed. 相似文献
967.
Henry Taylor Jane Teas Thomas Richie Charles Southwick Ram Shrestha 《Primates; journal of primatology》1978,19(2):343-351
In 1,506 hours of field observations on free-ranging rhesus monkeys in Kathmandu Valley, Nepal, in 1974 and 1975 18 cases
of favorable social interactions between adult males and infants were observed. Eleven of these were brief encounters of play
or grooming; seven were more extended cases of male care. One of the latter was a complete adoption of a neonatal orphan by
a dominant male. This adoption was possessive and restrictive and it resulted in the death of the infant by starvation within
three days. A similar adoption involving the same male occurred in 1976 and it also resulted in the death of the infant. Most
of the favorable male-infant interactions occurred during the winter and spring when the infants were 6 to 12 months of age.
These favorable social interactions involved eight males in six different troops, out of a total of about 48 males in 12 troops
in our study population of approximately 600 monkeys. These observations are discussed in light of current sociobiological
theories. 相似文献
968.
Fertile and sterile frond segments of the lyginopterid seed fern Feraxotheca culcitaus are described. In both the fertile and sterile specimen three orders of frond axes are borne alternately and in the same plane. Antepenultimate and penultimate frond axes are characterized by a C-shaped vascular bundle and numerous canals containing a golden-colored material in the fossilized condition. Synangia with only four sporangia demonstrate radial symmetry; bilateral symmetry is present in larger synangia. Pinnules possess dichotomous venation, with a single vein entering each lobe of the deeply incised lamina. A single canal occurs below each vein, and vein ends have an amplified vascular bundle. Morphologically Feraxotheca compares most closely with the compression genus Crossotheca. The morphology of the vascular bundle in the largest pinna is similar to a Lower Carboniferous specimen of Rhodea. 相似文献
969.
A 10-month-old infant was found to have an isolated congenital arteriovenous fistula between the right subclavian artery and vein. Ligation of the fistula resulted in complete anatomic correction and rapid resolution of cardiomegaly. 相似文献
970.
T M John E Thomas J C George F W Beamish 《Archives internationales de physiologie et de biochimie》1977,85(5):865-870
The effect of injections of arginine vasotocin (AVT) on plasma free fatty acid (FFA) levels was studied in anadromous sea lampreys collected in the St. John River, New Brunswick, during their upstream spawning migration. Plasma FFA was significantly higher in lampreys injected with a single dose of 1 000 mU vasotocin/kg body weight than in those receiving only the vehicle solution, the difference being the greater at 90 than at 30 min post-injection. The significance of AVT in migration is discussed. 相似文献