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51.
Photosynthetically fixed 14C was analyzed in various chemical fractions from leaves and stems of cottonwood (Populus deltoides Bartr. ex. Marsh.) during dormancy induction. Dormancy was induced by 8-h photoperiods and 20/14°C temperature regimes. Within 4 weeks under short days, terminal buds were set and leaf expansion and stem elongation had stopped. 14C2 was fed to a leaf at Leaf Plastochron Index 7 for 30 min. Either after this 30 min feeding period or after a 48-h translocation period the plants were sampled, freeze-dried, extracted and analyzed for14C. 14C-fixation decreased during dormancy induction from 60% to 17% of the 3.7 MBq 14C applied at 0 week and 8 weeks, respectively. Percentage distribution of 14C in chemical fractions of source leaves reflected leaf age and translocation inhibition. In rapidly growing plants, considerable 14C was incorporated into leaf protein while most of the soluble14C-sugars were either metabolized or translocated out of the leaf. After terminal bud set, the percentage of 14C in the protein and residue fractions decreased rapidly and that in the sugar fraction increased. Percent distribution in stems closely reflected changing metabolic pathways of carbon flow as influenced by dormancy induction. For example, the 14C in structural carbohydrates decreased in 5 weeks under short days from 65 to less than 10% of the 14C recovered in the chemical fractions, thus indicating cambium inhibition. At the same time the percentage of 14C in starch and sugar increased indicating storage. Short term (after 30 min) incorporation of 14C into the protein and starch fractions of leaves changed relatively little throughout the 8-week induction period. In contrast the turnover rates of these fractions (14C present after 48 h) increased considerably after active growth of the whole plant stopped. 相似文献
52.
Summary Inclusion of sucrose in the solution applied to soybean (Glycine max L. merr.) leaves much reduced the severity of the damage to the leaves from application of urea and, to a lesser extent, from application of phosphorus (P) as orthophosphoric acid. Sucrose had no evident effect on P absorption. Damage to the leaves from joint application of orthophosphoric acid and urea exceeded the sum of the damage caused by the substances individually. Urea did not seem to influence P absorption, but the effect, if any, was not readily determined because nearly all values for P absorption exceeded 90%.Neutralization of orthophosphoric acid with nitrogen-containing organic bases, including choline, guanidine, and guanyl urea, did not prove useful as a technique for increasing the quantity of orthophosphate that could be applied without damage to the leaves.Absorption and translocation of orthophosphate by corn (Zea mays L.) and soybean leaves were not influenced by the pH of the solution within the range from 2 to 10. Absorption of tripolyphosphate by corn leaves decreased with an increase in pH of the solution applied, but translocation of the absorbed P was not influenced by pH. With soybeans, absorption of tripolyphosphate decreased with an increase in pH of the solution. Translocation of P applied to soybean leaves as tripolyphosphate was less than 5% of the amount absorbed within the first 24 hr and decreased with an increase in pH after 10 days. 相似文献
53.
P/2e ratios were calculated from anaerobic chemostat cultures of Paracoccus denitrificans with nitrogenous oxides as electron acceptor. P/2e ratios were calculated, using the Y
ATP
max
values determined for aerobic cultures. When succinate was the carbon and energy source the average P/2e values of the sulphate-and succinate-limited cultures with nitrate as electron acceptor were 0.5 and 0.7, respectively, and of the nitrite-limited culture 0.9. With gluconate as carbon and energy source the average P/2e values of the gluconate-limited with nitrate as electron acceptor and nitrate limited cultures were 0.9 and 1.1, respectively.H+/O ratios measured in cells obtained from sulphate-, succinate, nitrite-, gluconate-and nitratelimited cultures yielded respective average values of 3.4, 4.5, 3.5, 4.8 and 6.2 for endogenous substrates. From our data we conclude that sulphate-and nitritelimitation causes the loss of site I phosphorylation. Nitrite has no influence on the maximum growth yield on ATP. We propose that metabolism in heterotrophically grown cells of Paracoccus dentrificans is regulated on the level of phosphorylation in the site I region of the electron transport chain. 相似文献
54.
The contribution of different steps to the control of oxidative phosphorylation in isolated rat liver mitochondria was investigated by a combination of experiments and computer simulations. The parameters of the mathematical model of phosphorylating mitochondria were derived from experimental data. The model correctly describes the competition between ATP utilization inside and outside mitochondria for the ATP generated in mitochondria. On the basis of the good agreement between experiments and simulations, the contribution of different steps to the control of respiration was estimated by computing their control strengths, i.e., the influence of their activities on the rate of respiration. The rate-controlling influences vary depending on the load of oxidative phosphorylation. The predominant steps are: in the fully active state (State 3) — the hydrogen supply to the respiratory chain; in the resting state (State 4) — the proton leak of the mitochondrial inner membrane; in states of non-maximum ATP export — the adenine nucleotide translocator. Titrations of respiration with phenylsuccinate, antimycin, oligomycin and carboxyatractyloside completely support these conclusions. 相似文献
55.
Using BrdU-labeling and acridine orange staining, the behavior of X-chromosome replication was studied in 28 XXX and 19 XXY digynous mouse triploids. In some of these the paternal and maternal X chromosome could by cytologically distinguished. Such embryos were obtained by mating chromosomally normal females with males carrying Cattanach's X chromosome which contains an autosomal insertion that substantially increases the length of this chromosome. In the XXX triploids there were two distinct cell lines, one with two late-replicating X chromosomes, and the other with only one late-replicating X. The XXY triploids were also composed of two cell populations, one with a single late-replicating X and the other with no late replicating X chromosome. Assuming that the late-replicating X is genetically inactive, in both XXX and XXY triploids, cells from the embryonic region tended to have only one active X chromosome, whereas those from the extra-embryonic membranes tended to have two active X chromosomes. The single active X chromosome was either paternal or maternal in origin, but two active X chromosomes were overwhelmingly maternal in origin, suggesting paternal X-inactivation in extra-embryonic tissues. 相似文献
56.
D. C. Sigee 《Protoplasma》1982,110(2):112-120
Summary The uptake of63Ni into cells of the binucleate dinoflagellateGlenodinium foliaceum was investigated using insoluble compound light and electron microscope autoradiography. Cells labelled over a period of 2 hours showed active uptake throughout the whole population, with an increase in mean cell grain count when the labelling period was extended to 4 hours and 24 hours. The mean grain count did not vary with type of fixation (glutaraldehyde, paraformaldehyde or acetic alcohol) suggesting that retention of63 Ni is not a specific fixation-binding artefact. At light microscope level, silver grains were not localised to any major cell component, but with the greater resolution of electron microscope autoradiography, a high degree of localisation was demonstrated in the typical dinoflagellate (dinocaryotic) nucleus-which contained about 83% of the cell label (cytoplasm 16%, supernumerary nucleus 1%). Silver grain distribution within the dinocaryotic nucleus was consistent with some degree of localisation to the condensed chromatin.The autoradiographic results corroborate previous X-ray microanalytical data which demonstrated high levels of transition metals in dinoflagellate nuclei. The distinction between the two types of nucleus inGlenodinium is further emphasised, giving additional support to the concept of a separate phyllogenetic origin of the supernumerary nucleus. 相似文献
57.
Cytokinin activity in Lupinus albus 总被引:1,自引:0,他引:1
The distribution and metabolism of {8-14 C}zeatin incorporated into the transpiration stream of fruiting white lupin plants ( Lupinus albus L.) has been studied. The distribution pattern of 14 C in the different aerial organs suggests that the amount of cytokinin being incorporated into any one organ may have been a function of its transpiration rate. Once in these organs, particularly the leaves, zeatin was rapidly metabolised and or utilised. This resulted in the formation of a number of labelled compounds that did not give a response with the soybean callus bioassay. Substances co-eluting with zeatin glucoside and ribosylzeatin appeared to be the principal biologically active metabolites. From the present evidence it can be concluded that the leaf and side shoots received a major proportion of the applied labelled cytokinin. However, the presence of a small amount of radioactivity co-eluting with zeatin and ribosylzeatin in the fruits indicates that the high levels of cytokinins normally associated with these organs need not necessarily all have been synthesised in situ. 相似文献
58.
Summary Results of numerous tests of tropical and temperate legume hosts and Rhizobium strains accumulated between 1952 and 1966 were examined for a relation between N percent (y) and dry weight per plant (x). The data fitted the equation y=A–be–cx. The most effective Rhizobium strains can be selected on the basis of dry matter yields of whole plants or plant tops only, without the need for N analyses, using statistical analyses. A previously proposed method which employs the linear relation between N-yield and dry matter yield was shown to apply only when data for strains which are not fully effective are excluded.It is postulated that symbiotically fixed N forms a different compound from that resulting from applied mineral N and that this compound cannot be remobilised before flowering.deceased 相似文献
59.
In a comparative study the requirement of several strains of autotrophic hydrogen-oxidizing bacteria for nickel was examined. Autotrophic growth was studied both in liquid media, previously freed from trace metals; and on solidified media, using a plate diffusion assay. The latter assay was based on the observation that EDTA causes complete inhibition of autotrophic growth on agar medium as a result of nickel deficiency. Nickel was shown to be required as a trace element in five strains of Alcaligenes eutrophus, in two strains of Xanthobacter autotrophicus, in Pseudomonas flava, in Arthrobacter spec. 11X and in strain 12X. In these bacteria nickel was not replaceable by cobalt, copper, manganese or zinc ions. No significant nickel requirement was detected by these methods, however, for Paracoccus denitrificans and Nocardia opaca 1b. 相似文献
60.
Maria P. Abbracchio R. Mark Evans J. Daniel Heck Orazio Cantoni Max Costa 《Biological trace element research》1982,4(4):289-301
The effects of serum components and amino acids on the uptake and cytotoxicity of NiCl2 were examined in cultured Chinese hamster ovary (CHO) cells. CHO cells maintained in a minimal salts/glucose medium accumulated
10-fold more63Ni than did cells maintained in complete medium supplemented with 10% fetal bovine serum. Cell-surface binding of63Ni appeared to account for the majority of this increased accumulation of cell-associated nickel observed in the simple maintenance
medium since such increases were reduced 70% by trypsin treatment. The addition of the Ni2+-binding amino acids cysteine or histidine to the salts/glucose medium markedly decreased63Ni accumulations, an effect not observed following addition of any of several amino acids that do not bind Ni2+. Supplementation of the salts/glucose medium with fetal bovine serum decreased in a concentration dependent fashion both
the63Ni2+ uptake and cell detachment caused by Ni2+, while dialyzed (amino acid-free) serum was 3–5-fold less effective than undialyzed serum at reducing63Ni2+ uptake and similarly exhibited only a slight protective effect against nickel-induced cytotoxicity. Supplementation of dialyzed
serum with cysteine at levels approximating those in whole serum partially restored its inhibitory activity toward nickel
uptake by cells and restored completely its inhibition of nickel's cytotoxicity, indicating the predominant role of specific
amino acids over serum proteins in regulating the uptake and subsequent cytotoxicity of Ni2+. Addition of cysteine to the salts/glucose medium during a 2 h exposure of cells to either 100 μM HgCl2 or 1 mM NiCl2 masked the cytotoxic effects of these metal ions. These results demonstrate the importance of extracellular small molecular
weight metal ion chelators in altering the biological effects of metal ions at the level of metal uptake. 相似文献