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31.
Hepatic coma was induced in rats chronically treated with CCl4, by means of a single injection of ammonium acetate. The activities of glutamate decarboxylase (GAD) and GABA transaminase (GABA-T), as well as the synaptosomal uptake and release of [3H]GABA, were measured in the following brain areas of the comatose rats: cortex, striatum, hypothalamus, hippocampus, midbrain and cerebellum. Hepatic coma was associated with a general decrease of GAD activity, whereas GABA-T activity was diminished only in the hypothalamus, striatum and midbrain. During hepatic coma, the K+-stimulated [3H]GABA release was notably diminished in the striatum and cerebellum, whereas a significant increase was observed in the hippocampus. [3H]GABA uptake increased in most regions after CCl4 treatment, independently of the presence of coma. The results indicate that GABAergic transmission seems to be decreased in most cerebral regions during hepatic coma. 相似文献
32.
Analysing partitioning of recently fixed and of reserve carbon in reproductive Phaseolus vulgaris L. plants 总被引:3,自引:2,他引:1
Abstract. Partitioning of recently-fixed carbon among plant organs and subsequent distribution of reserve carbon were studied by supplying whole shoots of bean plants ( Phaseolus vulgaris L.) with 14 C-labelled CO2 of constant specific radioactivity throughout a photoperiod. The gain of tracer carbon in each part revealed net accumulation of recently-fixed carbon from direct fixation, import or both. Growth rate coefficients describing the present pattern of plant growth were calculated from ratios of tracer carbon to total carbon present in plant organs and were used to project future plant form. The period 10–20 d after the start of flowering was marked by a major increase in partitioning of recently-fixed carbon to reproductive growth. Growth rates for the plant and its parts during this period were projected on the basis of growth rate coefficients and were found to be similar to rates measured by gravimetric growth analysis. Changes in tracer carbon recovered in individual organs after chase periods of various lengths revealed net decreases for leaves and stems. About 9% of the carbon distributed to fruits came from reserves even in the absence of obvious stress. Respiratory loss during the chase period was determined from the progressive drop in recovery of the original tracer carbon. The methods are being applied to measure current net accumulation rates in studies of sink organ physiology, and to compare partitioning of recently-fixed and of stored carbon in several plant species under defined growth conditions. 相似文献
33.
J. A. BUNCE 《Plant, cell & environment》1988,11(3):205-208
Abstract. Gas exchange measurements were made on single leaves of three C3 and one C4 species at air speeds of 0.4 and 4.0 m s−1 to determine if boundary layer conductance substantially affected the substomatal pressure of carbon dioxide. Boundary layer conductances to water vapour were 0.4 to 0.5 mol m−2 s−1 at the lower air speed, and 1.2 to 1.5 mol m−2 s−1 at the higher air speed. Substomatal carbon dioxide pressures were about 5 Pa lower at low boundary layer conductance in the C3 species, and about 3 Pa lower in the C4 species when measurements were made at high and moderate photosynthetic photon flux densities. No evidence of stomatal adjustment to altered boundary layer conductance was found. Photosynthetic rates at high photon flux densities were reduced by about 20% at the low air speed in the C3 species. The commonly reported values of substomatal carbon dioxide pressure for C3 and C4 species were found to occur only when measurements were made at the higher air speed. 相似文献
34.
In vitro enzyme activities of glycolysis, pentose-phosphate pathway and dark CO2 fixation were assayed in batch cultures of heterotrophic Catharanthus roseus cells under various gassing rates and partial pressures of carbon dioxide. Detrimental effects of low pCO2 culture conditions on the growth characteristics could be linked to marked changes in levels of enzymes of primary metabolism during growth. The enzyme levels observed during the early stages of growth were found to be more stable when a constant pCO2 (20 mbar) was maintained and enabled exponential growth to be reached more rapidly.The importance of carbon dioxide as a conditioning factor of the culture medium is discussed. 相似文献
35.
Collagen gene expression during volume overload-induced cardiac hypertrophy was investigated in adult male rats. Hypertrophy of the left ventricle (22%) and right ventricle (37%) occurred following 27 days continuous exposure to 700 ppm carbon monoxide; hematocrit increased nearly 47%. To examine potential cellular and molecular control of restructuring in the heart, we investigated the expression of two specific procollagen mRNAs for collagen types which have different structural-functional roles [Type I (alpha-1) & Type IV]. Type I (interstitial) mRNA levels increased at least 100% relative to controls within 3 days of initial exposure to 700ppm CO, then declined afterwards; type IV(basement membrane) mRNA levels increased more modestly at first, and increased further afterwards. The ratio of type I/type IV RNA's also increased initially, then later declined, with the greatest differences in the relative responses of type I and IV mRNAs seen in the right ventricle. These data suggest that types I and IV collagen mRNA expression is not coordinately expressed during this type of volume overload-induced hypertrophy in rat heart. 相似文献
36.
Abstract. Gas exchange measurements were performed to test the hypothesis that failure of stomata to open in senescing leaves of Nicotiana glauca is caused by elevated concentrations of carbon dioxide in the intercellular spaces of leaf mesophyll tissue (ci ). Senescing leaves selected for experiments were completely chlorotic and lacked positive rates of photosynthesis. When stomata in detached epidermis from senescing leaves were illuminated in CO2-free air, they opened to similar apertures as those in detached epidermis from nonsenescing leaves. To compare the effects of changes in ci on stomatal responses of the two leaf types, leaf 'flags' of either nonsenescing or senescing leaves were illuminated at a photosynthetic photon flux density of 500 μmol m−2 s−1 in a gas exchange cuvette. Leaf temperatures were maintained at 23.5 ± 0.5°C, and vapour pressure differences between leaves and the air were maintained between 0.70 and 0.75kPa. Ci was adjusted by changing external concentrations of carbon dioxide in air circulating through the cuvette. Conductances and photosynthetic rates of nonsenescing leaves changed in response to changes in ci , but neither the conductances nor the photosynthetic rates of senescing leaves were affected significantly by changes in q. We conclude that guard cells of senescing leaves of Nicotiana glauca do not lose the capacity to respond to changes in carbon dioxide concentration and that increases in ci resulting from declining rates of mesophyll photosynthesis are not the sole cause of maintenance of stomatal closure during leaf senescence. The data suggest that factors external to guard cells may prevent them from responding to changes in carbon dioxide concentrations in intact senescing leaves. 相似文献
37.
Leaf photosynthetic rate is correlated with biomass and grain production in grain sorghum lines 总被引:11,自引:0,他引:11
Significant genetic variation in leaf photosynthetic rate has been reported in grain sorghum [Sorghum biocolor (L.) Moench]. The relationships between leaf photosynthetic rates and total biomass production and grain yield remain to be established and formed the purpose of this experiment. Twenty two grain sorghum parent lines were tested in the field during the 1988 growing season under well-watered and water-limited conditions. Net carbon assimilation rates were measured at mid-day during the 30 day period from panicle initiation to head exertion on upper-most fully expanded leaves using a portable photosynthesis system (LI-6200). Total biomass and grain production were determined at physiological maturity. The lines exhibited significant genetic variation in leaf photosynthetic rate, total biomass production and grain yield. Significant positive correlations existed between leaf photosynthesis and total biomass and grain production under both well-watered and water-limited conditions. The results suggest that leaf photosynthetic rate measured prior to flowering is a good indicator of productivity in grain sorghum. 相似文献
38.
Photoautotrophic and photomixotrophic growth of strawberry plantlets in vitro and changes in nutrient composition of the medium 总被引:3,自引:0,他引:3
T. Kozai K. Iwabuchi K. Watanabe I. Watanabe 《Plant Cell, Tissue and Organ Culture》1991,25(2):107-115
Explants excised from strawberry (Fragaria x ananassa Duch.) plantlets were cultured in vitro for 21 days on half-strength MS (Murashige & Skoog 1962) basal liquid medium with 20 g l-1 sucrose and without sugar in the vessels capped with gas permeable microporous polypropylene film. The experiments were conducted under CO2 nonenriched (350–450 mol mol-1 in the culture room) and CO2 enriched (2,000 mol mol-1 during the photoperiod in the culture room) conditions with a PPF (photosynthetic photon flux) of 200 mol m-2 s-1. The CO2 concentration in the vessels decreased to approximately 200 mol mol-1 during the photoperiod on day 21 under CO2 nonenriched conditions. The fresh and dry weight, net photosynthetic rate (NPR) per plantlet, NPR per g leaf fresh weight, NPR per g leaf dry weight, the number of unfolded leaves, and ion uptake of PO4
3-, NO3
-, Ca2+, Mg2+ and K+ on day 21 were the greatest under photoautotrophic (no sugar in the medium) and CO2 enriched conditions. The residual percent of PO4
3- was 3% on day 21 under photoautotrophic and CO2 enriched conditions.Abbreviations MS
Murashige & Skoog (1962) basal medium composition
- NPR
net photosynthetic rate
- PPF
photosynthetic photon flux 相似文献
39.
C. Andrew Cole 《Wetlands Ecology and Management》1992,2(3):135-142
An early successional wetland complex on a reclaimed surface coal mine in southern Illinois was studied 1985–1987. Seasonally, biomass was low, with above-ground values of 10–210g m–2 and below-ground biomass of 1.5–2435 g m–2. Biomass peaked in spring and did not vary much throughout the remainder of the growing season. Stem densities were high (179–1467 m–2) because large numbers of seedlings became established as falling water levels exposed large areas of mudflats. Fluctuating water levels led to a lack of community zonation. Species diversity (H) was low to moderate over all sites with diversity values ranging between 1.86 and 3.27. 相似文献
40.
ACladosporium species produced large amounts of cellulase enzyme components when grown in shake-culture with medium containing carboxymethylcellulose. There was significantly less activity when Avicel, filter paper or cotton were used as substrates. KNO3 was better than NH4Cl or urea for the production of cellulase. Tween 80 at 0.1% (w/v) increased the production of cellulase by 1.5 to 4.5-fold. All the cellulase components were optimally active in the assay at pH 5.0 and 60°C. 相似文献