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981.
Summary Three gram varieties varying in susceptibility to pre-emergence damping-off caused byRhizoctonia bataticola were compared for amounts of seed exudation. The results showed that the greatest seed exudation occurred with the variety G-130 which is the most susceptible to pre-emergence damping-off compared with the resistant varieties BG-203 and C-214. Germinating gram seeds exuded greater quantities of soluble carbohydrate and amino acids when incubated at 35°C than at 15 or 25°C. Exudates from seeds germinated at 35°C stimulated more mycelial growth ofR. bataticola than did exudates from seeds incubated at 15 or 25°C. Evidence is presented suggesting that increased seed exudation is a major factor contributing to increased pre-emergence damping-off of gram seedlings byR. bataticola at high temperatures. 相似文献
982.
The temperature ranges for axenic growth of Entamoeba histolytica strain HM-1 and Entamoeba invadens strain 165 clone II in TYI-S-33 medium were: 32 to 40 C for E. histolytica with an optimum of 35.5 to 37 C; whereas the range for E. invadens 165 II was 20 to 30 C, optimum 24 to 27 C. Growth of strain HM-1 at 40 C was dependent upon the cell density of the culture used as a source of the inoculum. Clonal growth in agar was used to assay survival of Entamoeba spp. trophozoites after exposure to deleterious physical conditions. The lowest temperature for thermal killing of E. histolytica HM-1 was 41.5 C and for E. invadens 165, 35.5 C. Both were killed rapidly at 42 C, but slowly at 0 C. Killing of E. histolytica HM-1 trophozoites by exposure to increased oxygen tensions was a function of temperature and time. At 24 C and 35.5 C, there was little loss of viability during the first 7 hr exposure, then killing was quite rapid. The cells were killed sooner if the medium was preexposed to air. In contrast, at 0 C there was less killing by oxygen. E. invadens 165 II appeared to be more oxygen sensitive at 24 than at 0 C. Other E. histolytica strains tested were similar to HM-1 in their responses to temperature and air. 相似文献
983.
Seeds (nutlets) of Rumex obtusifolius L. fail to germinate in darkness at 25° C, but are stimulated by short exposure to red light (R) the effectiveness of which can be negated by a subsequent short exposure to far red light (F) indicating phytochrome control. Short periods of elevated temperature treatment (e.g. 5 min at 35° C) can induce complete germination in darkness. Although short F cannot revert the effect of 35° C treatment, cycling the phytochrome pool by exposure to short R before short F results in reversion of at least 50% of the population. Prolonged or intermittent F can also revert the germination induced by 35° C treatment. The effect of elevated temperature treatment is interpreted on the basis of two possible models; (i) that it increases the sensitivity of the seeds to a low level of pre-existing active form of phytochrome (Pfr) (ii) that it induces the appearance of Pfr in the dark. In both cases it is envisaged that elevated temperature treatment and Pfr control germination at a common point in the series of reactions that lead to germination.Abbreviations D
Dark
- F
far red light
- P
phytochrome
- Pr
red absorbing form of P
- Pfr
far red absorbing form of P
- R
red light 相似文献
984.
Estimating net primary productivity of grasslands from field biomass measurements in temperate northern China 总被引:16,自引:0,他引:16
Data on field biomass measurements in temperate grasslands of northern China (141 samples from 74 sites) were obtained from
23 Chinese journals, reports and books. Net primary productivity (NPP) of grasslands was estimated using three algorithms
(peak live biomass, peak standing crop and maximum minus minimum live biomass), respectively, based on availability of biomass
data in sites. 135 samples which have aboveground biomass (AGB) measurements, have peak AGB ranges from 20 to 2021 g m–2 (mean = 325.3) and the aboveground NPP (ANPP) ranges from 15 to 1647.1 g m–2 per year (mean = 295.7). 72 samples which have belowground biomass (BGB) measurements, have peak BGB ranges from 226.5 to
12827.5 g m–2 (mean = 3116) and the belowground NPP (BNPP) ranges from 15.8 to 12827.5 g m–2 per year (mean = 2425.6). In total 66 samples have the total NPP (TNPP), ranging from 55.3 to 13347.8 g m–2 per year (mean = 2980.3). Mean peak biomass and NPP varied from different geographical sampling locations, but they had a
general rough regularity in ten grasslands. Meadow, mountain and alpine grasslands had high biomass and NPP (sometimes including
saline grassland). Forested steppe, saline grassland and desert had median values. Meadowed and typical steppes had low biomass
and NPP (sometimes including desert). The lowest biomass and NPP occurred in deserted steppe and stepped desert. Grassland
ANPP has significant positive relationships with annual and summer precipitation as well as summer temperature (all p<0.01).
However, grassland BNPP and TNPP have more significant negative relationships with summer temperature (p<0.01) than with annual
temperature (p<0.05). The analysis of climate – productivity correlations implied that aboveground productivity is more controlled
by rainfall, whereas belowground and total productivity is more influenced by temperature in the temperate grasslands of northern
China. The present study might underestimate grassland NPP in northern China due to limitation of biomass measurements. Data
on relative long-term aboveground and belowground biomass dynamics, as well as data of standing dead matter, litterfall, decomposition
and turnover, are required if grassland NPP is to be more accurately estimated and the role of temperate grasslands in the
regional to global carbon cycles is to be fully appreciated.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
985.
Temperature-sensitive phenotypes of peroxisome-assembly processes represent the milder forms of human peroxisome-biogenesis disorders. 总被引:2,自引:1,他引:1
A Imamura T Tsukamoto N Shimozawa Y Suzuki Z Zhang T Imanaka Y Fujiki T Orii N Kondo T Osumi 《American journal of human genetics》1998,62(6):1539-1543
986.
Marinus C. Pannevis Dominic F. Houlihan 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1992,162(5):393-400
Summary To establish the energetic cost of protein synthesis, isolated trout hepatocytes were used to measure protein synthesis and respiration simultaneously at a variety of temperatures. The presence of bovine serum albumin was essential for the viability of isolated hepatocytes during isolation, but, in order to measure protein synthesis rates, oxygen consumption rates and RNA-to-protein ratios, BSA had to be washed from the cells. Isolated hepatocytes were found to be capable of protein synthesis and oxygen consumption at constant rates over a wide range of oxygen tension. Cycloheximide was used to inhibit protein synthesis. Isolated hepatocytes used on average 79.7±9.5% of their total oxygen consumption on cycloheximide-sensitive protein synthesis and 2.8±2.8% on maintaining ouabain-sensitive Na+/K+-ATPase activity. The energetic cost of protein synthesis in terms of moles of adenosine triphosphate per gram of protein synthesis decreased with increasing rates of protein synthesis at higher temperatures. It is suggested that the energetic cost consists of a fixed (independent of synthesis rate) and a variable component (dependent on synthesis rate).Abbreviations BSA
bovine serum albumin
- dpm
disintegrations per min
-
k
s
fractional rate of protein synthesis
- HEPES
N-2-hydroxyethylpiperazine-N-2-ethane sulphonic acid
- PHE
phenylalanine; PO2 oxygen tension
- PCA
perchloric acid 相似文献
987.
Marianna Max Michael Menaker 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,170(4):479-489
Summary The pineal gland of the rainbow trout, Salmo gairdneri, when kept under in vitro perifusion culture conditions, displays a consistently elevated level of melatonin production in darkness (Gern and Greenhouse 1988). Upon light exposure melatonin production falls and stabilizes at a new lower level that is dependent upon the irradiance of the stimulus. To achieve the maximal response for each irradiance, the duration of the stimulus must exceed 30 min. The response amplitude is maximally sensitive to photons presented over durations of 30–45 min; is very insensitive to shorter light exposures; and is maintained with no evidence of adaptation over longer exposures. Temperature plays a role in regulation of melatonin production both in darkness and during light exposure; increased temperature increases melatonin production in darkness and also increases the sensitivity of the response to light. The action spectrum for the response is best fit by the Dartnall nomogram for a vitamin A1 based rhodopsin with peak sensitivity near 500 nm. The possible adaptive significance of control of melatonin synthesis by light and temperature is considered.Abbreviations
LD
lightdark cycle
-
RIA
radioimmunoassay
-
I
125
Iodine
-
HIOMT
hydroxyindole-O-methyltransferase 相似文献
988.
Robert J. Full Alexa Tullis 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(5):573-581
Summary The capacity for sustained, terrestrial locomotion in the cockroach. Blaberus discoidalis, was determined in relation to running speed, metabolic cost, aerobic capacity, and ambient temperature (T
a=15, 23, and 34°C; acclimation temperature=24°C). Steady-state thoracic temperature (T
tss) increased linearly with speed at each T
a.The difference between T
tss and T
awas similar at each experimental temperature with a maximum increase of 7°C. Steady-state oxygen consumption (VO2ss) increased linearly with speed at each T
aand had a low thermal dependence (Q10=1.0-1.4). The minimum cost of locomotion (the slope of the VO2ss versus speed function) was independent of T
a.Cockroaches attained a maximal oxygen consumption (VO2max). increased with T
afrom 2.1 ml O2·g-1·h-1 at 15°C to 4.9 ml O2·g-1·h-1 at 23°C, but showed no further increase at 34°C, VO2max increased 23-fold over resting VO2 at 23°C, 10-fold at 34°C, and 15-fold at 15°C. Endurance correlated with the speed at which VO2max was attained (MAS, maximal aerobic speed). Temperature affected the kinematics of locomotion. compared to cockroaches running at the same speed, but higher temperatures (23–34°C), low temperature (15°C) increased protraction time, reduced stride frequency, and reduced stability by increasing body pitching. The thermal independence of the minimum cost of locomotion (Cmin), the low thermal dependence of VO2ss (i.e., y-intercept of the VO2ss versus speed function), and a typical Q10 of 2.0 for VO2max combined to increase MAS and endurance in B. discoidalis when T
awas increased from 15 to 23°C. Exerciserelated endothermy enabled running cockroaches to attain a greater VO2max, metabolic scope, and endurance capacity at 23°C than would be possible if T
tss remained equal to T
a. The MAS of B. discoidalis was similar to that of other arthropods that use trachea, but was 2-fold greater than ectotherms, such as salamanders, frogs, and crabs of a comparable body mass.Abbreviations
T
a
ambient temperature
-
T
t
thoracic temperature
-
T
tss
steady state thoracic temperature during exercise
-
T
trest
thoracic temperature during rest
- VO2
oxygen consumption
- VO2rest
oxygen consumption during rest
- VO2ss
steady-state oxygen consumption during exercise
- VO2max
maximal oxygen consumption; MAS maximum aerobic speed
-
C
min
minimum cost of locomotion
-
t
end
endurance time 相似文献
989.
Summary Frog pancreatic tissue was pulse-labelled in vitro with 3H-leucine and protein transport was studied in exocrine cells by electron microscope autoradiography. The proteins appeared to be synthesized in the RER and transported to the secretory granules along a similar route and with the same velocity as previously described under in vitro conditions.Evidence was obtained for the involvement of the vesicular and tubular elements at the periphery of the Golgi system in transferring protein from the RER to the Golgi cisternae.Kinetics of the release of newly synthesized proteins from the RER and their appearance in the condensing vacuoles are discussed and related to results reported from other tissues.The transport velocity in this poikilothermic system was studied in relation to the incubation temperature and compared with results reported from its mammalian counterpart. At temperatures between 20 and 30° C intracellular protein transport occurs faster in the frog than in the Guinea pig pancreas. At higher temperature the transport process was severely disturbed in the frog. 相似文献
990.
Alan H. Gibson William R. Scowcroft Jeffrey J. Child Janet D. Pagan 《Archives of microbiology》1976,108(1):45-54
Nutritional and physical conditions affecting nitrogenase activity in the strain of cowpea rhizobia, 32H1, were examined using cultures grown on agar medium. Arabinose in the basic medium (CS7) could be replaced by ribose, xylose, or glycerol, but mannitol, glucose, sucrose, or galactose only supported low nitrogenase (C2H2 reduction) activity. Succinate could be replaced by pyruvate, fumarate, malate, or 2-oxoglutarate, but without any carboxylic acid, nitrogenase activity was low or undetectable unless a high level of arabinose was provided. Inositol was not essential. Several nitrogen sources could replace glutamine including glutamate, urea, (NH4)2SO4 and asparagine.The maximum nitrogenase activity of cultures grown in air at 30°C was observed under assay conditions of pO2=0.20–0.25 atm and 30°C incubation. Greatest activity occurred after a period of rapid bacterial growth, when viable cell count was relatively constant.Compared with results obtained on the CS7 medium, nitrogenase activity could be substantially increased and/or sustained for longer periods of time by using 12.5 mM succinate and 100 mM arabinose, by increasing phosphate concentration from 2 to 30–50 mM, or by culturing the bacteria at 25°C. 相似文献