The Effect of VA Mycorrhizal Infection and Phosphorus Status on Sunflower Hydraulic and Stomatal Properties

Koide, R. 1985. The effect of VA mycorrhizal infection and phosphorusstatus on sunflower hydraulic and stomatal properties.—J. exp. Bot. 36: 1087–1098. Mycorrhizal (M) and non-mycorrhizal (NM) sunflower plants weregrown in a soil of low phosphorus availability (with and withoutphosphorus amendment) and in a soil of moderate phosphorus availability(without phosphorus amendment). Using the Ohm's law analogyand measured leaf water potentials, stem water potentials, andtranspiration rates, hydraulic resistances were calculated forthe whole plant, leaf, and below leaf components. Mycorrhizalinfection (as high as 89%) was shown to have no effect on theintrinsic hydraulic properties of the soil/plant system overa wide range of transpiration rates in either soil when M andNM plants of equivalent root length were compared. When grownin the soil of moderate phosphorus availability, calculatedhydraulic resistances under given environmental conditions werethe same for M and NM plants, as were stomatal resistances andtranspiration rates. When grown in the soil of low phosphorusavailability, calculated values of hydraulic resistance werelower for M plants than for NM plants under given sets of environmentalconditions. These differences in calculated hydraulic resistancewere not due to a difference in the intrinsic hydraulic propertiesof M and NM plants. The differences were evident because stomatalresistances were lower and transpiration rates higher for Mplants and because hydraulic resistance varied inversely withtranspiration rate. When plants of significantly greater rootlength were compared to plants of lesser root length, the calculatedhydraulic resistances under given environmental conditions weremuch lower for the plants of greater root length. This differencewas largely due to a difference in the intrinsic hydraulic propertiesbetween large and small plants, and not because of differencesin transpiration rate. The elevated transpiration rates exhibitedby M plants were attributed to an enhanced phosphorus status.Short term phosphorus amendments made to phosphorus-deficientNM plants improved transpiration; transpiration rates were similarfor M and NM plants before NM plants became phosphorus-deficient,and phosphorus-amended M and NM plants had similar transpirationrates. The data are discussed in relation to other reports ofmycorrhizal influence on hydraulic and stomatal resistances.Possible mechanisms for the influence of infection on stomatalresistance are also briefly discussed. Key words: Hydraulic resistance, stomatal resistance, mycorrhizas     

The Effect of Digestive Capacity on the Intake Rate of Toxic and Non-Toxic Prey in an Ecological Context

Digestive capacity often limits food intake rate in animals. Many species can flexibly adjust digestive organ mass, enabling them to increase intake rate in times of increased energy requirement and/or scarcity of high-quality prey. However, some prey species are defended by secondary compounds, thereby forcing a toxin limitation on the forager’s intake rate, a constraint that potentially cannot be alleviated by enlarging digestive capacity. Hence, physiological flexibility may have a differential effect on intake of different prey types, and consequently on dietary preferences. We tested this effect in red knots (Calidris canutus canutus), medium-sized migratory shorebirds that feed on hard-shelled, usually mollusc, prey. Because they ingest their prey whole and crush the shell in their gizzard, the intake rate of red knots is generally constrained by digestive capacity. However, one of their main prey, the bivalve Loripes lucinalis, imposes a toxin constraint due to its symbiosis with sulphide-oxidizing bacteria. We manipulated gizzard sizes of red knots through prolonged exposure to hard-shelled or soft foods. We then measured maximum intake rates of toxic Loripes versus a non-toxic bivalve, Dosinia isocardia. We found that intake of Dosinia exponentially increased with gizzard mass, confirming earlier results with non-toxic prey, whereas intake of Loripes was independent of gizzard mass. Using linear programming, we show that this leads to markedly different expected diet preferences in red knots that try to maximize energy intake rate with a small versus a large gizzard. Intra- and inter-individual variation in digestive capacity is found in many animal species. Hence, the here proposed functional link with individual differences in foraging decisions may be general. We emphasize the potential relevance of individual variation in physiology when studying trophic interactions.     

Influence of Coliform Source on Evaluation of Membrane Filters

Four brands of membrane filters were examined for total and fecal coliform recovery performance by two experimental approaches. Using diluted EC broth cultures of water samples, Johns-Manville filters were superior to Sartorius filters for fecal coliform but equivalent for total coliform recovery. Using river water samples, Johns-Manville filters were superior to Sartorius filters for total coliform but equivalent for fecal coliform recovery. No differences were observed between Johns-Manville and Millipore or Millipore and Sartorius filters for total or fecal coliform recoveries using either approach, nor was any difference observed between Millipore and Gelman filters for fecal coliform recovery from river water samples. These results indicate that the source of the coliform bacteria has an important influence on the conclusions of membrane filter evaluation studies.     

The Influence of Hydraulic Gradient and Rate of Erosion on Hydraulic Conductivity of Sand-Bentonite Mixtures

The use of sand-bentonite mixtures as liner materials for waste disposal is very common. In the laboratory, this study investigated hydraulic conductivities of such mixtures at different hydraulic pressure (hydraulic gradient), dry unit weights, and bentonite contents. The bentonite content and the dry unit weight of the samples were both important factors, significantly affecting the hydraulic conductivity of the liner material. A bentonite content of 5% was found to be sufficient in reaching a hydraulic conductivity under 10^?9 m/s, when the liner material was compacted under near optimum moisture content. Nevertheless, hydraulic conductivity was found to increase with hydraulic pressures, especially for the 5% bentonite mixtures subjected to pressure above 40 kPa, suggesting some degree of internal erosion (washing out of particles).

Therefore, this paper discuses the influence of internal erosion of the mixtures under a given hydraulic gradient, on the final value of k. The internal erosion of the tested mixtures was found to be influenced mainly by porosity, which can be reduced by properly selecting the sand particle size distribution and the bentonite percentage. Furthermore, this study proposed an empirical expression to predict the risk of internal erosion in the sand-bentonite mixtures, and therefore of k being higher than planned. This expression can be used for designing bentonite content and compaction to achieve very low permeability.     

The Effect of Reservoirs on Phosphorus Concentration

The annual average degree of phosphorus retention (both TP and OP) in reservoirs was found to depend mainly on the theoretical retention time (RT). The phosphorus retention (RP) is shown for some reservoirs in Czech Republic to be well approximated (standard deviation = 10.9) with RP_(TP) = 74.7* (1-exp(-0.0255* RT)) (N = 38, 7 ≤ RT ≤ 604 days). The inclusion of 13 additional reservoirs for which data were assembled from literature resulted in an almost identical relationship: RP_(TP) = 76.1* (1-exp(-0.0282* RT)) (N = 51, range of RT nearly unchanged). The retention of soluble reactive phosphorus RP_(OP) studied on data from literature seems to be higher than that of TP. Statistical comparison with data for RP_(TP) of lakes has shown a significantly lower retention in lakes than in reservoirs for comparable RP, resulting in RP_(TP) = 66.0* (1-exp(-0.00419* RT)) (N = 59, 5.8 ≤ RT ≤ 260000 days). The differences between RP_(OP) and RP_(TP) and differentiation of lakes and reservoirs are discussed and a need for more thorough theoretical analysis stressed. Consequences for watershed management are summarized.     

氮磷含量对微生物修复油污土壤的影响

以甘肃西峰市油田附近土壤中的土著微生物为菌源,富集培养、筛选分离得到5种菌属的降解石油菌。通过向油污土壤中添加尿素、磷酸氢二铵的现场试验,历时63 d。研究了氮、磷含量在由5种菌制得的混合菌剂对油污的降解中的影响。结果表明,人为增加土壤中氮、磷元素对混合微生物菌剂修复油污土壤具有显著促进效果。在含油量1.5%和3%的污染土壤中,氮、磷元素的变化表现为两个阶段,前28 d氮、磷含量迅速减少,后35 d氮、磷含量变化表现出波动性,且在浓度为3%的污染土壤中,微生物菌剂的修复效果更为明显,最大降油率达到52.5%。利用GC-MS测定分析混合菌剂对石油主要成分藿烷的降解程度和演化规律的研究表明,混合菌剂对油污土壤中霍烷类化合物的降解均在80%以上,降解率较高,其中最高的是芒柄花根烷,达到86.3%.     

The Effect of Outflow Depth on Phosphorus Retention in a Small,Hypertrophic Temperate Reservoirwith Short Hydraulic Residence Time

Stratification and phosphorus fluxes (input, output, sedimentation, and release from sediments) were studied in České údolí Reservoir (49°43′N, 13°21′E; V – 2.65 × 10⁶ m³; A – 1.04 × 10⁶ m²; z_max – 5.5 m; surface altitude – 314 m a.s.l.) during two summer stratification periods which differed in outlet operation and in hydraulic residence time (1997: surface outlets and 14 days; 1998: bottom outlets and 23 days). Use of bottom outlets resulted in weaker thermal stratification, a less pronounced oxygen deficit in the hypolimnion, and significantly lower P retention (17%) in comparison with surface discharge (42%). Factors apparently contributing to lower retention of P during the use of bottom outlets were: (i) faster flushing of the hypolimnion which intensified longitudinal transport of particles, (ii) more intense P release from sediments due to a lower concentration of nitrate in the water column and to more frequent contact of sediments in the shallows with water of pH >9. During both periods, phytoplankton production was limited only by light, not by nutrients. Phytoplankton biomass was comparable in both years despite some differences in vertical distribution.     

Effect of Specific Growth Rate on Fermentative Capacity of Baker’s Yeast

The specific growth rate is a key control parameter in the industrial production of baker’s yeast. Nevertheless, quantitative data describing its effect on fermentative capacity are not available from the literature. In this study, the effect of the specific growth rate on the physiology and fermentative capacity of an industrial Saccharomyces cerevisiae strain in aerobic, glucose-limited chemostat cultures was investigated. At specific growth rates (dilution rates, D) below 0.28 h⁻¹, glucose metabolism was fully respiratory. Above this dilution rate, respirofermentative metabolism set in, with ethanol production rates of up to 14 mmol of ethanol · g of biomass⁻¹ · h⁻¹ at D = 0.40 h⁻¹. A substantial fermentative capacity (assayed offline as ethanol production rate under anaerobic conditions) was found in cultures in which no ethanol was detectable (D < 0.28 h⁻¹). This fermentative capacity increased with increasing dilution rates, from 10.0 mmol of ethanol · g of dry yeast biomass⁻¹ · h⁻¹ at D = 0.025 h⁻¹ to 20.5 mmol of ethanol · g of dry yeast biomass⁻¹ · h⁻¹ at D = 0.28 h⁻¹. At even higher dilution rates, the fermentative capacity showed only a small further increase, up to 22.0 mmol of ethanol · g of dry yeast biomass⁻¹ · h⁻¹ at D = 0.40 h⁻¹. The activities of all glycolytic enzymes, pyruvate decarboxylase, and alcohol dehydrogenase were determined in cell extracts. Only the in vitro activities of pyruvate decarboxylase and phosphofructokinase showed a clear positive correlation with fermentative capacity. These enzymes are interesting targets for overexpression in attempts to improve the fermentative capacity of aerobic cultures grown at low specific growth rates.     

The Behavior of Organic Phosphorus under Non-Point Source Wastewater in the Presence of Phototrophic Periphyton

To understand the role of ubiquitous phototrophic periphyton in aquatic ecosystem on the biogeochemical cycling of organic phosphorus, the conversion and removal kinetic characteristics of organic phosphorus (Porg) such as adenosine triphosphate (ATP) were investigated in the presence of the periphyton cultured in artificial non-point source wastewater. The preliminary results showed that the periphyton was very powerful in converting P_org evidenced by the fact that inorganic phosphorus (P_inorg) content in solution increased from about 0.7 to 14.3 mg P L⁻¹ in 48 hours in the presence of 0.6 g L⁻¹ periphyton. This was because the periphyton could produce abundant phosphatases that benefited the conversion of P_org to P_inrog. Moreover, this conversion process was described more suitable by the pseudo-first-order kinetic model. The periphyton was also effective in removing P_org, which showed that the P_org can be completely removed even when the initial P_org concentration was as high as 13 mg P L⁻¹ in 48 hours in the presence of 1.6 g L⁻¹ periphyton. Furthermore, it was found that biosorption dominated the P_org removal process and exhibited the characteristics of physical adsorption. However, this biosorption process by the periphyton was significantly influenced by biomass (absorbent dosage) and temperature. This work provides insights into P_org biogeochemical circulation of aquatic ecosystem that contained the periphyton or similar microbial aggregates.     

比生长速率和氮源对毕赤酵母生产重组鲈鱼生长激素的影响

对毕赤酵母胞内表达重组鲈鱼生长激素(rljGH)的发酵罐上生产进行了研究.建立了指数流加甲醇的策略并考察了不同比生长速率对rljGH生产的影响.结果表明,随着比生长速率的增加,平均比生产速率相应增加,但是胞内持续积累rljGH的时间减少.最大比rljGH产量(0.58 mg/g WCW)在比生长速率为0.029/h时获得.进一步考察了在诱导阶段添加硫酸铵、蛋白胨和酵母抽提物的影响.结果表明,添加硫酸铵和蛋白胨对于rljGH生产没有显著影响;添加2.5 g/L酵母抽提物有助于胞内rljGH的积累,并使胞内积累持续时间由17 h增加到23 h,提高了发酵稳定性.     

Effect of Precursor Loading on the Synthesis Rate and Release of Dopamine and Serotonin in the Striatum: A Microdialysis Study in Conscious Rats

The effects of systemic administration of tyrosine and phenylalanine on the extracellular levels of tyrosine and dopamine were determined by microdialysis in the striatum of awake rats. In addition, the effects of these precursors on in vivo 3,4-dihydroxyphenylalanine (DOPA) formation were determined during continuous infusion of a decarboxylase inhibitor. Both precursors increased the dialysate levels of tyrosine sixfold, but only phenylalanine administration stimulated DOPA formation. However, neither precursor affected the release of dopamine. When the precursor administration was repeated in rats in which the release of dopamine was stimulated by haloperidol pretreatment, again no effect was seen on the release of dopamine. Systemic administration of tryptophan (100 mg/kg, i.p.) during continuous infusion of a decarboxylase inhibitor induced a threefold increase in the formation of 5-hydroxytryptophan and caused an increase in the release of serotonin during infusion of an uptake inhibitor to about 150% of controls. Finally, we investigated whether dietary precursors were able to influence neurotransmitter formation and release. Rats trained to consume their daily food in a period of 2 h were implanted with microdialysis probes. Scheduled eating induced a small increase in the extracellular levels of tyrosine (135% of controls), but the release of dopamine and the formation of 5-hydroxytryptophan during continuous infusion of a decarboxylase inhibitor were not affected.     

Binding of Rat Brain Hexokinase to Recombinant Yeast Mitochondria: Effect of Environmental Factors and the Source of Porin

Heterologous binding of rat brain hexokinase to wild type, porinless, and recombinant yeast mitochondria expressing human porin was assessed, partially characterized, and compared to that in the homologous system (rat liver mitochondria). With porin-containing yeast mitochondria it is shown that (i) a significant, saturatable association occurs; (ii) its extent and apparent affinity, correlated with the origin of porin, are enhanced in the presence of dextran; (iii) the binding requires Mg ions and apparently follows a complex cooperative mechanism. This heterologous association does not seem to differ fundamentally from that in the homologous system and represents a good basis for molecular studies in yeast. With porinless yeast mitochondria, binding occurs at much lower affinity, but to many more sites per mitochondrion. The results indicating a major but not exclusive role for porin in the binding are discussed in terms of (i) the mode and mechanism of binding, and (ii) the suitability of the rat hexokinase–yeast mitochondria couple for the study of heterogeneous catalysis in reconstituted cellular model systems.     

The Effect of Atrophic Rhinitis on Growth Rate

Growth rate in pigs with turbinate atrophy was compared to growth rate in pigs without turbinate atrophy in 9 herds with atrophic rhinitis (AR) in which toxigenic strains of Pasteurella multocida had been isolated. Average reduction in growth rate in pigs with severe turbinate atrophy was 4.7 % as compared to pigs without turbinate atrophy. The difference was statistically significant only in some herds. Pigs with moderate AR gained on average 1.1 % less than unaffected ones. Thus, the study supports the assumption that AR is of economic significance in modern pig farming.     

The Effect of Flower Induction on the Rate of Leaf Initiation

Vegetative plants of four short-day and five long-day specieswere exposed to inductive or non-inductive daylengths continuously,or to inductive conditions for just long enough to induce flowering.One day-neutral species was given long days throughout the experiment.The rate of leaf initiation was significantly greater in floweringthan in vegetative shoots in all photoperiodically sensitivespecies following induction until the formation of a terminalflower. A significant increase in the rate of leaf initiationwas also noted when floral initials began to appear in the day-neutralspecies. It is concluded that floral induction and stimulationof leaf initiation are likely to be universally associated whetherspecies are photoperiodically sensitive or not. It is also suggestedthat, together with apical elongation and early developmentof axillary buds, this stimulation is an essential step in themorphological sequence by which flower initials are produced.     

Binding of Radioactive Benzylpenicillin to Sporulating Bacillus Cultures: Chemistry and Fluctuations in Specific Binding Capacity

The chemistry of the binding of (14)C-benzylpenicillin to sporulating cultures of Bacillus megaterium and B. subtilis is similar to that in a 4-hr vegetative culture of Staphylococcus aureus. Unlabeled penicillins prevent the binding of (14)C-benzylpenicillin, but benzylpenicilloic acid and benzylpenilloic acid do not. Bound antibiotic can be removed from cells with neutral hydroxylamine at 25 C. Sporulating cultures display two intervals of enhanced binding, whereas binding to stationaryphase S. aureus cells remains constant. The first period of increased binding activity occurs during formation of the spore septum or cell wall primordium development, and the second coincides with cortex biosynthesis.     

The Effect of Dietary Protein on the Renal Gluconeogenic Capacity of Rats

Kidney cortex slices and homogenates of rats fed a high protein diet for 7 to 14 days had higher gluconeogenic capacity from fructose or oxaloacetate and fructose 6-phosphate or fructose 1, 6-diphosphate, respectively, than those of rats fed a high carbohydrate diet containing adequate protein. Levels of gluconeogenic enzymes, especially glucose 6-phosphatase and phosphoenolpyruvate carboxykinase, are good indicators of an increased capacity of renal gluconeogenesis of rats fed the high protein diet. Activities of renal glycolytic enzymes and glutamic-oxaloacetic and glutamic-pyruvic transaminases did not change and citrate concentrations of rat kidney decreased by feeding the high protein diet. Urinary excretion of ammonia of rats fed the high protein diet increased.     

Toxicological Approach for Assessing the Heavy Metal Binding Capacity of Soils

A toxicological approach was taken to determine the heavy metal binding capacity of soils. A soil heavy metal binding capacity (SHMBC) methodology was developed and was based on the use of the MetPLATE ^TM toxicity test kit, a bioassay that is specific for heavy metal toxicity. SHMBC test is based on the heavy metal binding capacity (HMBC) concept that has been considered in the assessment of the metal binding capacity of surface waters (Huang et al., 1999 Huang, F., Bitton, G. and Kong, I.-C. 1999. Determination of the heavy metal binding capacity of aquatic samples using MetPLATE?: a preliminary study. Sci. Total Environ, 234: 139–145.  [Google Scholar]) and solid wastes landfill leachates (Ward et al., 2005 Ward, M., Bitton, G. and Townsend, T. 2005. Heavy metal binding capacity (HMBC) of municipal solid waste landfill leachates. Chemosphere, 60: 206–215. [Crossref], [PubMed], [Web of Science ®] [Google Scholar]). SHMBC is the ratio of the EC ₅₀ of an added metal in a soil sample divided by the EC ₅₀ of a metal in a reference soil (clean Ottawa sand). A higher SHMBC value indicates higher metal binding to soil and lower bioavailability and potential toxicity to the test bacteria.

Five soils (two sandy soils, two organic soils and a clay soil) were used to determine their binding capacity towards Cu, Zn, and Hg, using the developed SHMBC test. The test measured the ability of the solids to reduce metal bioavailability and toxicity. SHMBC was highest for the clay soil and lowest for the sandy soils. The potential application of this relatively rapid (a few hours) test to predict metal toxicity to terrestrial plants is discussed.