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81.
We investigated in situ the temporal patterns and spatial extent of organic acid anion exudation into the rhizosphere solution of Lupinus albus, and its relation with the nutrient anions phosphate, nitrate and sulfate by means of a rhizobox micro suction cup method
under P sufficient conditions. We compared the soil solution in the rhizosphere of cluster roots with that in the vicinity
of normal roots, nodules and bulk soil. Compared to the other rhizosphere and soil compartments, concentrations of organic
acid anions were higher in the vicinity of cluster roots during the exudative burst (citrate, oxalate) and nodules (acetate,
malate), while concentrations of inorganic nutrient anions were highest in the bulk soil. Both active cluster roots and nodules
were most efficient in taking up nitrate and phosphate. The intensity of citrate exudation by cluster roots was highly variable.
The overall temporal patterns during the lifetime of cluster roots were overlaid by a diurnal pattern, i.e. in most cases,
the exudation burst consisted of one or more peaks occurring in the afternoon. Multiple exudation peaks occurred daily or
were separated by 1 or 2 days. Although citrate concentrations decreased with distance from the cluster root apex, they were
still significantly higher at a distance of 6 to 10 mm than in the bulk soil. Phosphate concentrations were extremely variable
in the proximity of cluster roots. While our results indicate that under P sufficient conditions cluster roots take up phosphate
during their entire life time, the influence of citrate exudation on phosphate mobilization from soil could not be assessed
conclusively because of the complex interactions between P uptake, organic acid anion exudation and P mobilization. However,
we observed indications of P mobilization concurrent with the highest measured citrate concentrations. In conclusion, this
study provides semiquantitative in situ data on the reactivity of different root segments of L. albus L. in terms of root exudation and nutrient uptake under nutrient sufficient conditions, in particular on the temporal variability
during the lifetime of cluster roots. 相似文献
82.
83.
Michael?P.?MatottEmail author Philip?J.?Motta Robert?E.?Hueter 《Environmental Biology of Fishes》2005,74(2):163-174
Synopsis Studies of feeding in bony fishes have almost universally demonstrated the ability of individuals to modulate their method
of capture in response to differing stimuli. Preliminary evidence indicates that morphologically specialized inertial suction
feeding sharks are the most likely fishes to lack inherent modulatory ability. We examined the ability of the nurse shark,
Ginglymostoma cirratum, to modulate its feeding behavior based on different food types and sizes. G. cirratum is an inertial suction feeding fish that is apparently stereotyped in its food capture behavior. Electromyography showed
no statistical difference between feeding motor patterns based on food type (squid or fish) or size (gape width or twice gape
width), although there were slight inter-individual differences in the onset of muscle firing for some muscles. Kinematic
analysis showed a statistical difference in variables associated with durations for different food types, with the durations
for all variables being faster for squid bites than fish bites, but no difference based on the size of the food item. This
apparent lack of modulation may be associated with specialization of the morphology and behavior of G. cirratum for obligate suction prey capture. This functional specialization constrains the method in which G. cirratum captures prey but does not appear to result in dietary specialization. An unusual post capture spit-suck manipulation allows
this shark to handle and ingest large prey. 相似文献
84.
Acid related stress in soils might be caused by high concentrations of H+ and Al3+ in soil solution. Sampling of soil solution so far integrates over a relatively large soil volume, in the range of dm3. In order to study the microscale heterogeneity of acidity related stress-parameters the soil profile of a podzolic cambisol was covered by a 10×6 matrix of micro suction cups with a grid distance of 2 cm. The soil solution collected at 10 sampling events was analyzed for free cations and anions by capillary electrophoresis and for total metal content by a micro injection technique on ICP-OES. pH and UV absorption were also measured.There was a general trend of increasing pH and decreasing UV absorption with increasing soil depth, however without a clear correlation of concentration isolines to soil horizon borders. The latter was also true for total Al (Altot) and Al3+, with the exception of the soil horizon border Ahe/Bh,which was very well reflected by Al3+ and also by the fraction of bound Al. In the Ahe horizon less than 30%, in deeper mineral soil less than 50% of Altot were present as free Al3+. This fact is critical when calculating Ca/Al ratios as a stress parameter, because total metal content measured by ICP clearly overestimates the risk of root damage, even in deeper horizons of acid forest soils, where organic complexation of Al is of minor importance. The heterogeneity of soil solution chemistry and toxicity parameters on the cm-scale was found to be significant, for example with gradients of more than 0,5 pH-units within 2 cm. Because plant roots also experience soil on a microscale, high resolution investigations of soil solution chemistry offer a new approach for looking at the chemical environment relevant for root growth and plant nutrition. 相似文献
85.
Kamruddin Ahmed Hironori Masaki Iran Cong Dai Akitoyo Ichinose Yoshiaki Utsunomiya Misao Tao Tsuyoshi Nagatake Keizo Matsumoto 《Microbiology and immunology》1994,38(10):767-771
Sputum during the acute exacerbation of chronic respiratory diseases were observed under the electron microscope, to determine the in vivo expression of surface structures of Branhamella catarrhalis (B. catarrhalis), the polymorphonuclear neutrophil (PMN) response to B. catarrhalis infections, and the composition of sputum. It was found that during infection fimbriae are expressed in B. catarrhalis. However, there were sparsely to densely fimbriated bacteria in each sputum sample. The length of the fimbriae were from 50 to 76 nm. In the sparsely fimbriated B. catarrhalis, external to the cell wall, a thin, granular, electron-dense layer was observed. Due to the presence of fimbriae, this layer was not seen in densely fimbriated B. catarrhalis. Blebs were also found in B. catarrhalis. PMNs were found to phagocytose both B. catarrhalis and debris. Evidence was found that debris were formed mainly by the destruction of PMNs. Bacteria as well as debris were phagocytosed by PMNs. 相似文献
86.
Effects of temperature on aphid phenology 总被引:2,自引:0,他引:2
XILONG ZHOU RICHARD HARRINGTON IAN P. WOIWOD JOE N. PERRY JEFFREY S. BALE† SUZANNE J. CLARK‡ 《Global Change Biology》1995,1(4):303-313
Daily samples between 1964 and 1991 from suction traps throughout Great Britain were used to study the migration phenologies of five aphid species: Brachycaudus helichrysi, Elatobium abietinum, Metopolophium dirhodum, Myzus persicae and Sitobion avenae, and their relationship with temperature. Regression relationships have been established between characteristics of aphid phenology and temperature, latitude and longitude for each species. There were differences between species in the period for which temperature was most strongly associated with aphid phenology. The study indicates that temperature, especially winter temperature, is the dominant factor affecting aphid phenology, for all five species. A 1 °C increase in average winter temperature advanced the migration phenology by 4–19 days depending on species. Effects of temperature on the aphid phenology are similar between holocyclic and anholocyclic species, unlike the effects of temperature on date of first flight record which have been previously shown to be important only in anholocyclic species. 相似文献
87.
Mark R. Wade Brad C.G. Scholz Richard J. Lloyd Amanda J. Cleary Bernie A. Franzmann & Myron P. Zalucki 《Entomologia Experimentalis et Applicata》2006,120(2):139-153
Predatory insects and spiders are key elements of integrated pest management (IPM) programmes in agricultural crops such as cotton. Management decisions in IPM programmes should to be based on a reliable and efficient method for counting both predators and pests. Knowledge of the temporal constraints that influence sampling is required because arthropod abundance estimates are likely to vary over a growing season and within a day. Few studies have adequately quantified this effect using the beat sheet, a potentially important sampling method. We compared the commonly used methods of suction and visual sampling to the beat sheet, with reference to an absolute cage clamp method for determining the abundance of various arthropod taxa over 5 weeks. There were significantly more entomophagous arthropods recorded using the beat sheet and cage clamp methods than by using suction or visual sampling, and these differences were more pronounced as the plants grew. In a second trial, relative estimates of entomophagous and phytophagous arthropod abundance were made using beat sheet samples collected over a day. Beat sheet estimates of the abundance of only eight of the 43 taxa examined were found to vary significantly over a day. Beat sheet sampling is recommended in further studies of arthropod abundance in cotton, but researchers and pest management advisors should bear in mind the time of season and time of day effects. 相似文献
88.
Jarkko T. Iivarinen Rami K. Korhonen Jukka S. Jurvelin 《Computer methods in biomechanics and biomedical engineering》2016,19(10):1089-1098
Exact physiological mechanisms behind the potential positive treatment effects of pathological tissue swelling (edema), such as increased interstitial fluid flow, are poorly understood. Finite-element model was created and the model response was matched with the deformation data from the negative pressure (suction) measurements in human (N = 11) forearm. Two experimental suction protocols were simulated to evaluate their impact on interstitial fluid flow in soft tissues. Simulated continuous suction was up to 27 times more efficient in fluid transportation compared to the cyclic suction. The continuous suction that transports the interstitial fluid effectively may help to decrease soft tissue edema. 相似文献
89.
Kamruddin Ahmed Tran Cong Dai Akitoyo Ichinose Hironori Masaki Tsuyoshi Nagatake Keizo Matsumoto 《Microbiology and immunology》1993,37(7):523-529
Sputum from patients with acute exacerbation of respiratory infection by Pseudomonas aeruginosa was observed under the electron microscope. External to the cell wall of P. aeruginosa a granular, electron-dense material was observed which is suggestive of capsule. It is supposed that stabilization of capsule occurred by the host antibody, which was produced due to chronic infection by P. aeruginosa. Mucoid type of microcolonies were observed with a fibrous matrix of exopolysaccharide. Other types of microcolonies were surrounded by granular substances or fine fibers. Neutrophil was found to be partially surrounding the microcolony in an attempt to defense. Debris was formed mainly by the destruction of the neutrophil. Most neutrophils were found full of phagocytosed debris; in contrast only a few neutrophils were found to have phagocytosed P. aeruginosa. This study concludes that instead of phagocytosing bacteria, neutrophil phagocytosed debris and bacteria were not completely eradicated. Therefore, this might be one of the factors in the pathogenesis of respiratory infection and persistent colonization by P. aeruginosa. 相似文献