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181.
Fast pollen tube growth in Conospermum species 总被引:2,自引:0,他引:2
BACKGROUND AND AIMS: An unusual form of pollen tube growth was observed for several Conospermum species (family Proteaceae). The rate of pollen tube growth, the number of tubes to emerge and the ultrastructure of these tubes are given here. METHODS: Pollen was germinated in vitro in different sucrose concentrations and in the presence of calcium channel blockers, and tube emergence and growth were recorded on a VCR. Measurements were taken of the number of tubes to emerge and rate of tube emergence. Pollen behaviour in vivo was also observed. The ultrastructure of germinated and ungerminated pollen was observed using TEM. RESULTS: After 10 s to 3 min in germination medium, up to three pollen tubes emerged and grew at rates of up to 55 micro m s(-1); the rate then slowed to around 2 micro m s(-1), 30 s after the initial growth spurt. Tubes were observed to grow in pulses, and the pulsed growth continued in the presence of calcium channel blockers. Optimal sugar concentration for pollen germination was 300 g L(-1), in which up to 81 % of pollen grains showed fast germination. Germination and emergence of multiple tubes were observed in sucrose concentrations of 100-800 g L(-1). The vegetative and generative nuclei moved into one of the tubes. Multiple tubes from a single grain were observed on the stigma. Under light microscopy, the cytoplasm in the tube showed a clear region at the tip. The ultrastructure of C. amoenum pollen showed a bilayered exine, with the intine being very thick at the pores, and elsewhere having large intrusions into the plasma membrane. The cytoplasm was dense with vesicles packed with inner tube cell wall material. Golgi apparatus producing secretory vesicles, and mitochondria were found throughout the tube. The tube wall was bilayered; both layers being fibrous and loosely packed. CONCLUSIONS: It is proposed that, for Conospermum, initial pollen tube wall constituents are manufactured and stored prior to pollen germination, and that tube extension occurs as described in the literature for other species, but at an exceptionally fast rate. 相似文献
182.
Summary Recently, we found that the anti-microtubule drugs colchicine and propham caused the absence of microtubules and thus loss of cytoplasmic zonation in in vitro growing pollen tubes ofNicotiana sylvestris, but did not seriously affect growth. In the present study we used the herbicide carbetamide as an anti-microtubule drug. It had the same effect as colchicine and propham: the cytoplasm, including the generative cell, was no longer concentrated in the tip but was distributed randomly. In addition, ultrastructural investigations have shown that even the vesicle zone, usually found at the very tip of pollen tubes, had disappeared in some tubes. Nonetheless, in vitro growth was not inhibited by more than 20% over a period of 22 h.In contrast, tube growth in plants ceased 1 cm down in the style when carbetamide was applied to the stigma before pollination. At the lowest concentration causing this effect, microtubules of the vegetative cell had disappeared and the cytoplasm was distributed randomly, as it was for in vitro grown tubes. It can be concluded that microtubules of the vegetative cell are essential for pollen tube growth in the style.Abbreviations DAPI
4,6-diamidmo-2-phenylindole
- EGTA
ethyleneglycerol-bis-(aminoethyl ether) tetraacetic acid
- DIC
differential interference contrast
- GC
generative cell
- IC50
inhibition concentration 50%
- MF
microfilament
- MT
microtubule
- PEM-buffer 50 mM PIPES
1 mM EGTA, 2 mM MgSO4, pH 6.9
- PBS
phosphate buffered saline
- PIPES
piperazine-bis-ethanesulphonic acid
- PTG-Test
pollen tube growth test
- SAM
substrate adhesion molecule
- VC
vegetative cell 相似文献
183.
Siyabonga P. Khoza Sarah Ford Ernest P. Buthelezi Donald M. Tanyanyiwa 《Journal of Medical Biochemistry》2021,40(4):358
BackgroundBarricorTM Lithium heparin plasma tubes are new blood tubes that have been introduced to overcome the effects of gel in serum separator tubes (SST) and the shortcomings of standard Lithium heparin plasma. We aimed to evaluate BarricorTM tubes as an alternative to serum separator tubes and compare the stability between the tubes.MethodsForty-four paired samples were collected using both BarricorTM and SST. We compared five analytes at baseline (<6 h) and after every 24 h using the PassingBablok and Bland-Altman plots. Aspartate aminotransferase (AST), potassium (K), phosphate (PO4) , lactate dehydrogenase (LDH), and creatinine were analysed in both tubes. We calculated the percentage difference for each analyte between the baseline and time intervals to assess analyte stability. The percentage difference was compared to the desirable specification for bias and reference change value (RCV).ResultsAll analytes were comparable at baseline. Statistical differences (p<0.001) became evident after 24 h. PO4, K, and creatinine had a mean difference that exceeded the desirable specification for bias (-9.59%, - 9.35%, and -4.59%, respectively). Potassium was stable up to 24 h in both tubes. LDH showed better stability in SST (144 h vs 96 h). PO4 concentrations were more stable in both tubes with the SST (96 h vs 72 h). Creatinine and AST had the longest stability in both tubes compared to other analytes (144 h).ConclusionsData demonstrated variability and similarities in analyte concentrations and stability, respectively, in both tubes. 相似文献
184.
A survey of 96 sites in a range of riparian habitats in the catchments of five rivers during June–August 1998 used the bait tube method to investigate the geographical distribution and habitat occurrence of Water Shrews (Neomys fodiens) in the Weald of South‐East England. Water Shrews were found at 42% of sites, and were widely distributed in all river catchments except the Mole. They occurred in many riparian habitats, including rivers, streams, canals and ditches, with a range of physical and biotic characteristics. There were no signs of habitat avoidance in response to human disturbance but Water Shrews were absent from the river catchment with lowest water quality. Logistic regression analysis was used to model the effect of habitat variables on the presence of Water Shrews, with current speed, water depth, bank incline and bank‐side vegetation identified as important variables. Fast‐flowing shallow waters had a significant positive effect on their presence, whereas scarce herbaceous vegetation and a bank of low incline had a significant negative effect. These habitat variables appear to be reliable indicators of the probability of finding Water Shrews at a particular site, and have implications for habitat management and conservation. 相似文献
185.
Estimation of abundance or biomass of benthic invertebrates requires considerable effort to process samples. Consequently,
it has been suggested to process only organisms retained by a relatively coarse meshed sieve and apply size-specific correction
factors based on the probability that a sieve retains individual organisms. Benthic samples were collected from 10 sites in
2 regions and processed to validate an existing empirical model predicting sieve retention probabilities, to test whether
periphyton biomass affects probability of retention, and to determine the optimal strategy that minimizes both cost and variability
of estimates. The existing model predicting sieve retention probabilities corrected for organisms lost through sieves and
mostly corrected for underestimation of biomass, but this model lead to overestimates of the frequency of the smallest organisms.
Inclusion of algal biomass improved slightly the proportion of correct predictions (whether an organism is retained or not
by a sieve) by 0.6% relative to the existing model (from 90.8% to 91.4%), and removed the bias. Density and biomass estimates
obtained by only processing organisms retained by 1- or 2-mm sieves and applying correction factors derived from the predicted
retention probabilities were accurate and only marginally less precise than estimates obtained by processing all organisms.
The reduced precision of estimates from subsets of organisms could be compensated by increasing sample size and still lead
to a reduction of 40–60% of the number of organisms processed. Even though the use of subsets introduces additional analytical
variability, this variability is relatively small compared to the natural spatial variability among replicates.
Handling editor: K. Martens 相似文献
186.
Structures involved in the binding of human fibrinogen to Candida albicans germ tubes 总被引:3,自引:0,他引:3
Véronique Annaix Jean-Philippe Bouchara Guy Tronchin Jean-Marcel Senet Raymond Robert 《FEMS microbiology letters》1990,64(3):147-154
Abstract Recent evidence for the interaction between human fibrinogen and Candida albicans germ tubes have led us to attempt to characterize the structures involved. Using 125 I-radiolabeled proteins, fibrinogen purified by affinity chromatography and its plasmin degradation products, the binding sites on the fibrinogen molecule appeared to be located specifically in the D-domain. Conversely to the fibrinogen and the fragment D, radiolabeled fragment E, however, did not interact with cell. The binding was time-dependent, saturable and reversible. Scatchard analysis of the data obtained revealed an average of 6000 binding sites per germ tube with dissociation constant ( K d ) of 5.2 × 10−8 M. No potent competition was observed for a range of different proteins and carbohydrates. Fibrinogen fragment D binding proteins were identified using a dithiothreitol-iodoacetamide extract of the fungus. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting, one compotent of 68 kDa was detected. Thus, the presence of fibrinogen binding proteins specifically localized on the cell wall surface of C. albicans germ tubes may constitute one of the factors involved in the development of candidosis. 相似文献
187.
J. P. F. G. Helsper 《Planta》1979,144(5):443-450
A membrane fraction, isolated from pollen tubes of Petunia hybrida, catalyses the incorporation of glucose from UDP-glucose into sucrose, cellodextrins, -glucans, sterol glucosides and polyprenol monophosphate glucose. Incorporation studies with isolated lipids and kinetic and double-labelling studies indicated that glucolipids are not intermediates in the synthesis of -glucans in this system. 相似文献
188.
The aim of the study was to show which tissues and cell types of the cotyledon of Ricinus communis L. are responsible for uptake of sucrose by H+-sucrose symport. The cotyledons were incubated in labelled sucrose for up to 20 min and then the amount of radioactivity in each cell type of the cotyledon was assessed by microautoradiography. It was found that 50% of the label was present in the spongy mesophyll, and 10–15% was in the bundles, the epidermal layers and the palisade parenchyma. The sieve tubes contained only 2–3% of the label. The addition of sucrose to cotyledons depolarized the membrane of spongy-mesophyll cells by 33 mV. Therefore, it was concluded that the previously found H+-sucrose symport is at least partly located at the spongy mesophyll. No precursor-like behaviour of the label in mesophyll or bundle-sheath cells was observed in pulse-chase experiments, which indicates a direct uptake of sucrose by the sieve tube-companion cell complex from the apoplast.This work was funded by Deutsche Forschungsgemeinschaft. The valuable help by Ina Möller, Elke Schmidt, Christian Schobert (all from Bayreuth, FRG), Dr. Dieter Gradmann (Göttingen, FRG), Dr. Jörg Tittor (MPI Biochemie München, FRG), Dr. Pavlovkin (Plant Pathology, Bratislava), Dr. K. Köhler (Botany Department Würzburg, FRG) and the intense discussions with Dr. Enno Brinkmann (Bayreuth) are gratefully acknowledged. The technical assistance by Beatrix Tannhäuser-Hofmann and Hildegard Stork was of great help for this work. 相似文献
189.
In phragmoplast-assisted cytokinesis of somatic cells, vesicle fusion generates a cell plate that matures into a new cell wall and its flanking plasma membranes. Insight into this dynamic process has been gained in the past few years and additional molecular components of the basic machinery of cytokinesis have been identified. Specialized modes of cytokinesis occur in meiosis and gametophyte development, and recent studies indicate that they are genetically distinct from somatic cytokinesis. 相似文献
190.
María Guadalupe Reyes-García Francisca Hernández-Hernández Fernando García-Tamayo 《Mycoscience》2012,53(1):36-39
Candida albicans is a commensal yeast in humans that disseminates in immunocompromised persons. Its spreading is modulated by melanin, hormones, or some neurotransmitters, among other factors. The neurotransmitter gamma-aminobutyric acid (GABA) is used by bacteria, plants, and fungi as a carbon and nitrogen source. In this article, the in vitro effect of different doses of GABA on germ-tube formation and expression of phospholipase B1 (PLB1) mRNA in two Candida albicans strains was investigated. Results demonstrated that GABA increases both germ-tube formation and PLB1 mRNA expression in the two Candida strains in a dose-dependent manner, which suggests that GABA promotes the growth of C. albicans. 相似文献