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1.
ISHIZAKA NOBUYUKI; TOMIYAMA KOHEI; KATSUI NOBUKATSU; MURAI AKIO; MASAMUNE TADASHI 《Plant & cell physiology》1969,10(1):183-192
Rishitin, a norsesquiterpene alcohol, found in infected, resistantpotato-tuber tissue completely inhibited zoospore germinationand germtube elongation of Phytophthora infestans (MONT.) DEBARY at 103M. There was little difference in sensitivityto rishitin among races of Phytophthora infestans. IAA-inducedelongation of Avcna coleoptile sections and GA3-induced elongationof wheat leaf sections were also inhibited by rishitin. Theinhibition of IAA-induced elongation of Avena coleoptiles wasrelieved to some extent by increasing IAA concentration. However,little relief of the inhibition of GA3-induced elongation ofwheat leaf sections was obtained by increasing GA3 concentration.No plant injury was observed at this concentration of rishitin(103M). Examination of a series of rishitin derivatives indicated thatthe hydroxyl group at C-3 is indispensable for antifungal activity.This activity was intensified by saturating the double bondbetween the rings of rishitin and/or that of the isopropenylgroup at C-7, though activity decreased when oxygenated functionalgroups were introduced into the side chain. Aromatization of the A ring did not lower biological activities.The antifungal activities of most rishitin derivatives almostparalleled their activities as plant growth retardants. However,some compounds without antifungal activity were active as growthretardants.
1Studies on the phytoalexins (5). (Received August 14, 1968; ) 相似文献
2.
The spawning rate of laboratory-reared Centropages typicus fedHymenomonas elongala increases with food concentration, up toa value of {small tilde}2800 µg C (16 500 cells) ml1.An alternation of a low food (1000 cells ml1) and highfood concentration (16 500 cells ml1) is not favourableto egg release when its periodicity is 1 or 2 days, whereasit may be of advantage if it is longer (36 days). Inthe latter case, Centropages typicus will benefit best fromthe rich food diet if this coincides with (or just follows)the last moult. 相似文献
3.
RAJASEKHAR V. K.; GUHA-MUKHERJEE SIPRA; SOPORY SUDHIR K. 《Journal of experimental botany》1983,34(11):1444-1454
In 5-d-old etiolated seedlings of Sorghum bicolor, 12 h of darknessafter 5 min in red light eliminated a lag before the accumulationof chlorophylls in subsequent continuous white light. Increasingthe dark period to 24 h and 36 h, increased the rate of chlorophyllaccumulation in the later stages of greening. Exogenous -aminolevulinicacid neither completely removed the lag, nor increased the rateof chlorophyll accumulation. Cycloheximide (25 µg ml1)and 6-methyl purine (5.0 µg ml1), given continuouslyor only until the 12 h dark period following the red light irradiation,restored the lag and decreased the rate of chlorophyll accumulation.D-threo-chloramphenicol (400µg ml1) also decreasedthe rate of chlorophyll accumulation but did not restore thelag. Addition of these inhibitors even 12 h after red lightirradiation decreased the rate of chlorophyll accumulation.Rifampicin (Rifamycin SV, 400 µg ml1) did not havesuch effects. Key words: Chlorophylls, Phytochrome, -Aminolevulinic acid, Sorghum bicolor 相似文献
4.
The relationships between photosynthesis and photosyntheticphoton flux densities (PPFD, P-l) were studied during a red-tideof Dinophysis norvegica (July-August 1990) in Bedford Basin.Dinophysis norvegica, together with other dinoflagellates suchas Gonyaulax digitate, Ceratium tripos, contributed {small tilde}50%of the phytoplankton biomass that attained a maximum of 16.7µg Chla 1 and 11.93 106 total cells I1.The atomic ratios of carbon to nitrogen for D.norvegica rangedfrom 8.7 to 10.0. The photosynthetic characteristics of fractionatedphytoplankton (>30 µm) dominated by D.norvegica weresimilar to natural bloom assemblages: o (the initial slope ofthe P-l curves) ranged between 0.013 and 0.047 µg C [µgChla]1 h1 [µmol m s1]1the maximum photosynthetic rate, pBm, between 0.66 and 1.85µg C [µghla]1 h1; lk (the photoadaptationindex) from 14 to 69 µ,mol m2 s1. Carbonuptake rates of the isolated cells of D.norvegica (at 780 µmolm2 s1) ranged from 16 to 25 pg C cell1h and were lower than those for C.tripos, G.digitaleand some other dinoflagellates. The variation in carbon uptakerates of isolated cells of D.norvegica corresponded with PBmof the red-tide phytoplankton assemblages in the P-l experiments.Our study showed that D.norvegica, a toxigenic dinoflagellate,was the main contributor to the primary production in the bloom. 相似文献
5.
The nutritional value of different sized fractions of naturalplankton was investigated for the growth of Eodiaptomus japonicusBurckhardt by comparing the development of its naupliar andcopepodid stages fed on differentially fractionated planktonicassemblages of a eutrophic pond, at 20°C. Water filteredthrough a 0.8 µm Nuclepore filter, containing mainly smallcoccoid bacteria (0.450.6 µm in cell diameter),at a concentration of 82.7 µg C 11 could not supportthe development of E.japonicus. The 3 µm filtered water,containing bacteria and picoalgae. at a total concentrationof 259 µg C 11, supported development but not eggproduction. The 20 µm filtered water, containing bacteria,picoalgae and large algae, at a total concentration of 2600µg C 11, supported rapid development of the juvenilesand continuous egg production by the adults. The separated 320µm fraction, containing only large algae, could not supportthe development at concentrations of 131 and 196 µg C11. However, the same rapid development of the juvenilesand continuous egg production by adults occurred at all of thetested concentrations between 261 and 3920 µg C11of the large algae. The results suggest that E.japonicus favoursalgae larger than 3 µm during its complete lifespan, andthat the threshold food concentration for its development variesbetween 200 and 250 µg C 11. 相似文献
6.
Ephyra larvae and small medusae (1.795 mm diameter, 0.01350mg ash-free dry wt, AFDW) of the scyphozoan jellyfish Aureliaaurita were used in predation experiments with phytoplankton(the flagellate Isochrysis galbana, 4 µm diameter, {smalltilde}6 x 106 µg AFDW cell1), ciliates (theoligotrich Strombidium sulcatum, 28 µm diameter, {smalltilde}2 x 103 µg AFDW), rotifers (Synchaeta sp.,0.5 µg AFDW individual1) and mixed zooplankton(mainly copepods and cladocerans, 2.13.1 µg AFDWindividual1). Phytoplankton in natural concentrations(50200 µg C I1) were not utilized by largemedusae (4495 mm diameter). Ciliates in concentrationsfrom 0.5 to 50 individuals ml"1 were consumed by ephyra larvaeand small medusae (314 mm diameter) at a maximum predationrate of 171 prey day1, corresponding to a daily rationof 0.42%. The rotifer Synchaeta sp., offered in concentrationsof 100600 prey I1, resulted in daily rations ofephyra larvae (25 mm diameter) between 1 and 13%. Mixedzooplankton allowed the highest daily rations, usually in therange 540%. Large medusae (>45 mm diameter) consumedbetween 2000 and 3500 prey organisms day"1 in prey concentrationsexceeding 100 I1. Predation rate and daily ration werepositively correlated with prey abundance. Seen over a broadsize spectrum, the daily ration decreased with increased medusasize. The daily rations observed in high abundance of mixedzooplankton suggest a potential scope for growththat exceeds the growth rate observed in field populations,and this, in turn, suggests that the natural populations areusually food limited. The predicted predation rate at averageprey concentrations that are characteristic of neritic environmentscannot explain the maximum growth rates observed in field populations.It is therefore suggested that exploitation of patches of preyin high abundance is an important component in the trophodynamicsof this species.
1Present address: University of Bergen, Department of MarineBiology, N-5065 Blomsterdalen, Norway 相似文献
7.
Cyanobacteria and cyanobacterial toxins in three alkaline Rift Valley lakes of Kenya--Lakes Bogoria, Nakuru and Elmenteita 总被引:4,自引:0,他引:4
Ballot Andreas; Krienitz Lothar; Kotut Kiplagat; Wiegand Claudia; Metcalf James S.; Codd Geoffrey A.; Pflugmacher Stephan 《Journal of plankton research》2004,26(8):925-935
For decades frequent mass mortalities of Lesser Flamingos (Phoeniconaiasminor Geoffroy) have been observed at alkaline-saline KenyanRift Valley lakes. To estimate the potential influence of toxiccyanobacteria on these mass deaths, the phytoplankton communitieswere investigated in Lakes Bogoria, Nakuru and Elmenteita. Cyanobacterialtoxins were analyzed both in the phytoplankton from the threelakes and in isolated monocyanobacterial strains of Arthrospirafusiformis, Anabaenopsis abijatae, Spirulina subsalsa and Phormidiumterebriformis. Lake Bogoria was dominated by the cyanobacteriumA. fusiformis. In L. Nakuru and L. Elmenteita the phytoplanktonmainly consisted of A. fusiformis, A. abijatae and Anabaenopsisarnoldii, and in L. Nakuru an unknown Anabaena sp. was alsofound. Furthermore, this is the first time A. abijatae and theunknown Anabaena sp. have been found in Kenyan lakes. Phytoplanktonwet weight biomass was found to be high, reaching 777 mg L1in L. Bogoria, 104 mg L1 in L. Nakuru and 202 mg L1in L. Elmenteita. Using HPLC, the cyanobacterial hepatotoxinsmicrocystin-LR, -RR -YR, -LF and -LA and the neurotoxin anatoxin-awere detected in phytoplankton samples from L. Bogoria and L.Nakuru. Total microcystin concentrations amounted to 155 µgmicrocystin-LR equivalents g1 DW in L. Bogoria, and 4593µg microcystin-LR equivalents g1 DW in L. Nakuru,with anatoxin-a concentrations at 9 µg g1 DW inL. Bogoria and 223 µg g1 DW in L. Nakuru. In L.Elmenteita phytoplankton, no cyanobacterial toxins were found.A. fusiformis was identified as one source of the toxins. Theisolated strain of A. fusiformis from L. Bogoria was found toproduce both microcystin-YR (15.0 µg g1 DW) andanatoxin-a (10.4 µg g1 DW), whilst the A. fusiformisstrain from L. Nakuru was found to produce anatoxin-a (0.14µg g1 DW). Since A. fusiformis mass developmentsare characteristic of alkaline-saline lakes, health risks towildlife, especially the Arthrospira-consuming Lesser Flamingo,may be expected. 相似文献
8.
Density and distribution of bacterioplankton and planktonic ciliates in the Bering Sea and North Pacific 总被引:3,自引:0,他引:3
The total number of planktonic bacteria in the upper mixed layerof the Bering Sea during the late spring-early summer periodranged between 1 and {small tilde}4 x 106 ml1 (biomass1040mg C m3). In the northern Pacific, along 47526N,the corresponding characteristics of the bacterioplankton densityin the upper mixed water layer were: total number 12x 106 cells ml1 and biomass 1546mg C m3Below the thermocline at 50100 m, the density of bacterioplanktonrapidly decreased. At 300 m depth, it stabilized at 0.10.2x 106 cells ml1. The integrated biomass of bacterioplanktonin the open Bering Sea ranged between 1.2 and 3.6 g C m2(wet biomass 618 g m2) Its production per dayvaried from 2 to 23 mg C m3 days1 in the upper0100 m. The numerical abundance of planktonic ciliatesin this layer was estimated to be from 3 to l0 x 103 cells l1,and in the northern Pacific from 0.4 to 4.5 x 103 l2.Their populations were dominated by naked forms of Strombidium,Strombilidium and Tontonia. In some shelf areas, up to 40% ofthe total ciliate population was represented by the symbioticciliate Mesodinium rubrum. The data on the integrated biomassof basic groups of planktonic microheterotrophs are also presented,and their importance in the trophic relationships in pelagiccommunities of subarctic seas is discussed. 相似文献
9.
Community structure, biomass and productivity of size-fractionated summer phytoplankton populations in lower Narragansett Bay, Rhode Island 总被引:1,自引:0,他引:1
Seventeen size-fractionation experiments were carried out duringthe summer of 1979 to compare biomass and productivity in the< 10, <8 and <5 µm size fractions with that ofthe total phytoplankton community in surface waters of NarragansettBay. Flagellates and non-motile ultra-plankton passing 8 µmpolycarbonate filters dominated early summer phytoplankton populations,while diatoms and dinoflagellates retained by 10 µm nylonnetting dominated during the late summer. A significant numberof small diatoms and dinoflagellates were found in the 108µm size fraction. The > 10 µm size fraction accountedfor 50% of the chlorophyll a standing crop and 38% of surfaceproduction. The <8 µm fraction accounted for 39 and18% of the surface biomass and production. Production by the< 8 µm fraction exceeded half of the total communityproduction only during a mid-summer bloom of microflagellates.Mean assimilation numbers and calculated carbon doubling ratesin the <8 µm (2.8 g C g Chl a1 h1; 0.9day1)and<5 µm(1.7 g C g Chl a1h1; 0.5day1)size fractions were consistently lower than those of the totalpopulation (4.8 g C g Chl a1 h1; 1.3 day1)and the <10 µm size fraction (5.8 g C g Chl a1h1; 1.4 day 1). The results indicate that smalldiatoms and dinoflagellates in fractionated phytoplankton populationscan influence productivity out of proportion to their numbersor biomass.
1Present address: Australian Institute of Marine Science, P.M.B.No. 3, Townsville M.S.O., Qld. 4810, Australia. 相似文献
10.
Yamane Hisakazu; Nohara Kumiko; Takahashi Nobutaka; Schraudolf Helmut 《Plant & cell physiology》1987,28(7):1203-1207
Antheridic acid was identified by retention time and full massspectra from GCMS analysis as an antheridiogen in Anemia rotundifoliaand A. flexuosa. In the dark spore germination assay, antheridicacid was active down to 1010 and 5 ? 1012g.ml1in A. rotundifolia and A.flexuosa, respectively. In the antheridiumformation assay, antheridic acid was active down to 1010g.ml1 in both A. rotundifolia and A.flexuosa (Received April 14, 1987; Accepted July 8, 1987) 相似文献
11.
Quantitative Aspects of Leaf Acid Phosphatase Activity and the Phosphorus Status of Tomato Plants 总被引:1,自引:0,他引:1
The relation between tomato leaf acid phosphatase activity andleaf tissue P content has been examined, and a study made ofthe effects of leaf development, variation in nitrogen supply,and variation in the growing medium on this relationship. Tomatoplants were grown in sand and given various concentrations ofphosphate. Plants were also grown for an initial period in peatcontaining an adequate level of phosphate, then transferredto peat to which was added 0 or 2.3 kg superphosphate m3and supplied with either 50 of 300 µg N ml1. Expressed on a unit tissue f. wt basis, acid phosphatase activityin the control plants in sand (given 41 µg P mlminus;1)was highest in extracts from the expanding leaves and decreasedwith leaf maturity. However, when given a reduced supply ofphosphate, the enzyme activity in the more mature leaves wasequal to, or greater than, that in the expanding leaves. Thephosphatase activity increased first in the young, fully-expandedleaves and in the mature leaves (with 4.1 µg P ml1),but did not increase in the expanding leaves until the supplywas restricted to 2.1 µg P ml1. On closer examination,the increase in enzyme activity appeared to be associated withthe P level in the leaf tissues, the activity increasing whenthe level fell below about 0.25 per cent (g P per 100 g drywt tissue). The same relation was found with the plants grownin peat, and was independent of the concentration of nitrogensupplied to the plants. The fully expanded leaves showed the best enzyme response whenthe phosphate supply was restricted and the activity reflectedclosely the local levels of tissue P. The assay of the enzymein unpurified leaf extracts is simple and rapid, and could beused in a test to detect P-deficiency in tomato plants. Lycopersicon esculentum L, tomato, acid phosphatase activity, phosphorus status 相似文献
12.
Photosynthetic 14C fixation by Characean cells in solutionsof high pH containing NaH14CO3 gave a measure of the abilityof these cells to take up bicarbonate (H14CO3). Whereascells of Nitella translucens from plants collected and thenstored in the laboratory absorbed bicarbonate at 11.5µµmoles cm2 sec1, rates of 38µµmoles cm2 sec1 were obtained withN. translucens cells from plants grown in the laboratory. Influxesof 56 µµmoles cm2 sec1 wereobtained with Chara australis, 38 µµmolescm2 sec1 with Nitellopsis obtusa, and 15µµmoles cm2 sec1 with Tolypella intricata.It is considered that these influxes represent the activityof a bicarbonate pump, which may be an electrogenic process. In solutions of lower pH, H14CO3 uptake would be maskedby rapid diffusion of 14CO2 into the cells: the four Characeanspecies fixed 14CO2 at maximum rates of 3040 µµmolescm2 sec1 (at 21° C). 相似文献
13.
Wickham Stephen A.; Gilbert John J.; Berninger Ulrike-G. 《Journal of plankton research》1993,15(3):317-334
Daphnia can suppress ciliates and rotifers through predationand interference competition, but it is not known whether thisproduces any direct benefit to Daphnia. We conducted survivorshipand cohort lifetable experiments to determine whether Daphniacan utilize ciliates and rotifers as food. Three species ofoligotrich ciliates (Halteria grandinella, Strobilidium gyransand Strobilidiumvelox) and one rotifer (Keratella cochlearis)were used. Lifetable experiments were conducted with a basallevel of algae (Cryptomonas sp.), plus either ciliates or rotifers,while survivorship experiments had only the rotifers or ciliates.Densities of 30 H.grandinella ml1, 50 S.gyrans ml1and 15 S.velox ml1 enhanced Daphnia pulex's populationgrowth rate 3550% over controls with only algae. TenS.gyrans ml1 did not produce a significant change inDaphnia's growth rate. Densities of 100 and 300 K.cochlearis1 increased Daphnia population growth rates by II and10%, respectively. Both 10 and 50 S.gyrans ml1 enhancedDaphnia's survivorship compared to starved controls, but neither100 nor 300 K.cochlearis l1 enhanced its survivorship.The amount of enhancement of Daphnia growth rates by rotifersand ciliates is roughly proportional to the death rates imposedby Daphnia. The death rate imposed by Daphnia on rotifers isa function of both algal density and Daphnia size. Per unitbiomass, neither ciliates nor Keratella appear to be as nutritiousfor Daphnia as is Cryptomonas. 相似文献
14.
Biomass, feeding and production of Noctiluca scintillans in the Seto Inland Sea, Japan 总被引:1,自引:0,他引:1
The abundance and biomass of the large heterotrophic dinoflagellateNoctiluca scintillans, together with the changes in its potentialprey items, were monitored in the Seto Inland Sea, Japan, duringsummer 1997 (17 July-11 August). Growth and grazing rates ofNscintillans fed natural plankton populations were also measuredeight and seven times, respectively, during the survey period.The abundance and biomass of N scintillans averaged over thewater column (19 m) were in the range 1345 cells 11(temporalaverage = 93 cell11) and 0.149.6 µg C l1(temporalaverage = 13.8 µg C l1; three times higher thanthat of calanoid copepods during the same period). Noctilucascintillans populations followed the changes in phytoplankton:N.scintillans biomass was increasing during the period of diatomblooms and was at a plateau or decreasing during periods oflow chlorophyll a. The growth rates of N.scintillans (µ)were also consistent with the wax and wane of the N.scintillanspopulation: N.scintillans showed highest growth rates duringdiatom blooms. A simple relationship between µ and chlorophylla concentration was established, and the production of N.scintillanswas estimated using this relationship and the measured biomass.The estimated production averaged over the water column wasin the range >0.15.2 µg C l1 day1(temporalaverage = 1.4 µg C l1 day1; 64% of the productionof calanoid copepods during the same period). Diatom clearancerates by N.scintillans were in the range 0.100.35 mlcell1 day1, and the phytoplankton population clearanceby N.scintillans was >12% day1. Thus, although thefeeding pressure of N.scintillans on phytoplankton standingstock was low, N.scintillans was an important member of themesozooplank-ton in terms of biomass and production in the SetoInland Sea during summer. 相似文献
15.
The effects of five inhibitors of protein synthesis, viz. streptomycin,aurin tricarboxylic acid, tetracycline, chloramphenicol, andcycloheximide, on the calcification of Gloeotaenium loitlesbergarianumHansgirg, a freshwater green alga were studied. Streptomycinhad no effect while aurin tricarboxylic acid at 50 µgml1 and tetracyline, chloramphenicol and cycloheximideat 20 µg ml1 completely inhibited calcificationin the alga. High concentrations of chloramphenicol and cycloheximidewere not completely inhibitory when added 26 h and 32 h respectivelyafter the material was incubated in the induction medium. Itis concluded that the effects by these substrates are the resultsof inhibition of protein synthesis, which is directly or indirectlylinked to calcification. calcification, Gloeotaenium loitlesbergarianum Hansgirg, green alga, chlorophyceae, protein synthesis inhibitors 相似文献
16.
The total and heterotrophic bacterial microflora of gut andfecal pellets of the copepod Temora stylifera was studied inthe coastal zone of the northwestern Mediterranean basin. Digestivetracts and feces were always found to contain bacteria. Withmean values close to 1011 cells ml1and 1010 colony-formingunits (CFU) ml1, both total and heterotrophic communitiesfound in fecal pellets largely exceeded the corresponding bacterialmicroflora observed in surrounding seawater (105 cells ml1 and103 CFU ml). In the same way, the frequency of dividingcells and mean cell volumes increased, respectively, from 3%and 0.12µm3 in seawater to >6% and 0.24 µm3 infecal pellets. The bacterial community structure was investigatedby carrying out 29 morphological and biochemical tests on 147isolated strains. Although Pseudomonas was always the most frequentlyencountered genus, the bacterial communities found in copepodfecal pellets clearly differ from those inhabiting seawater.Vibrio species, which were not detected in seawater microflora,were always present in fecal pellet communities. The close correspondenceobserved between the potential metabolic characteristics ofthe fecal bacterial communities isolated from a subantarcticdeposit feeder (Mytilus edulis) and from zooplankton in thisMediterranean study suggests that the fecal community differentiationis an even more general feature. 相似文献
17.
The seasonal abundance of the phototrophic ciliate Mesodinium rubrum in Southampton Water, England 总被引:1,自引:0,他引:1
The abundance of the marine phototrophic planktonic ciliateMesodinium rubrum was monitored throughout an annual cycle attwo stations in the Southampton Water estuary. Seasonal changesin the concentration of nitrate, ammonia and phosphate weremonitored both at the inner estuary station (NW Netley) andouter estuary station (Calshot). Nutrient levels in the winterwere similar at both stations, and were diminished during sequentialdiatom blooms dominated initially by Sketetonema costatum andthen by Rhizosolenia dclicatula. Nitrate was reduced to a seasonalminimum in the outer estuary following these spring diatom blooms,but in the inner estuary was sustained >500 µg I1until the onset of the M.rubrum bloom. During the developmentof a visible red tide of M.rubrum in June/July at NW Netley,nutrient concentrations were considerably reduced. Cell numbersof M.rubrum varied between 2 and 3 cells ml during winterto >400 cells ml1 during the bloom at NW Netley, whereasat Calshot cell abundance did not increase above 25 cells ml1at any time of the year. At NW Netley, dense accumulations ofthe ciliate occurred over restricted depth intervals duringthe bloom and possible factors influencing the observed verticaldistribution of cells are considered.
1Present address: Biology Department, Faculty of Science, AddisAbaba University, PO Box 1176, Addis Ababa, Ethiopia 相似文献
18.
Dillon PF Root-Bernstein RS Lieder CM 《American journal of physiology. Cell physiology》2006,291(5):C977-C984
Ascorbate has previously been shown to enhance both 1- and 2-adrenergic activity. This activity is mediated by ascorbate binding to the extracellular domain of the adrenergic receptor, which also decreases the oxidation rate of ascorbate. H1 histamine receptors have extracellular agonist or ascorbate binding sites with strong similarities to 1- and 2-adrenergic receptors. Physiological concentrations of ascorbate (50 µM) significantly enhanced histamine contractions of rabbit aorta on the lower half of the histamine dose-response curve, increasing contractions of 0.1, 0.2, and 0.3 µM histamine by two- to threefold. Increases in ascorbate concentration significantly enhanced 0.2 µM histamine (5500 µM ascorbate) and 0.3 µM histamine (15500 µM ascorbate) in a dose-dependent manner. Histamine does not measurably oxidize over 20 h in oxygenated PSS at 37°C. Thus the ascorbate enhancement is independent of ascorbate's antioxidant effects. Ascorbate in solution oxidizes rapidly. Transfected histamine receptor membrane suspension with protein concentration at >3.1 µg/ml (56 nM maximum histamine receptor) decreases the oxidation rate of 392 µM ascorbate, and virtually no ascorbate oxidation occurs at >0.0004 mol histamine receptor/mol ascorbate. Histamine receptor membrane had an initial ascorbate oxidation inhibition rate of 0.094 min·µg protein1·ml1, compared with rates for transfected ANG II membrane (0.055 min·µg protein1·ml1), untransfected membrane (0.052 min·µg protein1·ml1), creatine kinase (0.0082 min·µg protein1·ml1), keyhole limpet hemocyanin (0.00092 min·µg protein1·ml1), and osmotically lysed aortic rings (0.00057 min·µg wet weight1·ml1). Ascorbate enhancement of seven-transmembrane-spanning membrane receptor activity occurs in both adrenergic and histaminergic receptors. These receptors may play a significant role in maintaining extracellular ascorbate in a reduced state. molecular complementarity; vitamin C; seven-transmembrane-spanning membrane receptors 相似文献
19.
Cytokinin was found to be a controlling or limiting factor invessel regeneration around a wound in internodes of Coleus blumeiBenth. in which the endogenous cytokinin level was minimized.The cytokinin was applied in aqueous solution to the base ofexcised, mature internodes that had an active vascular cambium.Each internode also received IAA in lanolin at its apical end.Under low (0.1 %, w/w) or high (10%, w/w) auxin concentrations,the control internodes (without exogenous cytokinin) exhibitedsmall amounts of vessel regeneration. At appropriate concentrationszeatin, kinetin and 6-benzylamino-purine (BAP) induced a significantincrease in vessel regeneration around the wound. The threecytokinins also induced novel patterns of supplementary regenerationfurther from the wound surface. Kinetin and BAP showed the strongestpromoting effect at 5 and 10 µg ml1, while zeatinwas most effective at 20 µg ml1. At a low (0.1%) auxin level zeatin was the most effective cytokinin, whereaskinetin was the most effective one at high (1 %) auxin. An inhibitoryeffect on vessel regeneration was observed at the highest kinetinconcentration tested (50 µg ml1). The regenerationof vessels induced by cytokinin was very polar. Many more regeneratedvessel members differentiated below the wound than above it,and the regeneration process proceeded acropetally from thebase of the internode to its upper parts. Our results implya basipetal polar increase in cambium responsiveness along thestem axis from internode 5 to 7. The possible significance ofsuch a basipetal increase in cambium sensitivity in wood formationin trees is discussed. Auxin, Coleus blumei, cytokinin, vascular differentiation, vessel regeneration, wound xylem 相似文献
20.
The Permeability of Ammonia, Methylamine and Ethylamine in the Charophyte Chara corallina (C. australis) 总被引:1,自引:0,他引:1
Ritchie, R. J. 1987. The permeability of ammonia, methylamineand ethylamine in the charophyte Chara corallina (C. australis).J.exp. Bot. 38: 6776 The permeabilities of the amines, ammonia (NH3), methylamine(CH3NH2) and ethylamine (CH3CH2NH2) in the giant-celled charophyteChara corallina (C. australis) R.Br. have been measured andcompared. The permeabilities were corrected for uptake fluxesof the amine cations. Based on net uptake rates, the permeabilityof ammonia was 6?4?0?93 µm s1 (n = 38). The permeabilitiesof methylamine and ethylamine were measured in net and exchangeflux experiments. The permeabilities of methylamine were notsignificantly different in net and exchange experiments, norto that of ammonia (Pmethylamine = 6?0?0?49 µm s1(n = 44)). In net flux experiments the apparent permeabilityof ethylamine was slightly greater than that of ammonia andmethylamine (Pethylamine, net = 8?4?1?2 µm s1 (n= 40)) but the permeability of ethylamine based on exchangeflux data was significantly higher (Pethylamine, exchange =14?1?2 µm s1 (n = 20)). Methylamine can be validlyused as an ammonium analogue in permeability studies in Chara. The plasmalemma of Chara has acid and alkaline bands; littlediffusion of uncharged amines would occur across the acid bands.The actual permeability of amines across the alkaline bandsis probably about twice the values quoted above on a whole cellbasis i.e. the permeability of ammonia across the permeablepart of the plasmalemma is probably about 12 µm s1. Key words: Chara, permeability, ammonia, methylamine 相似文献