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1.
Arborescent stem succulents in tropical and subtropical deserts depend on scarce and uncertain rainfall. Gas exchange and the diurnal acidity fluctuation of bark and ephemeral leaves were measured under both dry and moist soil conditions in Fouquieria columnaris (cirio or boojum tree) and Pachycormus discolor (torote bianco or elephant tree) and in stems of the columnar cactus Pachycereus pringlei (cardon) in the Central Desert of Baja California, Mexico. Results demonstrated that ephemeral leaves were the only site of exogenous CO2 assimilation in F. columnaris and P. discolor; there was no measurable gas exchange across the green photosynthetic bark. The pattern of gas exchange in F. columnaris and P. discolor was consistent with that of C3 plants. P. pringlei was shown to be a typical Crassulacean acid metabolism plant on the basis of acid fluctuations and gas exchange. Chlorophyll fluorescence studies of the green bark of F. columnaris and P. discolor indicated that this tissue is photosynthetically functional, and that CO2 assimilation can rise above the compensation point under high CO2 concentrations, such as may occur within the plant. The green photosynthetic bark of these species may be an adaptation for surviving prolonged drought and may function to recycle endogenous respiratory CO2, thus maintaining the plant's energy reserves and permitting rapid production of leaves in response to infrequent rains.  相似文献   

2.
Localization of acid phosphatases (phosphomonoesterases II EC3.1.3.2 [EC] ) was studied in the secretory cells of stalked glandtissue of Drosera rotundifolia L. using a modified Gomori procedurewith p-nitrophenol phosphate (pNP) as substrate. In unstimulatedand 24 h stimulated tissue, some acid phosphatase activity waslocalized in vacuoles, cell wall regions and cuticular poresof only a few cells. Following stimulation for either 48, 72or 96 h, acid phosphatase activity was additionally observedin most gland cells within the nuclear envelope, endoplasmicreticulum and dictyosome cisternae and their associated vesicles,suggesting a de novo synthesis of acid phosphatases. Acid phosphatase, cytochemistry, Drosera rotundifolia, secretory cells  相似文献   

3.
The response ofH+-ATPase to lethal acid stress isunknown. A mutant strain (called NHE2d) was derived from cultured inner medullary collecting duct cells (mIMCD-3 cells) following three cyclesof lethal acid stress. Cells were grown to confluence on coverslips,loaded with2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein, andmonitored for intracellular pH(pHi) recovery from an acid load. The rate of Na+-independentpHi recovery from an acid load inmutant cells was approximately fourfold higher than in parent cells(P < 0.001). TheNa+-independentH+ extrusion was ATP dependent and K+ independent and wascompletely inhibited in the presence of diethylstilbestrol, N, N'-dicyclohexylcarbodiimide,or N-ethylmaleimide. Theseresults indicate that theNa+-independentH+ extrusion in cultured medullarycells is mediated via H+-ATPaseand is upregulated in lethal acidosis. Northern hybridization experiments demonstrated that mRNA levels for the 16- and 31-kDa subunits of H+-ATPase remainedunchanged in mutant cells compared with parent cells. We propose thatlethal acid stress results in increased H+-ATPase activity in innermedullary collecting duct cells. Upregulation ofH+-ATPase could play a protectiverole against cell death in severe intracellular acidosis.

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4.
2C DNA content values for 70 orchid species from 26 genera,including 37Dendrobiumspecies from eight taxonomic sections,were analysed using flow cytometry. The resulting nuclear DNAcontent values for species other thanDendrobiumranged from 1.91pg 2C-1to 15.19 pg 2C-1nuclei forCadetia tayloriandVanilla phaeantha,respectively.Dendrobiumnuclear DNA content values ranged from1.53 pg 2C-1to 4.23 pg 2C-1nuclei forD. cruentumandD. spectabile,respectively. DNA content measurements varied greatly withinDendrobiumsectionsLatouria and Spatulata. Nuclear DNA content values for the sixspecies analysed within Latouria ranged from 1.88 pg 2C-1nucleiforD. macrophyllumto 4.23 pg 2C-1nuclei forD. spectabile. NuclearDNA content values for the 16 species analysed within Spatulataranged from 1.69 pg 2C-1nuclei forD. discolorto 4.05 pg 2C-1nucleiforD. samoense. The least variation in DNA content was foundwithin the section Phalaenanthe, with nuclear DNA content valuesof 1.79 pg  2C-1, 1.86 pg 2C-1and 1.98 pg 2C-1forD. bigibbum,D.affineandD. phalaenopsis, respectively.Copyright 1998 Annalsof Botany Company Orchidaceae,Dendrobium, flow cytometry, propidium iodide, nuclear DNA, genome size, 2C values.  相似文献   

5.
Laurie acid (1 mg/ml) sharply suppressed the cell division ofan acrA mutant strain of Escherichia coli K12. However, thewild type acrA$ strain was resistant to the fatty acid. Capricacid and myristic acid were not so toxic. Laurie acid inhibitedboth DNA and protein synthesis of the acrA mutant strain, withthe former being more sensitive than the latter. On the otherhand, DNA polymerase activity of toluene-treated cells was stimulatedrather than inhibited by the presence of 1 mg/ml of lauric acid.Fatty acid composition of phospholipids in the inner membranewas largely altered by the addition of lauric acid. These resultssuggest that addition of lauric acid to the medium causes adisorganization of the membrane lipids in the acrA mutant celland activities of DNA polymerase and other intramembranous enzymesare consequently inhibited. 1Present address: Osaka City Institute of Public Health andEnvironmental Sciences. Osaka 543, Japan. (Received January 28, 1983; Accepted November 15, 1983)  相似文献   

6.
When cells of acriflavine-sensitive (acrA) and acriflavine-resistant(acrA+) Escherichia coli K-12 strains were treated with a ratherhigh concentration (100 µg ml-1) of acriflavine in mediumthat had been adjusted to pH 8.1, distinct whirlpool-like structuresderived from the plasma membrane appeared not only in the acrAcells but also in the acrA+ cells. Chemical analysis was performedto determine the lipid composition of the cells by thin-layerchromatography on silica gel and gas-liquid chromatography.The amount of total fatty acids was significantly higher inthe acrA cells than in the acrA+ cells, when cells were culturedin the presence of acriflavine. This difference seems to becaused by the greater accumulation of unsaturated fatty acids(palmitoleic and cis-vaccenic acid) in the acrA mutant cellsthan in the acrA+ cells and by the acceleration of this accumulationas a result of the presence of the dye. A comparison of phospholipidcontents between the acrA and acrA+ cells cultured under acriflavine-freeconditions showed that the former cells contained more phosphatidylethanolamine(PE) and, in particular, more cardiolipin (CL) than the lattercells. However, the situation was reversed in the case of phosphatidylglycerol(PG). Addition of acriflavine to the medium led to a markedincrease in levels of PE and CL in both acrA and acrA+ cellsbut an increase in levels of PG was found only in the acrA+cells. (Received October 13, 1992; Accepted May 31, 1993)  相似文献   

7.
8.
Mesophyll cells isolated enzymatically from Vigna angularisleaves were fed 14Cglucose or 14C-erythrose and the time-courseof 14C incorporation into shikimic and quinic acids was examined.When 14C-glucose was fed to the cells, the highest radioactivityin quinic acid was observed after 10 hr of incubation, whilethat in shikimic acid was after 14 hr. In the experiment with14C-erythrose, the radioactivity in shikimic acid rose strikinglyup to the 3rd hour, but 14C in quinic acid increased graduallyduring the incubation. The incorporation of 14C into shikimicacid was enhanced when unlabeled shikimic or quinic acid wassupplied to the cells simultaneously with either 14C-glucoseor 14G-erythrose, whereas that into quinic acid was not significantlyincreased by these alicyclic acids. The difference in incorporationrate of 14C into quinic acid from that into shikimic acid wasmore conspicuous in the isolated mesophyll cells than in theepicotyls of V. angularis seedlings. 1 Present address: Department of Biology, Faculty of Science,Kumamoto University, Kumamoto 860, Japan. (Received September 22, 1978; )  相似文献   

9.
A gene encoding a novel geranylgeranyl pyrophosphate (GGPP)synthase from Arabidopsis thaliana has been identified and termedGGPS5. The gene has been sequenced and expressed in Escherichiacoli. The deduced amino acid sequence showed 64.5% and 57.5%identity with a putative GGPP synthase from Arabidopsis andCapsicum annuum, respectively. GGPP enzymatic activity was detectedin E. coli cells expressing the GGPS5 gene in two differentways. One was the direct measurement of GGPP synthase activityin cell extracts and the other was the yellow color productionof cells when the GGPS5 gene was co-expressed with crtB, crtI,crtX, crtY and crtZ genes derived from Erwinia uredovora. (Received May 20, 1996; Accepted December 14, 1996)  相似文献   

10.
Saplings of Azadirachta indica Juss. were exposed to sulphurdioxide (SO2) and some of the exposed saplings were treatedwith ascorbic acid (AA). The SO2 exposure alone inflicted heavydamage to the chloroplasts and cytoplasm in palisade cells.The degeneration of chloroplasts was followed by the rupturingof the outer envelope and the extrusion of plastoglobuli andstarch into the cytoplasm. AA treatment counteracted to a certainextent the toxic effects of SO2 on the ultrastructure of chloroplasts. Azadirachta indica, Sulphur dioxide, ascorbic acid, chloroplast, mitigation  相似文献   

11.
Micraspis discolor (Fabricius) (Coleoptera: Coccinellidae) is a widely distributed coleoptera predator in southern Asia in rice ecosystem, and adult M. discolor feed on both rice pollen and soft-bodied arthropods. Bitrophic bioassay and tritrophic bioassay were conducted to evaluate the potential impact of Cry1Ac/Cry1Ab-expressing rice Huahui 1 and its non-transgenic counterpart Minghui 63 on fitness parameters of adult M. discolor. The results showed that the survival, and fecundity of this beetle’ adults were not different when they fed on Bt rice or non-Bt rice pollen or Nilaparvata lugens (Stål) reared on Bt rice or non-Bt rice. Toxicity assessment to ensure M. discolor adults were not sensitive to Cry1Ab or Cry1Ac protein independent from the pollen background, M. discolor adults were fed with an artificial diet containing Cry1Ac, Cry1Ab or both protein approximately 10 times higher concentration than in Huahui 1 rice pollen. No difference was detected for any of the life-table parameters tested between Cry protein-containing and pure diet. Artificial diet containing E-64 (N-(trans-Epoxysuccinyl)-L-leucine 4-guanidinobutylamide) was included as a positive control. In contrast, the pre-oviposition and fecundity of M. discolor were significantly adversely affected by feeding on E-64-containing diet. In both bioassays, the uptakes of Cry protein by adult M. discolor were tested by ELISA measurements. These results indicated that adults of M. discolor are not affected by Cry1Ab- or Cry1Ac-expressing rice pollen and are not sensitive to Cry protein at concentrations exceeding the levels in rice pollen in Huahui1. This suggests that M. discolor adults would not be harmed by Cry1Ac/Cry1Ab rice if Bt rice Huahui 1 were commercialized.  相似文献   

12.
A histochemical study using light microscopy has been made ofthe distribution of acid phosphatase (EC 3.1.3.2 [EC] ) activity intransverse sections of fully expanded leaves of Lycopersiconesculentum grown in phosphate-deficient or sufficient media.Leaf tissues were prepared by two methods and were embeddedin paraffin wax. The location of acid phosphatase activity inleaf sections was determined by trapping orthophosphate releasedfrom p-nitrophenyl phosphate with lead acetate and subsequentlyconverting the lead phosphate to optically dense lead sulphide.In leaf sections from control tissue lead sulphide depositswere larpely confined to the spongy mesophyll cells. Whereasthe staining of the palisade cells was limited and of a granularnature, the staining of the spongy mesophyll cells was heavierand coincident with the outline of the individual cells. Moreover,the minor veins were more heavily stained than the surroundingmesophyll cells. Sections of phosphorus-deficient tissues wereheavily stained in both the palisade and spongy mesophyll layersand heavy deposits of lead sulphide were present in the regionsof the minor veins. It is suggested that the enhanced acid phosphataseactivity of the mesophyll cells in fully expanded leaves couldbe involved in the remobilization of phosphate within phosphorus-deficientplants, or be part of a phosphate transporting system, concentratingthe intracellular phosphate from the limiting supply in thesolution bathing the mesophyll cells. Lycopersicon esculentum L., tomato, acid phosphatase, phosphorus nutrition  相似文献   

13.
To explain the evolution of grouping, Hamilton's selfish herdtheory assumes that predators attack the nearest prey and thatboth are acting on a 2-dimensional (2-D) plane. This proximityassumption in his theory is one explanation for marginal predation,the phenomenon whereby predators attack peripheral members ofa prey group. However, in some ecological circumstances, predatorsmove in 3-dimensional (3-D) space and prey in 2 dimensions.Because a predator coming from above or below the group mayhave relatively equal access to all members, marginal predationcannot be assumed. In this paper, we test whether marginal predationoccurs in such a 3-D/2-D geometry. We carried out 3 controlledlaboratory experiments in which fish attack prey grouped atthe water's surface. Predators were bass (Micropterous salmoides)or goldfish (Carassius auratus), and prey groups were eitherfree-swimming whirligig beetles (Dineutes discolor) or a constrainedgroup of tadpoles (Bufo bufo). In all 3 experiments, predatorswere significantly more likely to attack the periphery of preygroups. Our experiments also show that marginal predation isrobust to differences in overall density within a prey groupand that the fish are not reacting to observable state or behavioralcorrelates to position within a prey group. Furthermore, ourresults showed that predators will attack group margins evenwhen there is no variation, due to position, in nearest neighbordistance.  相似文献   

14.
The effect of cellular differentiation on fatty acid uptake andintracellular diffusion was examined in transfected pluripotent mouseembryonic stem (ES) cells stably expressing intestinal fatty acidbinding protein (I-FABP). Control ES cells, whether differentiated orundifferentiated, did not express I-FABP. The initial rate and maximaluptake of the fluorescent fatty acid,12-(N-methyl)-N-[(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-octadecanoic acid (NBD-stearic acid), was measured in single cells by kinetic digital fluorescence imaging. I-FABP expression in undifferentiated EScells increased the initial rate and maximal uptake of NBD-stearic acid1.7- and 1.6-fold, respectively, as well as increased its effectiveintracellular diffusion constant(Deff) 1.8-foldas measured by the fluorescence recovery after photobleachingtechnique. In contrast, ES cell differentiation decreased I-FABPexpression up to 3-fold and decreased the NBD-stearic acid initial rateof uptake, maximal uptake, andDeff by 10-, 4.7-, and 2-fold, respectively. There were no significant differencesin these parameters between the differentiated control anddifferentiated I-FABP-expressing ES cell lines. In summary,differentiation and expression of I-FABP oppositely modulatedNBD-stearic acid uptake parameters and intracellular diffusion in EScells.

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15.
LU  CHIN-YI; VASIL  I. K. 《Annals of botany》1981,48(4):543-548
Embryogenic calluses derived from cultured immature embryosand young inflorescences of Panicum maximum Jacq. were placedin Murashige and Skoog's liquid medium supplemented with 1 mg1–1 2, 4- dichlorophenoxyacetic acid (2, 4-D) and 2.5per cent coconut water, to initiate suspension cultures. Suspensionsconsisted of two types of cells: small, richly-cytoplasmic andoften starch-containing embryogenic cells, and large, vacuolatednon-embryogenic cells. A presumed sequence of developmentalstages from single embryogenic cells to globular and heart-shapedstages of embyrogenesis was observed in the suspension cultures.Plantlets were produced from the embryoids when the suspensionswere plated in an agar medium without any hormone or with only0.2 mg 1–12, 4-D or naphthalene acetic acid. Embryogenicsuspension cultures derived from immature embryos as well asfrom inflorescence segments gave rise to plants which showedthe normal somatic chromosome number of 2n = 4x = 32. Panicum maximum Jacq., Guinea grass, embryogenesis, regeneration, suspension culture  相似文献   

16.
The pattern of radioactivity distribution in several amino acidsof Chromatium cells exposed to 14CO2 was determined. By transferringthe bacterial cells from an atmosphere of nitrogen to oxygenthere occurred a transient decrease of 14CO2 incorporation intoaspartate and glutamate, whereas that into glycine showed aprominent increase. The labeling of both serine and alaninedid not show a marked change under such conditions. The, activitiesof glycolate oxidase and glycolate dehydrogenase in crude extractsof the bacterial cells were very low. The formation of glycolic acid only occurred during the oxidativemetabolism of Chromatium cells grown on bicarbonate as a C source,being negligibly small in bacteria under nitrogen or after growthon malate or acetate. The activities of both ribulose- 1,5-bisphosphateoxygenase and phosphoglycolate phosphatase in the extract preparedfrom the bicarbonate-grown bacterial cells were very low andapparently could not account for the glycolic acid formationthrough these enzymic reactions. Metabolic patterns of glycolicacid in Chromatium are discussed in relation to the photorespiratoryphenomenon. (Received February 24, 1975; )  相似文献   

17.
18.
Epicuticular waxes were removed from the leaf surfaces of Oleaeuropaea and Prunus persica by washing with chloroform and theresulting rinses were analysed by high performance liquid chromatography(HPLC) for the presence of fluorescing compounds. Removal ofepicuticular waxes from leaves of some representative plantsby the same treatment resulted in a significant reduction inthe intensity of the blue fluorescence emitted from guard cells(Karabourniotis et al., 2001: Annals of Botany. doi:10.1006/anbo.2001.1386).Ferulic acid and p-coumaric acid, as well as a number of unidentifiedcompounds, were constituents of the rinses of both plants examinedbut only after alkaline hydrolysis of the samples. This indicatesthat both phenolic acids are tightly bound to the epicuticularwaxes of the leaves of these plants. HPLC chromatograms of rinsesderived either from the abaxial or adaxial surfaces of the hypostomaticleaves of O. europaea did not show significant qualitative differences.Nevertheless, ferulic acid (the main blue fluorescent component)was much more abundant in the abaxial than the adaxial surface.In P. persica, the composition of the sample derived from theabaxial surface was far more complex, and all constituents werepresent in much higher concentrations than in the sample derivedfrom the adaxial surface. Given the particular fluorescencecharacteristics of ferulic acid, the differences in its concentrationbetween abaxial and adaxial surfaces, and between the two species,and the fluorescence images of these surfaces under the microscope,we propose that this compound is probably the main epicuticularconstituent responsible for the blue fluorescence emitted byguard cells of the species examined. The functional significanceof the findings is discussed. Copyright 2001 Annals of BotanyCompany Cuticle, epicuticular waxes, ferulic acid, HPLC analysis, Olea europaea L., p-coumaric acid, phenolics,Prunus persica L., stomata  相似文献   

19.
Products of IAA decomposition by IAA destroying enzyme-inducedand non-induced cells of Arthrobacter sp. were examined. Catecholand pyrogallol, and 3-methyldioxindole were respectively identifiedfor non-induced and induced cells. Exogenous catechol was readilyoxidized by induced cells, but was not oxidized by non-inducedcells. Exogenous pyrogallol, 3-methyldioxindole, indole-3-aldehyde,skatole, 2,3-dihydroxindole, 3-methyleneoxindole, o-aminoacetophenone,3-hydroxyanthranilic acid, anthranilic acid and salicylic acidwere oxidized by neither induced nor non-induced cells. (Received June 16, 1969; )  相似文献   

20.
Identification of maize silicon influx transporters   总被引:1,自引:1,他引:0  
Maize (Zea mays L.) shows a high accumulation of silicon (Si),but transporters involved in the uptake and distribution havenot been identified. In the present study, we isolated two genes(ZmLsi1 and ZmLsi6), which are homologous to rice influx Sitransporter OsLsi1. Heterologous expression in Xenopus laevisoocytes showed that both ZmLsi1 and ZmLsi6 are permeable tosilicic acid. ZmLsi1 was mainly expressed in the roots. By contrast,ZmLsi6 was expressed more in the leaf sheaths and blades. Differentfrom OsLsi1, the expression level of both ZmLsi1 and ZmLsi6was unaffected by Si supply. Immunostaining showed that ZmLsi1was localized on the plasma membrane of the distal side of rootepidermal and hypodermal cells in the seminal and crown roots,and also in cortex cells in lateral roots. In the shoots, ZmLsi6was found in the xylem parenchyma cells that are adjacent tothe vessels in both leaf sheaths and leaf blades. ZmLsi6 inthe leaf sheaths and blades also exhibited polar localizationon the side facing towards the vessel. Taken together, it canbe concluded that ZmLsi1 is an influx transporter of Si, whichis responsible for the transport of Si from the external solutionto the root cells and that ZmLsi6 mainly functions as a Si transporterfor xylem unloading.  相似文献   

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