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1.
Callose formation in phloem tissue was promoted by 0.5% eosinin 1 cm segments taken from first year Willow (Salix viminalisL.) shoots and by localized heat treatments in intact secondyear shoots. The eosin did not cause any change in the incorporationof 14C from labelled sucrose into an insoluble fraction butless of the label: from UDP-glucose labelled in the glucosemoiety was incorporated when eosin was present. Localized heattreatments of intact second-year tissue which was translocating[14C]sucrose failed to cause an increase in the amount of labelin an insoluble fraction in the zone where callose formationwas stimulated. The results indicate that the callose formedrapidly in response to stress and wounding is not derived directlyfrom translocated sucrose. An alternative possible origin, fromsugar nucleotides released from ruptured plastids, is discussed.  相似文献   

2.
The kinetics of 14C-2-acetate assimilation by Chlorella pyrenoidosain the light were examined. Under aerobic conditions the primaryproduct of acetate assimilation was succinic acid which, afterten seconds, contained over 60 per cent of the 14C incorporatedby the cells. The percentage of the total 14C in succinate fellwith time, while that in citrate and glutamate increased. After1800 sec over 60 per cent of 14C was present in two compounds,glutamic acid and an unknown compound (X). Glucose-6-phosphate,fructose-6-phosphate, phosphoglyceric acid and phosphoenolpyruvicacid became labelled after 60 sec but together never containedmore than one per cent of the total 14C incorporated. Underanaerobic conditions succinate was still the primary productof acetate assimilation, and the absence of carbon dioxide resultedin a decrease in 14C incorporation into compound X. The patternof acetate assimilation in acetate grown and acetate adaptedChlorella was very similar to that in photo-autotrophicallygrown Chlorella. In the presence of 10–6M DCMU, succinicacid was the primary product of acetate assimilation, but therewas an early Incorporation of 14C into glutamate, aspartate,and malate. 4 x10–3M MFA did not effect the early incorporationof 14C into succinic acid, but resulted in accumulation of 14Cin citrate and a decreased amount in glutamate and in compound X.  相似文献   

3.
The effect of the substituted pyridazinone herbicides, Sandoz9785 and Sandoz 6706, on lipid metabolism was studied in greeningbarley leaves. The herbicides had no effect on chlorophyll formationbut caused an altered chloroplast morphology during greening.In leaves supplied with {14C} acetate, Sandoz 9785 decreasedincorporation of radioactivity into linolenate while Sandoz6706 decreased incorporation into both linolenate and trans-3-hexadecenoate.Decreased linolenate labelling was accompanied by an accumulationof {14C}linolenate in diacylgalactosylglycerol. {14C}Palmitateaccumulated in phosphatidylglycerol when synthesis of trans-3-hexadecenoatewas inhibited. The results are discussed in relation to thefunction of acyl lipids in fatty acid desaturation and the roleof lipids in chloroplast morphology. Key words: Chloroplast structure, Lipid synthesis, Substituted pyridazinones, Fatty acid desaturation  相似文献   

4.
S-Methyl-L-cysteine was actively metabolized in Chinese cabbageand carbon from its methyl group was distributed into both thesoluble and insoluble fractions. The high incorporation of 14Cfrom the methyl group into the insoluble fraction after administeringof S-methyl-L-cysteine-14CH3, and our previous results thatS-methyl-L-cysteine is demethylated to give cysteine, suggestthat S-methyl-L-cysteine might act as a methyl donor in Chinesecabbage. To obtain evidence for this possibility, incorporationof the methyl-14C of S-methyl-L-cysteine into methyl estersof pectic substances was investigated. Most of the 14C incorporatedinto pectic substances was liberated by treatment with dilutealkali and pectin esterase. The results show that S-methyl-L-cysteineacts as a methyl donor to form pectin ester. (Received October 12, 1971; )  相似文献   

5.
The effects of chloramphenicol and kinetin on uptake and incorporationof 35S-methionine and some 14C-amino acids have been investigatedin leaf-disks of Nicotiana rustica in light and dark. Chloramphenicolin a concentration of 1 mg per ml inhibits the uptake of aminoacids from 30 to 60 per cent compared with the water control.The incorporation of amino acids into bulk protein is stronglyinhibited in light (40 to 70 per cent), but only to a smalldegree in dark (10 to 20 per cent), as revealed also by 14CO2-photosynthesisof the disks and following treatment with chloramphenicol indark. The stimulating effect of kinetin on uptake and incorporationof amino acids is dependent upon its concentration (10–5to 10–6 M ; but 10–4 M solution inhibits stronglyboth uptake and incorporation). The stimulation seems to influencemore incorporation than uptake processes. Possible interactionsof chloramphenicol and kinetin in the protein metabolism oftobacco leaves have been discussed. (Received April 27, 1964; )  相似文献   

6.
A culture system of isolated mesophyll cells of Zinnia eleganswas used to examine the action of gibberellic acid (GA) on celldivision. Isolated Zinnia mesophyll cells cultured in a mediumcontaining auxin and cytokinin reinitiated cell division ina partly synchronized manner. When mesophyll cells isolatedfrom 21-day-old seedlings were used, GA added to the culturemedium at concentrations of 1 x 10–6 M or higher suppressedthe initial rise in the number of divided cells. Tracer experimentswith [3H]-dThd revealed that GA treatment inhibited the incorporationof [3H]-dThd into DNA in the nucleus without inhibiting theuptake of [3H]-dThd into the cells, indicating that GA inhibitedDNA synthesis. GA applied at 48 h inhibited the incorporationof [3H]-dThd into DNA during the following 24 h, but GA appliedat 72 h did not inhibit the incorporation during the subsequent24 h. This suggests that GA affects the process of reinitiationof DNA synthesis, but does not affect DNA synthesis once cellshave become proliferative. (Received January 14, 1986; Accepted March 31, 1986)  相似文献   

7.
Effect of Phytolectins on Isolated Protoplasts from Plants   总被引:1,自引:0,他引:1  
The effects of three phytolectins on isolated plant protoplastshave been examined. It was found that concanavalin A, phytohemagglutininand wheat germ agglutinin were all capable of agglutinatingprotoplasts isolated from a variety of plant species. The incorporationof 3H-uridine, 3H-thymidine and 14C-leucine into RNA, DNA andprotein respectively was also stimulated by the three lectinsin isolated protoplasts. Treatment with -methyl-D-mannosideabolished both the agglutinating and incorporation enhancingeffects of concanavalin A (Con A) on barley protoplasts. Protoplastswith a regenerated cell wall also failed to respond to lectintreatment. These results suggest that lectin-binding to theprotoplast membrane surface is required before either agglutinationor metabolic stimulation will result. isolated protoplasts, agglutination, lectins  相似文献   

8.
Carbon-specific phytoplankton growth rates: a comparison of methods   总被引:1,自引:0,他引:1  
Measurements of biomass and growth rate of two axenic algalcultures were carried out using three different methodologicalapproaches: the specific 14C-labelling of chlorophyll a, [3H]adenineincorporation into DNA and net organic carbon assimilation.Time-course experiments revealed that the specific activitiesof chlorophyll a were significantly higher than the specificactivity of total algal carbon in six of seven experiments.When the specific activity of chlorophyll a is used to calculatethe carbon biomass and growth rate, the carbon biomass of thealgae will thus be underestimated and the specific growth ratewill be too high. Determination of growth rates from incorporationof [3H]adenine gave lower values than those obtained from netorganic carbon assimilation and from 14C incorporation intochlorophyll a. Problems with adenine saturation are suggested.When [3H]adenine is used to measure growth rates in dense algalcultures, additions of >1 µM [3H]adenine are oftenrequired to maximally label the extracellular and intracellularadenine pools and hence DNA.  相似文献   

9.
Glycollate Formation during the Photorespiration of Acetate by Chlorella   总被引:1,自引:0,他引:1  
WhenChlorella pyrenoidosa photoassimilates 3H-14C-acetate theglycollic acid formed shows a high 3H/14C ratio, the only othercompounds showing similar ratios being glycerate and serine.The 3H/14C ratio of glycollate was unaffected by the TCA cycleinhibitors MFA, diethylmalonate and arsenite showing that 3Hin glycollate does not result from the oxidation of acetatevia the TCA cycle, the resulting NADP3H2 or NAD3H2 being usedfor the reduction of the glycollate precursor. Although DCMUdecreased the 3H/14C ratio, complete inhibition of glycollatelabelling was not observed with 10–6 M DCMU, at whichconcentration complete inhibition of the Hill reaction is achieved.Although the 3H/14C ratio was unaltered, total dpm of both 14Cand 3H in glycollate were increased by INH. The 3H/14C ratiosof glycerate and serine were decreased by INH, as were the totaldpm of 3H and 14C incorporated into these compounds. Thus, INHinhibits the further metabolism of glycollate to glycerate andserine. The effect of INH on incorporation of 14C-I-acetateinto various cell fractions was investigated. The incorporationof 14C into polysaccharide and lipid was decreased, while theincorporation of 14C into the water-soluble fraction of cellsand therelease of 14CO2 were little affected. Although glycollicacid was an early product of acetate photoassimilation in Chlorellapyrenoidosa, glycollate excretion does not take place undera wide range of environmental conditions shown to favour glycollateexcretion by other algae. However, small amounts of labelledglycollate were detected in the supernatant from the cells duringthe photoassimilation of 3H-14C-acetate, but this glycollatedid not show the high 3H/14C ratio of glycollate present withinthe cell. The failure of Chlorella pyrenoidosa to excrete appreciableamounts of glycollate when photoassimilating acetate or carbondioxide was considered to result from the presence of glycollateoxidase (EC 1.1.3.1 [EC] ) which allowed the further metabolism ofglycollate. Besides glycollate oxidase, glyoxylate reductasewas also demonstrated in Chlorella pyrenoidosa so that glycollatecould function in hydrogen transfer during the photoassimilationof acetate.  相似文献   

10.
The polar lipids and fatty acids of the microalgae Pavlova lutheriwere analyzed. The principal polar lipid components were monogalactosyldiacylglycerol(MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinovosyldiacylglycerol(SQDG), 1,2-diacylglyceryl-O-2'-hydroxymethyl-(N,N,N-trimethyl)-rß-alanine(DGTA) and 1,2-diacylglyceryl-3-O-carboxyhydroxymethylcholine(DGCC). Each polar lipid had a different set of combinationsof fatty acids, the most characteristic feature being the localizationof polyunsaturated fatty acids in the betaine lipids. The percentagesof polyunsaturated fatty acids in DGTA and DGCC were 70% and50%, respectively, and these fatty acids were localized at theC-2 position in the betaine lipids. An analysis of the incorporationof 14C-labelled compounds into the algal cells indicated theinvolvement of DGCC in acyl exchange. (Received October 17, 1994; Accepted October 2, 1995)  相似文献   

11.
The carbon-2 of glycine can be incorporated into the methylgroup of dimethyl-ß-propiothetin in Ulva lactuca.This conversion is stimulated by unlabelled methionine. Highconcentrations of unlabelled glycine inhibit the incorporationof either L-methionine-35S or L-methionine-methyl-14C into DMP.The specific activity of methionine, isolated from alga incubatedwith glycine-2-14C and a high concentration of unlabelled methionine,is too low to permit it to be an intermediate in glycine-2-14Cincorporation into DMP. The incorportaion of radioctivity fromL-methionine-35S and L-methionine-methyl-3H into DMP indicatesthat while at least one methyl group is derived from methionine,other compounds can donate a portion of the second methyl group.It is concluded that glycine incorporation into the methyl groupof DMP is not via methionine.  相似文献   

12.
A method suitable for the large-scale isolation of cereal protoplastsfrom up to 50 g of leaf material is described. Surface-sterilizedleaves from cultivars of wheat, barley, maize, sorghum, andTriticale were diced and vacuum infiltrated with enzyme mixturecomposed of cellulysin (1 per cent w/v), hemicellulase (1 percent w/v), and macerozyme (0.5 per cent w/v). With this procedure,yields of between 106 to 107 protoplasts per gram of leavescan be reproducibly obtained after only 1.5–3 h of enzymatictreatment. These protoplasts were almost 100 per cent viable(as determined by fluorescein diacetate staining) and incorporationof 3H-uridine and 14C-leucine into an acid-insoluble fractionwas demonstrated. Almost one-third of the ribosomes of theseisolated protoplasts were present as polysomes. cereals, leaf mesophyll, protoplast isolation  相似文献   

13.
All three races of Neotricula aperta, an epilithic, schistosometransmitting, snail of the Mekong and Mul rivers of NortheastThailand and southern Laos, were found to take up acetate froma dilute solution. After 48 h incubation the mean specific netuptake rates (µmol–1 g–1 h–1), from750 µM acetate, were: 1.86, -race; 1.39, ß-raceand 3.25, y-race. Over 48 h the snails were able to achievereductions in the ambient acetate concentration of up to 60%.Incubations under bacteriostatis suggested that bacteria arenot involved in the uptake of acetate by N. aperta. The uptakecharacteristics conform to the Michaelis-Menten model. The transportconstants, Jmax (µmol–1 g–1 h–1) andKt (µM) were 1.10 and 102 respectively (-race). Racialdifferences in uptake characteristics are discussed in relationto micro-habitat differences. HPLC indicated concentrations of acetate in y-N. aperta microhabitatsof around 325 µM. This suggests a pool size sufficientto satisfy only 6% of the snail's basal metabolic rate (BMR).Levels within the epilithic aufwuchs, however, are probablyhigh enough to provide for more than 50% of the BMR. The possible role of acetate in the energy metabolism of N.aperta is discussed. Short-chain carboxylic acids (such as acetate),arising from the decomposition of the aufwuchs, could representsources of fermentable organics that may be taken up by N. apertasnails and used to supplement their nutrition during times offood shortage. However, further investigations involving 14C-labellingtechniques are required. The findings of this investigationhave implications for the chemical ecology and life-cycle ofN. aperta. (Received 16 June 1994; accepted 28 July 1994)  相似文献   

14.
Photosynthesis under conditions known to favour glycollate excretionby algae did not result in glycollate excretion in a strainof Chlorella pyrenoidosa unless an inhibitor of glycollate oxidase,-hydroxypyridin-2yl-methane sulphonate (-HPMS), was present.This inhibitor increased the total amount of glycollate presentin the supernatant from the cells during photosynthetic carbondioxide fixation and gave accumulation of 14C in glycollateduring 14CO2 fixation under conditions favouring glycollatesynthesis. At pH 8.3 -HPMS did not stimulate photosynthetic14CO2 fixation in C. pyrenoidosa as occurs with some algae.Photoassimilation of acetate was inhibited by -HPMS, and thiswas shown to result from acetyl-CoA synthetase inhibition by-HPMS.  相似文献   

15.
When UDP-[14C]glucose or UDP-[14C]xylose was incubated witha particulate fraction from soybean cells, radioactive polymerswere synthesized. On digestion with Aspergillus oryzae enzymes,these polymers gave 14C-monosaccharides and a 14C-disaccharidewith chromatographic and electrophoretic mobilities indistinguishablefrom those of authentic isoprimeverose (6-O--D-xylopyranosyl-D-glucopyranose).The disaccharide consisted of xylose and glucose, and the latterwas located at the reducing end. Evidence that the disaccharideis isoprimeverose was provided by methylation analysis. Hydrolysisof the methylated disaccharide yielded 2,3,4-tri-O-methyl-D-xyloseand 2,3,4-tri-O-methyl-D-glucose. Thus, incorporation of radioactivityinto isoprimeverose, the smallest structural unit of xyloglucan,suggests that xyloglucan is synthesized in vitro from UDP-glucoseand UDP-xylose. (Received November 20, 1980; Accepted February 14, 1981)  相似文献   

16.
Photosynthetic carbon metabolism was studied with Chroomonassp. cells in which the rate of photosynthesis was inhibitedunder both an anaerobic condition and high concentrations ofoxygen. The time course of 14C-incorporation into photosyntheticproducts showed that 3-phosphoglycerate was the initial productof photosynthetic CO2 fixation in Chroomonas sp. cells. During5-min photosynthesis, a considerable amount of 14C was incorporatedinto the insoluble fraction (mostly cryptomonad starch), andoxygen predominantly affected 14C-incorporation into this fraction.Although 14C-incorporation into intermediates of the photorespiratorypathway increased with increasing O2 concentration, the amountswere much less than expected from the degree of oxygen inhibition.It is noteworthy that 14C-dihydroxyacetone phosphate accumulatedduring photosynthesis only under the anaerobic condition, whereasthe levels of the other phosphate esters were scarcely affectedby the oxygen concentration. Ribulose-1,5-bisphosphate carboxylase from Chroomonas sp. wascompetitively inhibited by oxygen, and its Km(CO2) value wassimilar to those of terrestrial C3 plant enzymes. (Received November 19, 1984; Accepted May 20, 1985)  相似文献   

17.
Gibberellic acid (GA3) at 58 µM, indoleacetic acid (IAA)at 29 µM, and (2-chloroethyl) phosphonic acid (Ethephon)at 70 µM promoted pollen tube growth in Crotalaria junceapollen suspension cultures both in water and basal medium. GA3stimulated [ l-14C]acetate incorporation into total lipids inboth media, whereas IAA enhanced incorporation in water culturesonly. On the contrary, Ethephon reduced the label in total lipidswhen supplemented in basal medium. Based on [l-14C lacetateincorporation into different phospho- and glycolipids, it isproposed that these growth regulators have a definite role inthe biosynthesis of lipid components of the membranes.  相似文献   

18.
A crude membrane fraction from Chlamydomonas reinhardii transferredradioactivity from UDP-[14C]galactose to endogenous lipids.Most of the radioactivity was detected in digalactosyl diacylglycerolmoieties in which only the distal galactose residue (-linkedto monogalactosyl diacylglycerol) was labeled. A second compoundwas identified as monogalactosyl diacylglycerol labeled in thegalactose moiety ß-linked to glycerol. In additionto these two galactolipid species, trace amounts of radioactiveglucose were detected in the aqueous phase after mild acid treatmentof the total lipid fraction. This demonstrates the presenceof a 4-epimerase and provides indirect evidence for the presenceof a small amount of polyprenyl-monophosphate-glucose whichwas presumably not detectable per se because of the bulk ofneutral galactolipids. The failure to detect polyprenyl-phosphate-galactoseor mild acid labile galactose at any time during the incubationsuggests that galactosylation of Chlamydomonas proteins mightoccur without the involvement of lipid intermediates. (Received May 10, 1982; Accepted August 21, 1982)  相似文献   

19.
The effect of changes in the environment on lipid metabolismhas been studied in the brown alga, Fucus serratus L. Lightstimulated the incorporation of radioactivity from /{I4C/}acetateinto oleic and, especially, into linoleic acid. The same effectwas caused by lowering the incubation temperature from 15 °Cto 4 °C. Incubations in the presence of Cd + +, Pb + + orZn+ + had no effect on the total uptake of /{14C/}acetate intothe frond tip samples, but lowered the labelling of total lipidsrelative to aqueous-soluble components. However, pre-exposureof the algae to heavy metal cations caused changes in the uptakeof radioactivity but had less effect on the relative labellingof lipids than incubations in the presence of heavy metal cations.Algae collected from sites where the dissolved levels of heavymetals were elevated, showed a decrease in the relative labellingof lipids from /{14C/}acetate. Concentrations of Cd+ +, Pb++ or Zn+ + at 10 x levels found at the collection site had littleeffect on the pattern of fatty acids made by Fucus serratus. Key words: Lipid metabolism, Fucus serratus L., Environmental changes  相似文献   

20.
Farnesol-2-14C was readily incorporated into ipomeamarone, oneof the furanoterpenoids produced in sweet potato infected withthe black rot fungus, Ceratocystis fumbriata. This was demonstratedby isolating labeled ipomeamarone and analyzing its radioauto-gramby silica gel thin layer chromatography of the extracts solublein chloroformmethanol (1: 1 , v/v), after farnesol-2-14C feedingto the tissue. Further proof for farnesol-2-14C incorporationinto ipomeamarone comes from the fact that the specific radioactivityof ipomeamarone semicarbazone was constant throughout the crystallizations.Fractionation of the label of farnesol-2-14C showed that radioactivitywas little distributed in the methanol-water fraction and wasmainly incorporated into ipomeamarone. Accordingly, it is notlikely that farnesol is incorporated into ipomeamarone afterits degradation to a small molecule(s) such as acetate. An additionalexperiment indicatedthat the incorporation of farnesol-2-14Cinto ipomeamarone markedly decreased under strict anaerobicconditions. This shows that some oxidative reactions are involvedin ipomeamarone biosynthesis from farnesol. 1 This paper constitutes Part 91 of the Phytopathological Chemistryof Sweet Potato with Black Rot and Injury. (Received February 3, 1971; )  相似文献   

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