共查询到20条相似文献,搜索用时 31 毫秒
1.
Oka Kotaro; Ikeshima Hiroko; Ishikawa Hideo; Ohta Eiji; Sakata Makoto 《Plant & cell physiology》1988,29(5):771-775
We showed that the surface charge density of protoplasts canbe estimated by the 9-aminoacridine method. The estimated surfacecharge density of the protoplasts isolated from elongating regionsof Vigna mungo root was 39 ? 8 mC/m2. The negative surfacecharge density increased when protoplasts were treated withglutaraldehyde or when EDTA was added to the protoplast suspensionmedium. These results support the validity of our estimationof the surface charge density of protoplasts by the 9-aminoacridinemethod. The concentration of amino groups at the surface ofthe protoplasts was estimated to be 34 mC/m2. (Received June 19, 1987; Accepted April 11, 1988) 相似文献
2.
The influences of light of different wavelengths and plant growthregulators on the respiration of protoplasts isolated from tissue0 to 5 mm above the basal intercalary meristem of barley (Hordeumvulgare L. cv. Patty) leaves were studied. Respiration was measuredusing oxygen electrodes and a Cartesian-diver technique. Red,far-red and blue light all stimulated respiration in the protoplastsbut not in mitochondria isolated from them. Gibberellic acid stimulated respiration in protoplasts but abscisicacid had the opposite effect. Physiological concentrations ofindole-3-acetic acid and kinetin had no influence in eitherdirection. Combinations of gibberellic acid with light of anywavelength always increased respiration. Red or far-red light treatments in the presence of abscisicacid decreased dark respiration and only blue light significantlyreversed the inhibitory effect of abscisic acid. Cycloheximidemarkedly increased dark respiratory activity; chloramphenicolwas without effect. These results indicate that mitochondrialactivity in the leaf basal intercalary meristem was partiallycontrolled through phytochrome and a blue light receptor, andby gibberellic and abscisic acids. Changes in cytosolic proteinsynthesis were important for the initiation of enhanced mitochondrialactivity in meristems. Hordeum vulgare L., barley, abscisic acid, Cartesian-diver microrespirometry, gibberellic acid, meristematic respiration, protoplasts 相似文献
3.
OWEN JOHN H.; HETHERINGTON ALISTAIR M.; WELLBURN ALAN R. 《Journal of experimental botany》1987,38(3):498-505
Owen, J. H., Hetherington, A. M. and Wellburn, A. R. 1986. Inhibitionof respiration in protoplasts from meristematic tissues by abscisicacid in the presence of calcium ions.J. exp. Bot. 38:498505. A study was made of the influences of abscisic acid (ABA) andcalcium ions on mitochondrial respiration in protoplasts fromcells close to the basal intercalary meristem of light-grownbarley (Hordeum vulgare L. cv. Patty) seedlings. This respirationwas inhibited by ABA only when calcium ions were present. Thecalcium channel agonist BAY K8644 caused a significant inhibitionof protoplast dark respiration, similar to that observed usingABA and calcium, presumably because it imitated the action ofABA by increasing calcium influx into protoplasts. These resultssuggest that ABA increases the permeability of the plasmamembraneto calcium and that calcium acts as a second messenger to regulatemitochondrial respiratory activity and thus the very early eventsassociated with plastid and meristematic cell development. Key words: Abscisic acid, calcium, meristematic respiration 相似文献
4.
Obi Ichiro; Kakutani Tadaaki; Imaizumi Nobutoshi; Ichikawa Yoshiaki; Senda Mitsugi 《Plant & cell physiology》1990,31(7):1031-1037
Electrophoretic mobilities of hetero-fused plant protoplasts,which were obtained by electrofusion of barley mesophyll cellprotoplasts and Rauwolfia serpentina cultured cell protoplasts,and those of the unfused parent protoplasts were measured invarious media of different pH values. At pH 5.2, the zeta potentialof the fused protoplasts was intermediate between those of thebarley and R. serpentina protoplasts and the average surfacecharge density of the fused protoplasts was closer to that ofR. serpentina than to that of barley. The distribution of thesurface charge density of fused protoplast obtained at pH 5.2is discussed in terms of the surface charge densities and thesizes of parent protoplasts. These results revealed that thesurface charge density of fused protoplasts was determined bythe surface charge densities and the ratio of the surface areasof the respective parent protoplasts. (Received December 28, 1989; Accepted August 10, 1990) 相似文献
5.
Pantoja, O. and Willmer, C. M. 1986. Pressure effects on membranepotentials of mesophyll cell protoplasts and epidermal cellprotoplasts of Commelina communis L.J. exp. Bot. 37:315320. Membrane potentials of epidermal cell protoplasts and mesophyllcell protopiasts of Comnelina communis were measured when theprotoplasts were immobilized in a suction micropipette. Whenzero suction was employed, membrane potentials of both protoplasttypes were near to zero. As suction pressure was increased,membrane potentials became increasingly more negative with gradientsof 14·3 mV/kPa and 10·5 mV/kPa for mesophyll cellprotoplasts and epidermal cell protoplasts, respectively. Theplasma membrane is stretched when suction pressure is appliedto protoplasts and it is considered that this simulates cellturgor pressure which is associated with negative membrane potentialsof intact cells. The results help to explain why some investigatorsobtain positive membrane potentials for protoplasts while othersobtain negative values. The results also indicate that considerablecaution is needed in the interpretation of ion flux data whenprotoplasts are used. Key words: Commelina communis, membrane potentials, pressure, protoplasts 相似文献
6.
Fitzsimons, P. J. and Weyers, J. D. B. 1987. Responses of Commelinacommunis L. guard cell protoplasts to abscisic acid.J.exp. Bot. 38: 9921001. Guard cell protoplasts (GCPs) isolated from the leaf epidermisof Commelina communis L. responded to abscisic acid (ABA) ina manner which was qualitatively and quantitatively similarto that of intact stomata. ABA inhibited swelling of GCPs underlow-CO2 conditions and swollen GCPs responded to the hormoneby shrinking. Both the absolute volume decrease and the initialrate of shrinking were commensurate with the extent and ratesof solute loss computed for ABA-treated intact, open stomata.This indicates that GCPs represent a suitable experimental systemfor studies of ABA-mediated solute fluxes. A radiotracer equilibrationmethod was developed for the rapid estimation of GCP osmoticvolume changes. Using this technique it was found that, on average,82% of the reduction in solute content caused by ABA treatmentwas due to the loss of K+. It is envisaged that electroneutralitymight be maintained during ABA-induced shrinkage of GCPs bynet inward proton movement leading to acidification of the vacuole. Key words: Abscisic acid, Commelina communis L., guard cells, protoplasts 相似文献
7.
Viable protoplasts were isolated for the first time from maturecarob (Ceratonia siliqua L.) endosperm tissue. After 5 d ofincubation 75% of the protoplasts were viable. During incubationthey underwent vacuolation and produced the carob endospermhydrolases, agalactosidase and endo-ß-mannanase, whichwere secreted in the incubation medium. The secretion of bothenzymes were under Ca2+ control. Many characteristics of -galactosidaseand endo-ß-mannanase production by protoplasts werethe same as those of whole endosperms: their production didnot require any hormonal signal and was inhibited in the presenceof ABA or the leachate from the carob endosperm/seed coat. Moderatewater stress (2.0 MPa) neither affected the activityof these hydrolases nor their secretion by endosperm protoplast.However, when the osmoticum of protoplast incubation mediumwas higher, the production and secretion of both hydrolaseswere reduced. Comparison of the hydrolases activities in theincubation media of leached carob endosperms, which were incubatedunder normal and water stress (1.5 MPa) conditions, withthe activities of the protoplast-secreted hydrolases indicatedthat (i) carob endosperm cell wall acts as a barrier for thesecreted enzymes and (ii) that water stress reduces the cellwall porosity of the carob endosperm cells, and thus the releaseof the secreted -galactosidase and endo-ß-mannanaseis inhibited. The isolation of carob endosperm protoplasts offersa potent experimental system for the study of aspects of endospermcell physiology, such as enzyme secretion Key words: Abscisic acid, carob endosperm, Ceratonia siliqua L, endo-ß-mannanase, -galactosidase, leachate, protoplasts, water stress 相似文献
8.
GARCIA-FLORENCIANO E.; CALDERON A. A; MUNOZ R.; BARCELO A. ROS 《Journal of experimental botany》1992,43(5):715-721
The functionality of the decarboxylative pathway of indole-3-aceticacid (IAA) was studied in both suspension-cultured cells andprotoplasts of grapevine (Vitis vinifera cv. Gamay) throughfeeding experiments with labelled IAA. The results showed that,although cells and protoplasts were capable of taking IAA fromthe media, the ability to oxidize IAA was restricted to thecell wall of cultured cells. These results suggest that thedecarboxylative pathway of IAA catabolism does not functionin grapevine protoplasts and they are discussed in relationto the co-localization of peroxidase (EC 1.11.1.7
[EC]
) and anthocyani(di)nsin vacuoles. This lack of function is presumably favoured bya strong compartmentalization (i.e. accumulation by a factorof 730) of IAA in the cytoplasm compared to vacuoles. Key words: Indole-3-acetic acid catabolism, anthocyani(di)ns, peroxidase, protoplasts 相似文献
9.
Separation and Purification of Protoplast Types from Commelina communis L. Leaf Epidermis 总被引:2,自引:0,他引:2
Guard cell and epidermal/subsidiary cell protoplasts obtainedby enzymic digestion of peeled Commelina communis leaf epidermiswere separated and purified by discontinuous density gradientccntrifugation with media based on Percoll (Pharmacia Fine ChemicalsAB, Uppsala, Sweden). The cell types were recovered over 99.9%pure at yields exceeding 50% efficiency, and mesophyll contaminationcould be virtually eliminated when desired. Osmotic characteristicsof the protoplast types were evaluated and compared to in vivovalues, and the viability of the protoplasts, assessed usinga range of criteria, was found to be high. Purified Commelinaguard cell protoplasts were able to evolve O2 when illuminated,and this was substantially reduced in the presence of the inhibitorDCMU, indicating that they possess photosystem II activity.Specific advantages of this method of protoplast purification,and the potential uses of separate suspensions of guard cellsand epidermal/subsidiary cells in experiments on stomatal physiologyare discussed. Key words: Commelina communis, Protoplasts, Epidermis 相似文献
10.
The metabolism of the major polar and neutral lipids of Viciafaba protoplasts isolated from 14CO2-fed leaves has been examined.The results show large losses in the radioactivity found inphosphatidylcholine and monogalactosyldiacylglycerol while thatof phosphatidylglycerol was stable. This loss was accountedfor by a rapid increase in the 14C content of the neutral lipids,particularly the triacylglycerols. Analysis of the fatty acidradioactivity in the lipids suggests that protoplast isolationinhibited fatty acid desaturation on phosphatidylcholine andpossibly on other lipids. These results also suggest a roleof phosphatidylcholine in the donation of fatty acids for triacylglycerolsynthesis in mesophyll protoplasts. The results are discussedin terms of the regulation of lipid metabolism and protoplastbiology. (Received April 20, 1984; Accepted August 27, 1984) 相似文献
11.
Regulation of Amino Acid Uptake into Oat Mesophyll Cells: A Comparison between Protoplasts and Leaf Segments 总被引:2,自引:0,他引:2
The uptake of -aminoisobutyric acid (AIB) into protoplasts andinto 1 cm sections of leaves from 7 d old light-grown oats (Avenasativa L. cv. Garry) was studied. Both protoplastsand leaf sections with cuticle and epidermis removed accumulatedAIB against a concentration gradient although the rate of uptakeinto protoplasts was one-third to one-sixth that into leaf sections.AIB uptake into both protoplasts and leaf cells in situ wasstimulated by aging, and low pH, and inhibitedby osmotic shock, respiratory poisons, and KCl concentrationsabove 1 mM. It was concluded that the rate of uptake of AIBand its accumulation ratio could be accounted for by the energyinherent in the proton-motive force, the proton-motive forcebeing the sum of the pH gradient and potential difference acrossthe plasma membrane. The similarities between oat mesophyllprotoplasts and leaf cells in situ suggest that these protoplastsare suitable material for the study of certain membrane-regulatedevents. 相似文献
12.
Inhibition of photosynthesis by Na2SO3 in mesophyll protoplastsisolated from Vicia faba leaves and uptake of sulfite by theprotoplasts were examined at various pH values of the incubationmedium containing Na2SO3. As the pH of the incubation mediumlowered, the rate of photosynthesis in the protoplasts decreasedand the amount of sulfite taken up by the protoplasts increased.Most of sulfite accumulated in the protoplasts was not metabolizedduring the dark incubation, as measured with an ion chromatograph.Photosynthetic O2 evolution by the chloroplasts isolated fromVicia mesophyll protoplasts was inhibited by exogenously-appliedNa2SO3 over pH region examined (7.49.0). The sulfiteconcentration required for a half inhibition of photosynthesisby the isolated chloroplasts was similar to the intracellularsulfite level required for that by the protoplasts. These resultsindicate that the intracellular sulfite accumulated in the protoplastsin an unmetabolized state is responsible for the inhibitionof protoplast photosynthesis. (Received January 24, 1985; Accepted May 29, 1985) 相似文献
13.
Peroxisomes were isolated by sucrose density gradient centrifugationfrom mesophyll and bundle sheath protoplasts of a C4 plant,Panicum miliaceum L. The equilibrium density in the gradientwas 1.25 for bundle sheath peroxisomes and 1.23 for mesophyllperoxisomes, the former density being similar to that of peroxisomesof wheat mesophyll protoplasts. Photorespiratory and other microbody enzymes were assayed forthe peroxisomes of P. miliaceum to detect possible differentiationat an enzyme level. The specific activities of photorespiratoryenzymes, except for hydroxypyruvate reductase, in bundle sheathperoxisomes were 4060% of those in wheat peroxisomes,when compared on a protein basis, and only 2030% in mesophyllperoxisomes. However, peroxisomes from both cell types containedsignificant levels of all the enzymes involved in the photorespiratoryglycolate pathway, when compared with castor bean glyoxysomes.The activity of hydroxypyruvate reductase in the peroxisomesof P. miliaceum was comparable to or higher than that in wheatperoxisomes. Two ß-oxidation enzymes and urate oxidasewere detected in the peroxisomes in a similar level to thatin wheat peroxisomes. These results suggest that the peroxisomes of mesophyll andbundle sheath cells of P. miliaceum are essentially similarto those of C3 plants, and that they cannot be differentiatedexcept for a difference in equilibrium density in a sucrosegradient. (Received December 24, 1984; Accepted April 9, 1985) 相似文献
14.
The distribution of amino acids and key enzymes involved innitrogen metabolism was determined in mesophyll cells (MC),mesophyll protoplasts (MP), and paraveinal mesophyll protoplasts(PVMP) isolated from fully expanded trifoliolate leaves of non-nodulatedsoybean. Qualitative and quantitative differences were foundin the distribution of amino acids, with MP containing the highestconcentrations. Activity of nitrate reductase, glycolate oxidase,glutamine synthetase and glutamate dehydrogenase was measuredin both tissue types and differences in activities between thetissue types were seen. PVMP had high glutamate dehydrogenaseactivity when compared to MP. Activities of glycolate oxidaseand glutamine synthetase were much higher in MP on a protoplastbasis while nitrate reductase activity was similar between thetwo protoplast types. These results, on the distribution ofmetabolites and associated enzymes, are discussed as to theirpossible significance to nitrogen metabolism in the soybeanleaf. Key words: Amino acids, glutamate dehydrogenase, Glycine max, nitrate reductase, nitrogen metabolism, paraveinal mesophyll, protoplasts 相似文献
15.
Commercially available cell wall-degrading enzymes frequentlyused for protoplast isolation inhibited CO2 fixation and photosyntheticO2 evolution, and stimulated dark respiration by leaf tissueand isolated mesophyll protoplasts of Nicotiana tabacum L. andAntirrhinum majus L. They also depolarized the membrane potentialof cells of leaf tissue, inhibited uptake of 86Rb by tobaccoleaf tissue and isolated mesophyll protoplasts, and stimulated36CI uptake by tobacco leaf tissue. Where studied, these effectswere found to be reversible. The depolarization effect on Antirrhinumleaf cells occurred even when the enzyme preparations had beendenatured, dialysed, or desalted, and the effect was greatestin those fractions of the enzyme preparation which showed thehighest cellulase activity. Plasmolysis of tobacco leaf tissue inhibited photosyntheticO2 evolution, CO2 fixation, and 86Rb uptake to levels belowthose exhibited by isolated protoplasts in media of the samecomposition and osmolarity. The implications of these resultsfor work with leaf tissue and isolated protoplasts are discussed. 相似文献
16.
Characterization of the vacuolar-type H+-ATPase from guard cell protoplasts of Commelina 总被引:1,自引:0,他引:1
Willmer C.M.; Grammatikopoulos G.; Lascve G.; Vavasseur A. 《Journal of experimental botany》1995,46(4):383-389
Characteristics of the vacuolar-type (V-type) H+-ATPase fromguard cell protoplasts of Commelina communis L. were investigatedusing a linked enzyme assay and nitrate inhibition as a diagnosticindicator of the enzyme activity. ATPase activity was completelyinhibited by about 50 mol m3 nitrate and activity wasoptimal near pH 8.0. The temperature optimum for activity wasabout 37 C and an Arrhenius plot indicated changes in activationenergy for the ATPase at 15C and possibly at about 30 C. Theenzyme was stimulated by Cl while Ca2+ inhibited activity(l50 = 1.5 mol m3). The apparent Km (MgATP) was 0.62mol m3. Incubation of guard cell protoplasts for up to 5 h in 50 µMabscisic acid (ABA) or 25µM fusicoccin (FC) did not affectsubsequent ATPase activity. In vitro assays with FC or ABA alsodid not affect enzyme activity. Activity was not affected bylight or potassium ferricyanide, two factors which are knownto influence stomatal activity. Beticoline was a potent inhibitorof activity (l50 = 50 µM) while DCCD was less effective(l50 = 90µM). On chlorophyll, protein and protoplast bases, V-type ATPaseactivity was greater in guard cell protoplasts than mesophyllcell protoplasts by 66, 13.9 and 1.9, respectively. On atonoplast surface area basis the enzyme activity was 5.6 timeshigher in guard cell protoplasts than in mesophyll cell protoplasts Thus, although the characteristics of the V-type, H +-ATPaseof GCP are very similar to those found in other cell types,rates of activity and probably tonoplast enzyme density aremuch greater in guard cell protoplasts than mesophyll cell protoplastsof C. communis which corresponds with the large and rapid ionfluxes across the tonoplast associated with stomatal movements Key words: Guard cell protoplasts, stomata, V-type H +-ATPase 相似文献
17.
Cantrel Catherine; Guillot-Salomon Th?r?se; Brown Spencer C.; Marie Dominique; Dubacq Jean-Paul 《Plant & cell physiology》1991,32(7):959-967
Two types of protoplasts were isolated from leaves of shootsor callus of subcultures of jojoba (Simmondsia chinensis (Link)Schneider). Protoplasts from leaves were rich in chloro-plastsand were about half the volume of protoplasts from callus. Theviability of preparations as determined by the Evans blue techniquewas 80%. From cell cycle analysis by flow cytometry of nuclei,leaf protoplasts were uniformly in a non-proliferating phase(G0-G1), while callus protoplasts presented many phases of thecell cycle. Protoplasts from calli had only half the Chi ofthose from leaves. Yet Chi a/b ratio, as well as protein andtotal lipid content per cell, were similar in both types ofprotoplasts. A major drop in polar lipids, chiefly in mono-and digalactosyldiacylglycerol, and a parallel increase in neutrallipids occurred during protoplast isolation. The 18:2/18:3 ratiodecreased in neutral lipids concomitant with an increase intriglycerides rich in linolenic acid. Our results suggest atriggering of lipolytic acylhydrolases during the protoplastisolation, as reported for other species. Plasmolysis of thecells with high osmolarity medium and long incubation timeswere required to get a good yield of jojoba protoplasts. Inthe course of this procedure water-deficit stress takes place.A parallel with lipid changes occurring under this type of stressis discussed. (Received April 22, 1991; Accepted July 3, 1991) 相似文献
18.
Guard cell protoplasts of Commelina communis L. reduced exogenousferricyanide at pH values lower than 5?0; upon addition of NADH,reduction of ferricyanide by guard cell protoplasts was stimulatedover the pH range 4?0 to 9?0 with two peaks of activity at pH5?0 and between pH 8?0 and pH 9?0. Calcium chloride (1?0 molm3) and MgCl2 (1?0 mol m3) increased the NADH-stimulatedreduction of ferricyanide. Superoxide dismutase and cyanidehad little effect on the NADH-stimulated reduction of ferricyanideby guard cell protoplasts, but, salicylhydroxamic acid completelyinhibited this activity. The NADH-stimulated reduction of ferricyanidealso occurred in the cell-free supernatant. Horseradish peroxidasedid not reduce ferricyanide in the absence of NADH over a broadrange of pH (4?0 to 9?0). However, in the presence of NADH,horseradish peroxidase reduced ferricyanide over the pH range5?0 to 9?0 with maximal activity at pH 8?0. The NADH-stimulatedreduction of ferricyanide by horseradish peroxidase showed similarproperties to those observed with guard cell protoplasts. Mannitol,superoxide dismutase, and cyanide did not inhibit the NADH-stimulatedreduction of ferricyanide by horseradish peroxidase; SHAM, however,completely inhibited the reduction of ferricyanide by horseradishperoxidase. Catalase inhibited the NADH-stimulated reductionof ferricyanide by horseradish peroxidase by 20%, while absenceof oxygen in the assay medium stimulated this activity over60%. We propose that the reduction of ferricyanide in the presenceof NADH by guard cell protoplasts, can be explained in termsof peroxidase activity associated with the plasma membrane andsecreted to the extracellular medium. However, the capacityof guard cell protoplasts to reduce ferricyanide at acid pHvalues where little peroxidase activity occurs may indicatethe presence of a plasma membrane redox system in guard cellsof C. communis. Key words: Commelina, guard cell protoplasts, ferricyanide reduction, peroxidase, redox system 相似文献
19.
Hypocotyls, cotyledons and etiolated half-expanded leaves ofCucumismeloGreen Delica were used as explants for protoplastisolation and culture. Protoplasts isolated from cotyledonsand etiolated half-expanded leaves cultured in Durand, Potrykusand Donn (DPD) medium supplemented with 0.9 µMbenzylaminopurine(BAP), 3.6 µM2,4-dichlorophenoxyacetic acid (2,4-D) and1% sucrose, using the agarose bead culture method, were ableto form cell walls and subsequently go through cell division.Pretreatment of half-expanded leaf explants in the dark for14 d provided the best material for protoplast isolation andcell division. Approximately one third of protoplasts from etiolatedhalf-expanded leaves formed microcolonies. For hypocotyl protoplasts,none of the treatments used were suitable to induce cell division.There was no significant difference between sucrose, glucose,and sucrose plus glucose, in culture media on the plating efficiencyof leaf protoplasts ofC. meloGreen Delica; however,bigger colonies were formed in media supplemented with 1% sucrose.No shoot or whole plant regeneration was achieved. However,the methods reported here provide further information onC. meloprotoplastculture.Copyright 1998 Annals of Botany Company Cucumis melo,protoplast culture, 2,4-D, BAP, yeast extract, casein hydrolysate. 相似文献
20.
Saladrigas M. Ver?nica; Ceriani M. Fernanda; Tozzini Alejandro C.; Arese Alicia I.; Hopp H. Esteban 《Plant & cell physiology》1990,31(6):749-755
Protoplasts were obtained from genetically related Argentinepotato (Solanum tuberosum tuberosum) cultivars: Serrana INTAand Huinkul MAG and from an European cultivar: Spunta. SerranaINTA is resistant to potato virus X (PVX) infection becauseit carries the major reaction gene Xi (believed to be the sameas Rxac1) while Huinkul MAG and Spunta are susceptible. Protoplastswere inoculated with a purified preparation of PVXcp (a SouthAmerican isolate) and then assayed for PVX concentration atdifferent times postinfection by enzyme-linked immunosorbentassay (ELISA), immunofluorescence and nucleic acid hybridization.PVX multiplication rates in Serrana INTA were about fifteentimes slower than in susceptible genotypes when cell-bound viruslevels just after infection were in the range of 0.01 to 0.1ng PVX per viable protoplast. However, when inoculum levelswere raised to 1 ng PVX per viable protoplast, PVX multiplicationwas about the same in all three genotypes. To rule out geneticbackground effects in this behaviour, protoplasts of an ArgentineS. acaule clone (PI: 320277) likely carrying the same resistancegene, were infected with PVX in similar conditions, reproducingthose results obtained with Serrana INTA. The comparison ofPVX replication in protoplasts and whole plants indicate thatalthough Xi gene confers resistance at the cell level it necessitatesof tissue structure to fully express immunity. (Received January 16, 1990; Accepted April 23, 1990) 相似文献