Studies on Foliar Penetration: 2. THE ROLE OF LIGHT IN DETERMINING THE PENETRATION OF 2,4 DICHLOROPHENOXYACETIC, ACID

A further study has been made of the factors determining thelevel of penetration of 2,4-dichlorophenoxyacetic acid (2,4-D)into leaves. The technique involves the use of leaf disks and2,4-D containing carbon-14 in the carboxyl group. For Phaseolus vulgaris the influence of the pH of the appliedsolution is greater in the light than in the dark. Between 0and 1,000 f.c. at 27° C there is a small increase in therate of penetration into the abaxial surface. Under these conditionsthe rates remain constant up to 56 hours. This linear relationshipholds for concentrations ranging from 100 to 1,000 mg/l, andthe rate of penetration is directly proportional to the concentration.For intensities in excess of 1,000 f.c. the light response ismarkedly different: over the first few hours there is a steadyand relatively slow rate of penetration which is followed bya second phase when the rate is greatly accelerated. This acceleratedrate can be reversed by transferring the disks to darkness,and does not take place at 1° C. Likewise, if excised disksare left for more than one hour in either the light or the darkbefore applying 2,4-D then there is subsequently no phase ofaccelerated penetration. The course of penetration into theadaxial surface exhibits no accelerated rate, and compared tothe abaxial surface the rates are lower. For leaves of Ligustrum ovalifolium, which lack stomata on theadaxial surface, the rates of penetration at 27° C intoboth surfaces remain constant in either light or darkness. Forboth the adaxial and abaxial surfaces, the rate progressivelyincreases from 0 to; 2000 f.c. and there is no phase of acceleratedpenetration. Penetration into the adaxial surface is less. At1° C the rates for both surfaces in either light or darknessare depressed. If disks of Phaseolus are irradiated with ultraviolet light,subsequent penetration is markedly depressed in the light at27° C, but in the dark or at 1° C it is enhanced. On the basis of these findings it is concluded that both physicaland metabolic factors control the rate of penetration of 2,4-DTransport through the cuticle will be dependent on adsorptionand the length of the diffusion paths. Once diffusion gradientshave been established between the surface of the cuticle andthe outer surface of the cytoplasm in the epidermal cells, thesteepness will be dependent on the rates at which 2,4-D is eitherconverted into some metabolite or moved away from the surfaceor into other cells. The relative importance of physical andmetabolic process will be dependent on the permeability andthickness of the cuticle and the level of metabolic activity.The possible role of ectodesmata in determining both the lengthand steepness of the diffusion paths is discussed.     

Studies on Foliar Penetration: VI. FACTORS CONTROLLING THE PENETRATION OF 4-AMINO-3,5,6-TRI-CHLOROPICOLINIC ACID (PICLORAM) INTO THE LEAVES OF PHASEOLUS VULGARIS

The evaluation of the factors controlling the penetration of4-amino-3,5,6-trichloropicounic acid (picloram), containing¹⁴C in the carboxyl group, into leaves of Phaseolus vulgarisis complicated by the ability of the leaf tissue to decarboxylatethe compound rapidly. The degradation system becomes fully activatedonly after some hours following treatment with picloram whilethe capacity for decarboxylation declines with the age of theleaf. When allowance for decarboxylation is made, the pattern of penetrationfor picloram resembles in particular that of 2,2-dichloropropionicacid (dalapon). At the abaxial surface penetration continuesover 24 h at a fairly constant rate but in light, which enhancespenetration, a ‘surge’occurs between the secondand sixth hour. Raising the external concentration promotespenetration and in light entry is directly proportional to concentrationup to at least 2.5 x 10^–l M. The response to varying lightintensity resembles that of dalapon rather than 2,4-D. Evenlow intensities promote penetration; the effect is maximal atabout 10 000 lx at the abaxial surface but continues at leastup to 20 000 lx at the adaxial surface. Penetration is retarded at 4°C but the decarboxylation systemremains functional. In light, but not in darkness, penetrationis strikingly reduced by 3-(3,4-dichlorophenyl)-l,l-dimethylurea(DCMU). Raising the external pH from 4.2 to 7.2 retards entry. It is concluded that the factors which determine the penetrationof picloram into Phaseolus leaves also control the entry ofa wide range of organic compounds and inorganic ions.     

Studies on Foliar Penetration: V. FACTORS CONTROLLING THE PENETRATION OF 2,2-DICHLOROPROPIONIC ACID (DALAPON) INTO THE LEAVES OF PHASEOLUS VILGARIS

The factors which control the penetation of 2,2-dichloropropionicacid (dalapon), containing ³⁸Cl, into leaf disks of Phaseolusvulgris have been investigated. In many respects the patternof penctration resembles that already reported for 2,4-dichlorophenoxyaceticacid (2,4-D) but in others the results dispaprate. In darknessthe rate of penetration is proportional to the external concentration,remains constant over at least 24 h, is unaffected by 3-(3,4-dichlorophenyl)-1,1-dimethlyrea(DCMU), and has a temperature coefficient ranging from 1.6 to2.3. Light intensities as low as 1500 lx enhance penetrationat both surfaces but, whereas the responses at the abaxial surfacea maximum at 10.000 lx, at the adaxial surface penetration continuesto increase slightly as the intensity is raised to 21 500 lx.After 4 or 8 h at the higher light intersities an accelertedphase of penetration is initiated, which is sensitive to bothlow temperature and DCMU. When leaf disks, exposed to dalaponin darkness,are translated to buffer, there is no outward diussusion,nor on adding non-radioactive dalapon does exchange take place.Dalapon taken up in the light is less firmly bound: it failsto diffuse out, but partial exchange is found. While penetrationfalls as the external pH is raised to 5.2, significant amountscontinue to enter which are unaffected by p H as the latteris raised to values which cause almost complete dissociation.It is concluded that, as with 2,4-D, uptake in light is ATP-drivenand both polar and non-polar pathways appear to be involvedduring penetration.     

Studies on Foliar Penetration: VII. FACTORS CONTROLLING THE PENETRATION OF CHLORIDE IONS INTO THE LEAVES OF PHASEOLUS VULGARIS

The pattern of penetration of chloride ions into the abaxialsurfaces of the primary leaves of Phaseolus vulgaris has severalfeatures in common with those previously recorded for 2,4-dichlorophenoxyaceticacid (2,4-D), 2,2-dichloropropionic acid (dalapon), and 4-amino-3,5,6-trichloropicolinicacid (picloram). In the dark the rate of entry of chloride ionsup to 24 h is constant, but in the light entry is at first slowand then more rapid. This acceleration does not occur at lowtemperature or when the tissue is treated with 3-(3,4-dichlorophenyl)-l,l-dimethylureaor phenylmercuric chloride. Neither does it take place at theadaxial surface or when the leaves are more mature. The most distinguishing feature of the pattern of penetrationof chloride ions is its dependence on external pH. In darknessentry is unaffected by changes in pH but in the light the rateof entry is increased as the pH falls, but this response isrestricted to young leaves. No binding of chloride seems tooccur within the tissue. These findings support the view that penetration of the abaxialsurface in young leaves of Phaseolus is largely determined bya membrane system. This system decreases in importance as theleaf matures and the overlying cuticle thickens. At the adaxialsurface the thicker cuticle is seemingly a major barrier topenetration even in very young leaves.     

Studies on Foliar Penetration: IV. MECHANISMS CONTROLLING THE RATE OF PENETRATION OF 2,4-DICHLOROPHENOXYACETIC ACID (2,4-D) INTO LEAVES OF PHASEOLUS VULGARIS

The effects of a wide range of metabolic inhibitors on the penetrationof 2,4-dichlorophenoxyacetic acid (2,4-D) into the leaf disksof Phaseolus vulgaris have been studied. While recognizing thelack of specificity of most inhibitors, compounds were chosenwhich are known to affect respiration, phosphorylation, photosynthesis,membrane permeability, protein synthesis, and the binding capacityof membrane systems. They were: fluoride, azide, arsenite, iodoacetate,arsenate, 2,4-dinitrophenol (DNP), 3-(3,4-dichlorophenyl), -I,I-dimethylurea (DCMU), phenylmercuric chloride, octenylsuccinicacid, decenylsuccinic acid, dimethyl sulphoxide, actinomycin-D,chloramphenicol, streptomycin, 5-fluorouracil, cycloheximide,and cetyltrimethylammoniumbromide (CTAB).At sub-toxic levelsall compounds had little or no influence on penetration in darknesssave for iodoacetate and decenylsuccinic acid, which causedsome enhanced entry at 10^-4M and 10^-3M respectively, and CTABwhich promoted penetration at concentrations known tolower thesurface tension of water.The much greater rate of penetrationof 2,4-D into disks exposed to bright light (16 000 lx) is unaffectedby fluoride, azide, DNP, octenylsuccinic acid, decenylsuccinicacid, dimethyl sulphoxide, or actinomycin-D. It is, however,progressively inhibited by increasing concentrations of arsenite,iodoacetate, arsenate, streptomycin, and 5-fluorouracil. Chloramphenicol,cycloheximide, and CTAB lower the rate of penetration at intermediateconcentrations but at high concentrations the affect is reversed.The most active inhibitors of light-induced penetration areDCMU and phenylmercuric chloride, compounds which block theproduction of ATP.These results are discussed in relation tomechanisms of transport, in particular the structureand stabilityof barriers likely to impede penetration.     

Studies on Foliar Penetration: IX. PATTERNS OF PENETRATION OF 2,4-DICHLOROPHENOXYACETIC ACID INTO THE LEAVES OF DIFFERENT SPECIES

The comparative patterns of penetration of 2,4-dichlorophenoxyaceticacid (2,4-D) into the leaves of Phaseolus vulgaris, Zea mays,Pisum sativum, Beta wlgaris, Helianthus annuus and Gossypiumhirsuium have been examined. Save for Zea and Gossypium where there is little change withthe stage of leaf development the rates of penetration intoboth surfaces decrease as the leaf matures. The relative ratesare dependent on the species and the age of the leaf but thereare differences between the surfaces. In Phaseolus the characteristicsof primary leaves differ from those of trifoliate leaves sinceonly in immature trifoliate leaves is penetration into the adaxialsurface greater. In darkness the rates of penetration over 24 h remain constantor fall but slightly for all species. Light consistently promotespenetration but with Beta there is a lag before entry is acceleratedinto the abaxial surface as has previously been reported foryoung primary leaves of Phaseolus. For the remaining speciesthe courses of penetration in both light and darkness into bothsurfaces follow similar patterns. As the light intensity isincreased entry is enhanced but the limit of response variesbetween species, between surfaces within species, and in trifoliateleaves of Phaseolus with age. For the six species the order of the relative rates of entryis closely similar whether comparisons are made in light ordarkness or between abaxial and adaxial surfaces: viz. Zea >Helianthus > Phaseolus (primary) > Phaseolus (trifoliate)> Pisum = Beta = Gossypium. The observed specific differencesare discussed in relation to variations in leaf structure, theproperties and thickness of the cuticle and the physiologicaland metabolic processes which influence transport within theepidermal tissues after it has passed through the cuticle bydiffusion.     

Studies on Foliar Penetration: III. THE EFFECTS OF CHLORINATION ON THE RATE OF PENETRATION OF PHENOXYACETIC ACID AND BENZOIC ACID INTO LEAVES OF PHASEOLUS VULGARIS

A comparative study has been made of the penetration into leafdisks of Phaseolus vulgaris of (a) phenoxyacetic acid and its2-, 4-, 2, 4-, 2, 6-, 3-5, 2, 4, 5-, and 2, 4, 6- chloro derivatives,and (b) benzoic acid and its 2-, 2, 4-, 2, 5-, 2, 3, 6-chloroand 3, 6-dichloro-2-methoxy derivatives. The methods of synthesisof each compound with ¹⁴C incorporated in the carboxyl groupare described. In the series of substituted phenoxyacetic acids it was establishedthat only for 2, 4, 5-T was there an appreciable loss of radioactivityfrom the system either in the light or darkness. In contrast,with the exception of 2, 4-DCBA, ¹⁴C is lost from each memberof the series of substituted benzoic acids. The level and pattern of penetration in the two series is differentiallyaffected by chlorination. In general progressive chlorinationof phenoxyacetic acid leads to an increase in the rate of penetrationin both light and darkness. There are, however, exceptions;for illuminated disks the rate of entry of 2,4,5-T is exceededby 2,4,6-T, 2, 4-D, and 2, 6-D whereas in the dark 2,4,5-T hasby far the highest rate of penetration. Progressive chlorinationof benzoic acid, however, depresses entry in both light anddarkness. Possible relationships between these findings and changes inselected physical properties of each series of compounds havebeen examined. Between members of the series of substitutedphenoxyacetic acids there is little variation in the dissociationconstant whereas for the substituted benzoic acids there isa marked lowering of the pK as the degree of chlorination increases.The rate of elution with chloroform of each compound from abuffered Silocel column gives a measure of the degree of partitioninto a lipid medium at a given pH. At pH 5.2 chlorination ofphenoxyacetic acid results in more rapid elution whereas chlorinationof benzoic acid causes a longer hold up. An apparatus was designed to enable measurements to be madeof the rate at which a compound moves from one aqueous phaseto another through a layer of lipid. Chlorination promotes therate of transfer of phenoxyacetic acid through octanol but retardsthe transfer of benzoic acid. The extent to which chlorinationdepresses the rate of transfer of benzoic acid matches the diminutionin the rate of leaf penetration. For the series of substitutedphenoxyacetic acids transfer rates and penetration rates followsimilar trends in the dark but in the light agreement is lessgood. These findings are discussed in relation to prior studies onthe rate of uptake and the metabolic fate of the ndividual compoundsin a number of plant tissues.     

FACTORS CONTROLLING THE SPORULATION OF YEASTS. I. THE PRESPORULATION PHASE

SUMMARY: Yeasts tend to dissociate into mixtures of cell types with different powers of sporulation; hence single cell isolates are recommended for sporulation studies. The ability of yeasts to produce 4-spored asci can be improved by single cell selection. Cells from actively fermenting cultures sporulate much better than those grown under aerobic conditions. Sporulating ability depends on fermentation 'age', reaching a maximum when 85–90% of the CO₂ has been evolved. Carbon dioxide assimilation in the presporulation phase appears essential for maximal sporulation, but complete anaerobiosis in this phase is detrimental to sporulating ability. Malt wort cultures of a baker's yeast have given remarkably constant figures, in successive tests, for sporulation; but some batches of wort have an adverse effect on sporulating ability. The same yeast, grown on Lodder-Rij's synthetic medium containing 4 or 8% (w/v) of glucose, is capable of 80% sporulation (proportion of cells forming asci) on sodium acetate agar, comparable to that obtainable with malt wort cultures. Sporulation is depressed by excess storage of fat, while storage of glycogen does not affect sporulating ability.     

Studies in the Physiological Action of 2, 2-Dichloropropionic Acid: I.: MECHANISMS CONTROLLING THE INHIBITION OF ROOT ELONGATION

The inter-relationships between time and concentration and thedegree of inhibition of root elongation have been examined forSorghum vulgare, Zea mays, Helianthus annuus, and Pisum sativum.For all species the inhibitory effect is cumulative but thereis a tenfold difference in the concentration required to halvethe elongation of the most sensitive (S. vulgare) and most resistantspecies (P. sativum). From a comparison of the growth of intactsroots and isolated segments, together with estimates of cellnumber, it has been established that the primary effect is tointerfere with meristematic activity in the root tip, wherethe mitotic cycle is arrested at prophase. Using 2, 2-dichloropropionic acid, containing chlorine-36, thecourses of uptake by both intact roots and isolated segmentshave been followes. In every instance uptake is cumulative withthe greatest accumulation in the root tip. There are again largespecific differences but of a reverse order; uptake is leastfor P. sativum and greatest for S. vulgare. For these two speciesand Z. mays, it is concluded that the magnitude of the equi-effectiveconcentration required to halve root elognation is dependenton the level of accumulation rather than on the reaction atcell level: the cells of H. annuus are more sensitive.     

斯氏线虫在进境原木害虫检疫处理上的应用前景

本文综述了我国进境原木上截获的主要害虫类群;总结了目前进境原木害虫的检疫处理技术;重点介绍了斯氏线虫Steinernema sp.对钻蛀性害虫的防治研究,探讨了斯氏线虫在进境原木害虫检疫处理上的应用前景,提出了应用斯氏线虫防治进境原木害虫所存在的问题及今后的研究方向.     

The Uptake of Growth Substances: I. FACTORS CONTROLLING THE UPTAKE OF PHENOXYACETIC ACIEDS BY LEMNA MINOR

An analysis has been made of the factors controlling the uptakeof 2:4-dichloro-phenoxyacetic acid (2:4-D) and related compoundsby Lemna minor, grown under controlled conditions. All compoundswere labelled with ¹⁴C in the carboxyl group and the ¹⁴C inthe plants, after liquid combustion, assayed as barium carbonate. With 2:4-D the rate of entry from concentrations of 8 to 32mg./l. is maximal in the first 20 minutes, then falls progressivelyuntil the rate is zero between 1 and 2 hours and in the thirdphase (up to 24 hours) there is a net loss from the plants dueto an outward movement of the compound back into the externalsolution. When the chlorine substitutions are in the 2:6-positionthe course of uptake is similar, save that loss to the solutiontakes place later. For the 2-chloro-substitution, after theinitial phase of uptake there is some loss but this is followedby a period of recovery and uptake again proceeds, but slowly.In contrast, the course of uptake over 24 hours of phenoxyaceticacid is normal, i.e. there is a steady accumulation. When plants are pretreated with labelled 2:4-D for 30–60minutes and transferred to water or culture solution then over90 per cent. of the ¹⁴C is found in the external medium after4:5 hours and this release cannot be accounted for in termsof exchange processes since the addition of unlabelled compoundto the medium retards the rate of loss. This loss is slowedbut not stopped at 1.25°C. and up to 22.5°C. the rangeof the Q₁₀ is 1.6–1.9. Uptake in the first 30 minutes is temperature sensitive between7.5 and 30°C. (Q₁₀ 2.3–2.6) and in general is positivelyand curvilinearly related to the external concentration. Pretreatmentwith unlabelled compound up to 2 hours progressively depressesthe subsequent initial uptake of labeled growth regulator. Itis concluded that initially the rate of entry greatly exceedsthe rate of loss but that with time the ratio steadily diminishesto less than unity. Initial uptake of 2:4-D is markedly dependent on the pH of thesolution and closely but not completely correlated with theexternal concentration of undissociated molecules. On the otherhand, the outward movement is relatively unaffected by the externalpH. Combinations of concentration and time of exposure which bringabout loss to the solution need not cause any permanent retardationof growth. In fact, exposure for 1 hour to 8 mg./l. significantlyaccelerated growth in the next 8 days. These results are discussed in relation to previous findingsand it is concluded that the pattern of uptake is determinedon the one hand by the chemical structure of the growth substanceand on the other by specific physiological differences at celllevel.     

Studies on Foliar Penetration: VIII. EFFECTS OF CHLORINATION ON THE MOVEMENT OF PHENOXYACETIC AND BENZOIC ACIDS THROUGH CUTICLES ISOLATED FROM THE FRUITS OF LYCOPERSICON ESCULENTUM L.

The effects of chlorine substitution on the movement of phenoxyaceticand benzoic acids through enzymatically-isolated cuticles ofLycopersicon fruits were determined by following the transferof each acid containing ¹⁴C from a donor to a receiver solution.This cuticle is characterized by an isotropic cutin matrix,within which patches of birefringent cuticular waxes are foundnear the outer surface. The outer, morphological surface isrelatively smooth while at the junction with the outer wallsof the epidermal cells there is extensive cuticular developmentextending down between the anticlinal walls. The epicuticularwax appears as a soft sheet-like covering of which the surfaceis relatively featureless. Chlorination of phenoxyacetic acid results in an enhanced transferacross the isolated cuticle. The order was 2,4,5- and 2,4,6-trichlorophenoxyacetic> 2,4- and 3,5-dichlorophenoxyacetic > 2-chlorophenoxyacetic> phenoxyacetic acid. Removal of the epicuticular wax resultedin greater permeability for all compounds; transfer of the morepolar acids was favoured. In contrast, chlorination of benzoicacid decreases passage through the cuticle; the rate is highestfor benzoic acid followed in descending order by 2-chlorobenzoic,2,4- and 2,5-dichlorobenzoic and 2,3,6-trichlorobenzoic acid.Chlorination also depresses the passage of both phenoxyaceticand benzoic acid through a dialysis membrane. The effects ofchlorination on the lipid solubility of both series of compoundsare discussed in relation to differences in transfer acrossthe cuticle.     

Studies in Abscission: I. FACTORS AFFECTING THE INHIBITION OF ABSCISSION BY SYNTHETIC GROWTH-SUBSTANCES

1. The general method is described for experimenting on applepedicelsor petioles from which the terminal organ has beenremoved.
2. Two quantitative techniques for applying growth-substancesaregiven in detail, one employing lanolin emulsion as the carrier,the other agar gel.
3. By these methods certain factors affectingthe inhibition ofabscission by the growth-substances -naphthylaceticacid (NAA)and 2:4-dichloro-phenoxyacetic acid (DPOA} have beeninvestigated. A relation between concentration of the growth-substanceandpersistence of the pedicel was established which was usuallylinear. In an experiment with NAA, for instance, the relationwas represented by— Persistence in days=6·52+0·0127xconcentrationin p.p.m.
4. The acid and the sodium salt of both NAA and DPOAgave similarresults when applied in lanolin emulsion.
5. Onboth young pedicels and young shoot internodes NAA was foundto exert a ‘formative’ influence resulting in increasein diameter which was not exhibited by DPOA to the same extent.
6. At least for concentrations of either growth-substance upto100 p.p.m., these were effective only when applied distallyto the abscission zone. At 1,000 p.p.m. there was an effectof application on the proximal side of the abscission region,but it was small compared with the effect of the same concentrationapplied distally.
7. The length of the path of the growth-substancefrom the pointof application to the abscission zone affectedthe degree ofinhibition inversely, the longer the path theless the effectof a given concentration in delaying abscission.The contrastbetween these findings for pedicels, and thoseof other authorsfor petioles, is briefly discussed.
8. A criticalperiod occurs shortly after removing the leaf-bladefrom itspetiole during which the abscission process is initiated,andto be effective in inhibiting this process growth-substancemust reach the abscission zone within this period. It is notat present established whether the pedicel shows a similar modeof behaviour.
9. A working hypothesis is given to account forthe control ofabscission by natural hormones, and extensionsare describedto embrace the results of experiments with syntheticgrowth-substances.

     

The Uptake of Growth Substances: VI. A COMPARATIVE STUDY OF THE FACTORS DETERMINING THE PATTERNS OF UPTAKE OF PHENOXYACETIC ACID AND 2,4,5-TRICHOLOROPHEN-OXYACETIC ACID, WEAK AND STRONG AUXINS, BY GOSSYPIUM TISSUES2

Using segments of etiolated hypocotyls of Gossypium, a comparativestudy has been made of the processes which determine the patternsof uptake of a very weak auxin, phenoxyacetic acid (POA), anda very powerful one, 2,4,5-trichlorophenoxyacetic acid (2,4,5-T). When segments are placed in solutions of POA-1-¹⁴C, a continuousincrease in the radioactivity of the tissues is accompaniedby the formation of radioactive metabolities which can be separatedfrom POA by techniques of paper chromatography. At the sametime there is a progressive increase in the amount of radio-activitywhich cannot be removed by transferring the tissues to buffer.Uptake is inhibited by low temperature, anaerobiosis, 2,4-dinitrophenol,and iodoacetate. It is concluded that the accumulation of POAinvolves its metabolic conversion to products which do not readilydiffuse out into the external medium. With 2,4,5-T-1-¹⁴C the radioactivity of the segments at firstincreases rapidly but this is followed after two hours by aphase of rapid decrease. No radioactive metoabolites can bedetected by paper chromatography and all of the ¹⁴C taken upcan be rapidly removed by transfer to buffer. The magnitudeof the decrease in radioctivity during the second phase of uptakeis balanced by a release to the medium of a matched amount ofradioactive 2,4,5-T. Uptake of 2,4,5-T is somewhat less sensitiveto temperature and anaerobiosis than uptake of POA and is bycontrast only slightly inhibited by 2,4-dinitrophenol and iodoacetate. Pretreatment of segments in buffer markedly alters the patternof uptake of 2,4,5-T but not that of POA. It reduces both theamount of 2,4,5-T initially taken up and the amount subsequentlyreleased to the medium. In addition, both net loss of radioactivityduring the course of uptake of 2,4,5-T and the reduction inthe extent of uptake following pretreatment are both arrestedby adding streptomycin, but not by the addition of pencillinor chloramphenicol. It is concluded that the uptake of 2,4,5-T involves reversibleaccumulation by a process whose efficiency decreases with time:the most likely systems are a metabolically linked mechanismfor the active transport across a membrane or reversible adsorptionon specific binding sites.     

FACTORS INFLUENCING THE RESPIRATION OF ERYTHROCYTES : I. PRIMITIVE AVIAN ERYTHROCYTES

1. The oxygen consumption of normal and "primitive red cells" of fowls'' blood has been determined at intervals in the course of an anemia produced by the injection of phenylhydrazine. The "primitive red cells" have an oxygen consumption at least twenty to twenty-five times greater than the normal red cells. 2. Suspension of the cells derived from the blood in anemia in sodium chloride solutions of various concentrations has comparatively little effect upon the oxygen consumption of the cells. 3. The red cells from anemic blood are sensitive to variations in the reaction of the medium in which they are suspended. The maximum oxygen consumption, after addition of a saline solution containing variable amounts of acid to the blood, took place at pH 7.75. They appeared somewhat more sensitive to variations on the acid side of this reaction than on the alkaline. 4. Addition of glucose to the medium increased the oxygen consumption of the cells. Their metabolism in a physiological saline solution containing 0.6 per cent of glucose was 15 per cent higher than in one in which no glucose was present. 5. Certain amino acids in low concentrations had little effect on oxygen consumption, though at higher concentrations some of them definitely diminished it.     

ACCUMULATION OF 4-O-β-D-GLUCOSIDE OF PROTOCATECHUIC ACID IN THE LEFT COLLETERIAL GLAND OF THE COCKROACH,PERIPLANETA AMERICANA.* I. PROPERTIES OF GLUCOSIDE SYNTHETASE.

As a preliminary to the study of the mode of action of juvenile hormone using the left colleterial gland of the cockroach, properties of the glucoside synthetase of protocatechuic acid were studied. For this purpose, a convenient assay method of phenolic glucoside synthetase (UDPG-phenol glucosyl transferase) was devised. The method is based on the determination of labeled protocatechuic acid glucoside which is synthesized from uridine diphosphate ¹⁴C-glucose and protocatechuic acid. The optimal pH for the glucoside synthetase reaction is 6.5. The enzyme activity is localized in a particulate fraction of fat body tissues and is partly found in the soluble fraction, presumably liberated during the course of centrifugation. In the female cockroach, the enzyme activity is distributed mainly in the fat body. Chemical analyses revealed that the reaction product is 4-O-β-D-glucoside of protocatechuic acid. The homogenate of fat body tissues can synthesize glucosides from UDPG and various phenols, such as O-aminophenol, p-nitrophenol and hydroquinone, as well as natural O-diphenols.     

微生物酶不对称水解合成S(+)-布洛芬的研究 Ⅰ.高度立体选择性菌株的筛选

从361株细菌和酵母菌中分别筛选到12株可不对称水解布洛芬乙酯生成R(-)-布洛芬的细菌(5株菌对映体过量(ee)可达85%)和15株具有不对称水解布洛芬乙酯活性的酵母菌,其中皮状丝孢酵母T158生成S( )-布洛芬,ee可超过92%.该酵母菌最适碳源为葡萄糖,浓度以1.0—1.5%适宜,蛋白胨浓度低于0.3%或高于0.5%对水解拆分均不利.酵母膏的加入显著提高水解活性,最适浓度0.3%.在培养基中添加表面活性剂吐温80(0.2%)既可提高拆分专一性,又能增强水解能力.     

八种因素对头孢霉菌丝脂肪酸不饱和指数的影响

为了探讨环境胁迫和真菌脂肪酸不饱和度的关系 ,用合成培养基探讨 8种单一因子对头孢霉(Cephalosporiumsp .)菌丝体脂肪酸不饱和指数的影响。结果表明 ,低起始 pH值 (4 .0～ 5 .0 ) ,低培养温度 (10～ 15℃ ) ,有利于获得高不饱和指数 ;随着三角瓶装液量的增加 ,脂肪酸不饱和指数逐步降低 ;接种量对脂肪酸不饱和指数影响不大 ;葡萄糖或蔗糖作为碳源 ,NH4 Cl或 (NH4 ) 2 SO4 作为氮源 ,低碳源浓度 (10～ 2 0g/L)有利于获得高不饱和指数 ;随着培养时间增加 ,脂肪酸不饱和指数逐步增加 ,至 10d时脂肪酸不饱和指数可达最高 ,为 170 .38