Physiological Studies in the Mucorales: PART I THE PHOTOTROPISM OF SPORANGIOPHORES OF PHYCOMYCES BLAKESLEEANUS

Previous views on the physical basis of phototropism in Phycomycessporangiophores are briefly discussed.

1. It was confirmed thatunilaterally illuminated sporangiophoresimmersed in liquidparaffin show strong negative phototropism.
2. Elongation growthceased and no phototropic response took placeunder anaerobicconditions.
3. By focusing a fine beam of light on to one edgeof the growingzone of a sporangiophore, leaving the other sidein darkness,it was established that greater elongation tookplace in theilluminated zone, the sporangiophore tending tobend out ofthe beam. Rapid reversal of the curvature followedwhen theillumination was transferred to the opposite edge ofthe sporangiophore.

Wassink and Boumann's suggestion that phototropism can be initiatedby a one-quantum-per-cell process is criticized in the lightof this result and other work by Castle.     

Factors controlling Flowering in the Chrysanthemum: II. DAY-LENGTH EFFECTS ON THE FURTHER DEVELOPMENT OF INFLORESCENCE BUDS AND THEIR EXPERIMENTAL REVERSAL AND MODIFICATION

1. Inflorescence buds, produced by vernalized Chrysanthemum plantsin long day, cease to grow, and die at an early stage if maintainedin long day, but will produce open flowers if transferred toshort day. Dissection of such buds reveals that developmentdoes not proceed beyond the formation of the bare receptacleand no florets are initiated, while inflorescence buds producedin short day have almost completed floret initiation when theybecome macroscopically visible.
2. Inflorescence buds producedin long day can be induced to completetheir development inlong day by:
   1. removal of all lateral shoots, and
   2. by re-rootingthe inflorescenceitself, leaving only a numberof bracts onits axis.
3. Inflorescence buds produced in short day canbe inhibited fromdeveloping by
   1. transfer to long day,
   2. transferto low light intensity in shortday, and
   3. application of auxinpaste.
4. All three methods of inhibition become progressivelyless effectivewith the advancing development of the bud.
5. Thelatest stage at which development was found to have beenarrestedwas that of ovule formation.
6. Heights of plants were determinedat budding and when the flowershad started to open; markeddifferences due to length of daywere found.
7. Teratologicaleffects noted in buds, exposed for extended periodsto longday, included formation of bracts on the receptacle(the absenceof which distinguishes the subtribe Chrysantheminaeof the Compositaeto which the Chrysanthemum belongs) as wellas secondary inflorescences,petaloid stamens, &c.
8. The results are discussed in relationto known effects of auxinon vegetative growth and reproduction.

     

The Metabolism of Glucose and Acetate in Aspergillus niger

1. The metabolism of a citric-acid-forming strain of A. nigerwhengrown on a glucose-acetate medium has been investigated.
2. Acetate greatly accelerated the rate of utilization of glucose.
3. Citric acid production from glucose was much increased bythepresence of acetate.
4. The formation of oxalate from glucose-acetatecultures was muchless than from acetate alone.
5. In some cultureslarge amounts of glucose and acetate were consumedbut no acidicproducts were formed.

     

An Examination of a Method of Auxin Assay using the Growth of Isolated Sections of Avena Coleoptiles in Test Solutions

1. Methods of auxin assay using the Avena coleoptile are discussed.
2. A review is given of experimental procedure and evaluationofresults in the straight-growth method using isolated sectionsof coleoptiles in test solutions.
3. Possible sources of variationin the straight-growth methodare investigated and discussed.
4. A revised experimental procedure for the straight-growth methodis described.

The author wishes to thank Professor E. Ashby for his adviceand encouragement during the course of the experiments. Thanks are also due to Mr. D. Payne, a technical assistant inthe Botany Department, for his assistance in some of the assays.     

Microbiological Synthesis of Fat: PRELIMINARY SURVEY OF THE FAT-PRODUCING MOULDS

1. A survey of potential fat-producing moulds has shown that atleast 40 strains from 10 species are of interest.
2. These havebeen grown on five different media and A. nidulans,P. spinu-losum,P. javanicum, P. piscarium, P. flavo-cinereum,P. oxalicum,A. flavus, A. flavipes have shown the most promise.
3. The fatcontent on felt weight was maximal at 39?7 per cent,with A.flavipes and 34?6 per cent, with F. lini, and on usedsugarwas maximal at 9?3 per cent, with A. flavipes and 6?7per cent,with A. nidulans.
4. The potential value of micro-organisms asfat producers is discussedwith reference to the moulds.

     

EFFECT OF SUCROSE ON FLOWER INITIATION OF PHARBITIS NIL IN ASEPTIC CULTURE

1. Pharbitis plants were cultured on a nutrient medium containing5% sucrose or no sucrose. They were subjected to various lightconditions at temperatures of 10? or 20?.
2. All the plants culturedon the sucrose-medium at 10? initiatedflower buds independentlyof the light to which the plants wereexposed.
3. Plants culturedon the sucrose-free medium at 10? initiatedflower buds undershort photoperiods, but did not under continuousillumination.
4. Plants cultured on the sucrose-medium at 20? initiated flowerbuds in total darkness or under short photoperiods regardlessof the intensity and quality of the light, but those subjectedto continuous illumination did not.
5. Plants cultured on thesucrose-free medium at 20? initiatedflower buds under shortphotoperiods but did not initiate themunder continuous illumination.

(Received June 9, 1960; )     

A Quantitative Study of Mitosis in Eudorina elegans in Culture

A list of the determinations in this work is given below:

1. Under standard conditions with a photoperiod, the generationtime is five days. The generation time is shorter in continuouslight.
2. There are temperature-dependent cleavage and mitoticgradientswithin a colony.
3. A diurnal peak of mitosis occurstwo hours before the onsetof darkness.
4. Under standard conditions(a) the mitotic index rises to a maximumof 10 per cent, twodays after inoculation; (b) the mitotictime is ten minutes;and (c) the mitotic rate is 71 cells per10³cells per hour atthe mitotic peak.

     

The Effect of Prolonged Chilling on Water Movement and Radial Growth in Trees

1. The woody shoots of young saplings of Fraxinus.excelsior andAcer Pseudo-platanus in pots were subjected to continuous coolingto about 2° C. during the growth season, with the resultthat radial growth was almost completely inhibited throughoutthe woody stem.
2. The chilling did not adversely affect extensiongrowth exceptthat it was later in commencement and proceededmore slowly.
3. If the temperature around the stem is loweredfrom 2° C.to 0° C., water conduction is cut down tosuch an extentas to cause wilting of the leafy shoots; turgidityis recoveredwhen the temperature is again raised to 2°C.
4. This wilting effect is discussed particularly in relationtothe part played by living cells in the upward movement ofwaterin the wood.

     

The Diageotropic Behaviour of Rhizomes

1. The geotropic behaviour of rhizomes of Aegopodium podagrariahas been investigated by time-lapse photographic recording usinginfra-red radiation in complete absence of light.
2. They havebeen shown to be very sensitive to light. Even a singleexposurefor 30 seconds to red light evokes a characteristicresponsein which the rhizome first turns downwards and thenturns upagain to the horizontal position. The exposure to lightduringthe process of digging up the rhizomes and setting upin theapparatus has similar effects which die away after about24hours.
3. After recovery from this initial light effect theycontinueto grow roughly horizontal if maintained in darknessor subjectedto infra-red radiation only. If inverted (turnedthrough 180?)the side which was lowermost during the inversiongrows forabout 2 hours relatively the more quickly, thus becomingconvex;then a rapid straightening and bending in the oppositedirectionoccurs. This is followed by further up-and-down movementswhichgradually die out and the rhizome then continues growingstraight.
4. Inversion for 10 minutes also evokes an essentiallysimilarresponse, which begins about 20 minutes after the invertedrhizomehas been returned to its original position. The importanttheoreticalsignificance of this is discussed in the text.
5. Displacementof rhizomes through angles other than 180? resultsin to-and-frobendings in which the side of the rhizome whichwas uppermostbefore the stimulus of displacement first becomesconvex. Therhizomes then turn gradually towards the horizontalplane.
6. Rhizomeswhich have recovered from the initial light effectand are thusgrowing in darkness horizontally are caused toturn upwardswhen the air surrounding them is replaced by air+5per cent,carbon dioxide.
7. The theoretical significance of these findingsis discussed.

     

EFFECTS OF PHOTOPERIOD AND GIBBERELLIN ON THE GERMINATION OF SEEDS OF BEGONIA EVANSIANA ANDR.

1. Seed germination of Begonia Evansiana ANDR. was investigatedat 29?C.
2. The germination was induced under long-day conditions,the criticaldaylength being about 8 hours. Exposure to at least2 or 3 cyclesof long days was necessary for germination. Theseeds couldgerminate under otherwise non-inductive photoperiods,when thedark period was interrupted with a short period ofillumination.Thus the photoperiodic behaviour of Begonia seedsin germinationis similar to that of typical long-day plantsin flowering.
3. The application of gibberellin brought aboutno germinationin complete darkness, but markedly reduced thecritical daylengthfor germination, even 1-minute photoperiodsbeing inductive.The germination under continuous light wasalso favoured bygibberellin application. The action of gibberellinin germinationof Begonia seeds may be to intensify the lightaction or tosubstitute for a part of it.

¹Present address: Dept. of Botany, Hokkaido University, Sapporo. (Received October 19, 1959; )     

INFLUENCE OF LIGHT ON ACETATE UTILIZATION IN GREEN EUGLENA

1. The kinetics of adaptation to exogenous acetate, measured asthe ability to stimulate respiration, has been studied in Euglenapreviously grown with autotrophic nutrition.
2. The continuedpresence of light significantly inhibits the fulldevelopmentof respiratory adaptation to acetate.
3. Carbon fixed in photosynthesisis routed almost exclusivelyinto protein when acetate is present.Acetate incorporated withconcomitant photosynthesis largelyenters lipid and polysaccharide,with only a small fractionincorporated into protein.

(Received December 25, 1964; )     

Factors Controlling Flowering of the Chrysanthemum: I. THE EFFECTS OF PHOTOPERIOD AND TEMPORARY CHILLING

1. Experiments are described which indicate that a temporary exposureto low temperature (vernalization) hastens inflorescence budinitiation in the Chrysanthemum, as measured by the time tothe macroscopic appearance of the bud and also by the numberof leaves produced. This effect is found in both long-and short-dayconditions.
2. In the absence of vernalization plants kept inshort day assumea diageotropic growth habit and remain vegetativefor long periods,frequently for much more than one year. Unvernalizedlong-dayplants also remain vegetative but have a normal geotropicreaction.
3. While the day-length effect is less important forinflorescencebud initiation, the opening and further developmentof budsformed in long day depend normally on subsequent day-lengthtreatment.
4. A vernalization period of only three weeks appearsto be fullyadequate.
5. The low-temperature treatment may begiven discontinuously,and evidence to hand appears to indicatethat it is more effectiveif given during the dark phase thanduring the light phase.Hence de-vernalization by temperaturesof about 20–25°C. does not appear to take place.
6. There is evidence that little or none of the stimulus is carriedover from one year to another.
7. The results are discussed inrelation to the auxin metabolismof the plant and also withregard to the absence in the literatureof previous mentionof the cold requirement.

The author is indebted to Professor F. G. Gregory and to Mr.F. J. Richards for their stimulating interest and helpful suggestionsin the course of this work, and to Dr. M. Holdsworth for providinghim with the results of earlier unpublished work. Messrs. H. Woolman Ltd. kindly supplied some of the plant materialused.     

The Isolation of l-Quinic Acid from the Apple Fruit

1. A method is described by means of which several grammes ofl-quinicacid were isolated from young fruits of the WorcesterPearmainapple stored for a number of days in nitrogen.
2. Theessential stages in the method are the removal of colouringmatter from extracts of the frozen ground pulp tissue of thefruit with charcoal, the removal of amino acids by absorptionon cation exchange resin, and the separation of the organicacid from sugars by adsorption of the former on anion exchangeresin. Finally, the quinic acid was separated from malic acidby fractional displacement from the anion exchange resin.
3. Thecharacterization of the isolated quinic acid, and of malicacidalso isolated from the fruits, is described.
4. Citric acid isshown to be formed by oxidation of quinic acidwith hot hydrogenperoxide.
5. The possible function of quinic acid in the applefruit andin plants generally is discussed.

     

The Peltier Effect and its Use in the Measurement of Suction Pressure

1. A method is described by means of which the suction pressureof living material may be measured by observations on its equilibriumvapour pressure.
2. It employs a very fine thermocouple whosetip is cooled by meansof the Peltier effect, below the dew-point.It collects a minuteamount of dew, and can thus be used asan exceedingly fine ‘wet-bulb’thermometer. As suchit is convenient to use, quick in action,and causes very littledisturbance to the system under observation.
3. The thermocoupleis calibrated by means of salt solutions ofknown strength.The scale is fairly linear.
4. The method possesses the advantagesof giving the suction pressureby direct observation ratherthan by interpolation; of speedin the actual measurement; ofnot subjecting the tissue to immersion;and of permitting organslike leaves, otherwise difficult tohandle, to be easily dealtwith. It also opens possibilitiesoutside the range of the conventionalmethods.

     

Measurement of Stomatal Aperture by Digital Image Processing

We developed a new digital image processing technique for exactlymeasuring the degree of stomatal opening, that is, the ratioof the width to the maximum length of a stomatal pore, and thepore area. We applied this technique to evaluate responses toSO₂ of neighboring stomata in a small region of an intact attachedleaf, with the following results:

1. The pore region could be exactly extracted even when the originaldigital image was of poor quality. The standard errors in theevaluation of the pore area, the pore length, and the pore widthwere 10 µm², 0.3 µm and 0.3 µm, respectively.
2. A wide variety of responses to SO₂ was found among neighboringstomata in a small region of an attached leaf. The differenceswere especially remarkable before water-soaking and wilting.When these began, k₁ showed a local maximum value, and thenall the stomata began to close. These results suggest that stomatalresponses of intact growing plants to air pollutants shouldbe examined from the standpoint of not only the average movementof many stomata but also the movement of each stoma and thatthe interrelationship among movements of neighboring stomatashould be investigated to clarify the mechanism of stomatalresponses to air pollutants.

(Received June 4, 1984; Accepted August 23, 1984)     

PHYSIOLOGICAL AND BIOCHEMICAL CHANGES OF CARROT ROOT CALLUS DURING SUCCESSIVE CULTURES

1. The longer the period of stock culture, the more remarkableis the growth inhibition by 8-azaguanine in callus.
2. Chloramphenicol,5-methyltryptophane and mitomycin C exert greaterinhibitionon growth in CCL than in CCS.
3. Bud formation is inhibited bysome concentrations of chloramphenicolwithout accompanyinginhibition of the growth.
4. Cell size and the contents of RNA,DNA, protein and lipid percell of CCL are greater than thoseof CCS, respectively. Thecontents per cell of RNA and lipidin "mitochondrial fraction"are higher in CCL than in CCS.
5. Incorporationof guanine-8-¹⁴C into RNA of CCS occurs rapidlyin the first12 hr and slows down thereafter, but that in CCL-RNAincreasessteadily for 16 hr. This difference in rate of theincorporationafter 12 hr between CCS and CCL is principallydue to the differencein rate of the incorporation into RNAof nuclear, mitochondrialand soluble fractions.

1. The rate of RNA breakdown in CCL wasnot so great as the rateof synthesis.
2. 8-azaguanine (10^–3and 10^–4M) inhibits incorporationof guanine-8.¹⁴C intoRNA of both CCS and CCL during 14 hr,but thereafter (up to25 hr) it inhibits the incorporation intoCCL-RNA alone leavingthat into CCS-RNA unaffected.

1. In CCL 510^–5M 8.azaguaninedoes not affect total radioactivityincorporated into bulk RNA,but inhibits incorporation intoRNA of "mitochondrial fraction".

(Received December 23, 1964; )     

CHANGES IN HYDROGENASE ACTIVITY DURING THE SYNCHRONOUS GROWTH OF SCENEDESMUS OBLIQUUS D3

1. A fairly good synchronization of Scenedesmus cells was obtainedby transferring the cells grown in a medium containing a lowconcentration of iron into a medium containing relatively highconcentration of iron.
2. During the synchronous culture in themineral medium, a goodparallelism between the average cellvolume and hydrogenaseactivity was observed.
3. Effect of glucoseon the development of the hydrogenase activitywas variabledepending on the stage of algal growth.
4. Iron is essentialfor the development of the hydrogenase activityand glucosesupplementary.

¹On leave from Laboratory of Applied Botany, Faculty of Agriculture,Kyoto University, Kyoto.     

STUDIES ON THE METABOLISM OF A SULFUR-OXIDIZING BACTERIUM: I. OXIDATION OF SULFUR

1. Thiobacillus thiooxidans, isolated in our laboratory, was foundto oxidize sulfur, but not thiosulfate. Tetrathionate is alsooxidized slightly. Its ability to oxidize sulfur is inactivatedeven by such a mild treatment as keeping the cells in a frozenstate.
2. Inhibitory action of alcohols on the sulfur oxidationincreasesas the length of carbon chain of alcohols increases.Carboxylicacids do not inhibit the sulfur oxidation at pH abovetheirpK, while they strongly inhibit the reaction at pH belowthepK.
3. The sulfur oxidation is inhibited by cyanide, azide,diethyldithiocarbamateand carbon monoxide, and the inhibitionby carbon monoxide isnot reversed by light. These results suggestthe presence ofmetal enzymes in the sulfur oxidation system.The terminal enzymeof this reaction appears to be differentfrom the usual cytochromeoxidase.

(Received May 13, 1960; )     

Apparatus for the Measurement of Gaseous Conditions inside an Apple Fruit

1. Two forms of apparatus are described, one for the routine analysisof the internal atmosphere of an apple fruit and another forthe measurement of (i) carbon dioxide output, (ii) internalgas concentrations, (iii) atmospheric pressure within the fruit,(iv) permeability of the fruit to gases.
2. The use of thesetwo apparatuses to follow changes within thefruit as a resultof the application of a skin-coating is describedand the resultsobtained are discussed.
3. It is shown that the fall in pressurewhich occurs as a resultof the cooling of the fruit due toevaporation of the appliedcoating can only form a small fractionof the total fall inpressure observed as a result of the applicationof the coating.
4. It is shown that coating the fruit with anoil-water emulsioncauses a deficit in the combined concentrationof CO₂ and O₂within the fruit below the 21 per cent, observedin similaruncoated fruit.
5. An explanation of this phenomenonis advanced, and it is suggestedthat the modification of theinternal atmosphere brought aboutby the skin-coating, if itcan be suitably controlled, willprove valuable in increasingthe cold-storage life of apples.

The work described in this paper was carried out as part ofthe programme of the Food Investigation Organization of theDepartment of Scientific and Industrial Research.     

Studies on the Germination of the Seeds of Striga hermonthica: II. THE EFFECT OF THE STIMULATING SOLUTION ON SEED RESPIRATION

1. Data are presented which show the effect of the natural stimulatingsolution on the respiration of the seeds of Striga hermonthica.
2. The stimulating solution has been shown to enhance the aerobicrespiration of seeds exposed to it, compared with that of seedsto distilled water at the same temperature. This effect on therespiration of the seeds is quite independent of any previousmoisture-treatment of the seeds, and thus of germination.
3. Themaximum anaerobic rate of carbon-dioxide output of air-dryseedsafter treatment with the stimulating solution may be upto fifteentimes greater than that of seeds moistened with distilledwater.The anaerobic respiration of air-dry seeds after exposuretothe stimulating solution is greatly reduced by 0?025 M. sodiumfluoride and 0?001 M. sodium monoiodoacetate.
4. The stimulatingsolution has been found to have little effecton the anaerobicoutput of carbon dioxide from seeds which hadbeen moisture-treatedfor 6 days at 22? C. before treatmentwith the stimulating solution.
5. No correlation could be established between the effects ofthestimulating solution on germination and respiration.