The Water Permeability of Unplasmolysed Tissues2

1. The permeability of unplasmolysed cells of beetroot, v. ‘CrimsonGlobe’, was determined from the rate of water loss ofbeet slices on placing in sucrose solutions having O.P. greaterthan the suction pressure of the beet. The absolute values obtainedwere about 0?7µ³ water per µ² cell-surface per hourper atmosphere osmotic pressure difference, i.e. 0?7 µ/hr./atm.
2. The permeability of similar beet cells plasmolysed withintheircell walls was found to be about 13µ/hr./atm.
3. Thepermeability of beet cells which had been plasmolysed andallowedto recover was shown to be approximately the same asthat ofunplasmolysed cells.
4. The hypothesis is advanced that the increasein water permeabilityon plas-molysis is due to those partsof the plasma-membranewhich had formerly been pressed againstthe micelles of thecell wall becoming free and able to takepart in water transfer.
5. The energy requirement for the maintenanceof an excess hydrostaticpressure of five atmospheres withina cell by its vital activitywas shown to be about one-tenthof the total respiratory energyreleased in freshly cut beetslices.

     

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 Absorption of Ions by Excised Root Systems: I. APPARATUS AND PRELIMINARY EXPERIMENTS

1. An apparatus is described by means of which the absorptionofions from a complete nutrient solution of constant compositionby excised root systems of plants, grown under known nutrientdeficiencies, may be measured in standard conditions of aerationand temperature. Results of some prelimi nary experiments aredescribed.
2. It was found that the roots readily absorbed theelement inwhich they were deficient, but tended to lose thoseelementswhich were already present in normal amounts.
3. Therewas almost invariably a loss in fresh weight of the rootsafterthe absorption period and also a loss in dry weight. Thislossappears to be complex and is partly attributable to lossofrespiratory material.
4. The addition of 2 per cent. sucroseto the solution from whichthe root systems of phosphorus-deficientbarley plants wereabsorbing increased the nitrogen and phosphoruscontents ofthe roots and maintained the potassium content,while in absenceof sucrose only the phosphorus content increased,but this increasewas significantly less than in the presenceof sucrose.
5. It was shown that roots excised from plants growingin soilwere capable of absorbing phosphorus or nitrogen—elementsin which they were apparently deficient.
6. The interpretationof data obtained from excised roots is discussed,and it isconcluded that excised roots from plants grown incomplete nutrientare not likely to behave in the same way,as regards absorption,as corresponding roots of intact plants,but that roots grownunder conditions of deficiency will behaverather similarlywhether excised or intact. This fact providesa potential methodfor diagnosing and evaluating nutrient deficiencies.
7. The low-saltcondition of roots postulated by Hoagland and Broyeris notnecessarily the primary requisite for rapid absorptionof aparticular ion. It is rather that the roots should be deficientin that ion. The roots could be high in other salts.

     

The Time Factor in Studies of Growth Inhibition in Excised Organ Sections

1. Apprehension over the adequncy of current techniques stimulateda detailed study of the time factor in the arsenate inhibitionof growth and respiration in excised stem and root sectionsof Pisum sativum.
2. Growth inhibition by arsenate sets in veryslowly, its rateof onset being related to the molar concentration(C) of arsenateate by the relation where T₅₀ is the time taken in hours to reduce the growthrateto 50 per cent of the control and K is a constant. An explanationof the physiological basis of this relationship is attempted.
3. Estimates were made of the final steady growth rate (relativeto control) in various arsenate concentrations. The inhibitionscalculated from this rate are held to approximate to the truearsenate effect and are shown to be very different from thosecalculated from ‘total growth’ measures.
4. Respirationof growing stem sections is not inhibited by thelow arsenateconcentrations that inhibit growth. Some inhibitionis indicatedat high concentrations (3 ? 10^–4M. and over)but onlyafter 15-20 hours of exposure.
5. Two per cent sucrose has noeffect on the arsenate inhibiitionof stem growth. Sucrose,however, markedly stimulates respirationin stem sections, butthis stimulation is prevented by arsenate.
6. The misinterpretationswhich may arise as a result of ignoringthe time factor in inhibitionstudies in excised organ sectionsare discussed and the desirabilityof constructing completegrowth curves in all such studies isstressed.

     

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.     

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 Effects of Sugar and Potassium on Extension Growth in the Root

1. A new technique for studying extension growth in the root isdescribed which is based on excising a zone which extends 1·5–3·0mm. from the tip. Large numbers of these segments are culturedwith different nutrient fluids in the dark at 25° C. withcontinual shaking.
2. The effects of a large number of nutrientson the growth ofthe segments have been studied, but only two,sugar and potassiumions, have been found to have stimulatingeffects.
3. The effects of water, three concentrations of sugar,and oneof potassium in air, and with an atmosphere containing5 percent. oxygen have been studied in detail in connexionwith lengthincrease, sugar absorption, content of free sugar,cellulosecontent, dry weight, and respiration.
4. It has beenshown that with increasing concentration of sugarin the medium,the rate of growth, the time during which growthproceeds, theinternal concentration, respiration, dry weight,and celluloseformation all increase. Also that potassium stimulatesthe rateof growth and respiration, and that with per cent,oxygen allthe aspects studied are depressed.
5. It is suggested that thestimulation due to sugar may be attributedto an accelerationof water absorption with a complementaryincrease in celluloseformation. It is further suggested thatsugar accelerates waterabsorption by accumulating in the vacuoleand thus sustainingthe osmotic pressure of the vacuolar sap.It is further suggestedthat potassium stimulates growth byincreasing water absorptionthrough an effect on respiration.The effect of respirationin this connexion may be to promotethe transport of water directlyto enhance the osmotic pressureof the sap by inducing an accumulationof inorganic ions inthe vacuole.

     

The Absorption of Ions by Excised Root Systems: III. OBSERVATIONS ON ROOTS OF PEA PLANTS GROWN IN SOLUTIONS DEFICIENT IN PHOSPHORUS, NITROGEN, OR POTASSIUM

1. Pea plants were grown in complete culture solution and in deficienciesof phosphorus, nitrogen, or potassium for a period of about5 weeks. Excised roots of these plants were treated with a complete,aerated culture solution for varying periods of time and thechanges in respiration rate, phosphorus, nitrogen, potassium,sugar, and starch contents measured.
2. There were changes infresh weight and dry weight of the excisedroots during treatment.The dry weight decreased with time butthe water content changeswere variable. Uptake of water wascorrelated with uptake ofpotassium and sucrose content in someinstances.
3. There wasno evidence of a ‘salt respiration’ inthose caseswhere active accumulation occurred.
4. The rates of gain or lossof phosphorus, nitrogen, or potassiumat 0 hours, 8 hours, and16 hours were calculated and it wasfound that the rate dependedboth on content of element in theroot and the sugar cotent.There was very little evidence thatone element affected therate of uptake of another. Simultaneousloss of one elementand gain of another occurred in some instances.
5. The observationsappear to be best explained on the assumptionthat the absorbedions are fixed in the cells in the form ofloosely bound compoundsand that these compounds are formedfrom sugars.

     

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.

     

Studies on Plant Growth Hormones: II. FURTHER BIOLOGICAL PROPERTIES OF 3-INDOLYLACETONITRILE

1. 3-Indolylacetonitrile is more active than 3-indolylacetic acidin the Avena straight-growth test, but less active in the Avenacurvature test at comparable concentrations. Reasons for thisare discussed, and results of previous work on plant extractsusing the curvature test as a means of assay are considered.
2. Transport of both the acid and the nitrile is polar, fromapexto base of the coleoptile. The nitrile can reach the growingcells as easily, and possibly more easily, than the acid. Thesignificance of these findings for a theory on the mechanismof action of the nitrile is discussed.
3. The nitrile is inactivein the pea curvature test and straight-growthof pea stem sectionsexcept at high concentrations. It is alsoinactive or only slightlyactive in lateral bud inhibition,root initiation, and petioleabscission at the concentrationstested.
4. It is less activethan the acid in root inhibition in cress,but approximatelyas active in Avena. It is approximately asactive as the acidin parthenocarpic fruit development, andinitiation of cambialactivity.
5. The significance of these results is discussed.

     

Studies in Stomatal Behaviour: IV. THE WATER-RELATIONS OF THE EPIDERMIS

1. It is shown that a dry external atmosphere exerts the followingeffects on stomatal movement:

1. A striking accelaration ofclosure in darkness.
2. A slight acceleration of opening in light.
3. If the water-supply to the leaf is impaired, an inabilitytomaintain full opening in the light.

Conversely, a saturatedexternal atmosphere induces sluggishness of movement and a tendencyto incomplete closure in darkness.

1. These results are consideredto support La Rue's contentionthat the epidermal water-supplyis drawn solely by lateral movementfrom the main veins, andnot from the underlying mesophyll.The stomatal phenomena themselvesdo not appear capable of anysimple explanation based on currentknowledge of guard-cellphysiology.
2. The biological significanceof these results is discussed, withparticular reference tothe problem of xeromorphic structures,for which a new interpretationis suggested.

     

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 Absorption of Ions by Excised Root Systems: II. OBSERVATIONS ON ROOTS OF BARLEY GROWN IN SOLUTIONS DEFICIENT IN PHOSPHORUS, NITROGEN, OR POTASSIUM

1. Barley plants were grown in complete culture solution and indeficiencies of phosphorus, nitrogen, or potassium for a periodof about 6 weeks. Excised roots of these plants were treatedwith a complete, aerated culture solution at 25? C. for varyingperiods of time, and the changes in respiration rate, phosphorus,nitrogen, potassium, sugars, and starch contents measured.
2. Therewere changes in fresh weight and dry weight of the excisedrootsduring treatment. The dry weight decreased with time butthewater-content changes were variable. There was a gain orlossof water by the roots according to the treatment.
3. In all casesthe deficient roots increased in content of theelement in whichthey were originally deficient. The roots ofthe plants suppliedwith full nutrient usually decreased incontent of phosphorus,nitrogen, and potassium, but exceptionsoccurred and the reasonsare discussed.
4. In most of the experiments described simultaneousloss of oneion and gain of another occurred.
5. Nitrogen-deficientroots accumulated nitrate when exposed toa complete nutrientsolution, and some of this was assimilatedwith formation ofprotein. Under similar conditions nitrogen-richroots decreasedin nitrogen content and proteolysis took place.
6. There wasa rapid fall in sucrose and reducing sugar contentof the excise'roots. The starch content was initially verysmall and showedlittle change with time.
7. The respiration rate declined withtime in all treatments exceptwhere a nitrogen deficiency existed.Here the respiration rateincreased to a maximum value at about8 hours and then fell.This increase in rate is attributed toprotein synthesis. Noevidence of a ‘salt respiration’was observed evenwhen active uptake of phosphorus or potassiumwas occurring.
8. In most instances the carbon dioxide evolvedin respirationgreatly exceeded the carbon dioxide equivalentof the sugarconsumed in the same period. Exceptions were foundwith thenitrogen-deficient roots where less carbon dioxidewas evolvedthan the equivalent of sugar consumed. It is probablethat apart, at least, of the sugar unaccounted for was usedin proteinsynthesis.
9. Where the carbon dioxide of respirationwas in excess of theequivalent of sugar consumed, protein oramino-acid is the mostprobable substrate. Respiration rateis found to be relatedboth to nitrogen and sugar content.

     

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.

     

Studies on Plant Growth Hormones: I. BIOLOGICAL ACTIVITIES OF 3-INDOLYLACETALDEHYDE AND 3-INDOLYLACETONITRILE

1. Two neutral plant hormones, one isolated recently from plants(3-indolylacetonitrile) and the other (3-indolylacetaldehyde)reported to be present in plants, are avaible as pure syntheticcompounds for investigation of their biological activities.This paper is mainly concerned with their effects on cellelongationin the Avena coleoptile
2. 3-Indolylacetaldehyde is considerablyless active than 3-indolylaceticacid in the Avena straight-growthtest; for example, a 1.0 mg./l.solution of the aldehyde showsan activity equivalent to thatof a 0.1 mg./l. solution of theacid
3. An acidic substance is produced in solutions of the aldehydeduring the period of assay. In some experiments it accountsfor all of the activity shown by the aldehyde solutions, onthe assumption that it is 3-indoylacetic acid, and in otherexperiments it shows a greater activity than that of the aldehydesolutions from which it was obtained. Therefore, it is concludedthat 3-indolylacetaldehyde, itself is either inactive or inhibitory.Acid production in aldehyde solutions in vitro is much lower,a fact which suggests that there is enzymatic oxidation of aldehydeto acid in the presence of coleoptiles.
4. The activities of3-indolylacetaldehyde in the pea test andin root-inhibitionand of 3-indolylacetone in the straight-growthtest are brieflyreported.
5. 3-Indolylacetonitrile is considerably more activethan 3-indolylaceaticacid in the Avena straight-growth test;for erample, a 0.1 mg./l.solution of the nitrile shows an activityequivalent to a 1.0mg./l. solution of the acid. The inhibitoryeffect at concentrationsabove 1.0–10.0 mg./l. is lesswith the nitrile than withthe acid.
6. There is negligible productionof acid in solutions of the nitrileboth in vitro and in thepresence of Avena coleoptiles at temperaturesranging from –18?to 25? C. for varying lengths of time.The possibility of enzymaticconvesion of nitrile to acid insidethe cells of the coleoptileis discussed
7. The activities of 3-indolylacetamide and of 2:4-dichlorophenoxyaceticacid and the corresponding nitrile are considered in this connexion
8. The nitrile is destroyed by treatment with alkali but notbyacid. In the light of these results, it is desirable to re-examineprevious work on identification of auxins in plants by theiracid and alkali sensitivity. Evidence for the existence of thenitrile in a number of other plants is presented.

     

The 'Diffuse' Centromere or Polycentric Chromosomes in Spirogyra

1. Among ten species of Spirogyra types are distinguished withlarge-, medium-, and small-sized chromosomes.
2. Evidence ofcompound structure is presented with regard to thelarge-andmedium-sized chromosomes.
3. Parallel separation of chromatids,first described by Geitlerfor S. crassa, is found in all specieshaving large chromosomesand to some degree in those with medium-sizedchromosomes.
4. It is suggested that the parallel separationof chromatids iscaused by their polycentric nature.
5. Polyploidyin the genus is only doubtfully comparable with thatin thehigher plants.
6. It is suggested that in Spirogyra the localizedcentromere mayhave evolved in a polycentric chromosome.
7. Comparisonsare drawn between Spirogyra and other organismsstated to have‘diffuse’ centromeres and it is suggestedthat theirchromosomes also are polycentric.

     

WATER PERMEABILITY OF THE CELL WALL IN NITELLA

1. A method has been developed to measure the hydraulic conductivityof the wall of the internodal cell of Nitella flexilis.
2. Therate of water penetration through the cell wall varies linearlywith the hydrostatic pressure difference between the two sidesof the wall, showing that water permeability of the cell wallremains independent of the pressure difference applied.
3. Waterpermeability of the cell wall is inversely proportionalto itsthickness It is 30µµmin^–3{dot}atm^–3when the thickness of the wall is 10 µ.
4. Water permeabilityof the cell wall is the same for inward andoutward water flow.The polar water permeability of the entiremembrane system (walland protoplasmic part) of the living celldemonstrated by KAMIYAand TAZAWA (1) is, therefore, due tothe living protoplasmicpart.
5. The ratio of the inward to outward permeability constantsofthe protoplasmic layer alone is higher than that of the entiremembrane system composed of protoplasmic layer and cell wall.

¹ Dedicated to Prof. H. TAMIYA on the occasion of his 60th birthday.The present work was supported in part by a Grant-in-Aid forFundamental Scientific Research from the Ministry of Education. ² Present address: Sh?in Women's College, Kobe. (Received July 21, 1962; )     

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.

     

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.     

CHANGES IN RESTING POTENTIAL AND ION ABSORPTION INDUCED BY LIGHT IN A SINGLE PLANT CELL

1. Effect of light on ion absorption and resting potential of theinternodal cell of Nitella flexilis was investigated under variousconditions.
2. On illumination, the resting potential increasedby about 30mVin 10^–4 M KCl and by about 60 mV in 10^–4M NaClsolution. A similar photoelectric response was also observedin 10^–3 M KCl, 10^–2 M CaCl₂ and 5 x 10^–2 MCaCl₂ solutions, but not at all in 10^–2 M KCl solution.
3. Absorption of ions by the cell took place in parallel withthelight-induced change in resting potential.
4. Red and bluelights were very effective in increasing the restingpotential,while green light was almost ineffective. These differenteffectsof color lights were in good agreement with their effectsinincreasing the osmotic value of the cell.
5. The photoelectricresponse was not affected by phenylurethane,which, on the otherhand, strongly inhibited the light-inducedion absorption.
6. Theuptake of ions by the cell from the external medium intothevacuole is assumed to proceed in two different steps: thefirstis the process involving the ion movements across theoutermostplasmalemma, and the second is that involved in thetransportof ions through the cytoplasmic layer and tonoplast.The formerprocess is considered to be influenced by the increasein restingpotential probably caused by the light absorbed bychlorophyll.The process was, however, suggested to be independentof photosynthesis.On the other hand, the latter process issupposed to be relatedto photosynthesis. A discussion was madealong this line.

(Received July 26, 1962; )