STUDIES ON THE MECHANISM OF GROWTH INHIBITING EFFECT OF LIGHT

1. A substance which inhibits indoleacetic acid (IAA)-and naphthaleneaceticacid (NAA)-induced elongation of Avena coleoptile section andIAA-induced Avena coleoptile curvature was found in an ethersoluble neutral fraction of water extract of sunflower leavesand in agar blocks containing the diffusate from young sunflowerleaves.
2. This substance also inhibits the growth of isolatedsunflowerepicotyl.
3. The R_f value (0.9) of the substance ona paper chromatogramdeveloped with ammoniacal iso-propanolindicates that it isidentical with the inhibitor reported byAUDUS et al. (1956),but not with inhibitor-ß.
4. Theinhibitor can be transported from leaf to stem, and thetransportseems to be accelerated by illuminating the leaf.
5. The auxindiffused from sunflower leaf into agar block may beidenticalwith IAA.
6. A substance, which has the same properties as theinhibitorfrom sunflower leaf, was obtained in crystalline formfrom theleaf of Jerusalem artichoke.
7. The mechanism of growthinhibition caused by this crystallinesubstance seems to involveinactivation of a sulfhydryl group.
8. The reason why the stemgrowth of sunflower seedlings is reducedby strong light isdiscussed: the amount of the inhibitor transportedfrom leafto stem is increased under strong light, and in thestem, growthinhibition is caused by a direct effect of thisinhibitor ongrowth and by its inhibiting effect on the transportof IAAfrom leaf to stem.

¹ Present address: Botanical Garden, Faculty of Science, Universityof Tokyo, Tokyo (Received February 15, 1961; )     

EFFECT OF SOME SULFHYDRYL REAGENTS ON LIGHT-INDUCED CO2-FIXATION IN CHLORELLA

1. Using intact cells of Chlorella ellipsoidea, investigationswere made on the effects of some SH-reagents (IAA, CMB and arsenite)upon various reactions pertaining to the primary photogenicagent (designated by R) formed in the mechanism of photosynthesis.
2. The pre-illumination experiments using ¹⁴CO₂ as a tracer haveled us to the inference that (i) the process of photochemicalformation of R is inhibited by IAA, that (ii) the spontaneousdecay of R in the dark is markedly accelerated by CMB and arsenite,but not at all affected by IAA, and that (iii) the participationof R in the cyclic path of carbon leading to the fixation ofCO₂ is not affected by IAA and CMB.
3. Based on the assumptionthat R is a reducing agent, it was discussedthat the fact mentionedunder (iii) is incompatible with theidea that the reductionof PGA to triose phosphate be the soleor rate-determining reductivestep in the cyclic path of carbonin photosynthesis.
4. The possibilitythat R may have a functional SH-group (s) wasinvoked to accountfor the observation that the decay of R inthe dark was markedlyaccelerated by CMB and arsenite.

(Received February 11, 1960; )     

CHEMICAL CONTROL OF MORPHOGENESIS IN MOSS PROTONEMA

1. The protonema of the moss, Funaria hygrometrica, grows continuouslyin calcium-free liquid media.
2. The growth was promoted by additionof oxalate, although themorphogenesis resulting in formationof gametophytic buds onthe protonema was suppressed by theaddition.
3. Calcium oxalate promoted the growth of protonema,while at ahigh concentration (10^–2 M) it caused the formationofclumped protonema (falsebuds).
4. Addition of plant growthhormones, such as IAA, NAA, 2,4-D andgibberellin retarded thegrowth of protonema, while 2,4-D ata low concentration stimulatedthe growth of protonema.
5. Kinetin greatly stimulated the formationof gametophytic budsin the protonema, but these buds were foundto be morphologicallyand physiologically abnormal.

(Received January 29, 1965; )     

Growth Regulator Interactions in the Growth of the Shoot System of Avena sativa Seedling: II. THE GROWTH OF THE FIRST LEAF AND THE COLEOPTILE1

1. Studies have been made of the growth in culture medium of thecomponent parts of compositesegments excised from 3 to 7-day-oldAvena sativa seedlings and comprising portions of coleoptileand first leaf bases and various lengths of first internodetissue.
2. The effects of various concentrations of gibberellicacid (GA)and indole-3- acetic acid (IAA) alone and in combinationhavebeen studied on the growth of these organs.
3. Both GA andIAA stimulate the growth of coleoptile base tissuebut in combinationtheir joint effects are less than additive.No synergism occurs.
4. The growth of the first-leaf base is greatly stimulated byGAbut is inhibited by IAA. In combination, the stimulatoryeffectof GA (up to 1 0 p.p.m.) may be virtually eliminatedby evenlow concentrations of IAA (0.01 p.p.m.).
5. The inclusionof first internode tissue in the segments considerablyincreasesthe growth of first leaf base tissue but has no consistenteffecton the growth of coleoptile base tissue. The presenceof firstinternode tissue also greatly increases the degreeof growthstimulation invoked by GA but does not influence thedegreeof IAA inhibition. It is postulated that the first internodetissue is the source of an unknown growth factor necessary forGA action in the first leaf and potentiating the action of endogenousgibberellin.
6. Kinetin, adenine sulphate, glutarnine, glutarnicacid, asparagine,glycine, arginine, histidine, lysine, aneurin,and pyridoxinewill not simulate the effects of this unknowngrowth factorin the growth of leaf tissue. Like IAA, kinetinvirtually eliminatesthe GA stimulation of leaf growth.
7. Astudy of extracts of internode tissue in various solvents,analysedby paper partition chromatography and assayed by thegrowthof the first leaf base, has indicated the presence ofgrowthinhibitors and gibberellin-like substances but has failedtoisolate the postulated endogenous GA-synergist.
8. The implicationsof these results for growth correlations andthe hormone controlof shoot growth in Avena sativa seedlingsis discussed.

     

The Growth-time Relationships of the Auxin- induced Growth in Avena Coleoptile Sections

1. 1. The growth rate of Avena coleoptile sections in the presenceof indoleacetic acid (IAA) is constant with time over a widerange of time intervals and IAA concentrations.
2. 2. Constancyof growth rate is dependent upon the maintenanceof constantconditions in which the concentration of IAA availableto thesection remains the chief factor limiting growth rate.
3. 3.Control of the pH of the medium in which the sections aregrownis essential to the maintenance of constant growth rate,particularlyin the presence of high concentrations of IAA.
4. 4. The lagperiod in establishment of steady growth rate bysections inthe presence of IAA is less than 10 minutes andis not detectableby present methods of measurement.

     

Growth responses of sunflower hypocotyl disks inoculated with Escherichia coli and Agrobacterium tumefaciens I. Morphological observations

Disks of sunflower hypocotyls 1 mm thick grown in light anddarkness on agar containing mineral salts and sucrose to whichIAA was added in varying concentrations, were inoculated withE. coli, A. tumefaciens or sterile synthetic medium. Light-growndisks inoculated with E. coli proliferated from the lower surfaceand formed numerous long roots but dark-grown disks were usuallyinhibited in comparison with uninfected disks. Inoculation withA. tumefaciens induced proliferation mainly from the upper surfaceand a few short roots were formed. Uninfected disks grown with0.01 ppm IAA proliferated in a manner similar to that of E.coli-infected light-grown disks on simple medium but in thedark similar treatments produced quite different morphologicaleffects. The form of proliferation induced by E. coli underall conditions of growth could not be equated with that inducedby A. tumefaciens or by different concentrations of IAA. (Received December 5, 1967; )     

Studies on the destruction of indole-3-acetic acid by a species of Arthrobacter I. On the induction of the enzyme responsible for the destruction

1. The induction of an IAA-destroying enzyme in Arthrobacter sp.that can utilize IAA as its sole source of carbon and nitrogenwas investigated.
2. 1. The enzyme was most effectively inducedby 10–³ to2x10–³ M IAA, at pH 6.5.
3. 2. All testedIAA analogs were unable to induce the enzyme.Analogs otherthan indole-3-lactic acid were rather inhibitoryon the inductionwith IAA.
4. 3. The induction period was shortened with the ageof culturein both polypeptone and acetate media.
5. 4. Pretreatmentof the bacterium with IAA caused a shorteningof the inductionperiod.
6. 5. The induction was inhibited by various antibiotics,aminoacid analogs and nucleobase analogs.
7. 6. The inductionwas less remarkable in actively proliferatingcells than itwas in slowly proliferating ones.

(Received July 1, 1967; )     

NUTRITIONAL STUDIES OF A YEAST

The present work deals with essential growth factor requirementsof a haploid strain of Saccharamyces sp., strain 19861, whichexhibits requirements for lysine, arginine and histidine.

1. The strain requires Ca-pantothenate, biotin and thiamine inaddition to the three amino acids.
2. In a synthetic medium containingthese amino acids and the threevitamins, tryptophan could replacehistidine completely.
3. Pyridoxine, leucine, isoleucine andvaline, as a group, couldreplace thiamine in the presence ofinositol.
4. In the above substitution, leucine could be removedwhen excessivevaline was added, the optimal ratio of isoleucineto valinebeing about 1:3 in the presence of tryptophan, insteadof histidine.
5. In a isoleucine-deficient medium, flocculationoccurred in fiveor more days.

(Received March 3, 1961; )     

PARTIAL PHOTO-REPRESSION OF THE GLYOXYLATE BY-PASS IN EUGLENA

1. Addition of exogenous acetate or ethanol to autotrophic culturesof Euglena gracilis strain Z induces formation of the glyoxylateby-pass.
2. Visible light decreases the activity of malate synthasein greenEuglena by about 50%. No such effect was found in apermanentlybleached mutant.
3. Aconitase activity parallelsthat of malate synthase, but isocitricdehydrogenase activityis constant under all conditions examined.
4. Oxygen consumptionis proportional to the activities of malatesynthase and aconitase,but not to that of isocitric dehydrogenase.
5. The results ofsimilar studies with other growth substrates(pyruvate, malate,succinate) suggest that some of the oxygenconsumed by C₂-grownEuglena may not be associated with energyproduction.

(Received March 25, 1966; )     

Effects of 3-Indolylacetic Acid and 3-Indolylacetonitrile on the Growth of Excised Tomato Roots

1. The inhibition by IAA (3-indolylacetic acid) and by IAN (3-indolylacetonitrile)of the growth of excised tomato roots cultured for 7 days at27 C. in a modified White's medium is described. 510^–9g./ml, IAA or 510^–6 g./ml, IAN cause approx, 50 per cent,inhibition of the linear growth of the main axis. With IAA decreasein number of laterals closely parallels the decrease in lineargrowth of the main axis; with IAN reduction in linear growthof the main axis occurs at concentrations above 10^–8 whereasnumber of laterals does not decrease until the concentrationexceeds 10^–6.
2. Study of the course of cell elongationin the exodermal cellsshowed that in the standard medium andin media containing 510^–9IAA or 510^–6 IAN theprocess takes about 7 hours; thefinal cell lengths in IAA andIAN media are lower than in standardmedium owing to a slowerrate of elongation. The decrease inlinear growth of the mainaxis in presence of IAA could be accountedfor by the decreasein cell length; this was not the case withIAN. The implicationsof this are considered.
3. Determinations of the distance (mm.)between, and of the numberof exodermal cells separating, theadjacent laterals in oneorthostichy showed that IAN enhancesthe frequency of lateralswhereas this is either unaffectedor decreased by IAA. The enhancementof lateral frequency inIAN arises from shortening of the cellsof the main axis anddecrease in the number of cells separatingadjacent laterals.
4. The results are considered to support the view that IAN haseffects on root growth different from those of IAA. Study ofthe degree of inhibition of main axis growth and of alterationsin lateral frequency resulting from treatment with mixturesof IAA and IAN provided data which could also be most easilyexplained on this hypothesis.

     

"GIGANTISM" OF CHLORELLA VULGARIS I. MECHANISM OF INDUCTION OF CIGANTISM

1. Based on the microscopic observations, two stages, "giant cellstage" and the subsequent "palmelloid body stage", were distinguishedin the process of formation of giant Chlorella induced by theaddition of sugars. The "giant cell" is much larger in sizethan the control cell, but the other morphological featuresare the same as those of the latter. The "palmelloid body" isa form composed of many conjoined autospores.
2. When a highconcentration of glucose was maintained in the medium,gigantismwas also maintained. Under this condition, the algashows acyclic transformation between "giant cell" and "palmelloidbody"without returning to the small single cells.
3. Large amountsof carbohydrate composed of hexose were foundto be accumulatedin the giant algal cells, and it was inferredthat this carbohydrateaccumulation causes greater enlargementof cell volume as comparedwith control cells.
4. Uronic acids, which were found to be absentin the control cells,were formed and lost in the cells culturedin the glucose mediumin parallel with the appearance and disappearanceof gigantism.
5. Pectic substances, from which uronic acids areconsidered tobe derived during the extraction procedure, werefound to bepresent only in giant Chlorella.
6. The conjoinedautospores in giant Chlorella (at the palmelloidbody stage)were separated to some extent by the addition ofEDTA, and theresulting cells were similar to control Chlorellacells.
7. Basedon these results it was inferred that inductive formationofthe pectic substances is causally related with the appearanceof "palmelloid body".

¹ Present address: Department of Chemistry, College of GeneralEducation, Osaka University, Toyonaka, Osaka.     

Auxin-Induced Changes in the Molecular Weight Distribution of Cell Wall Xyloglucans in Avena Coleoptiles

The effect of auxin on the molecular weight (Mw) distributionof cell wall xyloglucans was investigated by gel permeationchromatography using coleoptile segments of Avena sativa L.cv. Victory, and the following results were obtained.

1. The water-insoluble hemicellulose (HC-A) mainly consisted ofxyloglucans. Iodine staining method revealed that relativelylarge amounts of xyloglucans were present in the water-solublehemicellulose (HC-B) and water-soluble polysaccharide (WS) fractions.
2. IAA did not cause remarkable changes in xyloglucan contentsin the hemicellulose, but significantly increased the xyloglucancontent in the WS fraction.
3. IAA substantially decreased theweight-average Mw of HC-A. Thiseffect became apparent within30 min of the incubation period,and was not affected by the0.15 M mannitol or 2% sucrose applied.Hydrogen ions also causeda decrease in the weight-average Mwof HC-A; its effect beingreversible.
4. Neither IAA nor hydrogen ions caused any remarkablechangesin the weightaverage Mw of water-soluble xyloglucansin theHC-B.

These results suggest that cell wall xyloglucans have an importantrole in auxininduced cell wall loosening in oat coleoptile cells. (Received May 10, 1984; Accepted August 20, 1984)     

PROMOTION OF ADVENTITIOUS ROOT FORMATION BY HELIANGINE AND ITS REMOVAL BY CYSTEINE

1. Heliangine at 10^–4M promoted the adventitious root formationin hypocotyls of cuttings taken from light-grown (1,900 lux)seedlings of Phaseolus mungo. The promotion was almost completelyreduced by simultaneously supplied 310^–4M cysteine or1.510^–4M cystine, but not suppressed by 310^–4Mof reduced glutathione, alanine or serine.
2. A 4 hr pretreatmentwith 310^–4M cysteine made Phaseoluscuttings less sensitiveto heliangine, but cysteine suppliedafter the treatment withheliangine brought about no effecton the action of heliangine.
3. Cysteine also removed the inhibiting effect of heliangineonthe indoleacetic acid-induced elongation of etiolated Avenacoleoptile sections.
4. In an aqueous solution heliangine formedan addition productwith cysteine, indicating that cysteinecan inactivate helianginewithout any biological processes.
5. On Phaseolus adventitious rooting, no effect was observedofp-chloromercuribenzoic acid, N-ethylmaleimide, 1,4-naphthoquinone,coumarin or penicillin. Reactivity toward sulfhydryl groupsalone does not qualify a substance to be a promotor of rootformation.
6. Maleic hydrazide at 10^–4M promoted root formation,butits effect was not removed by cysteine.

¹ Contribution No. 13 from the Botanical Gardens, Faculty ofScience, University of Tokyo, Koishikawa, Tokyo.     

FLAVOPROTEIN IN CHLORELLA ELLIPSOIDEA CATALYZING TPNH-LINKED REDUCTION OF PLASTOCYANIN

1. An enzyme possessing a capacity of catalyzing reduction of thecopper protein, plastocyanin, with reduced pyridine nucleotides(TPNH-plastocyanin reductase) was isolated from Chlorella ellipsoidea.The procedures of purification and the properties of the purifiedenzyme are described.
2. From the results of chromatographicand enzymic tests, the prostheticgroup of the enzyme was identifiedas FAD. No evidence was obtainedto indicate the participationof metal ions in the reaction.
3. The enzyme utilizes both TPNHand DPNH as electron donors, butthe reaction is about 12 timesfaster with TPNH than with DPNH.
4. The enzyme, with TPNH aselectron donor, catalyzes the reductionof Chlorella plastocyanin,cytochrome c, 2,6-dichlorophenolindophenol and oxygen in adecreasing order of reaction rate.The reaction with oxygenas electron acceptor was found to bemuch more strongly acceleratedby the addition of higher concentrationsof flavins as comparedwith the reaction with other acceptors.FAD and FMN added tothe reaction mixture are not appreciablyreduced.
5. The propertiesof the enzyme are compared with those of alliedchloroplastenzymes reported by various investigators and thepossible roleof the new enzyme in photosynthesis is discussed.

(Received January 18, 1961; )     

Studies in the Physiology of Parasitism: XXIII. On the Parasitic Vigour of Certain Bacteria in Relation to their Capacity to Secrete Pectolytic Enzymes

1. 1. Three organisms, Flavobacterium sp., Pseudomonas sp. designatedNo. 169 and Pseudomonas syringae, were compared with a pathogenBacterium aroideae. Although they all produced pectolytic enzymeof equal activity on potato extracts, only the pathogen wasable to parasitize the vegetable tissue, except when the watercontent of the latter was increased.
2. 2. It was evident thatsuccess or failure of an attack was determinedwithin 24 hoursfrom inoculation. The events taking place duringthis periodwere studied in some detail with potato extractsand potatotubers. On dilute extracts the pathogen grew rapidly,with anacid drift of the medium, and pectolytic enzyme wasdetectablewithin a few hours from inoculation. The weaker organismsgrewslowly, with no acid-forming tendency, and showed a delayinenzyme secretion. Differences in growth and in secretionofenzyme were further accentuated when the extract approachedthe strength of potato sap.
3. 3. No obvious qualitative differenceswere found between thepectolytic enzymes secreted by the fourorganisms.
4. 4. The failure of the weak organisms to attacknormal potatotissue can be ascribed to their slower rates ofgrowth and enzymicsecretion which allow the host time to forma protective barrier.On the other hand, rapid growth and thesecretion of enzymewithin a few hours enabled B. aroideae tobecome establishedbefore a wound reaction could take place.

     

Studies on the destruction of indole-3-acetic acid by a species of Arthrobacter II. Properties of the oxidation system

1. Some properties of the IAA-oxidizing activity of lyophilizedcells of Artkrobacter sp. were examined.
2. 1. IAA oxidationseems not to be catalysed by peroxidase, polyphenoloxidase,laccase or dehydrogenase, but by an oxidase systemdifferentfrom the one reported earlier.
3. 2. The optimal pH for the oxidizingsystem is ca. 6.0, and thesystem is comparatively stable atpH 5 to 10.
4. 3. The optimal substrate (IAA) level is 10^–3M.
5. 4. Activity is inhibited by metal-chelating reagents, suchassodium azide, potassium cyanide, sodium diethyldithiocarbamate,potassium xanthogenate and 8-hydroxyquinoline, and sulfhydrylreagents, such as iodoacetamide, monofluoroacetic acid, p-chloromercuribenzoate,isatin, ß-naphthoquinone and ß-naphthoquinone-4-sulfonate.Hydroxybenzoic acid, sulfosalicylic acid and 2,4-dichlorophenolare also inhibitory.
6. 5. None of the IAA analogs tested (indole,skatole, 2,3-dihydroxyindole,indole-3-aldehyde, -3-carboxylicacid, -3-propionic acid, -3-lacticacid, -3-butyric acid, 5-hydroxyindole-3-aceticacid and D,L-tryptophan) are oxidized by the cells, and someanalogs (indole-3-carboxylicacid, -3-propionic acid, -3-butyricacid, 5-hydroxyindole-3-aceticacid, naphthalene-acetic acidand 2,4-D) are inhibitory at comparativelyhigh concentrations.
7. 6. The oxidizing activity is not stimulated by Mn⁺⁺ and isinhibitedby Co⁺⁺, Cu⁺⁺ and Hg⁺⁺.
8. 7. The oxidizing activitydisappears completely within 6 hrat 30, but is kept unchangedat least for two weeks at –20.

(Received August 7, 1967; )     

PHOTOCHEMICAL REDUCTION AND OXIDATION OF MENADIONE (VITAMIN K3) IN CHLOROPLASTS

1. Menadione (vitamin K³) was found to be completely reduced byilluminated spinach chloroplasts under highly anaerobic conditionand in the presence of ethylenediamine tetraacetate (EDTA) inthe reaction mixture. This photoreductive reaction is sensitivetoward heat-treatment and inhibited by 2?10^-3M hydroxylamine.
2. In the presence of oxygen, the reduced form of menadione israpidly photooxidized by chloroplasts. This photooxidative activityalso is suppressed by heat-treatment but not inhibited by hydroxylamine.
3. Dyes which are inefficient as HILL oxidants such as thionineand methylene blue were found to be readily reduced by illuminatedchloroplasts, if the experimental conditions were appropriateto prevent the reoxidation of the photoreduced dyes; i.e., exhaustiveremoval of oxygen and the addition of EDTA in the reaction mixture.Menadione was found to accelerate the HILL reaction with thesedyes as oxidant under such experimental conditions.
4. In thepresence of molecular oxygen in the reaction mixture,menadionewas found to inhibit the HILL reaction with 2,6–dichlorophenolindophenol as oxidant, while the reaction rate was little influencedin high anaerobiosis.
5. These findings are explained by theintermediary oxidation and(photo-) reduction of menadione asan intermediary hydrogencarrier, and by the trends toward rapidphotooxidation of reducedmenadione.

(Received July 2, 1960; )     

STUDIES ON THE METABOLISM OF A SULFUR-OXIDIZING BACTERIUM II. THE SYSTEM OF CO2-FIXATION IN THIOBAC1LLUS THIOOXIDANS

1. In the early stage of CO₂-fixation by Thiobacillus thiooxidans,which was incubated aerobically in the presence of sulfur, mostpart of the fixed carbon was found in the phosphate ester fraction.
2. The fixation was inhibited by NaF, picolinic acid, PCMB, azide,dipyridyl, o-phenanthroline, monoiodoacetic acid, and arsenite,each in the concentration range where the sulfur oxidation wasnot affected strongly.
3. The crude extract of this organismcould fix CO₂ in the presenceof ATP, R-5-P and Mg⁺⁺. Most partof the fixed carbon was foundin PGA.
4. The crude extract showedthe CO₂-fixation coupled with the H₂S-oxidationin the presenceof ADP.
5. An appreciable reduction of PGA could not be detectedin thepresence of reducing systems, involving TPNH and DPNH.

(Received March 6, 1962; )     

"GIGANTISM" OF CHLORELLA VULGARIS I. RELATION OF GIGANTISM TO CELL GROWTH AND DIVISION

1. The sugars which induced gigantism of Chlorella cells wereglucose,fructose, galactose, mannose, xylose and arabinose.These sugarswere utilized as respiratory substrates by thealgal cells.
2. The cellular division of Chlorella was stimulatedby glucoseand galactose, but suppressed by fructose, mannose,xylose andarabinose, while all these sugars evoked gigantism.No correlationwas found between cellular division and gigantism,
3. The photosynthetic activity of giant Chlorella varied withthesorts of sugars added. It was decreased by glucose, fructoseand mannose, but was unaffected by other sugars such as galactose,xylose and arabinose.
4. The respiratory activity of giant Chlorellacells as much higherthan that of control cells.
5. The amountsof protein-N and dry weight per unit volume of giantChlorellawere much less than those of control cells.

¹ Present address: Department of Chemistry, College of GeneralEducation, Osaka University, Toyonaka, Osaka.     

SYNCHRONOUS CULTURE OF CHLORELLA: I. KINETIC ANALYSIS OF THE LIFE CYCLE OF CHLORELLA ELLIPSOIDEA AS AFFECTED BY CHANGES OF TEMPERATURE AND LIGHT INTENSITY

1. Using the technique of synchronous culture, investigationsweremade of the effects of temperature and light-intensityon cellularlife cycle of Chlorella ellipsoidea. Some improvementsin theculture technique for obtaining a good synchrony of algalgrowthwere described.
2. By following the changes of averagecell volume and cell numberoccurring during culturing, therates of the following processesof life cycle were determined:(i) "growth" (or the increasein cell mass) occurring from thestage of smaller cells (D_a)to the stage of ripened cell (L₃),(ii) "ripening" (or processofformation of "nuclear substances"as estimated from the averagenumber of daughter cells formedfrom single mother cell), and(iii) " maturing and division" which leads to the full maturationof mother cells (L-cells)and their division into separate daughtercells (D-cells).
3. "Growth"and "ripening" were found to be dependent in light,"maturingand division" light-independent. The time requiredfor "growth"and "ripening" (C) is dependent on temperaturebut independentof light intensity, the onset of "maturing anddivision" occurringat the same time (D) of culturing undervaried light intensities.The average cell volume at this stage(L₃),however, was foundto be markedly modified by light intensity;larger with highertemperatures (see Fig. 4).
4. Changes in incubation temperature(under the condition of saturatinglight intensities) were foundto affect the life cycle in thefollowing way: (i) The timeof onset of "maturing and division"(D), varies markedly withculturing temperature; earlier athigher temperatures, (ii)The average cell volume at this stagealso depends on temperature; smaller at higher temperatures.
5. The average number of daughtercells (n) emerging from singlemother cells, was found to beuninfluenced by culturing temperature;(4.0–4.1 underthe conditions of the present study). Itwas found that thedivision number n is remarkably varied bychanging the lightintensity in the "growth" and "ripening"phases; 2.0 at 1 kilolux,3.7 at 5 kilolux, 4.2 at saturatinglight intensities (10 and25 kilolux). This finding was explainedby assuming a light-dependentformation of "nuclear substances"during the "growth" and "ripening"phases, the quantity of thesubstances in the cell at L₃ stagedeterminig the division number.
6. The experimental data wereanalyzed reaction kinetically, therate constants and othercharacteristics of the reactions constitutingthe processesof life cycle were determined, and values forthe apparent activationenergy for each reaction were computed.The reactions were discussedwith special reference to theirrelationship with photosyntheticprocess was discussed.

(Received November 7, 1959; )