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 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.

     

Observations on the Gaseous Exchanges which take place between Menyanthes trifoliata L. and its Environment: I. THE COMPOSITION OF THE INTERNAL GAS OF THE PLANT

1. As part of a general investigation into the exchange of gasesbetween the bogbean, Menyanthes trifoliata, and its environment,determinations have been made of the composition of the internalatmosphere of the plant at five different levels, viz. leafyshoot, three successive portions of stem, and roots.
2. Procedureis described for the analysis of small gas samplesusing a modificationof the Bonnier and Mangin apparatus.
3. In darkness with thelower part of the plant surrounded by anatmosphere of nitrogen,it has not been possible to show thepresence of a regular downwardsgradient of oxygen, such aswould be expected on a basis ofnormal gaseous diffusion.
4. Under these Air Top/Nitrogen Bottomconditions the roots areshown to contain between 12?5 and 17?5percent, of oxygen intheir intercellular gas system. The portionof stem immediatelyadjacent to the roots showed an oxygen levelof from 14?0 to18?0 per cent.
5. In plants kept under NitrogenTop/Air Bottom conditions in thedark for 48 hours, the concentrationof oxygen in the rootsfell to a level of 3?1 per cent, or belowin three plants andto 6?o per cent, in a fourth. The oxygenconcentration in theadjacent lowermost part of the stem wasas high as 18?0 percent., depending on the degree of aerationof the solution bathingthe stem. It is suggested that thisdistribution of oxygen canbe related to the relative impermeabilityof roots and of stemendodermis to gaseous diffusion from without,and it is thoughtthat the major part of the oxygen supply tothe roots is transportedto them through the stelar air passages.
6. Some evidence is presented to show that oxygen passes fromthelower parts of the plant into the medium surrounding it.

     

Factors concerned in the Rooting Responses of Isolated Leaves

The rooting responses of isolated leaves of the dwarf Frenchbean and the ivy were studied by applying solutions of growthsubstances to the petiole: ß-indolyl-butyric acid(I.B.A.) for the former and -naphthyl-acetic acid (N.A.A.) forthe latter. The following factors were investigated:

1. The variation in response of successive leaves from the apextowards the base of the plant.
2. The optimal concentrationsof the growth substances and therelation between duration ofapplication and concentration.
3. The relation of age of theleaf and optimal concentration(ivy).
4. The nutritive factorsconcerned in the response were studied,(a) by varying periodsof contact between lamina and petiole,(b) by varying durationof light, (c) by varying the amountof light, and (d) by feedingwith sucrose and asparagine.

The most responsive leaf in the bean was the 2nd from the apex,in the ivy the 9th leaf. Very young leaves were killed. Withpetioles immersed for 24 hours the optimal concentrations wereI.B.A. at 2·5 parts per million (p.p.m.) for the bean,and N.A.A. 100 p.p.m. for the ivy. It was shown that the activesubstance entered mainly through the cut end in the transpirationstream; entry through the cuticle was much slower. Starvation of the cuttings whether by low light intensity, darkness,or separation of the lamina from the petiole reduced root formation.Feeding with sucrose and asparagine increased the response. Analysis of the leaves was carried out at regular intervalsfor total sugar, total and soluble nitrogen. In the bean solublenitrogen increased slightly in the petiole during the first5 days after treatment, after which insoluble nitrogen continuedto accumulate until the 7 day, when the roots first emerged.After this the total nitrogen decreased. Sugar content of thepetiole at first increased but rapidly fell before the rootsemerged and then again increased. In the ivy petiole the increasein soluble and total nitrogen was very slow, the former beinggreatest on the 15th day and the latter on the 20th day aftertreatment. The total sugar increased to the 10th day, but thendecreased until the emergence of roots, after which it againincreased. Treated leaves of the bean and ivy of different agesand the leaves starved for varying periods were also analysedfor total sugars and total nitrogen. Treated bean leaves receivingvarying periods of daily illumination were also analysed toelucidate their rooting response. Histological examination showed that in the bean the roots arosein the rays between the vascular bundles and in the ivy externalto the vascular bundles opposite the phloem. The growth of the rooted leaves was followed for more than amonth in the bean and over one year in the ivy. Some growthwas found in the immature bean leaves which survived treatment,but the final size was much below that of the control leavesattached to the plant. In the ivy very little further growthoccurred although the leaves produced a large root system andafter 2 years are still alive: the original differences in sizeof the successive leaves at the time of removal from the plantstill remain.     

LACTATE OXIDATION SYSTEM IN ACETOBACTER SUBOXYDANS, WITH SPECIAL REFERENCE TO CARBON MONOXIDE-BINDING PIGMENT

1. Lactate oxidation system was investigated in Acetobacter suboxydans,which was found to have cytochromes a and b, but no cytochromec. Haemoprotein 558 was also found to exist.
2. Carbon monoxideinhibited the lactate oxidation in the darkbut not in the light.WARBURG'S partition constant was estimatedto be 7.
3. Additionof haemoprotein 558 noticeably enhanced the oxygenuptake bythe LDH preparation, which was obtained from bacterialcellsand partially purified.
4. Haemoprotein 558 has protohaem asits prosthetic group. Notonly its absorption spectrum is reminiscentof that of peroxidase,but it also shows peroxidase-like reactivitywith some ligandswith a few exceptions.
5. Ferrohaemoprotein558 reacts with oxygen, forming, at first,a complex, whichhas its SORET absorption peak at 423 mµ.The absorptionmaximum then shifts to 417 mµ, indicatinga transformationto another compound. One of these two productsis likely tobe the oxygenated ferro-haemoprotein 558.
6. The mutual transformationbetween cytochrome B and haemoprotein558 is discussed.

(Received October 8, 1965; )     

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 Effects of Certain Growth-regulating Substances on the Rhizomes of Aegopodium podagraria

1. The effects on elongation and geotropic behaviour of theimmersion of rhizomes of Aegopodium podagraria for periods ofminutes in solutions of ß-indolylacetic acid,2:4-dichiorophenoxyaceticacid, ascorbic acid, 2:3:5 -triiodobenzoic acid, and 2:4-dichloranisolewere investigated. 2. The experimental treatment was carried out in absence ofvisible light, the rhizomes being photographed every hour byinfra-red radiation. 3. After immersion in 10^– M. IAA, the rate of growth isapproximately doubled. About 5 hours later it declines to one-thirdor less of its original value and then gradually recovers. Thedepression in the growth rate can be reversed by a second immersionin IAA, indicating that it is not due to exhaustion of someother substance essential for growth. 4. Immersion in 10^–4 M. 2:4-D also stimulates growth,which then slowly returns to about the normal rate without showingany marked depression. 5. The possibility is suggested that IAA, which first accelerateselongation, is later converted into, or causes the productionof, an inhibitor. When successive immersions in IAA are repeatedevery 2 hours, the inhibition can be partially overcome so longas the treatment is continued. 6. Ascorbic acid slightly depresses the rate of elongation,but triiodobenzoic acid and dichloranisole produce no significanteffect. 7. Immersion of the horizontal rhizomes in IAA or 2:4-D causesthem to turn up. This suggests that an equilibrium is disturbedand supports the hypothesis that the diageotropic behaviourof these rhizomes is the result of a balance between the effectsof two opposing hormones.     

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.     

Origin of Exogenous Adventitious Roots in Rhizomes of the Fern Microsorium scolopendria (Polypodiaceae)

Adventitious roots of rhizomes of the fern Microsorium scolopendriaarise exogenously from apical initials which have their originin the cell layer directly beneath the epidermis. Divisionsof the apical initial and its derivatives produce the adventitiousroot apical meristem. Cells between the apical cell and themeristele of the rhizome develop into the root trace. Anatomy, light microscopy, Microsorium scolopendria Burm.) Copel     

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; )     

DIE MITWIRKUNG VON IONEN BEI DER OSMOREGULATION DER NITELLAZELLE

1. Die nach dem Verfahren von KAMIYA U. KURODA (1) hergestelltenZellh?lften aus Internodialzellen von Nitella flexilis und Nitellaaxilliformis wurden auf den Zusammenhang ihrer osmoregulatorischenT?tigkeit mit dem Ionenaustausch zwischen Zelle und Aussenmediumhin untersucht.
2. Zellh?lften (L-Zellen), deren osmotischerWert (o. W.) unterdem unbehandelter "Normal-Zellen" liegt,nehmen aus reinen KC1–oderNaCl– L?sungen K–bzw. Na-Ionen auf und erh?henihren o. W.
3. Licht und hohe Salzkonzentrationder Aussenl?sung beschleunigenbeide Vorg?nge bei L-Zellen betr?chtlich.
4. Zellh?lften (H-Zellen), deren o. W. ?ber dem Normalwert liegt,scheiden bei Kultur in reinen KC1– oder NaCl-L?sungenK–und meist auch Na-Ionen aus und erniedrigen ihren o.W.
5. Licht unterdr?ckt bei H-Zellen besonders stark die K-Ausscheidungund in wechselndem Mass auch die Erniedrigung des o. W.
6. DieNatur der Osmoregulation und die m?gliche Rolle des Protoplasmasbei der Osmoregulation werden diskutiert.

     

Physiological Studies in Plant Nutrition: XVI. The Mineral Nutrition of Bracken

1. The nutritional requirements of the bracken sporophyte wereexamined in a factorial combination of 3 potassium levels x2phosphorus levels x3 solution types, in which the cations weremainly Na, Ca, or NH₄.
2. The effects of nitrogen and phosphorusdeficiency and of shadingunder conditions of high and low potassiumsupply were alsoexamined.
3. Leaf area, total dry weight, andnet assimilation rates aremuch depressed by lack of eitherK or P.
4. Water contents of leaves and rhizomes are generallyincreasedby lack of K when Na is present in the culture mediumbut notwhen Ca is in excess.Phosphorus causes diminished succulence.
5. Starch content increases as phosphorus supply is lowered.Withincreasing doses of K, starch content falls in the highcalciumsolution, while increasing in the other two solutiontypes.
6. Reduction of light intensity is shown to have a beneficialeffectunder conditions of K deficiency.
7. Analysis revealscomplex interactions between the various factors,and possibletoxic effect of Na, NH₄, and excess P. An estimateof the relativeimportance of net assimilation rate, leaf numberand area perleaf in determining total plant size has been calculatedforthe different nutrient treatments. Comparisons are madewithprevious results for barley and flax.

     

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; )     

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.

     

Organic Acid Metabolism of Sedum praealtum

1. The organic acids present are citric, isocitric, and l-malic,with a small residue of unidentified acids.
2. The diurnal variationin acidity is due chiefly to changes,in malic acid, with aparallel fluctuation shown by citric acid.Under these conditionsisocitric acid shows little change.
3. The importance of carbondioxide during acidification is confirmed,and it is shown thatat room temperatures or higher the CO₂produced in respirationis sufficient to produce maximum acidification.At lower temperaturesthe supply of CO₂ limits acid production.
4. In the absence ofoxygen no acidification occurs, but even smallquantities (approx.1 per cent.) are sufficient to cause someacid production.
5. Completebalance-sheets are presented for acids, carbohydrates,CO₂ andoxygen for leaves maintained in the dark at high andlow temperatures.As acids are produced there is a correspondingloss of carbohydrate(chiefly starch). A scheme of reactionsis suggested to explainthe experimental results.

     

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.

     

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.

     

Stem types of Phragmites communis Trin.

The three usual stem types of Phragmites communis Trin. canbe arranged in a maturation sequence. The horizontal rhizomeis the juvenile type, responsible for renewing the stand; thevertical rhizome is intermediate and bears the aerial shoots;and the aerial shoot is the mature type, photosynthesizing,potentially flowering, and short lived, but not normally capableof renewing the population. The difference between horizontaland vertical rhizomes appears to be determined internally, andthat between vertical rhizomes and aerial shoots, by the environment.     

DEVELOPMENTAL CHANGES IN THE ALGAL COENOCYTE CAULERPA PROLIFERA (SIPHONALES) AFTER INVERSION WITH RESPECT TO GRAVITY

The algal coenocyte Caulerpa prolifera produces three types of organs, each with a different orientation. The effect of gravity in controlling the development of these organs was investigated. We inverted plants by rotating them 180° around the horizontal rhizome axis, then compared development of the inverted plants with plants matched by size and differentiation. Quantitative data were obtained from photographic records. After inversion the site of organ differentiation was changed with no change in the timing: the next rhizoid (and all subsequent ones) differentiated on the “now-under side” of the inverted rhizome, the next leaf formed on the “now-upper side.” Despite the fast change in the site of organ differentiation, other parameters were not changed by inversion (e.g., rate of elongation of rhizomes or leaves, rate of formation of leaves or rhizoids). Because such changes also occurred in plants with balanced lighting from two sides, it is clear that gravity alone can control these changes without reinforcement from top illumination. After leaves were initiated, they did not change their orientation, showing neither positive phototropism (at our light levels) nor negative geotropism, even when elongating substantially. Torsion of the rhizome tip did not precede the change in site of rhizoid initiation.     

STUDIES ON THE METABOLISM OF A SULFUR-OXIDIZING BACTERIUM III. POSTOXIDATIVE FIXATION OF CARBON DIOXIDE

1. The cells of Thiobacillus thiooxidans, which had been in contactwith sulfur or sulfide in air (or CO₂-free air), could fix addedCOa very rapidly after replacing air with nitrogen. This fixationis designated as the postoxidative fixation.
2. "Preoxidation"of the sulfur compounds is mandatory for theoccurrence of thepostoxidative fixation.
3. The cells which had preliminarilyoxidized sulfide could notshow the CO₂-fixation, when theywere placed under an anaerobiccondition in the absence of thesulfur compound.
4. These results indicate that sulfur compoundsmay have an importantrole as the electron donor for the reductionof CO₂, besidestheir role as the substrate of respiration tosecure energyfor the fixation of CO₂

(Received March 6, 1962; )