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; )     

INTERACTION BETWEEN HELIANGINE AND PYRIMIDINES IN ADVENTITIOUS ROOT FORMATION OF PHASEOLUS CUTTINGS

1. Heliangine at 110^–4 M promoted the adventitious rootformation in hypocotyls of cuttings taken from light-grown (1,900lux) Phaseolus mungo seedlings. The promotion was almost completelyreversed by 310^–4 M uracil, uridine, cytidine, oroticacid or 610^–4 M carbamoyl DL-aspartic acid, and partlyby 310^–4 M thymine or thymidine. Neither 310^–4M cytosine, adenine, adenosine, guanine, guanosine nor a combinationof 310^–4 M carbamoyl phosphate and 310^–4 M L-asparticacid reduced the promotion by heliangine.
2. Uracil did not reducethe inhibiting effect of heliangine onthe indoleacetic acidinduced elongation of etiolated Avenacoleoptile sections.
3. Helianginein an aqueous uracil solution was recovered unchangedafter24-hr incubation at room temperature.
4. The root formation ofPhaseolus cuttings was promoted also by2-thiouracil and 5-fluorouracil.The effect was reversed byorotic acid or carbamoyl asparticacid, but not by carbamoylphosphate plus aspartic acid.
5. Ribonucleaseat 100 µg/ml increased the number of rootsprotruded fromhypocotyls of cuttings by about 260%.
6. A possible interpretationfor the promotion of root formationby heliangine is offered.

¹ Contribution No. 15 from the Botanical Gardens, Faculty ofScience, University of Tokyo, Tokyo, Japan. ² Dedicated to Prof. Dr. H. SODING in commemoration of the 70thbirthday.     

CHANGES IN THE RESPONSE OF CARROT ROOT CALLUSES TO THE ROOT EXTRACT OCCURRING DURING THEIR SUCCESSIVE CULTURES

1. Alcohol extract of carrot root promoted the growth of the carrotroot callus which had been succesively cultured for more than18 months (CCL) on the medium containing WHITE'S inorganic salts,sucrose, yeast extract and 2, 4-D, but only a weak promotionwas observed for the growth of the carrot root callus whichhad been cultured for less than 14 months (CCS).
2. The activesubstances were fractionated by Amberlite IR-120and AmberliteIRA-400 into four fractions; C, D, E, and F. Eachfraction seemedto act synergistically to produce the effectof the whole carrotroot extract on the growth of CCL.
3. Fraction F of the carrotroot extract, which was adsorbed byAmberlite IRA-400 but notby Amberlite IR-120, promoted thegrowth of CCL in the presenceof other fractions, but had noeffect on the growth of CCS.So the different responses to thealcohol extract of the carrotroot calluses having differentlengths of successive cultureperiod seemed to depend mainlyon the ability of respondingto fraction F.
4. Using four strains of carrot root callusesof different origin,it was ascertained that different responsesof carrot root callusesto fraction F depended on the lengthof their culture and noton their strain-specific characters.
5. The substances active for the growth of CCL in the carrotrootextract passed through a dialysis membrane. These substanceswere little affected by autoclaving and remained in the aqueouslayer when shaken with several organic solvents: n-butanol,ethyl acetate, chloroform, benzene, ethyl ether and carbon tetrachloride.
6. Alcohol extract of carrot root also promoted the growth ofcarrotroot explant, tobacco stem callus and sunflower crowngall tissue.

(Received December 24, 1964; )     

Effects of cytokinins on the auxin requirement and auxin content of tobacco calluses

High concentrations (0.1–1 mg/liter) of kinetin permittedcontinuous growth of auxin-requiring and cytokinin-nonrequiringtobacco calluses on a medium without auxin. This effect of kinetindid not seem to be due to perpetuating change in the tissuecharacter, because tissue was auxin-requiring when returnedto a kinetin free medium. Cytokinins, i.e. benzylaminopurineand geranylaminopurine, showed the same effect as kinetin inmaking auxin-requiring calluses grow without a supply of auxin. In auxin-requiring and cytokinin-nonrequiring calluses subculturedfor 3 years on a medium containing 1 mg/liter kinetin withoutauxin, at least 3 auxins were detected by bioassay; 2 in theacidic and 1 in the neutral fraction. One was identified asIAA by paper chromatography (bioassay), thin-layer chromatographyand gas chromatography. Reduced or no auxin activity was foundin calluses transferred to a medium without kinetin. Kinetinwas apparently required to maintain the endogenous auxin levelin callus tissues. Kinetin may act on the auxin requirement of callus via its effectson auxin metabolism. ¹ Part XVI in the series "Studies on Plant Tissue Cultures". (Received April 11, 1972; )     

The Effect of Adenine and Mevalonic acid on the Endogenous Cytokinins of a Cytokinin-dependent Strain of Soya Bean Callus

The combined application of 10^–6 M adenine and 10^–6M mevalonic acid to soya bean callus accelerated its growth.Two biologically active compounds that co-chromatographed withzeatin and isopentenyl adenine were extracted from this callus.Studies with labelled adenine and mevalonic acid indicated thatthe cytokinin-dependent soya bean callus incorporated only avery small amount of the radioactive precursors into the biologically-activecompounds, making it extremely difficult to determine whetherthese compounds were synthesized de novo or whether they aroseas by-products of tRNA turnover. As cytokinins do not accumulatein rapidly-growing cytokinin-dependent soya bean callus culturedon kinetin as a source of cytokinin it seems as if biosynthesisde novo occurs when the callus is supplied with adenine andmevalonic acid. Glycine max (L.) Merrill, soya bean, callus culture, adenine, mevalonic acid, endogenous cytokinins     

INHIBITION OF LAMINA INCLINATION BY CYTOKININ IN EXCISED RICE LEAVES

Effects of kinetin and other purine and pyrimidine derivativeson lamina inclination in excised rice leaves have been examinedin this work. Kinetin inhibited the lamina inclination both in the presenceand in the absence of added IAA, and was effective even at 10^–7M. The decreasing order of inhibitory activities of kinetinand its analogs was as follows; 6-benzylaminopurine, kinetin,2-amino-6-furfurylaminopurine (2-aminokinetin), 2-amino-6-benzylaminopurine,kinetin-9-glucoside, 6-benzylaminopurine-9-glucoside. Otherpurine derivatives, 8-azaadenine, 2, 6-diaminopurine and 8-azaguanine,and colchicine also inhibited the lamina inclination. The inhibitiveaction of kinetin was not reversed by the addition of adenine,hypoxanthine, uracil and thymine. (Received May 20, 1965; )     

Biological activity of phyllosinol, a phytotoxic compound isolated from a culture filtrate of Phyllosticta sp.

1. Phyllosinol is a phytotoxic metabolite of Phyllosticta sp. Thissubstance at 100 µg/ml produced dark grey necrotic lesionson the leaf of red clover. Sensitivities of various plant speciesto phyllosinol differed both quantitatively and qualitatively.
2. Phyllosinol reduced root growth in rice seedlings by 60% at10^–4 M, whereas stimulation of root elongation occurredat a concentration range from 10^–9 to 10^–5 M.
3. Phyllosinolat 2.5x10^–4M promoted adventitious root formationin epicotylsof Azukia cuttings by about 100%. Promotion waspartly reducedby simultaneous application of cysteine.
4. IAA-induced elongationof isolated Avena coleoptile sectionswas inhibited by phyllosinolat a concentration range from 10^–5to 10^–3M.
5. Sulfhydrylcompounds, i.e. cysteine and glutathione relievedinhibitioncaused by phyllosinol in IAA-induced elongation ofAvena coleoptilesections.
6. GA₃-induced elongation of wheat leaf sections wasslightly inhibitedby phyllosinol at 10^–4M.
7. Phyllosinolalso has antibiotic activity. Among the organismstested, Phycomycetesand Gram-negative bacteria appeared mostsusceptible to phyllosinol.

(Received April 21, 1970; )     

Thiourea, a Growth Promoter of Callus Tissues1

Thiourea (TU) promoted growth in cytokinin-requiring soybean,tobacco, and apple callus tissues, in the absence of kinetin.The increase in fresh and dry weight obtained was a result ofcell multiplication. Callus tissues grew well when repeatedlysubcultured in kinetin-free medium containing TU. The best growthwas obtained with 10^–4-10^–3 M TU. At these concentrationssynergism was demonstrated between TU and the cytokinins, kinetin,benzyladenine, and zeatin. TU caused greater growth than diphenylureaand phenylthiourea. The possibility that a breakdown productof TU is responsible for the enhanced growth was not excluded.The dormancy-breaking effect of TU was suggested to be relatedto its growth-enhancing effect.     

Effect of External Supply of Growth Substances on Axillary Proliferation and Development in Dioscorea bulbifera

Bulbil development in cultured nodes of D. bulbifera proceededin the absence of growth substances from the medium. When IAAwas incorporated into the medium at the concentrations of 5mg l^–1 and 10 mg l^–1 the cultured nodes producedlarger bulbils than in its absences. When the concentrationof IAA was increased to 15 mg l^–1, however, the culturednodes produced a callus instead of a properly organized bulbil.The dry weight of bulbils increased when kinetin was added tothe medium at the concentrations of 0.05, 0.5, and 2.5 mg l^–1.The greatest increase was with 0.5 mg l^–1 kinetin. Onincreasing the concentration of kinetin in the medium to 5.0mg l^–1 the tissue produced had smaller dry weight thanthose produced in the absence of growth substances. Additionof different combinations of IAA and kinetin to the basal mediumresulted in the production of normal bulbils, roots, and shootsin some instances (suitable combinations) and in the productionof callus and abnormal shoots in others (non suitable combinations).     

Differentiation of Shoot Buds in vitro in Tissue 1Sisymbrium irio L.

Shoot bud formation was induced in the stem callus of Sisymbriumirio L., a Cruciferous plant. The callus was established onMurashige and Skoog medium with IAA (1?0 mg l^–1) and kinetin(0?5 mg l^–1). The effect of three purines (kinetin, 6-benzylaminopurine,and 6-methylaminopurine) incorporated singly along with IAAin MS medium was investigated. It was found that kinetin orMAP (3–5 mg l^–1) along with IAA (0?5 mg l^–1)were the most effective in inducing shoot bud formation. Adeninesulphate (10 mg l^–1) with kinetin (1?0 mg l^–1) alsoinduced bud differentiation. The morphogenetic potential of the callus to differentiate shootbuds was seemingly lost in 2 year old callus cultures. However,on successively subculturing on a regeneration medium shootbuds differentiated and the number of buds formed improved onfurther subculture. Two types of meristematic outgrowths were recognized: (i) arisingfrom superficial cells and (ii) arising from deep-seated cellsin the vicinity of tracheidal elements. However, both typesformed meristematic nodules on the surface of which shoot budsdifferentiated. Some embryoids were also recognized arisingsuperficially.     

Cyclic Nucleotides and In Vitro Plant Cultures: I. INDUCTION OF ORGANOGENESIS IN TOBACCO (NICOTIANA TABACUM CALLUS CULTURES

Mangat, B. S. and Janjua, S. 1987. Cyclic nucleotides and invitro plant cultures. I. Induction of organogenesis in tobacco(Nicotiana tabacum) callus cultures.—J. exp. Bot. 38:2059–2067. The possibility that cyclic nucleotides have a mediatory rolesimilar to cytokinins in plant tissue cultures was examined.Calli obtained from tobacco pith tissue were incubated on growthmedia supplemented with either cyclic AMP, cyclic GMP, adenosineor guanosine, in concentrations ranging from (mg dm^–3)0 to 2·0 together with 2·0 mg dm^–3 of IAA.Results were compared with identical calli grown on media containingcomparable amounts of kinetin and IAA. Increase in callus growthwas observed on all media containing cyclic AMP, cyclic GMP,adenosine, guanosine or kinetin. Adenosine or guanosine didnot promote organogenesis. Low concentrations (0·02 and0·05 mg dm^–3) of kinetin stimulated extensive rootdevelopment. Some root formation was also elicited with higheramounts of cyclic AMP (0·1 and 0·2 mg dm^–3)or cyclic GMP (0·2 and 0·5 mg dm^–3). Bothkinetin and cyclic GMP promoted shoot differentiation. However,in contrast to kinetin, cyclic GMP induced organogenesis atlower concentrations (0·02 and 0·1 mg dm^–3).The addition of 2·0 mg dm ^–3 of cyclic AM P toIAA-free growth media elicited shoot differentiation. This wasalso the case with a similar concentration of kinetin or cyclicGMP. Results suggest cytokinin activity for the two cyclic nucleotides. Key words: Tobacco, Nicotiana tabacum, tissue culture, cyclic nucleotides, cyclic AMP, cyclic GMP organogenesis     

AUXIN-INDUCED GROWTH OP TUBER TISSUE OP JERUSALEM ARTICHOKE: III. EFFECT OF ACTINOMYCIN D ON AUXIN-INDUCED EXPANSION GROWTH AND RNA SYNTHESIS

1. The following results were obtained using tissue slices excisedfrom cold-stored Jerusalem artichoke tubers.
2. Actinomycin Dat the concentration of 20 µg/ml given duringthe agingperiod did not affect the subsequent expansion growthcausedby auxin or auxin plus kinetin.
3. Actinomycin D given in thegrowth period, on the other hand,strongly inhibited the expansiongrowth of tissue slices agedin the absence of the antibiotic.
4. In the growth period, auxin or auxin plus kinetin promotedtheincorporation of uracil-2-¹⁴C into RNA fraction.
5. ActinomycinD inhibited the incorporation of ³²P orthophosphateinto ribosomalRNA during the aging period.
6. In the growth period, the incorporationof ³²P into RNA wasenhanced by auxin and was inhibited by actinomycinD, more remarkablyin ribosomal RNA than in lighter RNA.

¹A part of this paper was presented at the Conference on PlantGrowth Regulators held by the New York Academy of Sciences onMay 16, 1966.     

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.     

Investigation of the Radish Leaf Bioassay for Kinetins, and Demonstration of Kinetin-like Substances in Algae

This study is part of an investigation into the occurrence ofplant growth substances in marine unicellular algae. Auxinsand gibberellins have previously been detected. This paper reportsthe occurrence of phytokinins in algae, using the radish leaftest. The technique of the test is described and a few modificationsexamined. Radish leaves were shown to be more responsive thanswede leaves. Some requirement for a minimum temperature below7? C during the growing period of the plants appeared to bea factor for maximum response. The size and age of the leafwere shown to influence kinetin activity. Chemicals tested includedbenzyl adenine, a 9-substituted benzyl adenine, and kinetin.Kinetin showed lower activity than the benzyl adenines. Kinetinkept in the solid state at –20? C for 2 years was as activeas freshly prepared kinetin. Gibberellic acid (GA₂) at 10^–5g/ml sometimes showed activity equivalent to 10^–5 g/mlkinetin. Indole-3-yl acetic acid at concentrations of 10^–4to 10^–6 g/ml was inactive. The radish leaf test was successfully used to demonstrate phytokininsin extracts of two species of unicellular marine algae, andin marine phytoplankton samples. Amounts found were within therange 0.1 to 1.0 mg/kg with one exception of 10 mg/kg. Phytokininactivity in these extracts decreased over a period of a fewweeks when stored at –20? C.     

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; )     

In vitro Propagation of Red Cabbage (Brassica oleracea L. var. capitata)

By manipulation of various growth regulators and physical conditions,plants have been regenerated from excised roots, stem segments,cotyledons, leaves, and callus cultures of red cabbage (Brassicaoleracea var. capitata) grown under in vitro conditions. Shootbuds were induced on isolated root segments (1 cm long) culturedon Murashige and Skoog's medium and the frequency of bud formationwas greatly enhanced by the addition of kinetin (0.5 part 10^–6).Callus obtained from the seeds, cotyledons, and hypocotyl segmentscultured on a medium fortified with 2,4-D (1 part 10^–6),kinetin (0.1 part 10^–6), and coconut milk (10%, v/v) hasbeen repeatedly subcultured. The callus is slow growing, andon transference to a kinetin (2 parts 10^–6) and IAA (2parts 10^–6) medium underwent morphogenesis to give riseto plants. The significance of the propagation of red cabbageby in vitro culture is pointed out.     

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.

     

INHIBITORY EFFECT OF 5-BROMOURACIL AND 5-FLUOROURACIL ON PHOTOPERIODICALLY INDUCED GERMINATION OF ERAGROSTIS SEED

1. The inhibitory effects of 5-bromouracil and 5-fluorouracil onthe photoperiodically induced germination of Eragrostis ferrugineaseed were investigated. 5-BU was more effective than 5-FU ininhibiting germination, but less effective in suppressing seedlingelongation.
2. The inhibition of germination by 5-BU was specificallyex ertedon the inductive dark process, which i9 essential tothe photoperiodicgermination induction. A high concentration(10^–1:M) of5-FU also elicited a complete inhibition ofgermination. 5-FU,however, did not affect the photoperiodicinduction processes,but inhibited the processes subsequentto them. The inhibitionof germination by 5-BU or 5-FU was alleviatedby neither uracil,thymidine nor orotjc acid.
3. The 3eedlinggrowth was effectively inhibited by 5-FU, and theinhibitionwas reversed by uracil, uridine and orotic acid,but not bythymine and thymidine. The effect of 5-FU may, therefore,possiblybe by virtue of its depressing action upon ribonucleicacidsynthesis.

(Received April 18, 1963; )     

CHANGES IN ORGAN FORMING CAPACITY OF CARROT ROOT CALLUSES DURING SUBCULTURES

1. The formation of buds and roots in seven strains of carrotrootcallus successively cultured for various periods on a mediumcontaining WHITE'S inorganic salts, sucrose, 2,4-D and yeastextract was investigated. 2,4-D completely suppressed organformation during stock subculturing. It was confirmed that theorgan forming capacity of the callus in a 2, 4-D-free test mediumdiminishes and finally completely disappears with prolongedperiods of previous subculturing of the callus.
2. IAA promotedthe root formation. Yeast extract, casein hydrolysateand aminoacids mixture promoted the bud formation of callusesat earlieststeps of subculturing (Phase I).
3. At next steps of subculturing(Phase II), IAA-dependent rootforming capacity of calluseswas lost although the bud formingcapacity induced by yeastextract, casein hydrolysate and aminoacids mixture was retained.
4. At further advanced steps of subculturing (Phase III), yeastextract induced only root formation, while casein hydrolysatestill could induce buds. IAA and amino acids mixture did notaffect the organ formation.
5. No organ formation was observedin calluses subcultured over38 months under any conditionsattempted (Phase IV).
6. Single cells or small cell clumps obtainedfrom the callus subculturedfor 2 months formed only roots onthe medium containing IAAand formed buds and roots on the mediumcontaining yeast extract.
7. These differences in organ formingcapacity and in responsestowards various factors are interpretedto reflect the changesin physiological states of the callusduring successive cultureson the stock culture medium.

(Received December 24, 1964; )     

Comparative studies on auxin and fusicoccin actions on plant growth

Mode of action of FC was compared with that of auxin in differentexperimental systems and the following results were obtained.

1. FC, as well as auxin, primarily induced elongation of the epidermisof pea epicotyl segments, but it also promoted elongation ofthe inner tissue, as judged by its action in split stem tests,elongation of hollow-cylinder segments and elongation of unpeeledand peeled segments.
2. FC decreased the minimum stress relaxationtime (T₀) and increasedthe extensibility (mm/gr) of the epidermalcell wall of peaepicotyl segments, as did auxin.
3. FC failedto induce expansion growth of Jerusalem artichoketuber sliceswhen given alone or in combination with kinetinor gibberellicacid.
4. FC at concentrations lower than 10^–6 M, when givenwithauxin at concentrations lower than 0.03 mg/liter, promotedelongationof Avena coleoptile segments in an additive manner,to achievethe maximum elongation at higher concentrations.
5. An antiauxin, 2,4,6-trichlorophenoxyacetic acid, inhibitedtheelongation of Avena coleoptile segments due to auxin butnotthat due to FC.
6. Nojirimycin, an inhibitor of ß-glycosidases,inhibitedelongation of pea internode segments due not onlyto auxin butalso to FC.
7. At concentrations more than 10^–5MFC promoted root elongationof intact lettuce seedlings, whichwas inhibited by exogenousauxin.

From these results it is concluded that FC and auxin have acommon mechanism, which may involve hydrogen ion extrusion,leading to cell wall loosening and thus cell elongation. Thisgrowth is limited to the extent that the cells are capable ofelongating in response to hydrogen ions. Otherwise there isa definite difference in the mode of actions between FC andauxin, including the nature of cellular receptors for thesetwo compounds. (Received August 29, 1974; )