Plant Physiol. (1969) 44, 555-561

Auxins and Gibberellin-like Substances in Parthenocarpic andNon-parthenocarpic Syconia of Ficus carica L., CV. King

Farooq Lodhil, Muriel V. Bradley, and Julian C. CraneDepartment of Pomology, University of California, Davis, California 95616

Received July 22, 1968.

Abstract. In the King cultivar of fig, the first crop is parthenocarpic, develops on previousyear's growth, and a series of supernumerary ovules develops within the original ovules. Thesecond crop, formed on current-season's growth, requires fertilization. To determine whetherthe 2 crops differed in types, and in patterns of concentrations of total 'free' auxins and acidicgibberellins, they were extracted from weekly fruit samples. Timing of the 3 peaks of totalauxins and the single peak of gibberellins was identical in the 2 crops. The first auxin peakin both occurred at the end of fruit growth period I (first rapid growth period)., the secondshortly before the end of period II (period of slow growth), and the rise and fall in concen-trations of the third peak accompanied the rise and fall of the fruit growth rate in period III.The end of period II was marked by the single gibberellin peak. Additional peaks before thefirst sampling dates, of auxins in the first crop, of gibberellins in the second, were indicatedby high concentrations in the first samples and subsequent rapid decline. The same 4 indi-vidual auxins appeared in both crops. Auxins I and II were highest in concentration in thefirst total auxin peak of both crops. In the second peak of the first crop, auxins II and IIIwere highest, whereas in that peak of the second crop auxins II and IV were highest. Qualita-tive differences in gibberellins occurred in the 2 crops. In general, auxin concentrations werehigher in the first than the second crop, and gibberellin concentrations higher in the second.High concentrations of gibberellins coincided with low ones of auxins, and vice versa.

The fig produces 2 crops of fruit a year, butcertain structural features and environmental condi-tions during their development are different. First-crop figs develop in the sprin,g on 1-year-old wood,whereas those of the second crop develop in the sum-mer on current-season's wood. In the King cultivar,which belongs to the San Pedro group (6), first-cropfruits are parthenocarpic, are set about the end ofApril, and mature early in July. Although em-bryosand endosperm are lacking in the fruitlets, a seriesof stupernumerary ovules develops within the originalovules over a period of 9 weeks or longer (5).Fruits of the second crop, however, require caprifi-cation (fertilization), which occurs late in June, andthey mature at the end of August. Mature fruits ofthe first crop are generally larger than those of thesecond, and their form is more gradually taperedfrom the tip to the stem-end. Differences in sizeand shape and internal structures during fruit de-velopment in the 2 crops suggested the possibility ofquantitative and/or qualitative differences in nativehormones. Reported here are results of determina-tions of free auxins and acidic gibberellins, ex-tractedthroughout development from King fig fruits of bothcrops and compared with fruit growth rates.

1 Present address: College of Agriculture, Universityof Peshawar, W. Pakistan.

Materials and Methods

Fruits were sampled from trees in the WolfskillExperiment Orchard at Winters, California. Fruitgrowth data, to be correlated with results from auxinand gibberellin extractions, were obtained throughweekly measurements of basal first-crop and second-crop figs on each of 25 tagged branches; the hori-zontal diameter of the widest region of each fruitwas measured with a vernier caliper. Fruit samplesfor analyses of endogenous hormones were collectedat weekly intervals in 1965 on -the same dates whenfruit diameters were measured. The samples wereheld at - 100 until lyophilized and after lyophilizationwere stored at -100 until extraction.

The techniques for auxin extraction and bioassaywere standardized in preliminary trials with fruitscollected in 1964. In the procedure adopted, 250 mgof lyophilized tissue were extracted with absolutemethanol in a dry-ice bath in three 20-min extractionswith 25, 10, and 10 ml of methanol, respectively.The extracts were combined and evaporated to dry-ness under reduced pressure at about 2°. The resi-due, representing in each case extract from 25 mg ofdried figs of the first ocrop,, or 50 mg of secon'd-cropfigs, was dissolved in 1 ml of methanol and streakedon chromatogram paper. More than 1 extractionand assay were made from certain samples to checkthe consistency of results. Components of the crude

555

PLANT PHYSIOLOGY

extracts wvere separated by ascending chronmatographyon 3-cm-wide strips of \VNhatman No. 3 MMIM paper.The developing solvent generally used was isopro-panol-animo,nium hydroxide-water (8:1 :1 V/V). Toseparate the suspected neutral substances appearingat RI,, 0.7 to 1.0, those zones froml 4 chronmatogramiswrere ctut out, eluted in mlletlhalnol, and reclhroma-tographled in hexane-water (95 :5 v/v). Tlle stripswere equilihrated over the solvent for about 3 to 5hr and were dexveloped to 20 cml at rooml temlperatuire(230).

The dried chromatograms wrere tested for auxinactivity by the wlheat coleoptile section bioassay (3)."Ramona 50" wheat seeds were grown for about60 hr in a dark growvth chamber maintaiined at 260and 80 % relative humidity. Under a green light,4 mm sections were removed from coleoptiles 3 mmbelow the apex. The chromatograms were cut into20 equal sections, and each was placed in a test tubecontaining 1 nml of potassium phosphate-citrate bufferincludiing 2 % sucrose at pH 5 (25) and 10 coleoptilesections. The tubes were rotated oIn a roller drumat 1/5 rpm for 20 hr in the dark. For controls,3 sets of 10 coleoptile sections were prepared with achromatograni section taken 30 mm below the initialspot, and 30 and 50 mnm above the solvent front,respectively. The final lengths of the coleoptilesections were measured to the nearest 0.1 mm undera stereoscope.

For qtuantitative determination of auxin activity,elongation of coleoptile sections was plotted againstlogarithmic concentrations of synthetic indoleaceticacid (10-2-102 mg/ml), and from the standard curvemicrogram equivalents of IAA per granm of dryweight of fruit material were calculated. To com-pare the zones of promotion on the chromatograms offig extracts with synthetic auxins, IAA, IPA (in-dolepyruvic acid), IBA (indolebutyric acid), IAN(indoleacetonitrile), and IAE (ethyl ester of IAA)were chromatographed in isopropanol-ammoniumhydroxide-water. Chromatograms of IAN and IAEwere also prepared in hexane-water for comparisonof their RF values with those of some neutral auxinsin fig extracts. Chromatograms of fig extracts andsynthetic auxins were examined under ultravioletlight for the characteristic fluorescence of the latter.They were also sprayed with modified Salkowski'sreagent (26) or Ehrlich's reagent (27) for chromo-geniic color reactions.

The method of extraction of gibberellin-like sub-stances was essentially that of Kato (17). Each5 g sample of lyophilized fig fruit was given two24-hr extractions with 100 ml of fresh acetone-water(80:20 w/v) at 4°. The extracts were combinedand evaporated to the water phase at 350 under re-duced pressure. The water concentrate was adjustedto pH 8 with 20 % NaHCO3 and extracted withethyl acetate. The ethyl acetate fraction was dis-carded and the aqueous plhase was adjusted to pH 3with 1 N HCI and extracted with ethyl acetate 3

times. The extracts obtained at pH 3 were concen-trated under reduced pressuire to 2 ml1. This finalfraction, containing acidic gibberellin-like substances,was streaked on \Vhatnman No. 3 MIM paper (23 X57 cm). The solvent system in descending chroma-tographv wvas isop)ropanol-anmmonmitm hydroxide-water (10:1:1 v/v). Chromatogramis were devel-oped after 3 lhr e(quilibration over tlle solvent andrenmoved Nhen the solvent reached 35 cml below theinitial spot. The chromatogram wvas cut in 10 equtialsections, and eaclh was eluted for 6 hr w-ith acetone-water. The eluates were evaporated to (lrvness ina water bath at 350, and the residue was dissolvedin 0.05 % Tween 20 (polvoxvethvlene sorbitan ImloIno-laurate) in 50 % aqueous ethanol for bioassay. Amodification (12) of the dwarf pea bioassay ofKende and Lang (19) Nwas used. Analysis of vari-ance showed activity of the extracts greater than10 % of the control value to be significaint at the5 % level. A standard curve of activity of gibberellicacid (GA,) was prelpared as for extracted freeauxins. Chromatograms of GA, were prepared fromtime to time to compare its Rrvwith those of similarsubstances in the extracts.

For correlation of stages in development of ovarystructures with fruit growth phases and witlh changesin levels of extracted auxins and gibberellins, secondcrop figs wvere collected at weekly intervals, andpieces were fixed in Randolph's solution. The mate-rial was embedded in paraffin, and microtomiie sec-tions wvere stained with haematoxylin-fast green.Information correlating development of such struc-tures in first crop figs with fruit growth was takenfrom results of previous research (5), supplementedwhere needed by further study of the original slides.

Results and Discussion

Four zones on the chromatograms of extractsfrom each of the 2 fruit crops promoted elongation ofwheat coleoptile sections. In mature or nearly ma-ture syconia, a zone of inhibition was also detected.The zones of activity showed the following RFranges: Auxin I-RF 0.05 to 0.2; Auxin II-RF0.25 to 0.45; Auxin III-RF 0.5 to 0.7; and AuxinIV-RF 0.75 to 1.0. The zone of inhibition had anRF range of 0.6 to 0.8. The RF values were obtainedfrom the spots, as seen under UV light, of extractsfrom some of the most active samples of each crop;measurements were made on duplicate chromato-grams. Several typical chromatograms from eachcrop are shown in Fig. 1. Attempts to identify the4 endogenous auxins were not verv conclusive.Several times during the extraction work the svn-thetic auxins were spotted individually and in com-bination on strips of chromatogram paper and de-veloped ascendingly. They were also spotted onone-half of full size chromatograms on the other halfof which were spotted the extracts of selected sam-ples of both crops. The spots of the synthetic auxins

556

LODHI ET AL.-KING CULTIVAR OF FIG

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FIG. 1. Typical chromatograms of response of wheatcoleoptile sections to auxins in crude methanol extractsof first-crop (parthenocarpic) and second-crop (non-parthenocarpic) figs.

developed in reaction to the 2 spray reagents, andin non-sprayed chromatograms as viewed under UVlight, gave the following RF values: IAA, 0.42;IBA, 0.56; IPA, 0.50; IAN, 0.85; and IAE, 0.90.

The RF values and color of the active zones offig extracts under UV light were:

Auxin I. RF 0.07, light to deep yellow in thefirst crop, no color in the second.

Auxin II. RF 0.36, ash blue.Auxin III. RF 0.56, light gray.

Auxin IV. RF 0.93, pinkish gray.Ehrlich's and Salkowski's reagents gave no color

reaction with the spots at the active zones underUV light. The only exception was the developmentof a faint spot in a small area of auxin IV of a color

comparable to that of standard IAN with Salkowski'sreagent., Bentley (3) had listed many neutral com-

poun,d,s which accumulate at this RF. Since bothIAN and IAE when present in the mixture overlapin their RF values in the ammonium hydroxide:iso-propanol :water solvent system, Nitsch (24) sug-gested hexane and water as an effective separatingsolvent system for IAN and IAE. When the activezone close to the solvent front was cut out and itsconcentrated methanolic eluate was rechroma-tographed in hexane and water (95:5), the greateractivity as judged from elongation of coleoptile sec-tions remained at the base of the chromatogram.Detectable activity appeared also at RF 0.3, whichwas comparable to the RF of IAN in that solventsystem. The faint spot seen under UV light atRF 0.3 gave no color reaction with indole reagents.Therefore, it seems that activity at the zone equiva-lent to auxin IV in syconia of both crops was dueto 2 or more substances and that IAE is not a

component of that promotor-complex.

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FIG. 2. Changes during fruit growth in concentra-tions of each of 4 auxins in the first (parthenocarpic)and second (non-parthenocarpic) crops of fig syconia,as determined by growth-promoting activity of crudemethanol extracts on wheat coleoptile sections. IAAequivalents in *gm per gm dry wt of syconia tissue.

557

01%r

IC

PLANT PHYSIOLOGY

Identification of IAA as one of the auxins fromthe samples was not certain. The upper end ofthe spot at zone II always overlapped the lower endof the synthetic IAA spot in the control chromato-grams. The active spot gave no color reaction witheither of the spray rea,gents. Active zone III mostnearly approximated IBA, but gave no color reactionfor it. Active zone I seemed equivalent to thea-accelerator of Kefford (18) and similar substancesfound by Luckwill (23) in the apple aind Nitsch (24)in the strawberry. Hirai (13, 14) detected IAA andIBA in acidic and IAN in neutral fractions of ex-tracts from the Masui Dauphine fig.

The zones of inhibition on chromatograms frommature fruit of both crops had RF values of 0.6 to0.8, the sanme as those of the ,8-inhibitor complexdetected in many plant tissues, including ripeningfruits (2, 23, 28, 29).

The bar graphs of weekly fruit growth incrementin the 2 crops (Fig. 3) illustrate the 3 periods offig syconiutm growth. They were designated periodsI, II, and III by Crane (7) and correspond tosimilar growvth periods in drupaceous fruits in gen-eral (20,21,22), in which category the fruitlets ofthe fig belong. An initial period of rapid growtthwas followed bv a period of very slow growth, andthen a second period of rapid growNth. The durationsof each of the growth periods is shoWln by the markedline, the 3 sections of wlhich are labeled I, II, andIII, at the top of each half of Fig. 3. Growthperiod I was longer and period II shorter in thefirst than the second crop. It is recognized that notall 4 auxins would nrecessarily be active in fruitgrowth. Since they tended to form individual peaksOIn or close to the same dates, they have been coml-bined in Fig. 3 to facilitate correlation with the bargraphs of fruit growth.

The following simlilarities and differences in theextracted auxinis are seen in Fig. 2 anid 3. Thlreepeaks of total free auxins alpl)eared in both crops.An additional and earlier peak in the first crop, butnot the second, was evidenced by a considerabledrop in auxin level from the first to the secondsampling date. In both crops, the increase in auixinsto the first peak accompanied slowing of fruit growthfollowing the period of most rapid growth duringthe season, and the peak marked the enld of growthperiod I. In the firs't crop, the gradual increase inextracted auxins was associated with gradual slowingof growth, while in the second crop both the increasein auxins and retardation of growtlh were abrupt.This suggests that increase in free auxins ma) havebeen directly or indirectly related to decrease ingrowth rate. The first peak in the secon,d crop,as seen in Fig. 3, was higher than that in the firstcrop. Fig. 2 shows, however, that lack of svnchronyof auxin II wvith the other 3 auxins accounted for thelower peak in the first crop, for it formed a peak aweek in advance of the other 3 auxins.

In both crops, the rise in auxins to the secondpeaks followed plateaus of low concentration, in thefirst crop of a week's duration, in the second croplasting for 2 weeks. In both crops, the plateau, thesubsequent rise of auxins to a peak, and then declinefrom it spanned the period of very slow fruit growth.The 2 crops differed qualitatively in one of themajor auxins of the second peak. Whereas auxinIII was in highest concentration and auxin II at thenext highest level in the first crop, in th,e secondcrop auxin IV was highest and auxin II next highest(Fig. 2).

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FIG. 3. Weekly fruit growth increments, and changesduring the season in concentrations of total 'free' auxinsin crude methanol extracts and of total gibberellins inthe acidic ethyl-acetate fraction of figs of the first (par-thenocarpic) and second (non-parthenocarpic) crops asseparated by paper chromatography. Auxin content wasdetermined by growth-promoting activity of extracts onwheat coleoptile sections. Gibberellin activity was de-termined by activity of extracts on Progress No. 9 dwarfpea plants grown under red light. IAA and GA3equivalents in Agm per gm and per 5 gm, respectively,of syconium tissue.

5 19 3 17 31 14 28 12April May June July

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LODHI ET AL.-KING CULTIVAR OF FIG

In both crops, the rise and fall of auxins formingthe third and lowest peak accompanied the accelera-tion and deceleration of fruit growth in period III.Unlike the rapid fruit growth of period I, involvingboth cell division and enlargement, growth in periodIII resulted from enlargement of cells and inter-cellular spaces (1, 13), through influx of sugars.

water, and other substances. Crane and Brown (10)reported that more than 89 % of the total sugar and60 % of the total moisture in the Mission fig atmatturity were accumulated during the "final swell"of period III, and Hirai (13) also reported a rapidrise in reducing sugar content during that period inthe Masui Dauphine fig. The influx of fluid intothe fruits would no doubt have carried auxins as' well.

Of *the fig cultivars for which extracted auxinpatterns have been reported, only the Calimvrna(11) resembles the King fig in forming 3 auxinpeaks at approximatelv the same times during fruitgrowthl. In the Mission fig (11) only 2 peaks ap-

peared. corresponding in time to the first and thirdpeaks of the King fig. Similarly, when data takenfrom Hirai's (13) histograms of acidic and neutralauxins in the Mfasui Dauphine fig were conTbinedanld plotted against time, 2 peaks appeared at thesanme growth phases as the first and third peaks inKing figs. Certain developmental features of thedifferenlt cultivars might be related to presence or

absence of a third and intermediate peak. Missionand Masui Dauphine figs are parthenocarpic, andsome of their ovules form parthenogenetic endosperm.The endosperm in the Mission fig began to formnear the end of period I, but development continuedfor only about 2 weeks before degenerating, and thetissue produced consisted usually of only 1 to a fewlayers of free nucleate or cellular tissue beforedegeneration began. The Calimyrna is like second-crop King figs in developing normal seeds whencaprified. Normal endosperm began to form late inperiod I, the embryo somewhat later, and mitosis in1 or the other structure continued for more than3 weeks. The second auxin peak was formed atabout the time of completed development of endo-sperm and embryo. In the parthenocarpic first crop

of the King fig, supernumerary ovule developmentbegan near the middle of period I and continued forat least 9 weeks, although less actively in the lastfew weeeks (5). Development of the frequentlymassive tissues thus spanned the perio-d of rise and

fall of auxins of both first and second peaks. Theseobservations suggest that whether an auxin peakoccurs between the first and third peaks may dependon how much recently formed tissue, capable ofproducing auxins, was present in the ovules or seedsin that period.

The lack of positive correlation of increases anddecreases in auxin levels with changes in fruit growthrate in the King fig thus conforms in general to thesituation in the majority of fruits studied in thisrespect (e.g., 8,9). The possible exception was the

pattern of increase, then decrease of auxins, whichwas accompanied by increase, then decrease in thegrowth rate during period III. A cause-and-effectrelationship is questionable, however, for reasons

mentioned before., The fact that increase of auxinsto the first 2 peaks in both crops accompanied slow-ing of growth (of all vegetative tissues in the case

of the first peak, and of structures within the ovulesin connection with the second peak) suggests thatthe auxin increases represent primarily levels inexcess of those needed for growth.

The growth-promoting zones on the chromato-grams of acidic gibberellin-like sulbstances shiftedfrom 1 RF to another during fruit development (Fig.4). Qualitative differences between the gibberellins

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Ist. CROP 2nd. CROP

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pea plants grown under red light to ethyl-acetate-solublegibberellins of figs of first (parthenocarpic) and second(non-parthenocarpic) crops as separated by paper chro-matography. The GA3 marker indicates the positionto which authentic GA3 traveled on the chromatograms.

559

PLANT PHYSIOLOGY

in the 2 crops were shown by different active zonesat comparable stages of development. For examplethe individual gibberellins whiclh contributedc most tothe peaks on June 14 and August 9 in the 2 crops,respectively, were different. No attenmpt was nmadeto identify the active gibberellins.

The patterns of acidic gibberellin concentrationswere much alike in the 2 crops. The nmajor differ-ence was the exceptionally higlh level in the firstsample of the second crop, whlich dropped rapidly toa low in the followin-g w-eek. In both crops. gib-berellin concenitratioins increased from early in periodI to the single peak at the end of period II, but witlsome differences in rates of increase along the way.The peaks were followed in both crops by rapiddecrease in concentration during period III. Datafrom Hirai's (13) histogranms of acidic gibberellinsextracted fronm figs of the second crop of the MasuiDauphine cultivar, when plotted on a curve, showeda much nmore gradual drop fronm the initial concen-tration, only slightly higher than the peak at the endof period' II, to a low level 9 weeks later. Wlhetherthat represented a real difference between the 2 figcultivars, or was a matter of difference in theprocedures or in the bioassay material (Hirai usedthe second leaf sheath of rice seedlings) is not known.

Jackson and Coombe (16) and Iwahori et al.(15) found good correlations between rapid growthand high concentrations of extracted gibberellinsduring the first growth periods of the Moorparkapricot and a seeded grape cultivar, Tokay, respec-tively, and slow growth and low concentrations inperiod II were also associated. In *the apricot, thedata were not adequate to show whether a highconcentration of gibberellin was present during therapid growth of period III. In the grape, berrygrowvth became rapid in period III before a highlevel of gibberellin appeared, and the authors con-cluded that the increased concentration was the resultof growth and not the cause. Jackson and Coombeconsidered that extracted gibberellin-like substancesmay be a product of growth or may represent thedifference between production and utilization. Inneither of the fig crops was, rapid growth in period Iassociated with high concentrations of extracted gib-berellins, and in period II the growth rate was lowwhile gilbberellin levels were gradually increasing.The decreasing concentrations in period III couldhave indicated utilization in rapid cell growthl, how-ever.

The generally higher levels of total free auxinsin the first than the second crop, and the reverse inconcentrations of acidic gibberellin-like sulbstancessuggest that auxin activities were more prevalent inthe first crop than those of gibberellins, while thelatter were more active in the second crop than theauxins. The high concentrations of gibberellins con-sistently coincided with low concentrations of auxins,and the auxin peaks were reached when gibberellin

levels wvere relatively low. This suggests a balancingsystem of some type between the acidic gibberellinsanid free auxins, althouglh perhaps of inidirect origin.

Thuts, despite development of the partlenocarpicand non-parthenocarpic fig crops uinder differentenvironmental conditions, and the (lifferences inexternal form of tlle fruits and in some internalstrtucttures, the l)atternls of the free auxinis and totalaci(lic gibberellin-like substances were remarkablyalike in the 2 crops. In both, the auxins extractedwvere ap)parently sthe samie 4, in spite of the possibilityof genetic effects fromli the caprifig pollen parent onauxins fronm embryos and endosperimi in the non-

p)arthenocarpic figs and lack of it on auxins fromsupernumerary ovules in the partlheinocarpic crop.Also in both crops, the rises and falls of auixins aindof gibberellins bore the same relationslip to changesfrom 1 growth period to another. The chief differ-ences in the 2 crops were: 1) generally higherconcentrations of auxinls and lower ones of gibberellinin the first than the second crop; 2) a difference in1 of the major auxiiis in the second peak in the 2crops (aauxin III in the first and auxin IV in thesecond crop), also differences in lack of synchronyof peak concentrations of certain individual auxinswith the otlhers; and 3) the exceptionallv high con-

centration of gibberelliin at the beginning of period Iin the second crop in contrast to the very low levelin the first.

Literature Cited

1. BASKAYA, M. AND J. C. CRANE. 1950. Compara-tive histology of naturally parthenocarpic, hor-mone-induced parthenocarpic, and caprified figsyconia. Botan. Gaz. 111: 395-413.

2. BENNETT-CLARK, T. A. AND N. P. KEFFORD. 1953.Chromatography of the growth substances in plantextracts. Nature 171: 645-47.

3. BENTLEY, J. A. 1958. The naturally-occurringauxins and inhibitors. Ann. Rev. Plant Physiol.9: 47-80.

4. BENTLEY, J. A. AND S. HoUSLEY. 1952. Studieson plant growth hormones. I. Biological activi-ties of 3-indolylacetaldehyde and 3-indolylacetoni-trile. J. Expt. Botany 3: 393-405.

5. BRADLEY, M. V. AND J. C. CRANE. 1965. Super-numerary ovule development and parthenocarpy inFicus carica L., var. King. Phytomorphology 15:85-92.

6. CONDIT, I. J. 1955. Fig varieties: a monograph.Hilgardia 23: 323-538.

7. CRANE, J. C. 1948. Fruit growth of four figvarieties as measured by diameter and freshweight. Proc. Am. Soc. Hort. Sci. 52: 237-44.

8. CRANE, J. C. 1964. Growth substances in fruitsetting and development. Ann. Rev. Plant Physiol.15: 303-26.

9. CRANE, J. C. The role of hormones in fruit setand development. Hort. Sci. In press.

10. CRANE, J. C. AND J. G. BROWN. 1950. Growth ofthe fig fruit, Ficus carica var. Mission. Proc. Am.Soc. Hort. Sci. 56: 93-97.

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LODHI ET AL.-KING CULTIVAR OF FIG

11. CRANE, J. C., M. V. BRADLEY, AND L. C. LUCKWILL.1959. Auxins in parthenocarpic and non-parthe-nocarpic figs. J. Hort. Sci. 34: 142-53.

12. HAYASHI, F., S. BLUMENTHAL-GOLDSCHMIDT, ANDL. RAPPAPORT. 1962. Acid and neutral gibberel-lin-like substances in potato tubers. Plant Physiol.37: 774-80.

13. HIRAI, J. 1966. Anatomical, physiological andbiochemical studies of the fig fruit. Bull. Univ.Osaka Prefecture, Series B, 18: 169-218.

14. HIRAI, J., N. HIRATA, AND S. HORIUCHI. 1967.Effect of oleification on hastening the maturityof the fig fruit. II. Respiration and changes inthe concentrations of metabolic substances in thetreated fig fruit with rape seed oil. J. Jap.Soc. Hort. Sci. 36: 36-44.

15. IWAHORI, S., R. J. WEAVER, AND R. M. POOL.1968. Gibberellin-like activity in berries of seededand seedless Tokay grapes. Plant Physiol. 43:333-37.

16. JACKSON, D. I. AND B. G. COOMBE. 1966. Gib-berellin-like substances in the developing apricotfruit. Science 154: 277-78.

17. KATO, J. 1964. Isolation of a gibberellin-like sub-stance from bamboo shoots and its biological ac-tivity. In: Regulateurs Naturels de la CroissanceVegetale. J. P. Nitsch, ed. Colloq. Intern. CentreNatl. Rech. Sci. Paris No. 123: 273-86.

18. KEFFORD, N. P. 1955. The growth substancesseparated from plant extracts by chromatography.I. J. Exptl. Botany 6: 129-51.

19. KENDE, J. AND A. LANG. 1964. Gibberellins andlight inhibition of stem growth in peas. PlantPhysiol. 39: 435-40.

20. LILLELAND, 0. 1930. Growth study of the apricotfruit. Proc. Am. Soc. Hort. Sci. 27: 237-45.

21. LILLELAND, 0. 1932. Growth study of peach fruit.Proc. Am. Soc. Hort. Sci. 29: 8-12.

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