. . .-.... ...-...-.p-.;.-.7.:.f.; I~§6L.L7-..u-—.. mm”..— ROOTING INVESTIGATIONS 0F POINSETTIA STEM CUTTINGS Thesis for the Degree of M. S._ MICHIGAN STATE UNIVERSITY GARY R, BECK 1973 l ' Iyfi‘qzfimTifi‘w-?‘~‘.~?«;3{3;".:'t.;$:;;-11«:-';?.H;' " ' _ "I " v ‘ \ ‘3'", . . flit-79M."- -2- I ..... LIBRARY Michigan State University v BINDING BY =' IIIIAII & SUNS' 800K BINDEPY IN . L IIRARV IN- "5:35 ABSTRACT ROOTING INVESTIGATIONS OF POINSETTIA STEM CUTTINGS By Gary R. Beck A study was made to determine the rooting response of poinsettia terminal stem cuttings to auxins, growth regu- lators, and experimental chemicals. Experiments were designed to evaluate these compounds for root promotion, explore the response of several poinsettia cultivars, study the effect of root-promoters during the time cuttings are in the propagation bench, and assess the subsequent growth and flowering of auxin—treated cuttings. Of the 25 chemicals evaluated, the auxin—containing substances promoted rooting the greatest. Jiffy Grow (IBA and NAA) at 1000 ppm and Hormodin No. 2 (0.3% IBA) applied separately and in combination produced the greatest root number and root fresh and dry weights of all chemicals tested. Chloromone, which contains an auxin—like compound, at 750 ppm also enhanced rooting. With these chemicals, an increase in root fresh weight accompanied the increases in root number, thus resulting in a higher quality rooted cutting. Gary R. Beck The nine poinsettia cultivars responded similarly to the auxin-containing chemicals. The dual treatment of a liquid dip into either Jiffy Grow at 1000 ppm or Chloromone at 750 ppm followed by a powder dip into Hormodin No. 2 stimulated rooting the greatest in all cultivars studied except Marble Hegg. In the winter, the combination treat— ment of Jiffy Grow and Hormodin significantly increased rooting over the separate application of these chemicals, while in the summer there was increased benefit with use of the dual treatments with only cultivars C-l Red and Annette Hegg Supreme. Those cultivars, as 0-1 Red and Ecke White, which produce low root number and fresh root weight without root-promoters, responded the greatest to the auxins. In both the summer and winter, auxins produced cut- tings which rooted as well or better at 20 days after stick— ing than untreated cuttings at 1“ days. The combination treatments of Jiffy Grow plus Hormodin and Chloromone plus Hormodin promoted rooting the greatest at all four sampling dates. Separate applications of these chemicals stimulated rooting as well as the dual treatments in the summer, but not in the winter. Plant height at flowering was increased over control plants by use of these auxin—containing substances during propagation. Increases in bract diameter were nonsignifi— cant. The time to flower was reduced by 5 to 9 days. ROOTING INVESTIGATIONS OF POINSETTIA STEM CUTTINGS By Gary R. Beck A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Horticulture 1973 ACKNOWLEDGEMENTS The author wishes to express sincere thanks to Dr. Kenneth C. Sink for his guidance and assistance as a major professor. I also extend thanks and appreciation to the members of my guidance committee: Dr. William J. Carpenter, Dr. Hugh Price, and Dr. Henry Foth. I thank Miss Linda Knowlton for her assistance in the collection of data. Appreciation is extended to Jim Mikkelsen and Paul Ecke, Jr., for supplying the plant material and financial support for conducting the experiments. ii TABLE OF CONTENTS PAPER I AN EVALUATION OF GROWTH REGULATORS AND AUXINS FOR ROOT PROMOTION OF POINSETTIA CUTTINGS Introduction Materials and Methods Results Discussion LITERATURE CITED PAPER II. THE RESPONSE OF POINSETTIA CULTIVARS TO AUXINS IN ROOT PROMOTION OF CUTTINGS Introduction Materials and Methods Results Discussion LITERATURE CITED PAPER III THE EFFECT OF AUXINS DURING ROOTING OF CUTTINGS AND ON SUBSEQUENT GROWTH AND FLOWERING OF POINSETTIA Introduction Materials and Methods . . . . . . . Results . . . . . . . . . . . . . . Discussion LITERATURE CITED iii Page H NONUOH 2A 214 25 145 A8 51 51 52 67 7O Table LIST OF TABLES PAPER I Growth regulators and auxins tested for stimu- lating rooting of poinsettia cuttings The effect of B-Nine, Hormodin No. 2, Hormex No. l, Ethrel, IBA, and Jiffy Grow on stimulat- ing rooting of poinsettia cuttings . . The effect of Jiffy Grow, Hormodin No. 2, Ethrel, B—Nine, Alar, Cycocel, A—Rest, and several experimental chemicals on stimulating rooting of poinsettia cuttings The effect of Rutin, CUTstart, Chloromone, RH 531, and H—12AA on stimulating rooting of poin— settia cuttings . . . . The effect of CUTstart, Chloromone, RH 531, and Rootone F on stimulating rooting of poinsettia cuttings . . . The effect of CPTA, Atonik, Chlorflurenol, Jiffy Grow, Hormodin No. 2, and Chloromone on stimulating rooting of poinsettia cuttings The effect of TH 6239, TH 62AO, and TH 62Ul on stimulating rooting of poinsettia cuttings The effect of liquid and powder combination treatments on stimulating rooting of poinsettia cuttings . The effect of method of application of Hormodin No. 2 on stimulating rooting of poinsettia cuttings . . PAPER II Auxin-containing chemicals tested for stimu- lating rooting of poinsettia cuttings iv Page 10 ll 12 IA 15 16 26 Table Response of all poinsettia cultivars to auxins Response of poinsettia cultivars to all root promoters in the trial conducted from March 18 to April 10 . . . . The rooting response of poinsettia cultivars to auxin—containing chemicals Response of all poinsettia cultivars to auxins Response of poinsettia cultivars to all root promoters in the trial conducted from September 29 to October 19 ' The rooting response of poinsettia cultivars to auxin—containing chemicals PAPER III Auxin-containing chemicals tested for stimu- lating rooting of poinsettia cuttings The effect of chemical promoters on the root— ing response of poinsettia cuttings harvested 1A, 16, 18 and 20 days after sticking The effect of chemical promoters on the root— ing of poinsettia cuttings harvested 1“, 16, 18, and 20 days after sticking . . . The effect of auxin—containing substances on root promotion of poinsettia cuttings in soil mix . . . . . The effect of auxin-containing substances employed during propagation on the subsequent growth and flowering of poinsettia Page 28 31 37 38 39 53 55 58 6A Figure 1. LIST OF FIGURES PAPER II Page Mean number of roots per cutting of poin- settia cultivars in response to auxin treat- ments . . . . . . . . . . . . . . 33 Mean root fresh weight per cutting of poin- settia cultivars in response to auxin treat- ments . . . . . . . . . . . . . . 35 Mean number of roots per cutting of poin- settia cultivars in response to auxin treat- ments . . . . . . . . . . . . . . A2 PAPER III Mean number of roots on poinsettia cuttings at A sampling dates in response to auxin treatments . . . . . . . . . . . . 59 The rooting response of cuttings of Dark Red Annette Hegg at 20 days to (left to right) Jiffy Grow 1000 ppm, Hormodin No. 2, Jiffy Grow 1000 ppm and Hormodin No. 2, Chloromone 750 ppm, Rootone F and untreated . . . . . 62 vi PAPER I AN EVALUATION OF GROWTH REGULATORS AND AUXINS FOR ROOT PROMOTION OF POINSETTIA CUTTINGS Introduction The use of root—inducing substances in the propagation of vegetative cuttings of floricultural plants has been of great interest for many years. Curtis in 1918 (6) found that l—2% potassium permanganate solution promoted rooting of cuttings, while inorganic nutrient solutions had no effect. Van der Lek (15,16) showed that the presence of leaves promoted root formation at the base of a cutting. This report stimulated investigations on the role of hor- mones in the initiation of roots. F. W. Went (3A) extracted heteroauxin, the root-forming hormone, which he termed rhizocaline, from leaves and germinating barley which, when applied to cuttings, promoted the development of new roots. F. A. F. C. Went (33) investigated the root- forming substance in Brygphyllum calycinum. These reports encouraged plant physiologists in the 1930's to study the effects of auxins and their methods of application on the root formation in the propagation of ornamental plants. In the span of one decade, studies were performed using indole-3-acetic acid (5,8,12,17,22,28,36, 37,38), alpha-naphthaleneacetic acid (l2,28,30,37,38), 3—indolebutyric acid (12,13,1A,22,30,3l,32,37,38), indole- 3—propionic acid (l,ll,27,37,38), and phenylacetic acid 1 (36,37,38). Indolebutyric acid and naphthaleneacetic acid were found to be most effective. While most of this work involved prolonged immersion of the base of cuttings in dilute water solutions of varying concentrations of auxins for six hours to two days, some experimentation was done with lanolin pastes containing auxins (ll,28,29,37,38). These pastes applied to the base of cuttings were found to be inferior to water solutions of auxins (12). Quick dipping of the bases into concentrated solutions was shown superior over all other methods of application (17). Auxins mixed into talcs were just as effective as water solutions (9,12,20,25,26). In addition, powder treatments possess definite advantages such as greater ease of application and safe use, in that disease organisms are not spread as readily. Since the extensive work with auxins and application methods, researchers have explored other factors affecting cutting propagation of poinsettia. Fertilizer misting (18, 19), drenches of fungicides (2,10), treatment combinations of auxins and fungicides (7), cutting size (35), and type of growing medium (3) have been studied more recently. The effects of plant growth regulators on the propagation of poinsettia have been a topic of recent interest (A,2A). These studies were undertaken to evaluate the effec- tiveness of various chemicals on the rooting of vegetative cuttings of two poinsettia cultivars. Materials and Methods Vegetative terminal cuttings of pOinsettia, Euphorbia pulcherrima Willd., cvs. Dark Red Annette Hegg and Mikkel White Rochford, were cut uniformly to 8.75 cm. For liquid treatments, the cuttings were dipped 2.5 cm into the solu- tion for fifteen seconds; for powder treatments, cuttings were dipped and excess powder removed by tapping the side of the cutting.' Cuttings then were placed into a 15 cm deep sand medium in a raised propagation bench, under intermit- tent mist. Thermostatically controlled bottom heat of 22- 25°C was maintained in the sand medium. Greenhouse air temperatures throughout the studies ranged between 21 and 2A°C in the winter and 21 and 27°C in the summer. During the winter, photoperiodic lighting was employed from 10 PM to 2 AM. There were five cuttings in each treatment per variety in each replication. Number of replications varied from 2 to A throughout the experiments. After twenty days, cuttings were harvested and the number of roots and root fresh and dry weights were recorded. The results were analyzed statistically with analysis of variance obtained for each rooting variable, and mean separation was done by Tukey's H.S.D. The chemicals employed, their chemical name, the source, and the concentrations used are shown in Table l. The dates for each experiment are in the table headings. 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For each experiment, there were two to four replications per variety, each with five cuttings. Cuttings were rooted under intermittent mist in a raised propagation bench filled with coarse sterilized sand to a depth of 15 cm. Thermo— statically controlled bottom heat of 22-25°C was maintained in the sand. Greenhouse air temperatures during the winter study ranged between 21 and 2AOC; the summer study between 21 and 27°C. During the late winter propagation study, photoperiodic lighting was employed from 10 PM to 2 AM. After 22 days, cuttings were dug and the number of roots and root fresh and dry weights were recorded. The results were analyzed statistically with analysis of variance obtained for each rooting variable, and mean separation was done by Tukey's H.S.D. Results The effects of the chemicals on root stimulation from the first study conducted in the late winter (March) are shown in Table 2. Dips in Jiffy Grow at 1000 ppm followed by Hormodin No. 2 highly significantly (1% level) increased the number of roots and root fresh and dry weights in comparison to untreated cuttings. This combination treat- ment produced a number of roots highly significant over Jiffy Grow and Hormodin when each was applied separately. Both Jiffy Grow and Hormodin separately caused significant 28 Table 2. Response of all poinsettia cultivars to auxins. Study was conducted from March 18 to April 10. Mean Mean Mean Treatment Concn. no. fresh Mean dry fresh wt.(g) wt. per roots wt.(g) root Jiffy Grow 1000 ppm 26.6 1.366 0.155 0.0U89 Hormodin No. 2 36.1 1.299 0.152 .0355 Jiffy Grow & 1000 Hormodin No. 2 55.7 1.508 0.187 .0296 Check 13.7 0.765 0.090 .037A 11.3.0. (5%) 11.4 0.3114 0.067 .0118 (1%) 13.9 0.385 0.082 .01A5 29 increases in root number and fresh weight over untreated cuttings. Poirnuattiri culirivarwt‘testexizare imrlicalxyi in 'Wible ’3, together with the mean results for the variables measured. C—l Red and Annette Hegg Supreme produced the least number of roots and root fresh and dry weights, while Dark Red Annette Hegg and M. White Rochford produced the greatest values for these variables. Fresh weight per root was greatest with cv. M. White Rochford. The combination treatment of Jiffy Grow at 1000 ppm and Hormodin No. 2 stimulated the greatest number of roots and root fresh and dry weights for all cultivars except Annette Heflg Supreme and M. Imp. Rochford (Table A and Figures 1 and 2), and resulted in significant increases in rooting over Jiffy Grow and Hormodin when each was applied separately. These results are highly significant when compared to untreated cuttings. Cultivars Annette Hegg Supreme and M. Imp. Rochford responded similarly to the auxin treatments, with separate applications producing rooting values as great as the combination treatment. Overall, Hormodin No. 2 tended to produce a greater number of roots although lower fresh and dry root weights than Jiffy Grow at 1000 ppm on all cultivars. The results of the late summer (September) cultivar rooting study are indicated in Tables 5, 6 and 7. With cultivars combined, the dual treatment of Jiffy Grow at 1000 ppm and Hormodin No. 2 was the only treatment 30 Table 3. Response of poinsettia cultivars to all root promoters in the trial conducted from March 18 to April 10. Variety No. Fresh Dry Fresh wt. roots wt.(g) wt.(g) per root M. Improved Rochford 38.5 1.37“ 0.166 0.038“ Paul Mikkelsen 3“.5 1.205 0.13“ .0390 Dark Red Annette Hegg “7.8 1.725 0.22“ .0“20 M. White Rochford “0.1 1.7“1 0.2“3 .0“88 C-l Red 17.9 0.“8l 0.056 .0232 Annette Hegg Supreme 17.9 0.818 0.073 .0“““ Ecke White 27.6 0.8“5 0.088 .0338 H.S.D. 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V ].M_ 1.068 H8385 37 Table 5. Response of all poinsettia cultivars to auxins. Study was conducted from September 29 to October 19. Variet Concn No. Fresh Dry Fresh wt. y ’ roots wt.(g) wt.(g) per root Jiffy Grow 1000 ppm “0.0 0.772 0.075 0.0211 Jiffy Grow 1000 & Hormodin NO. 2 5“.6 0.76“ .085 .0131 Hormodin No. 2 “2.7 0.65“ .063 .0161 Chloromone 750 37.1 0.67“ .083 .0188 Chloromone 750 & Hormodin NO. 2 50.2 0.706 .07“ .0136 Rootone F 32.3 0.697 .06“ .0209 Check 2“.7 0.“33 .O“7 .0168 H.S.D. (5%) 18.8 .s. N.S .0081; (1%) 22.8 .S. N.S. N.S. 38 Table 6. Response of poinsettia cultivars to all root promoters in the trial conducted from September 29 to October 19. Variet No. Fresh Dry Fresh wt. y roots wt.(g) wt.(g) per root C-l Red 59.5 0.838 0.082 0.0151 Annette Hegg Supreme 3“.8 0.618 .071 .0183 M. Improved Rochford 36.2 0.696 .069 .0188 Pink Hegg 3“.3 0.651 .069 .0191 Marble Hegg 36.2 0.55“ .059 .0150 H.S.D. (5%) 114.7 N.S. N.S N.S (1%) 18.0 N.S. N.S N.S. 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HH5. m.m: 0m5 mcoEOLOHso . . . . m.oz :Heoswom a mmHo 00H H00 H : m0 coo: some spews mmoo. moo. 0H5.o m.55 m.oz canoewom m:Ho.o :mo.o moo.H m.H5 000H 2000 sense .80 A00 A00 .mpw pea .pz .pz .cOcoo pcmEpwmpB .pz .pm mp0 :mmsm .oz Gem HID A.U.ucoov 5 mHQmB “l significantly higher in root number than the untreated cuttings (Table 5). Neither Chloromone at 750 ppm nor the dual treatment of Chloromone and Hormodin, which were not tested in the first study, resulted in significant increases in root number. The increases in fresh and dry root weights and fresh weight per root were nonsignificant. The cultivar C—l Red produced a significantly greater number of roots than the other cultivars tested (Table 6). Although C-l Red produced a greater root fresh weight than the other cultivars, there was no significant difference in any root weight variable. Marble Hegg responded best to treatment with Chloromone at 750 ppm alone (Table 7 and Figure 3). The number of roots was significantly greater than untreated cuttings with treatments of Hormodin No. 2, Jiffy Grow at 1000 ppm followed by Hormodin No. 2, Chloromone, and Chloromone followed by Hormodin No. 2, but no difference was found among these treatments. Jiffy Grow alone and Rootone F did not stimulate rooting. There was a definite, yet nonsig- nificant increase in fresh and dry root weights when cuttings of Marble Hegg were treated with Chloromone and Hormodin in combination. The dual treatment of Jiffy Grow and Hormodin No. 2 increased root number, root fresh and dry weights the greatest in Pink A. Hegg. Jiffy Grow, Jiffy Grow plus Hormodin, and Chloromone plus Hormodin significantly increased root number over the check. The two combination .0H stOPOO ow 0m LmQEmpamw Sosa Umposvcoo mm: mUSpm .mpcmspmmsp 2 u. :Hxsm op mmsommmp CH msm>HpH30 mHupemcHoa mo wcHupSO s00 mpoop 0o gmnEsc :00: .m msstm “3 .3. {on . .om: 00m: uqmcdi mam caam 36m: .< m . . ,1 o. . m a m g .. 3 ., H 8 . . g _ m a. on . 1 3 a; a H i. O¢ u ..... m 31 382:5 55%).. . on u u. 2.28: 5!. ..... £36..on 2889.25 om n 2362020 58on a 35 :2. on. $363: .35 :2. out _u o amouzoox ou>omn§ .3 com: sz o_ I g g m o. - m g m 0.. x g cm I ow I 05 I 00 0. ON on 0? On cm 05 0. ON on 0v 0m. 0w 05 ow 8100! 'ON 9.1.008 'ON ““ treatments produced root numbers significantly greater than the other chemicals tested. Jiffy Grow more than doubled the fresh weight per root in Pink Hegg. Chloromone and Hormodin in combination and Jiffy Grow increased root number, fresh and dry root weights in Annette Hegg Supreme. Root number was significantly increased by these two treatments and by Jiffy Grow and Hormodin in combination. The addition of Hormodin to Chloromone increased root number over treatment with Chloromone alone, but Hormodin in combination with Jiffy Grow did not produce a greater rooting response than separate treatment of the two chemicals. Rootone F and Chloromone increased fresh weight per root, although nonsignificantly. The two combination treatments (Jiffy Grow with Hormodin and Chloromone with Hormodin) highly significantly increased root number in M. Imp. Rochford over untreated cuttings. Rootone F produced the largest fresh root weight, although it was a nonsignificant one. The two combination treatments did not stimulate rooting significantly over these three chemicals used separately on this cultivar. C-l Red responded best to the combination treatment of Jiffy Grow and Hormodin. Root number was increased significantly by all treatments except Rootone and Chloro- mone. Fresh and dry root weights tended to be greatest using Jiffy Grow, either alone or followed by Hormodin No. 2. “5 Discussion Hormodin has been reported to stimulate rooting of poinsettia (13,22,23). Hormodin A (IBA) caused faster rooting of cuttings and increased the percentage of cut- tings which rooted. IBA and NAA have been found to sur- pass all other auxins in root induction (9,10,18,19,22). Application methods of auxin-containing talcs or dipping in concentrated auxin solutions have proved to be superior to all other methods (10,12,17,18). Recently, growth regulators have been tested for their effectiveness as root promoters of cuttings of poinsettia (3,16). B-Nine at 1250 and 2500 ppm, Cycocel at 100 ppm, and Benzyladenine (BA) at 0.5 ppm increased root number and fresh weight over untreated cuttings. When Hormex No. l (0.1% IBA) was used in combination with each of these chemicals, significantly greater number of roots and root fresh weight were observed (3). Previous experiments indicated that auxin—containing substances exceeded experimental growth regulators in root promotion of poinsettia. In the winter study, the poin- settia cultivars tested responded similarly, with the combination treatment of Jiffy Grow at 1000 ppm and Hormodin No. 2 generally increasing rooting the best. Treatment with Chloromone alone or with Hormodin No. 2 were not included in this study. Treatment dips in Jiffy Grow followed by Hormodin No. 2 resulted in increased rooting over treatment with these substances separately, “6 with the exception of Annette Hegg Supreme and M. Imp. Rochford. All cultivars tested in the winter with the exception of Annette Hegg Supreme produced the greatest number of roots after treatment with both Jiffy Grow and Hormodin, and the greatest fresh and dry root weights except for Annette Hegg Supreme and M. Imp. Rochford. In the summer, the cultivars tested responded best to the combination treatments, with the exception of Marble Hegg, where Chloromone resulted in the best rooting. Jiffy Grow with Hormodin and Chloromone with Hormodin stimulated rooting to an equal degree, except with C—l Red, where Jiffy Grow with Hormodin produced significantly greater root numbers and fresh and dry root weights than Chloromone with Hormodin. Rootone F did not significantly increase root number with any cultivar tested. In comparing the two studies, lower root number, root fresh and dry weights were observed in the winter propaga- tion study than in the summer. Lower greenhouse air temperatures and light intensities may account for this observation. In the winter, the addition of Hormodin No. 2 to treatment dips in Jiffy Grow at 1000 ppm caused a significant increase in rooting over these chemicals when applied separately for all cultivars tested except Annette Hegg Supreme, while in the summer this occurred only with cv. Pink Hegg. The dual treatment of Chloromone at 750 ppm and Hormodin No. 2 significantly increased root number in the summer study over separate applications of these “7 chemicals only with cvs. Pink Hegg and Annette Hegg Supreme. Rootone F did not increase rooting in any cultivar. The results tend to show that the combination treatments are only beneficial in winter propagations. Separate applica— tions of either Jiffy Grow, Chloromone, or Hormodin stimu- late rooting in the summer to as great a degree as the combination treatments. The cvs. Annette Hegg Supreme, Ecke White, and C-1 Red which produce the least amount of roots and lowest fresh weights when cuttings are not treated, responded best to the combination of Jiffy Grow and Hormodin No. 2. Root number and fresh weight were increased 750% over untreated cuttings of C-1 Red. The combination treatment increased root number 700% and root fresh weight 360% over untreated cuttings of Ecke White, and 200% and 300% respectively over control cuttings of Annette Hegg Supreme. The cultivars which produce fairly great root number and weights without auxins did not result in such great percent increases with the use of auxins. All poinsettia cultivars tested showed an increase in rooting response when pretreated with one of the auxin—containing substances. LITERATURE CITED Bauguess, L. C. 1935. Plant responses to some indole derivatives. Amer. Jour. Bot. 22:910. Boodley, J. W. 1968. Poinsettia propagation and fungicides. Florists' Review l“6:29,56-57. Carpenter, W. J. and W. H. Carlson. 1971. Drenches of plant growth regulators improve poinsettia rooting. Florists' Review 1“9:25,6“-65. Cooper, W. C. 1935. Hormones in relation to root formation on stem cuttings. Plant Physiol. 10:789-79“. Doran, W. L. 1952. Effects of treating cuttings of woody plants with both a root-inducing substance and a fungicide. Proc. Amer. Soc. Hort. Sci. 60:“87-“91. Grace, N. H. 1939. Physiologic curve of response to phytohormones by seeds, growing plants, cuttings, and lower plant forms. Can. Jour. Res. 15(c):538-5“6. Grimes, J. H., D. C. Kiplinger, H. K. Tayama. 1969. Effects of Dexon and Terrachlor and various media on rooting of poinsettias, Chrysanthemums and geraniums. Florists' Review l“7:l3—15,6“-65. Hitchcock, A. E. 1935. Indole-3-n-propionic acid as a growth hormone and the quantitative measurement. Contrib. Boyce Thompson Inst. 7:87-95. , and P. W. Zimmerman. 1936. Effect of growth substances on the rooting response of cuttings. Contrib. Boyce Thompson Inst. 8:63—79. , and . 1939. Compara- tive activity of root—inducing substances and methods for treating cuttings. Contrib. Boyce Thompson Inst. 10:“61-“90. Kirkpatrick, H. 1939. The use of root-inducing sub- stances. Florists Exchange 92(2):13,18. “8 l2. l3. 1“. 15. 16. l7. l8. 19. 20. 21. 22. 23. 2“. 25. “9 Lek, H. A. A. var der and E. Krijthe. 1937. Stimula- tion of the rooting of cuttings by growth substances. Meded. Landbouwhoogesch. Wageningen “1(2):50. Maxon, M. A., B. S. Pickett, H. W. Richey. 1936. Effect of Hormodin A, a growth substance, on the root- ing of cuttings. Florists Exchange 89(10):15. Myhre, A. S. and C. D. Schwartze. l9“8. Rooting ever— green cuttings with hormones. Proc. Amer. Soc. Hort. Sci. 51:639. Oliver, R. W. 1938. Preliminary tests with plant hormones in the rooting of greenwood cuttings. Sci. Agric. 18:379—387. Read, P. R. and V. C. Hoysler. 1971. Improving root- ing of carnation and poinsettia cuttings with succinic acid-2,2-dimethylhydrazide. HortSci 6(“):350—35l. Stoutemyer, V. T. 1939. Talc as a carrier of sub— stances inducing root formation in softwood cuttings. Proc. Amer. Soc. Hort. Sci. 36:817—822. Swartley, J. and L. C. Chadwick. 1939. Synthetic growth substances as aids to root production on ever- green and softwood deciduous cuttings. Proc. Amer. Soc. Hort. Sci. 37:1099-110“. Thimann, K. V. and J. Behnke. 1950. The use of auxins in the rooting of woody cuttings. Maria Moors Cabot Found. Pub. 1. , and J. B. Koepfli. 1935. Identity of the growth—promoting and root-forming substances of plants. Nature 135:101. Tincker, M. A. H. and F. S. Wisley. 1936. Experiments with growth substances or hormones and the rooting of cuttings. Jour. Roy. Hort. Soc. 61:510-516. Watkins, J. V. 1937. Experiments with Hormodin on tropical and semi-tropical plants. Florists Exchange 89(3):20,36. 1938. Experiments with Hormodin on semi—tropical plants. Florists Exchange 90(10):l2,13. Weaver, J. G. 1938. Use of organic acid in rooting cuttings. Ext. Circ. N.C. Agric. Egp. Sta. 221:12. Went, F. A. F. C. 1930. Uber wurzelbildende substanzen bei Bryophyllum calycinum. Zeitschr. Bot. 23:35-39. 26. 27. 28. 50 Went, F. W. 1929. On a substance causing root forma- tion. Proc. Kon. Akad. Wetensch. Amsterdam 32:35-39. Zimmerman, P. W. and A. E. Hitchcock. 1935. The response of roots to root-forming substances. Contrib. Boyce Thompson Inst. 7:“39-““5. , and F. Wilcoxon. 1935. Several chemical growth substances which cause initiation of roots and other responses in plants. Contrib. Boyce Thompson Inst. 7:209-229. PAPER III THE EFFECT OF AUXINS DURING ROOTING OF CUTTINGS AND ON SUBSEQUENT GROWTH AND FLOWERING OF POINSETTIA Introduction The promotion of rooting of cuttings by treatment with growth regulators and auxins has been studied on many horticultural plants. F. A. F. C. Went (23) reported that root—forming substances are produced in leaves of plants. F. W. Went (2“) first isolated the auxin indole-3-acetic acid from barley coleoptiles and found that it promoted rooting of cuttings. These studies encouraged researchers to study the response of cuttings to auxins and experimental plant growth regulators. Auxins found to stimulate rooting were indole—3—acetic acid (7,12,1“,l6,26,27), 3—indolebutyric acid (l2,16,22,26,27), a—naphthaleneacetic acid (12,22,26, 27), indole-3-propionic acid (l,1l,2l,26,27), and phenyl— acetic acid (26,27). The auxins most effective in root promotion are IBA and NAA. Growth regulators such as B-Nine (succinic acid—2,2-dimethylhydrazide), Chlormequat, and Benzyladenine were reported to stimulate rooting of poin- settia cuttings (“,19). Root stimulation was observed by treatment with several fungicides (2,8,9). Studies which we conducted demonstrated that auxin—containing substances are superior to growth regulators in root promotion. 51 52 Although coarse sand has been widely accepted as the best propagation medium (20), mainly for its good aeration and aseptic conditions, other media promote rooting at least as well as sand: vermiculite (13,17), screened cinders (l8), peat moss (15,25), peat and perlite (9), and sand mixed equally with either peat (10,15,25) or vermicu— lite (5). No significant differences in growth and flower- ing of poinsettia plants were found among twenty soil mixes (3). The purpose of this study was to determine the effect of several auxin—containing substances during the rooting of poinsettia cuttings and to observe the subsequent growth and flowering response of plants initially treated with these compounds. Materials and Methods Vegetative terminal cuttings of poinsettia, Euphorbia pulcherrima Willd., cvs. Dark Red Annette Hegg and Mikkel White Rochford, were cut uniformly to 8.75 cm. The basal 2.5 cm of five cuttings was dipped for 15 seconds for liquid treatments or dipped singly in the powder treatments and tapped lightly to remove the excess. Chemicals tested for root promotion were Jiffy Grow (1000 ppm auxins), Chloromone (750 ppm auxin-like substance), Hormodin No. 2 (3000 ppm IBA) and Rootone F (1700 ppm auxins) (Table 1). These compounds were previously found to be the most effec— tive on poinsettia. For each experiment there were two to four replications, each with five cuttings. In the two time 53 sewzoa EQQ 000H 58005: musseowm 3 was a Empficp UHom oszpsanoccHnm mGHEmpmom mcmHmzpnamCIHlenmeIm UHow OHpeom mcmHmnpnamannHmnmeIm mUHEMpeom memHmcpnamslH UHom QHmesanoccHum UHom OHpmowmcmHmcpzamslm m mcouoom sows swefle smczoa m .02 xopez UHom OHmesneHovcHnm cHuoELom mOHLmE< mo Ema 0m5 .0900 HHm£QOLOH£0 mcHEmpmomecuzgws mHovsH ecoEOLOHzo CQHpmspcmosoo mchHQQSm mstEoo was: HmOHEmno msms HwHopoEEoo .mwchpSO mepmmcHoa mo wsHpoos wsHpMHSEHpm pom 00pmmp mHmoHEmso mchHmpCOOICHxs< .H mHQmB 5U interval studies, in August and November, cuttings were stuck in a raised propagation bench filled to a depth of 15 cm with sterilized coarse sand and equipped with over— head intermittent mist system. Thermostatically controlled bottom heat maintained the medium at 21 to 25°C; air tem- peratures were 21 to 27°C day and night. Photoperiodic lighting was employed nightly in the second study from 10 PM to 2 AM. Groups of cuttings were harvested at 1“, 16, 18 and 20 days after sticking, and data on number of roots, fresh and dry root weights were taken. To study subsequent growth and flowering as influenced by root promoters, the cuttings were stuck October 8, 2.5 cm deep in 5 x 5 cm square plastic pots filled with 1:1:1 (soil, peat, perlite) soil mix. Bottom heat was maintained as before, and after 20 days, rooting data was taken on two replications, and the remaining four replications were planted in the same soil mix, three cuttings of one treat- ment and cultivar in a 15 cm clay pot. Plant height, number of mature and immature leaves were recorded at potting. Data on plant height, bract diameter, and plant quality were measured December 18. The results were analyzed statistically, with analysis of variance obtained for each rooting variable and mean separation done by Tukey's H.S.D. Results The results of the first study are shown in Table 2. These data were not analyzed statistically due to the loss 55 :Hmo. mmo. mm:.o m.Hm mwfio. mzo. mam. :.ma xoono :Hmo. omfi. wmm.a m.H: mmmo. Hmo. mmm. s.mm m mcouoom some. wHH. m:0.H m.mm mmmo. moo. mmm. 0.5m ems mcoEogoano mmao. :ma. mam.a :.Hw :wao. mmH. mmm. m.mm m.oz CHUoELom . . . . . . . . m.oz canoepom w ozao oma mno H w on omao mHH wow u :m oooa 30pm mMMHh memo.o mmH.o moo.a m.mm mmao.o mmo.o mmm.o H.m: oooa 30pm mmmam mmma om mmmo mH moao. omo. mma. w.:a mmoo. Hoo. moo. o.m xomzo oamo. mso. no». m.mm mmao. use. mam. m.mH m mCOpoom omao. mmo. 05m. >.mm mwoo. mmo. mmH. m.:a 0mm mCOEopoaso wmao. Hwo. Hon. :.mm mmoo. mac. mmo. :.ma m.oz CapoEpom . . . . . . . . m.oz cfiothom a mmao mHH Hmm 0 am oooo mmo mHH : ma oooa 20pm zmmflh msfio.o mmo.o Has.o m.m: mmoo.o mmo.o mma.o m.ma oooa 30pm mmmflh .pp Loo va.pz Amv.p3 mwowp ..ph pom va.pz va.p3 mmoop .Cocoo pcmEpmmLB .pz :mopm mpo :mohm 02 p3 :mogm mpg gmopm oz mmmo ma mzmo :H .H meEmeom on ma pmsws< Bosh omposo Icoo mm: mUSpm .mcfixOfipm Looms wasp om new ma .0H .2H Umpmm>pw£ meHuQSo mappomcfloo mo mmcoommp wcflpoop onp so mumpoEopo aonEmgo mo powwow one .m maome 56 of some cuttings to heat injury caused by a malfunctioning heating cable. The number of roots, fresh and dry root weights were recorded at 14, 16, 18, and 20 days after the cuttings were stuck. All of the chemicals stimulated root- ing when compared to those untreated. A fifteen second dip in an aqueous solution of Jiffy Grow at 1000 ppm followed by a dip into Hormodin No. 2 powder resulted in the greatest number of roots throughout the experiment. Jiffy Grow and Hormodin separately produced almost the same number of roots. Chloromone at 750 ppm and Rootone F increased root number to a lesser degree. Fresh and dry root weights were increased over the control cuttings to a similar degree among chemical treatments, with Hormodin No. 2 producing the greatest fresh root weight at 20 days. These treatments also resulted in higher fresh weight per root than the con- trol, except at the end of the experiment. Rootone F pro- duced the greatest fresh weight per root at the four sampling dates. The cuttings were also observed at 10 and 12 days after sticking. At 10 days, those cuttings treated with the auxin—containing compounds had formed a larger callus tis— sue than the untreated cuttings. Hormodin No. 2 and in combination with Jiffy Grow caused callus formation along the basal 2.5 cm of the cutting. After 12 days in the propagating bench, all cuttings but the control were root- ing or root initials were visible. Root length varied 57 between .5 and 2.5 cm with Rootone F producing the longest roots. Untreated cuttings were callused but no roots had formed. The second experiment was conducted in November with an additional treatment of Chloromone at 750 ppm followed by Hormodin No. 2 (Table 3 and Figure 1). At 1“ days, Jiffy Grow at 1000 ppm followed by Hormodin No. 2 increased root number highly significantly over untreated cuttings. Chloromone at 750 ppm followed by Hormodin No. 2 produced a significant increase in root number. No significant differences among treatments were found in root number or root weights. After 16 days in the bench, all cuttings treated with a root-inducing chemical produced significantly greater root number, root fresh weight and fresh weight per root. Root dry weight was significantly increased by all treat— ments except Chloromone and Rootone F. Jiffy Grow and Hormodin No. 2 in combination produced significantly greater fresh and dry root weights than all other treat- ments except the combination of Chloromone and Hormodin. Chloromone and Hormodin together did not differ signifi- cantly from Chloromone treatment alone. At 18 days, Jiffy Grow followed by Hormodin No. 2 increased root number significantly over all treatments but Chloromone followed by Hormodin. All chemicals but Rootone F caused significant increases in root number over the untreated cuttings. Increases in root fresh and dry 58 .m.z .m.z .m.z m.eH .m.z .m.z .m.z e.mm Agfie .m.z .m.z .m.z e.eH .m.z .m.z .m.z m.eH Amme .e.m.m eeme. flee. wee. m.efi emHe. eme. MHH. e.e xemee efime. see. ewe. H.Hm Name. eee. mam. e.mm m meoeoom meme. mHH. mme. m.He eefie. eeH. eme. e.me mmmz wwwmwmmmew emme. meH. Hme. m.mm eefie. mmH. emm. m.mm ems mgoEopoaee . . . . . . . . m.oz :Heosnom e smme emH eme e um eeHe eeH mme e em eeeH zone seeee mmme.e mee.e eee.e e.em Heee.e HNH.e mem.e e.em eeeH zone geese mNflQ om mmmo ma Hme. mmm. H.em H.mm RHV mme. Hem. e.ee e.Hm eme .e.m.m mHo. :m0. 0.: 0.: xoono eme. mem. H.em H.5H m econoom . . . . m.oz :HeoELOm e HHH eme e me e mm ems ecosopoase mee. wee. e.sm m.Hm ems mgoEopoaee . . . . m.oz :Heosnom s mmH see H mm e mm eeeH zone eeefle eee.e mme.e m.mm e.mm eeeH zone seefie .pL Loo Amv.p3 va.p3 mpoop .pp Loo va.p3 Amv.p3 mpoop . .pz Emmgm mp0 :mmpm .02 .p3 nmopm ham V :mmpm .oz Cocoo pcmEpmeB mama ma mama 2H .mm pmoEm>oz on w Lmon>oz Sopm voposocoo mm: mozpm .wcfiXoHpm Looms mzmo om Ucm .mH xmfl .2H Umpmm>pmn mmcflppSO mappmmcfioo mo msfipoop map so mumposopo HmowEmzo go poommm one .m mabme 59 Figure 1. Mean number of roots on poinsettia cuttings at A sampling dates in response to auxin treatments. NO. ROOTS 50;- 3.; 6O H30 5% - _CHL0R0M0NE a HORMODIN '°.. JI-‘FY snow a moons ,,_,,_ ,noorous r 30 r ,/ °°---.m-'Fv snow 0’ 0’ /- °_ -..-.,.4.’../" ~ “-74- -cm.onouou£ /’ ./.“'~. ./ L ’ ’ ‘ 20 o/' / CONTROL / IO /’ P I ’/ ~ - _ - / 1 1 A 1 l4 l6 IO 20 DAYS AFTER STICKING 61 weights and fresh weight per root were not statistically different from the control at the 5% level. While Chloromone with Hormodin produced a significantly greater root number than Chloromone alone at 20 days after sticking, Jiffy Grow with Hormodin did not differ in root number from Jiffy Grow alone. All treatments but Chloromone alone significantly increased root number over the control (Figure 2). Increases in root fresh and dry weights were not significant at the 5% level, and no significant differ— ences were found in fresh weight per root. The subsequent growth and flowering of plants propa- gated with various auxins was studied. Cuttings were stuck in a soil mix of 1:1:1 soil, peat, perlite, and at the end of 20 days, a portion was harvested (Table A), and the remainder planted 3 each in a 15 cm clay pot. All treat— ments except Hormodin No. 2 significantly increased the root number over control cuttings, with the two combination treatments and Rootone F producing highly significant increases. Jiffy Grow and Hormodin in combination produced significantly greater root number than either chemical separately. Chloromone with Hormodin significantly exceeded the root numbers produced by the two chemicals separately. The combination treatments did not signifi- cantly increase root fresh and dry weights over the chemicals used separately. The only significant difference in fresh root weight among chemicals was that of Rootone F over Hormodin No. 2. Dry root weight was not significantly 62 .H LoQEopaom 0» NH pmsms< Eogm omposv Icoo mm: mUSpm .cmumoppcs new m oCOpoom “Eda omw ocoEopoano .m .02 CapoELom ece see eeeH zone seefie .m .02 neeospom .eee eeeH zone geese Aeneas on pmmfiv on mmmp om pm wmmm mppmcc< pom game no mwcaupSO mo mmcoommg mcfipoop one .m ogsmfim 63 64 Table u. The effect of auxin—containing substances on root promotion of poinsettia cuttings in soil mix. The study was conducted from September 8 to September 28. Mean Mean Treatment Conc $882 fresh Meigogry fresh n. no root wt ( ) wt. per ° wt.(g) ' g root Jiffy Grow 1000 53.“ 1.105 0.08M 0.0210 Jiffy Grow 1000 & Hormodin No.2 81.2 0.916 0.070 .0113 Hormodin No.2 52.2 0.688 .058 .0136 Chloromone 750 53.5 1.013 .076 .019“ Chloromone 750 & Hormodin No.2 92.6 1.007 .089 .0126 Rootone F 66.0 1.355 .096 .0201 Check 25.8 0.U35 .036 .0153 H.S.D. (5%) 26.6 0.508 .0u2 .0092 (1%) 33.8 0.6uu .05A N.S. 65 different among treatments. The only significant differ- ence in fresh weight per root was found with Jiffy Grow over the combination of Jiffy Grow and Hormodin. 0n the date that the remaining cuttings were potted, the height and number of mature and immature leaves were recorded (Table 5). Plant height of cuttings treated with Rootone F was significantly greater than untreated cuttings. No significant difference was found among chemicals tested. Jiffy Grow at 1000 ppm and Chloromone at 750 ppm in separate application produced a significantly greater number of mature leaves at potting than the two chemicals used in combination with Hormodin or Hormodin alone. No significant differences in number of immature leaves were found. Plant height was recorded also on November 9 (Table 5). Plants propagated with all the root-inducing substances except Rootone F and Chloromone were signifi— cantly taller than the control plants, with Hormodin No. 2 resulting in highly significantly taller plants. There was no difference in plant height among treatments. Plant height of auxin—treated cuttings at flowering (Table 5) was significantly taller than control plants at the 1% level with Hormodin No. 2, and at the 5% level with Jiffy Grow and Chloromone plus Hormodin. Final height was not different among the chemicals tested. No significant increases in bract diameter were found. Days to flower (number of days from initiation of short days, October A, to anthesis) was reduced by Hormodin No. 2 and Chloromone 66 .m.z e.s .m.z m.e e.m .m.z e.H m.m AeHe .m.z e.m .m.z e.m m.m .m.z e.e e.H Asme .e.m.m m.H m.me H.em e.HH e.e e.m m.m m.s somee m.m e.ss e.em e.eH e.mH m.m e.m m.e m meoeoom m.m s.ms m.em e.mH e.mH m.m e.m e.e mmmz mmmmmMmmew e.H m.ss e.eH m.MH e.eH e.m m.m s.e ems ecososoHee m.m e.ms m.mm e.mH e.mH e.m m.m e.e m.oz :Heospom . . . . . . . . m.oz :Heoseom e m m H es e mm m mH H MH m m m m m s eeeH zoee seeHe e.m s.es m.em e.mH e.mH m.m H.m e.e eeeH zose seeHe wm\m m\m ecHeem pmone eH\mH eH\mH e\HH .m>H mm>H em\e .eecoe eeeEeeess Op mmmo .Emflo.gm AEoVum AEonm AEovpm .meEH.oz .me.oz .mHuuomcfiOQ mo mcHsmzoam 62m susosm pcosqomQSm map so coHpmumdogQ w:wsso Umhoaasm moocmmeSm mcHCHmpclecHxsm mo poommo mze .m mfibme 67 plus Hormodin at the 1% level, and by Jiffy Grow and Jiffy Grow plus Hormodin at the 5% level. Days to flower were not different among treatments. The plants at flowering were not significantly different in quality rating as related to treatment (1 = poor, 2 = average, 3 = excellent). Discussion Chadwick and Kiplinger (6) reported that Rootone and 3-indolebutyric acid at 1, 3 and 5 mg per 100 cc increased the rooting percentage of poinsettia cuttings over the time they remained in the propagating bench. They concluded that the time required to reach normal rooting was decreased by using these auxins. Our results of the data taken at time intervals of 14, 16, 18 and 20 days show that in the summer, Jiffy Grow (NAA and IBA) at 1000 ppm, Hormodin No. 2 (0.3% IBA), and these two chemicals in combination produced Cut— tings which rooted to a greater degree after 16 days in the bench than the untreated ones after 20 days. Chloromone at 750 ppm and Rootone F also speeded rooting. At 20 days, cuttings treated with these auxins had greater root number and root fresh and dry weights than untreated cuttings. In the winter, the root-inducing chemicals produced cuttings at 14 days which rooted as well or better than untreated cuttings after 20 days in the propagating bench. A combina— tion treatment of Jiffy Grow at 1000 ppm followed by Hormodin No. 2 resulted in consistently significant increases in root number at the 1% level. 68 All treatments except Hormodin No. 2 significantly increased root number over untreated cuttings in soil mix. The two combination treatments produced root numbers greater than all other treatments. Root fresh weight was greatest after treatment with Jiffy Grow and Rootone F. In comparing the results of the first time interval study conducted in the summer with the winter study, the rooting values were greater in the summer at 18 and 20 days after sticking. At 1U and 16 days, the seasonal factor did not affect root promotion. In the summer, there was not a great benefit by using a combination treatment of Jiffy Grow and Hormodin in comparison to the two chemicals used separately. All chemicals stimulated rooting similarly after 14 and 16 days. At 18 and 20 days, Hormodin No. 2 and Jiffy Grow plus Hormodin produced much greater root numbers than the other treatments. Fresh root weight was not appreciably different among treatments. In contrast, the addition of Hormodin No. 2 to treatments of Jiffy Grow or Chloromone benefited root production in the winter. The use of these root-inducing chemicals in the propa- gation of poinsettia results in benefits in subsequent growth and flowering. Significant height increases at flowering were observed with treatments of Jiffy Grow, Hormodin No. 2, and Chloromone plus Hormodin. Increases in bract diameter were nonsignificant. All treatments but Rootone F and Chloromone significantly reduced the number of days to flower, by as great as 9 days. The addition of 69 Hormodin to chemical treatments of Jiffy Grow or Chloro— mone did not significantly improve subsequent growth and flowering over separate application of these two chemicals. Root production in soil mix was greatly enhanced by use of these auxins. All chemicals tested significantly increased root number over the control. The addition of Hormodin to treatments of Jiffy Grow or Chloromone signifi- cantly increased root number over the two chemicals in separate application. These auxin—containing substances have been shown in previous experiments to increase rooting of poinsettia cuttings. The results presented here demonstrate that the time necessary to root cuttings is reduced with application of these chemicals at sticking and that they perform as well in soil mix as in a sand medium. The final height of plants treated at propagation with several of these chemi- cals can be increased over that of the control plants and the time to flower can be reduced byg5 to 9 days. 10. 11. LITERATURE CITED Bauguess, L. C. 1935. Plant responses to some indole derivatives. Amer. Jour. Bot. 22:910. Boodley, J. W. 1968. Poinsettia propagation and fungicides. Florists' Review 146:29,56-57. Carlson, W. H. and K. C. Sink. 1966. The effect of soil mixes on the growth, flowering and soil and foliar nutrient content of poinsettia, Paul Mikkelsen. Mich. Florist 441:13,l8,21. Carpenter, W. J. and W. H. Carlson. 1971. Drenches of plant growth regulators improve poinsettia rooting. Florists' Review 149:25,64-65. Chadwick, L. C. 1949. The effect of certain mediums and watering methods on the rooting of cuttings of some deciduous and evergreen plants. Proc. Amer. Soc. Hort. Sci. 53:555—566. , and Kiplinger, D. C. 1938. The effect of synthetic growth substances on the rooting and subse— quent growth of ornamental plants. Proc. Amer. Soc. Hort. Sci. 36:809-816. Cooper, W. C. 1935. Hormones in relation to root formation on stem cuttings. Plant Physiol. 10:789—794. Doran, W. L. 1952. Effects of treating cuttings of woody plants with both a root—inducing substance and a fungicide. Proc. Amer. Soc. Hort. Sci. 60:487-491. Grimes, J. H., D. C. Kiplinger, H. K. Tayama. 1969. Effects of Dexon and Terrachlor and various media on rooting of poinsettia, Chrysanthemums and geraniums. Florists' Review 147:13-15,64—65. Hitchcock, A. E. 1928. Effect of peat moss and sand on rooting response of cuttings. Contrib. Boyce Thompson Inst. 1:439-466. 1935. Indole-3-n-propionic acid as a growth hormone and the quantitative measurement. Contrib. Boyce Thompson Inst. 7:87-95. 70 l2. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 71 , and P. W. Zimmerman. 1936. Effect of growth substances on the rooting response of cut- tings. Contrib. Boyce Thompson Inst. 8:63—79. Houston, R. and L. C. Chadwick. 1947. Some results of the effect of controlled humidity, mediums, and watering methods on the rooting of cuttings of some deciduous and evergreen plants. Proc. Amer. Soc. Hort. Sci. 49: 410-416. Lek, H. A. A. van der, and E. Krijthe. 1937. Stimula- tion of the rooting of cuttings by growth substances. Meded. Landbouwhoogesch. Wageningen 41(2):50. Long, J. C. 1932. The influence of rooting media on the character of roots produced by cuttings. Proc. Amer. Soc. Hort. Sci. 29:352—355. Oliver, R. W. 1938. Preliminary tests with plant hormones in the rooting of greenwood cuttings. Sci. Agric. 18:379-387. O'Rourke, F. L. and M. A. Maxon. 1948. Effect of particle size of vermiculite media on the rooting of cuttings. Proc. Amer. Soc. Hort. Sci. 51:654-656. Pridham, A. M. S. 1948. Comparison of quartz sand, cinders, vermiculite in rooting of evergreen cuttings. Proc. Amer. Soc. Hort. Sci. 51:657-8. Read, P. R. and V. C. Hoysler. 1971. Improving root- ing of carnation and poinsettia cuttings with succinic acid-2,2—dimethylhydrazide. HortSci. 6(4):350—351. Stewart, L. B. 1927. Methods of prOpagation. Jour. Roy. Hort. Soc. 52:33-39. Thimann, K. V., and J. B. Koepfli. 1935. Identity of the growth-promoting and root-forming substances of plants. Nature 135:101. Watkins, J. V. 1937. Experiments with Hormodin on tropical and semi-tropical plants. Florists Exchange 89(3):20,36. Went, F. A. F. C. 1930. Uber wurzelbildende substanzen bei Bgyophyllum calycinum. Zeitschr. Bot. 23:35-39. ' Went, F. W. 1929. On a substance causing root forma- tion. Proc. Kon. Akad. Wetensch. Amsterdam 32:35-39. Zimmerman, P. W. 1925. Vegetative propagation with special reference to cuttings. Proc. Amer. Soc. Hort. Sci. 22:223-228. 26. 27. 72 , and A. E. Hitchcock 1935. The response of roots to root-forming substances. Contrib. Boyce Thompson Inst. 7:439-445. , and F. Wilcoxon. 1935. Several chemical growth substances which cause initiation of roots and other responses in plants. Contrib. Boyce Thompson Inst. 7:209-229. IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII IllllllllllNllllllllHlllllllllfllllfllflllw 3 1293 030 1