A Review of Literature Concerning the Use of Growth Regulators to Induce Lateral or Basal Shoot Production in Ornamental Tropical Foliage Plants

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University of Florida, IFAS
Central Florida Research and Education Center - Apopka
CFREC-Apopka Research Report RH-90-12

R.J. Henny*

Introduction: An important characteristic of foliage plant cultivars is production of enough lateral or basal shoots to give a full and compact appearance. In some cases it may be necessary to treat nonbranching cultivars with growth regulators that induce lateral or basal shoot development to achieve this result. The most commonly used branching-inducers are N⁶ -benzyladenine (BA) and 6-benzylamino-9 -(tetrahydropyran 2-yl)-9H-purine (PBA) both are synthetic cytokinins that have been shown to increase shoot number in a number of plant species. This paper is a review of published research dealing with synthetic branching agents and their effects on foliage plants.

Summary of Literature

Anthurium (ref. #9) - Anthurium 'Southern Blush' treated with 250 or 500 ppm BA resulted in plants that had more basal shoots than control plants. Treated plants were also shorter and had smaller leaves. In this study BA was applied as a 10 ml soil drench at the base of rooted liners from tissue culture growing in 4-inch pots.

(ref. #10) - Mature Anthurium 'Ozake Red' plants in 6-inch pots were sprayed to runoff with 0, 100, 500, 1000 and 1500 ppm ethephon, PBA or BA. Lateral buds longer than 1-inch were counted 4 months after treatment. The 2 best treatments were 1000 ppm BA (3.6 laterals per plant) and 1500 ppm PBA (2.2 laterals). Ethephon was highly phytotoxic and resulted in chlorotic foliage within 24 hours of treatment; these leaves eventually senesced and abscised.

(ref. #11) Juvenile Anthurium 'Marian Seefurth' 4-6 inches in height were given a foliar spray to runoff with gibberellic acid (GA₃) at 0, 125, 250, 375 or 500 ppm. Both topped and untopped plants were treated. At 6 months after treatment a linear increase in number of shoots produced in topped plants was evident with increasing GA₃ concentration. Conversely, a slight linear decrease in shoots number occurred on untopped plants with increasing GA₃ concentration.

A second experiment involved Anthurium 'Mauna Kea' plants of similar size to those in the first experiment. In this test GA3 (500 ppm) and BA (500 and 1000 ppm) were applied to topped and untopped plants. Topping alone increased the average number of new shoots to 4.5 versus 1.8 for intact plants. The number of new shoots increased linearly with increasing BA concentration and was not affected by topping. GA₃ at 500 ppm increased shoot number for both topped and intact plants.

Cordyline (ref. #13) - BA at 0, 100, 250 or 500 ppm was applied weekly as a foliar spray to runoff to Cordyline terminalis 'Celestine Queen' plants for 8 weeks. The mean number of axillary shoots was 0, 7, 25 and 35 at the 0, 100, 250 and 500 ppm BA rates respectively. The average length of harvested shoots was smaller at the 500 ppm rate compared to the lower BA rates. Rootability of cuttings was 100, 86 and 48% from the 100, 250 and 500 ppm BA treatments respectively.

Dieffenbachia (ref. #6) - Foliar application of BA at 500, 1000 or 2000 ppm to Dieffenbachia 'Welkeri' increased lateral shoot development. Plants treated at all BA levels average approximately 6 lateral shoots compared to 2 for untreated plants. Plant height was unaffected by BA-treatment.

In this study ethephon and dikegulac were also tested at the same rates as BA. Neither had any effect on lateral shoot development.

(ref. #18) - A nonbranching Dieffenbachia hybrid was treated with foliar sprays of BA at 0, 250, 500 or 750 ppm. Results showed that 3 foliar sprays, on consecutive days, stimulated more lateral shoot development than one or two sprays. Treatment with 500 or 750 ppm yielded more shoots than 250 ppm. New shoots were visible 4 weeks after treatment and developed normally. Plants receiving 3 foliar sprays with 750 ppm BA had an average of 9.8 basal shoots versus 0.0 for untreated plants.

Dracaena (ref. #1) - Cutting production was studied in Dracaena marginata 'Tricolor' plants that were topped and the remaining foliage sprayed with BA or PBA solutions at 100 and 250 ppm once a month for 4 months. Significantly more cuttings were produced only from plants treated with 250 ppm PBA - a mean of 3.7 versus 2.2 for controls.

There was a slight reduction in rooting of cuttings from cytokinin-treated stock plants. However, differences were eliminated by the use of rooting hormones.

Epipremnum (ref. #14) - Golden pothos in 6-inch pots were treated weekly for three weeks with a foliar spray of PBA at 0, 100, 200 or 300 ppm in an attempt to stimulate lateral bud growth. PBA-treatment caused swelling of some lateral buds but none grew out.

Hedera helix (ref. #12) - Unpruned English ivy plants treated twice with a 300 ppm GA₃ spray on alternate weeks averaged 8.3 primary breaks compared to 0 for controls. However, new branches emerged only on growth occurring from buds maturing after treatment. Pruned plants treated with GA₃ produced secondary shoot growth which did not occur on intact plants - this growth consisted of lateral bud break on primary lateral shoots.

In the same study treatment with PBA at rates up to 1000 ppm had no effect on lateral shoot growth.

Hylocereus (ref. #15) - Hylocereus trigonus is a rootstock used for many of the colorful grafted cactus. This study showed that treatment of cuttings with BA before rooting can increase the number of axillary shoots. A 3-cm cm long apical portion of a 7-cm long cutting was soaked for 24 hours in 3 solutions of 0, 25, 50 or 100 ppm. Cuttings were then air dried for 3 hours before placement in a rooting medium. Data was recorded 80 days later. Untreated cuttings usually had only 1 uppermost bud develop after rooting. Among BA-treated cuttings, the first 6 uppermost buds were induced to sprout at the same time although buds lower than the third usually aborted. Optimum results indicated that shoot yield could be increased from 1 to 3 by BA treatment.

The basal end of some cuttings was soaked in BA, however, this treatment method was less effective than the apical treatment.

Pellionia pulchra (ref. #4) - A single foliar spray with 200 ppm PBA resulted in an average of 14.9 lateral shoots on treated plants versus 6.6 on untreated plants.

Peperomia (ref. #5) - Peperomia obtusifolia growing in 5-inch pots were sprayed to runoff with 0, 250, 500 or 1000 ppm BA. All treatments increased the number of lateral branches compared to controls. The average number of lateral shoots was 4.6, 7.4, 9.4 and 10.4 at 0, 250, 500 and 1000 ppm BA treatment levels. Treated plants were also shorter due to decreasing internode length.

Pilea cadierei (ref. #4) - A single foliar spray with 200 ppm PBA resulted in an average of 11.6 lateral shoots per treated plant versus 7.7 for untreated plants.

Schlumbergera truncata (ref. #3) - Application of 100 ppm BA as a foliar spray increased the number of flower buds by 40% when sprayed 2 weeks after initiation of a short day treatment to stimulate flowering. The same BA-treatment increased the number of phylloclades from an average of 2.1 for controls to 5.3 for plants treated under long day photoperiod.

Spathiphyllum (ref. #2) - Spathiphyllum 'Viscount' liners from tissue culture, ranging in age from 16-32 weeks, were treated with 500 ppm BA. The liners, growing in 72-celled plastic trays, received a 5 ml drench applied at the plant base in each individual cell. Treatment of plants that were 24-, 28- or 32-weeks-old resulted in more basal shoots than plants treated at 16- or 20-weeks of age. BA-treated plants at 28- and 32-weeks of age averaged almost double the number of basal shoots as untreated plants the same age.

(ref. #7) - In this study Spathiphyllum 'Tasson' growing in 4-inch pots were treated with BA at 0, 250 or 500 ppm. Treatment consisted of a foliar spray to runoff or a 10 ml drench applied at the base of each plant. The soil drench treatment significantly increased the number of basal shoots compared to untreated plants or plants treated with a foliar BA spray. Newly developing basal shoots were clearly visible 4 weeks after treatment; the largest increase in the number of shoots on drenched plants occurred during the first 8 weeks following treatment.

Increase in height of drenched plants was less compared to untreated or sprayed plants at 20 weeks after treatment. The fresh weight of the main stems from sprayed and drenched plants (less roots) was less than controls, whereas fresh weight of basal shoots was greater for treated plants. However, the combined weights of the main shoot and basal shoots for all sprayed and drenched plants were not significantly different from the controls.

(ref. #8) - This report compared the effects of 3 different cytokinins on basal shoot development of Spathiphyllum 'Bennett'. BA, kinetin and 2iP were each tested at 0, 125, 250 and 500 ppm; treatments were applied as a 10 ml drench per 4-inch pot. Identical experiments were conducted in the fall and winter to test seasonal effects.

Kinetin and 2iP were not effective at stimulating basal shoot development in this study. BA-treatment at 500 ppm resulted in 12.2 basal shoots compared to 4.9 for untreated in the fall study and 8.2 versus 3.9 in the winter study. These results indicate that summer treatment may be more effective than winter treatment.

Synqonium Podophyllum 'White Butterfly' (ref. #16 and #17) - BA was applied as a foliar spray to 'White Butterfly' cuttings at rates of 0, 250, 500, 750, 1000 and 2000 ppm at the l-, 3-, and 5-leaf stage. There was no effect on lateral branching or growth of plants treated at the 1-leaf stage. At the 3- and 5-leaf stage BA treatment induced earlier development of basal lateral shoots and decreased elongation of the main shoot which resulted in bushier plants. Plants treated at the 3- and 5-leaf stage showed visible growth of the lateral buds within l week of treatment. There was no subsequent effect on the size or number of leaves on the main shoot which was desirable. At termination of the experiment total number of lateral shoots was not increased by BA. However, lateral shoots were larger in BA-treated plants because of the earlier initiation.

In a related study 4-cm long single-node 'White Butterfly' cuttings were soaked for 5 minutes in 0, 400 or 800 ppm PBA. Cuttings were then rooted under mist for 4 weeks and placed under 73% shade. Although initial shoot development was promoted by PBA at both concentrations according to measurements taken 2 weeks after treatment, later plant development was substantially delayed. At the 800 ppm level PBA reduced leaf number to half that of the control. Some PBA-treated cuttings did not root.

Table 1. A summary of growth regulators used to induce basal or lateral branching of foliage plants.

*Professor of Plant Genetics, Central Florida Research and Education Center - Apopka, 2807 Binion Road, Apopka, FL 32703-8504.

Literature Cited

1. Criley, R.A. 1980. Stimulating lateral bud break on Dracaena. Plant Propagator 26(2):3-5.

2. Fooshee, W.C. and R.J. Henny. 1986. BA-induced basal shoot production in Spathiphyllum 'Viscount' affected by plant age. Proc. Fla. State Hort. Soc. 99:240-241.

3. Heins, R.D., A.M. Armitage and W.H. Carlson. 1981. Influence of temperature, water stress and BA on vegetative and reproductive growth of Schlumbergera truncata. HortScience 16(5):679-680.

4. Henley, R.W. and R.T. Poole. 1974. Influence of growth regulators on tropical foliage plants. Proc. Fla. State Hort. Soc. 87:435-438.

5. Henny, R.J. 1985. BA induces lateral branching of Peperomia obtusifolia. HortScience 20(1):115-116.

6. Henny, R.J. 1986. Increasing basal shoot production in a nonbranching Dieffenbachia hybrid with BA. HortScience 21(6):1386-1388.

7. Henny, R.J. and W.C. Fooshee. 1985. Induction of basal shoots in Spathiphyllum 'Tasson' following treatment with BA. HortScience 20(4):715-717.

8. Henny, R.J. and W.C. Fooshee. 1986. Comparison of BA, Kinetin and 2iP for inducing basal shoot production in Spathiphyllum 'Bennett'. CFREC-Apopka Research Report RH-86-13. 4pp.

9. Henny, R.J. and W.C. Fooshee. 1989. BA-treatment stimulates basal shoot production in Anthurium X 'Southern Blush'. CFREC-Apopka Research Report RH-89-16. 3pp.

10. Higaki, T. and H.P. Rasmussen. 1979. Chemical induction of adventitious shoots in Anthurium. HortScience 14(1):64-65.

11. Imamura, J.S. and T. Higaki. 1988. Effect of GA3 and BA on lateral shoot production on Anthurium. HortScience 23(2):353-354.

12. Lewnes, M.A. and B.C. Moser. 1976. Growth regulator effects on apical dominance of English ivy. HortScience 11(5):484-485.

13. Maene, L.J. and P.C. Debergh. 1982. Stimulation of axillary shoot development of Cordyline terminalis 'Celestine Queen' by foliar sprays of 6-benzylamino purine. HortScience 17(3):344-345.

14. McConnell, D.B. and R.T. Poole. 1972. Vegetative growth modification of Scindapsus aureus by ancymidol and PBA. Proc. Fla. State Hort. Soc. 85:387-389.

15. Shimomura, T. and K. Fujihara. 1980. Stimulation of axillary shoot formation of cuttings of Hylocereus triqonus (Cactaceae) by pre-soaking in benzyladenine solution. Scientia Horticulturae 13:289-296.

16. Wang, Y.T. 1988. Branching agents. Greenhouse Manager. 7:136-141.

17. Wang, Y.T. and C.A. Boogher. 1987. Effect of stock plant shading, developmental stage and cytokinin on growth and lateral branching of Syngonium 'White Butterfly'. Scientia Horticulturae 33:137-145.

18. Wilson, M.R. and T.A. Nell. 1983. Foliar applications of BA increase branching of 'Welkeri' Dieffenbachia. HortScience 18(4):447-448.