Water Use and Growth of Eight Foliage Plants Influenced by Paclobutrazol

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University of Florida,
Central Florida Research and Education Center-Apopka
CFREC-Apopka Research Report RH-92-23

R.T. Poole and C.A. Conover*

Growth retardants are being used by foliage plant growers for a variety of purposes, from holding a finished 3-inch pot crop for a short time, to maintaining size indefinitely in an interior environment. Slowing plant growth is the main purpose of growth retardant treatment but other effects could also benefit producers.

Many researchers have reported reduced water loss through transpiration or increased resistance to drought stress as an effect of growth retardant treatments (4, 5, 8). In previous research, poinsettias and beans treated with growth retardants lost less water through transpiration than untreated plants, yet total transpiration rate per unit of leaf area was not altered (1). Paclobutrazol treated chrysanthemums showed anatomical changes like smaller stomatal apertures and thicker cuticle, which tended to increase drought resistance (7).

These findings indicate that less irrigation may be needed to produce crops treated with growth retardants. Foliage plant growers are in the process of developing new water management practices that minimize groundwater contamination from site runoff (2, 3, 6, 10). Chances of ground water contamination can be reduced when crops are grown with less irrigation water (9). Less frequent watering schedules would also reduce labor and equipment costs per crop. The following research was conducted to determine the effect of the growth retardant paclobutrazol on water use and quality of eight foliage plants.

Materials and Methods

Plants used in this experiment were Begonia coccinea 'Pink' (angel-wing begonia), Brassaia actinophylla (schefflera), Codiaeum variegatum 'Petra' ('Petra' croton), Epipremnum aureum 'Golden Pothos' (golden pothos), Gynura aurantiaca 'Purple Passion' (purple passion plant), Hibiscus rosa-sinensis 'Duda Red' ('Duda Red' hibiscus), Hibiscus rosa-sinensis 'Double White' ('Double White' hibiscus) and Rademachera sinica 'China Doll' ('China Doll' Rademachera). Research began on 2 March 1992 when small plants of the eight species listed, growing in cavity trays or 3-inch pots, were transplanted into 6-inch containers using Fafard Growing Medium #4 (Fafard Inc., Apopka, FL 32703). One realized from reduced labor, fertilizer and equipment use.

Table 1. Height or vine length of eight species of foliage plants drenched with various rates of paclobutrazol. Plants grown from 3 March until 29 May 1992.

^zContainers were drenched with a 100 ml Bonzi™ (0.4% active ingredient paclobutrazol) (ICI Americas, Inc., Goldsboro, NC) solution at 0.25, 0.50, 0.75 or 1.0 ml/liter, or received 100 ml tap water on 10 March 1992.
^yns, **; Results nonsignificant or significant at P = 0.01, respectively.

Table 2. Evapotranspiration from containers of eight species of foliage plants receiving various rates of paclobutrazol medium drench. Water loss measured from 3 March until 29 May 1992.

^zContainers were drenched with a 100 ml Bonzi™ (0.4% active ingredient paclobutrazol) (ICI Americas, Inc., Goldsboro, NC) solution at 0.25, 0.50, 0.75 or 1.0 ml/liter, or received 100 ml tap water on 10 March 1992.
^y*, **; Results significant at P = 0.05 and 0.01, respectively.

Table 3. Electrical conductivity (µmhos/cm) and pH of leachate from containers of Codiaeum variegatum 'Petra' drenched with various rates of paclobutrazol. Plants were grown from 3 March until 29 May 1992, drenched on 10 March 1992.

^zContainers were drenched with a l00 ml Bonzi™ (0.4% active ingredient paclobutrazol) (ICI Americas, Inc., Goldsboro, NC) solution at 0.25, 0.50, 0.75 or 1.0 ml/liter, or received 100 ml tap water on 10 March 1992.
^yns, *, **; Results nonsignificant, significant at P = 0.05 or P = 0.01, respectively.

*Professor of Plant Physiology, and Professor of Environmental Horticulture and Center Director (retired 7/96), respectively, Central Florida Research and Education Center-Apopka, 2807 Binion Road, Apopka, FL 32703-8504.

Literature Cited

1. Barrett, J.E. and T.A. Nell. 1979. Effects of growth retardants on plant water use. Proc. Plant Growth Regulator Working Group 6:69-74.

2. Biernbaum, J., W. Carlson and R. Heins. 1989. Limit runoff with slow release fertilizers, quality media, wetting agents and absorbent gels. Grower Talks 53(5):48, 50, 52.

3. Elliott, G. 1990. Reduce water and fertilizer with ebb and flow. Greenhouse Grower 8(6):70-72, 74-75.

4. Halevy, A.H. and B. Kessler. 1963. Increased tolerance of bean plants to soil drought by means of growth-retarding substances. Nature 197:310-311.

5. Latimer, J.G. 1992. Drought, paclobutrazol, abscisic acid and gibberellic acid as alternatives to daminozide in tomato transplant production. J. Amer. Soc. Hort. Sci. 117(2):243-247.

6. Martens, J.A. 1991. Growing in the year 2000: making zero runoff a reality. Grower Talks 54(9):21-22, 24, 26, 28.

7. Smith, E.F., A.V. Roberts and J. Mottley. 1990. The preparation in vitro of chrysanthemum for transplantation to soil. 2. Improved resistance to desiccation conferred by paclobutrazol. Plant Cell Tissue Organ Cult. 21:133-140.

8. Swietik, D. and S.S. Miller. 1983. The effect of paclobutrazol on growth response to water stress of apple seedlings. J. Amer. Soc. Hort. Sci. 108:1076-1080.

9. Wilkerson, D.C. 1990. Irrigation management and our natural resources. Florida Foliage 16(7):5-7.

10. Zimmer, B. 1990. New look at irrigation. Greenhouse Manager 9(5):110-112, 114, 116.