Proc. Fla. State Hort. Soc. 106:283-286. 1993. EFFECT OF GROWTH REGULATORS ON LEAF DEVELOPMENT OF CALADIUM S. E. Nixon of basal shoots of Anthurium (Henny and Fooshee, 1989), Auburn University to increase the number of lateral shoots of Dieffenbachia Auburn, Alabama (Wilson and Nell, 1983), and to increase the number of phylloclades and flowers of Schlumbergera (Heins et al., G. J. WlLFRET 1981). PBA increased the number of lateral shoots of An Gulf Coast Research & Education Center thurium (Higaki & Rasmussen, 1979), increased the IFAS, University of Florida number of cuttings produced from Dracaena (Criley, Bradenton, FL 34203 1980), and increased the number of lateral shoots of Pel- lionia (Henley and Poole, 1974) and Pilea (Henley and Additional index words, dikegulac, thidiazuron, benzyladenine, Poole, 1974). Thidiazuron (TDZ), used to defoliate mature tetrahydropyranylbenzyladenine, tuber, Caladium x Hor- green leaves in cotton, has been used to stimulate in vitro tulanum. shoot formation in apple (van Niewkerk et al., 1986). Henny and Fooshee (1990) showed that a TDZ drench at Abstract. Growth regulators N6-benzyladenine (BA), tetra the base of Alocasia plants increased the number of elon hydropyranylbenzyladenine (PBA), dikegulac, and thidiazu gated buds but reduced root growth. Similar TBZ treat ron (TDZ) were evaluated to ascertain their ability to negate ments of Syngonium yielded numerous elongated basal apical dominance of the terminal buds of caladium tubers buds which failed to develop and produce new leaves and to stimulate the development of lateral eyes. BA and (Henny and Fooshee, 1991). Dikegulac has been shown to PBA, at concentrations of 0, 12.5, 25, or 50 ppm applied as promote lateral branching on herbaceous plants such as a 15 min tuber soak on intact or de-eyed caladium 'Can- salvia and verbena (Anon., 1970) and has been used as a didum' and 'Postman Joyner', had no effect on number of chemical pinching agent on azaleas (Heursel, 1975; Lar leaves, leaf length, time to marketability, and plant height. son, 1978). Carter and Mahotiere (1991) reported that di BA, at concentrations of 0, 50, 100, 250, or 500 ppm on kegulac increased shoot number, decreased plant height, 'Elise', had no effect on leaf development and number. Di and had no effect on leaf area in "scooped" and intact kegulac (concentrations of 0, 100, 200, or 400 ppm) and caladium tubers. The objective of this research was to thidiazuron (concentrations 0, 0.5, or 1 ppm) were applied as evaluate the effect of four growth regulators when applied a 24-hr tuber soak on 'Candidum' and 'Postman Joyner'. No as a tuber soak on development of caladium leaves. differences were measured with dikegulac but thidiazuron retarded plant height and inhibited leaf development. Chem icals used: (1-methylethylidene)-a-L-xylo-2-hexulofuranoionic Materials and Methods acid, N6-benzyladenine, 6-benzylamino-9-(tetrahydropyran- Caladium tubers were planted in 6-inch diameter pots 2-yl), and N-phenyl-N^l^^-thiadiazol-S-ylurea. (1.6 qt) which were spaced on 10-inch centers on a raised bench in a glass greenhouse. The glass was shaded to Caladiums {Caladium x Hortulanum Birdsey) are an im exclude 40% of ambient light. One jumbo tuber (2.5-3.5 portant, attractive tropical foliage plant produced from a inches diameter) was placed in each container and covered tuber (Harbaugh and Tjia, 1985). They are grown as single with a medium of Florida sedge peat, coarse white builder's or multiple units in containers ranging from 4 to 24 inches sand, coarse vermiculite, and perlite (5:3:3:1, v/v) amended in diameter (Black and Tjia, 1979). Each tuber has a (per yd3) with dolomite limestone (7.5 lb), hydrated lime minimum of one dominant eye, which if allowed to grow (3 lb), granular calcium carbonate (7.5 lb), single super unaltered, will produce a single large leaf. This growth phosphate (5 lb), and Nutricote® 13N-5.7P-10.8K) (6 lb). type yields a tall plant and reduces the plant's marketabil Medium pH was initially 6.0. Pots were arranged on the ity. A preplant process known as "de-eying," which excises bench in a randomized split plot design with three replica the dominant eye, allows the lateral eyes to develop and tions per treatment and three pots per replication. Main produce more leaves (Harbaugh and Tjia, 1985). Unfortu plots were tuber type (intact vs. de-eyed) and subplots were nately de-eying is a very time consuming process and re chemical and concentration. Each cultivar was analyzed quires many hours of manual labor to do a large quantity separately using ANOVA through the SAS program. of tubers. Expt. 1. Tubers of 'Candidum' and Tostman Joyner' Several foliage plants have been treated successfully were either left intact or were de-eyed on 12 June 1991. with growth regulators to induce basal and lateral shoot After de-eying, tubers were immersed for 15 min in BA development. The most commonly used chemicals are N6- or PBA at concentrations of 0, 12.5, 25, or 50 ppm on 13 benzyladenine (BA) and 6-benzylamino-9-(tetrahydiapyran June and allowed to dry for 24 hr at 75°F. On 14 June, all 2-yl)-9H-purine (PBA) (Henny, 1990). BA has been shown tubers were planted and placed in the glass greenhouse. to increase the number of axillary shoots of Hylocereus (a The plants were observed daily and the date when the first rootstock used for many of the colorful grafted cactus) leaf was fully expanded was recorded. The number of ma (Shimomura and Fujihara, 1980), to increase the number ture leaves in each pot was counted weekly, starting on 28 June and finishing on 31 July. Date of marketability, de fined as 10 mature leaves per pot, was recorded daily. On Florida Agricultural Experiment Station Journal Series No. N-00834. 31 July and 1 August, the plants were measured for the Research partially supported by the University of Florida's LASER Pro following parameters: maximum height, length of the four gram for high school science students. Proc. Fla. State Hort. Soc. 106: 1993. 283 longest petioles per pot, length of the largest leaf blade, Table 2. Effect of BA and PBA preplant tuber soak on leaf development and total foliage weight. of caladium 'Postman Joyner' (1991). Expt. 2. Tubers of 'Elise' were left intact or de-eyed on 18 Aug., 1991. They were soaked for 30 min in BA at No. concentrations of 0, 50, 100, 250, or 500 ppm on 19 Aug., days to No. Plant Cone first days to Total height allowed to dry at 75°F for 24 hr, and were planted on 20 Tuber type Chemical (ppm ) leaf market leaves (inches) Aug. Data were collected on 20 October and the parameters recorded were: number of leaves per pot, maximum plant De-Eyed BA 0 19.1 28.7 22.4 19.2 height, and length and width of the largest four leaf blades. 12.5 19.8 31.4 24.2 18.8 25 18.8 Expt. 3. Tubers of 'Candidum' and Tostman Joyner' 29.0 24.1 18.8 50 20.0 31.0 22.4 20.4 were de-eyed or left intact on 15 June 1992. They were Intact BA 0 12.1 34.7 14.7 21.6 soaked for 24 hr in solutions of dikegulac (0, 100, 200, or 12.5 13.8 34.8 12.1 22.4 400 ppm) or TDZ (0, 0.5, or 1.0 ppm) and allowed to dry 25 11.5 29.0 19.6 20.7 for 24 hr. Tubers were planted on 18 June and placed in 50 11.4 34.0 16.2 21.1 De-Eyed PBA 0 21.9 32.9 21.2 the greenhouse. Plants were observed each day and the 20.0 12.5 18.9 31.1 26.2 20.0 date was recorded when the first leaf matured and when 25 19.7 30.3 27.1 19.9 the unit was marketable. Number of mature leaves per pot 50 19.6 30.8 24.1 20.9 was recorded weekly starting on 3 July and continuing Intact PBA 0 13.4 34.8 13.9 21.7 through 7 Aug. On 8 Aug. the plants were measured for 12.5 15.6 36.9 11.6 20.8 25 13.6 38.6 11.8 20.4 total leaves per pot, maximum height, length of the four 50 13.8 35.2 12.0 21.9 longest petioles per pot, and the weight of the total foliage. LSD (« = 0.05) 2.7 2.9 3.8 1.2 Results and Discussion Table 3. Composite effect of BA and PBA preplant tuber soak on Expt 1. BA and PBA had no significant effect on the caladium leaf development (1991). number of leaves or any of the other parameters measured (Table 1,2). The only significant differences found were No. days to between the intact and de-eyed treatments (Table 3). Tubers No. Plant first days to Total height of Tostman Joyner' treated with either BA or PBA and Cultivar Tuber type leaf market leaves (inches) left intact produced the first mature leaf 6.5 days earlier than from de-eyed tubers. 'Candidum' intact tubers pro Candidum De-Eyed 20.4 34.6 17.8 23.3 duced the first leaves only 2.4 days earlier than de-eyed Intact 18.0 38.8 13.4 25.7 LSD (« = 0.05) 1.8 3.1 2.6 1.2 tubers. Tubers of both cultivars which had been de-eyed Postman Joyner De-Eyed 19.7 30.6 24.0 19.8 produced marketable plants 4 days earlier than those left Intact 13.2 34.8 14.0 21.4 intact (Table 3).