SHEEHAN AND MURASHIGE: PLUMERIA PHOTOPERIOD 477 LITERATURE CITED period and CCC effects on growth and flowering of Gardenia jasminoides 'VeitchuV Proc. Fla. St. Hort. Soc. 75: 449-541. 1. Boodley, J. W. and J. W. Mastalerz. 1S59. The use 4. Lang, A. 1957. The effect of gibberellin upon flower of gibberellic acid to force azaleas without a cold tempera formation. Proc. Nat. Acad. Sc. 43: 709-717. ture treatment. Proc. Amer. Soc. Hort. Sci. 74: 681-685. 5. Laurie, A., D. C. Kiplinger and K. S. Nelson. 1958. 2. Cathey, H. M. and N. W. Stuart. 1958. Growth Commercial Flower Forcing. McGraw-Hill Book Company, and flowering of Chrysanthemum morifolium Ramat. as af Inc. New York. fected by time of application of gibberellic acid. Proc 6. Lindstrom, R. S. and S. H. Wittwer. 1957. Gibberellin Amer. Soc. Hort. Sci. 71: 547-554. and higher plants: IX. Flowering in geranium (Pelar 3. Joiner, J. N. and R. T. Poole. 1962. Variable photo- gonium hortorum). Mich. St. Univ. Quart. Bull. 40: 225-231. GROWTH RESPONSE OF PLUMERIA TO PHOTOPERIOD AND GIBBERELLIC ACID1 T. J. Sheehan and T. Murashige2 (0, 1, 10, 100 and 1000 ppm). Gibberellic acid was applied, in an aqueous solution, weekly for Plumeria blossoms are one of the most popu a period of 6 weeks. Plants were sprayed until lar lei flowers used in the Hawaiian Islands, but runoff. unfortunately during the peak of the winter Data were collected on growth, by measuring tourist season they are in minimum supply. The increases in stem length and number of leaves plants are dormant from late fall until spring produced, number of flowers and injury due to and this dormancy appears to be associated with chemicals. onset of short days during late fall. Plumeria At the termination of the experiment the might therefore respond to photoperiodic or plants were rated for injury using the following chemical treatment similar to other tropical rating score: plants, such as poinsettia (1) and orchids (2). An experiment was initiated in the fall of 1. No injury—plants normal 1962 to determine whether daylength and/or 2. Slight distortion of leaf margins—faint gibberellic acid might induce winter growth and/ chlorosis or flowering of plumeria. 3. Moderate distortion—leaves strap-shaped —slight marginal burning—slight leaf drop Methods and Materials 4. Very pronounced strap-leaves—moderate Tip cuttings, 12-15 inches long, of Plumeria marginal burning—moderate leaf drop 'Sherman White' were taken on September 27, 5. Plant dead 1962, air dried for one week and stuck in one The experiment was terminated on April 19, gallon cans in a mixture of V2 sterilized compost 1963. and V2 sterilized soil and allowed to root. On November 8, 1962 the plants were placed on a Results raised bench in the horticulture greenhouse (Uni versity of Hawaii) and subjected to long days Experimental results are summarized in (lighted nightly 10:00 p.m. to 2:00 a.m.). All Tables 1 and 2 and Fig. 1, 2 and 3. plants were in active growth by December 13, Stem length—Photoperiod did not affect stem 1962, after 35 long days, at which time the ex length (Pig. 1 and 2), but stem length increased periment was initiated. A split-plot design was as levels of gibberellic acid increased above 10 employed, with daylength treatments as whole ppm (Table 1). There was a highly significant plots and gibberellic acid treatments as sub-plots. increase at 1000 ppm as compared with 100 ppm. There were 6 replications and the experimental Leaf production—Effects of treatments on leaf unit was 1 plant. production are summed up in Table 1 and Fig. The two photoperiod treatments were used: 3. * Sherman White' plants grown under LD normal days (ND), and long days (LD) — treatment produced more leaves than plants ex lighted nightly from 10:00 p.m. to 2:00 a.m. posed to ND. Average number of leaves produced There were five levels of gibberellic acid (GA) by plants under LD conditions was 18.5 as com pared to 9.7 for ND. There was considerable in crease in the number of leaves produced as levels .lFlorida Agricultural Experiment Stations Journal Series No. 1778. of gibberellic acid increased above 10 ppm (Table 2Associate Orn. Hort., Fla. Ag. Exp. Station, Gainesville, and Asst. Hort., Hawaii Ag. Exp. Station, respectively. 1). There was no interaction between photoperiod 478 FLORIDA STATE HORTICULTURAL SOCIETY, 1963 Figure 1.—The effects of levels of gibberellic acid on stem Figure 3.—The effects of photoperiod on leaf production length of Plumeria 'Sherman White' plants growing under of Plumeria 'Sherman White.' Left long days and right long days. Left 0 ppm of gibberellic acid and right 1000 normal days. ppm. between levels of gibberellic acid and photoperiod treatments. Plants growing under LD conditions exhibited increased injury as levels of gibberel lic acid increased. Plants under ND conditions exhibited no injury symptoms up to 100 ppm of gibberellic acid and only mild (2.0) symptoms at 1000 ppm. Reason for the injury under LD conditions is not known. Strap leaf symptoms are evident in Figure 1 on upper foliage of the plant marked 1000 ppm gibberellic acid. This picture was taken during early stages of injury and the malformation be came more pronounced when readings were taken on April 19. 1963. Although flowering data were taken, they are Figure 2.—The effects of levels of gibberellic acid on not to be included as they are considered incon stem length of Plumeria 'Sherman White' plants growing under normal days. Left 0 ppm of gibberellic acid and clusive. Approximately 30% of the plants right 1000 ppm. flowered during the course of the experiment. Plants under LD treatments flowered 14 days be treatments and gibberellic acid as far as leaf fore those that had 35 LD's and then were trans production was concerned. ferred to ND. The transfer was made in Decem Although all plants were actively growing ber; consequently, the ND treatments were actu on December 13, 1962 when treatments were in ally short days and active growth was arrested. itiated, most of the plants subjected to ND went Any flower buds visible at the time of transfer dormant very rapidly. Partially developed leaves continued to develop. Plants growing under ND expanded but no new leaves were produced under produced 343 flowers as compared to 214 for ND conditions. The days being short at this sea plants subjected to LD. Although these data son of the year, the only plants that remained are not conclusive and further studies should be in active growth under ND treatments were those made, a relationship between cutting stem di receiving 1000 ppm of gibberellic acid. ameter and flowering was indicated since only Gibberellic acid treatments were discontinued cuttings with the largest stem diameter produced after 6 weeks when plants receiving 1000 ppm flowers. of gibberellic acid were obviously being injured. Plants were allowed to grow under photoperiod treatments until the experiment was terminated Summary on April 19, 1963, or approximately 10 weeks. The injury ratings are summarized in Table A split-plot experiment was initiated in the 2. There was a highly significant interaction fall of 1962 to determine effects of photoperiod SHEEHAN AND MURASHIGE: PLUMERIA PHOTOPERIOD 479 TABLE 1. EFFECTS OP PHOTOPERIOD AND G33BERELLIC ACID LEVELS ON STEM LENGTH AM) NUMBER OP LEAVES PRODUCED BY PLUMERIA 'SHERMAN WHITE1 GA Stem length : No. of leaves Levels (cm) : GA. levels : Daylength 0 ppm 6.0 J 0 ppm 10.3 Long days 18.5 1 ppm 10. If j 1 ppm 12.8 , Normal days 9.7 10 ppm 10.1 : 10 ppm H.9 100 ppm 15.8 : 100 ppm 15 A 1000 ppm 37.3 j : 1000 ppm 19.7 LSD .05 k.5 3.0 3.1 .01 6.1 k.o < 4.1 and levels of gibberellic acid on the growth and eraged 10.3 leaves as compared to 19.7 leaves in flowering of Plumeria 'Sherman White.' plants receiving 1000 ppm of gibberellic acid. The levels of gibberellic acid had a significant There was a significant interaction between effect on stem length. Plants which received 0 levels of gibberellic acid and photoperiod treat ppm level grew an average of 6.0 cm as compared ments on leaf injury. Plants growing under long to 37.3 cm of growth on plants receiving 1000 day conditions exhibited more injury as levels ppm of gibberellic acid. The photoperiod treat of gibberellic acid increased than plants grown ments employed had no effect on stem length. under normal daylength at the same gibberellic Photoperiod treatments had a significant effect acid levels. on the number of leaves produced. Plants grown The data on flowering were inconclusive and under long days produced 18.5 leaves as com are not presented herein. pared to 9.7 leaves on plants grown under nor mal daylengths. There was also a highly sig LITERATURE CITED nificant increase in number of leaves produced 1. Post, K. 1949. Florist Crop Production and Market ing. Orange Judd Co., New York. 891 pp. 427 figs. as levels of gibberellic acid increased. Plants 2. Rotor, G. 1952. Daylength and Temperature in Re treated with the 0 level of gibberellic acid av lation to Growth and Flowering of Orchids. Cornell Ext>. Sta. Bui. 885. TABLE 2. EFFECTS OF GIBBERELLIC ACID LEVELS AM) PHOTOPERIOD ON DEGREE OF FOLIAR INJURY OF PLUMERIA 'SHERMAN WHITE1 Daylength Daylength 0 1 10 100 1000 : Means Long Days 1 .0 1.3 1 .7 3.1 3 • 9 ' 2.2 Normal Days 1 .0 1.0 1 .0 1.0 2 .0 : 1.2 Gibberellic Acid Means 1 .0 1.15 1 •35 2.05 2 •95 i LSD .01 Me.ans Within Table • 03 To* .