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James E. Faust and Royal D. Heins

The effects of temperature and daily-integrated photosynthetic photon flux (PPFDI) on African violet (Saintpaulia ionantha Wendl.) flower initiation and development were quantified to provide the basis for an inflorescence development model. The percentage of leaf axils in which an inflorescence initiated and continued development increased as the PPFDI increased from 1 to 4 mol·m-2·day-1, while the rate of inflorescence development was a function of the average daily temperature (ADT). The appearance of a visible flower bud (VB) in a leaf axil was related to the growth of the subtending leaf blade. A polynomial model based on ADT and PPFDI was used to describe leaf blade length at visible bud (LBLVB). A nonlinear model was used to describe the influence of ADT on leaf expansion rate (LER). Inflorescence appearance in the leaf axil was predicted by measuring LBL and estimating the time for the leaf blade to develop to the length required for VB. A phasic-development scale was developed to quantify inflorescence development. Days required for an inflorescence to develop from VB to first open flower was described as a function of ADT and either inflorescence height or inflorescence development stage (IDS). Days from leaf emergence to first open flower for the inflorescence initiated in that leaf axil decreased from 86 to 55 as ADT increased from 18 to 26C.

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James E. Faust and Royal D. Heins

Leaf unfolding rate (LUR) was determined for `Utah' African violet plants grown in growth chambers under 20 combinations of temperature and photosynthetic photon flus (PPF). A nonlinear model was used to predict LUR as a function of shoot temperature and daily integrated PPF. The maximum predicted LUR was 0.27 leaves/day, which occurred at 25C and a daily integrated PPF of 10 mol/m2 per day. The optimum temperature for leaf unfolding decreased to 23C, and the maximum rate decreased to 0.18 leaves/day as the daily integrated PPF decreased from 10 to 1 mol/m2 per day. A greenhouse experiment using 12 combinations of air temperature and daily integrated PPF was conducted to validate the LUR model. Plant temperatures used in the model predicted leaf development more accurately than did air temperatures, but using average hourly temperature data was no more accurate than using average daily temperature data.

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James E. Faust and Royal D. Heins

Axillary buds of African violet develop vegetative shoots or reproductive inflorescences. Vegetative axillary development results in a multiple-shoot plant and reduces plant quality. We determined the effect of temperature and plantlet size on axillary bud development. Plantlets were removed from leaf cuttings, graded according to stem diameter, directly stuck into pots 10 cm in diameter, and placed in greenhouses at 18, 22, or 26C. Vegetative development was related to temperature, plantlet size, and nodal position. The number of vegetative axillary shoots per plant decreased from 3.7 to 1.3; that of leaves per vegetative axillary shoot decreased from 10.3 to 4.8 as temperature increased from 18 to 26C. The eight to 10 basipetal nodes developed vegetative shoots or were devoid of axillary development. The percentage of leaf axils in which inflorescences developed increased from 14 on node eight to 100 on nodes 12 and higher. The larger plantlets at the time of transplant had 20% fewer vegetative axillary shoots, whereas reproductive inflorescence development was not affected by plantlet size.

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Kee-Yoeup Paek and Eun-Joo Hahn

Adventitious buds regenerated from homogenized leaf tissue of Saintpaulia ionantha Wendl. `Crimson Frost' were micropropagated to determine types and frequencies of the variants obtained. Plants grown for one year in a greenhouse showed 67% variation and 33% normality. A higher rate of variation was observed in leaf color rather than in leaf shape. The variations in leaf color and leaf shape were 67% and 19%, respectively. In regard to flower type, greater numbers of semidouble and double types were obtained as compared to single types. Both flower types showed a much higher rate of normal (mixed) color (81%) as compared to pink, red or white (19%). An sodium dodecylsulfate polyacrylamide gel electrophoresis profile of protein extracted from leaves of the stock plants and the variants indicated no difference between them and did not reflect the variation in phenotype.

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Zhenghui Tang, Honghui Lin, Lei Shi, and Weilun Chen

. Sci. 39 1378 1380 Kukulczanka, K. Suszynska, G. 1972 Regenerative properties of Saintpaulia ionantha Wendl. leaves cultured in vitro Act. Soc. Bot. Pol. 41 503 510 Li, Z.Y. Wang, Y

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Seong Min Woo and Hazel Y. Wetzstein

adventitious shoot development. For example, regeneration via shoot organogenesis and somatic embryogenesis was obtained in African violet ( Saintpaulia ionantha Wendl.) leaf and petiole explants ( Mithila et al., 2003 ) and leaf tissues of Rosa L. hybrid

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Matthew G. Blanchard, Erik S. Runkle, Arend-Jan Both, and Hiroshi Shimizu

temperature at night than a crop grown without a curtain ( Kittas et al., 2003 ). Studies with other crops such as African violet ( Saintpaulia ionantha Wendl.), tomato ( Lycopersicon esculentum Mill.), and vinca have also reported higher canopy, leaf, or

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Joaquin A. Chong, Uttara C. Samarakoon, and James E. Faust

( Saintpaulia ionantha Wendl.) J. Amer. Soc. Hort. Sci. 118 747 751 Faust, J.E. Heins, R.D. 1996 Axillary bud development of poinsettia ‘Eckespoint Lilo’ and ‘Eckespoint Red Sails’ ( Euphorbia pulcherrima Willd.) is inhibited by high temperatures J. Amer. Soc

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Xiuli Shen, William S. Castle, and Frederick G. Gmitter Jr

ionantha Wendl.) Plant Cell Rep. 21 408 414 Mok, M.C. Mok, D.W.S. Armstrong, D.J. 1982 Cytokinin activity of N-phenyl-N-1,2,3-thidizaol-5-ylurea (TDZ) Photochem. 21 1509 1511 Murashige

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Jane Kahia, Margaret Kirika, Hudson Lubabali, and Sinclair Mantell

. Hall, J. Victor, J.M.R. Saxena, P.K. 2003 Thidiazuron induces shoot organogenesis at low concentrations and somatic embryogenesis at high concentrations on leaf and petiole explants of African violet ( Saintpaulia ionantha Wendl.) Plant Cell Rpt. 21 5