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Thomas H. Boyle

The effects of BA concentration on flowering and dry-matter partitioning in shoots of `Crimson Giant' Easter cactus [Rhipsalidopsis gaertneri (Regel) Moran] were investigated. Treatments were applied 12 days after starting the forcing phase (before flower buds were visible) and included BA at 0, 10, 50, 100, and 200 mg·liter–1. Relative to the controls, BA increased the total number of flower buds per plant and delayed flowering by 2 to 3 days. The percentage of aborted flower buds increased more than 3-fold as BA concentration increased from 0 to 50 mg·liter–1 and increased further when 100 or 200 mg·liter–1 was applied. The number of flower buds that reached anthesis increased quadratically with increasing BA concentration and was maximal when plants were treated with 50 mg·liter–1. As BA concentration increased from 0 to 200 mg·liter–1, total dry weight of phylloclades decreased, whereas dry weight of floral tissue increased by a nearly equivalent amount. BA increases flowering and alters partitioning of dry matter in reproductive plants of `Crimson Giant'. Chemical name used: N-(phenylmethyl)-1H-purine-6-amine (BA).

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Susan S. Han and Jennifer Nobel

The study was conducted to determine if ethylene or ethephon, an ethylene-releasing compound, can be used to induce abscission of phylloclades of four cultivars of Easter cactus [Rhipsalidopsis gaertneri (Regel) Moran] to increase efficiency in vegetative propagation. Abscission occurred within 24 hours after commencement of the ethylene treatments. Phytotoxicity, as exhibited by water soaking, transparency, and darkening of the phylloclades, as well as percent abscission, increased with increasing concentrations of ethephon (0 to 10,000 μl·liter–1). Ethylene released from ethephon, not the acidity of the solution, was determined to be the cause of the phytotoxicity. In three out of the four cultivars, vegetative and root growth from propagated phylloclades was significantly restricted by treatments with ethephon. In comparison, vegetative growth from phylloclades treated with ethylene at 20 μl·liter–1 was the same as from those treated with air. Root growth of the ethylene-treated phylloclades was not studied. The acidity of the ethephon solutions likely affected the growing regions, resulting in a reduction in growth. The study shows that treatment with ethylene gas or the use of pH-adjusted ethephon solutions may be an alternative to the labor-intensive procedures associated with vegetative propagation of Easter cactus. Chemical name used: 2-chloroethylphosphonic acid (ethephon).

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Thomas H. Boyle, Michael Marcotrigiano, and Suzanne M. Hamlin

Investigations were performed to determine the influence of gibberellic acid (GA3) on intact plants and cultured phylloclades of `Crimson Giant' Easter cactus [Rhipsalidopsis gaertneri (Regel) Moran]. Responses of intact plants depended on GA3 concentration, number of spray applications, and application time. Single GA3 applications delayed flowering and reduced the percentage of apical phylloclades flowering and number of flower buds per plant when applied before floral primordia formation [from 20 days before to the start of long days (LDs)], but hastened flowering and did not affect the percentage of apical phylloclades flowering or number of flower buds per plant when applied during floral bud development (20 days after the start of LDs). When sprays were applied at or before the start of LDs, increasing the GA, concentration resulted in fewer plants flowering, longer flowering delays, and further decreases in the number of flower buds per plant. Multiple GA3 applications were more inhibitory to flowering than single applications. Whole plants and cultured phylloclades exhibited similar reactions to GA3, but cultured phylloclades were more responsive to GA3 than intact plants. Intact plants and cultured phylloclades generally produced more new phylloclades as GA3 concentration increased. Spine growth also increased when phylloclades were cultured in a GA3-containing medium. Flowering was accelerated by ≈55 days when GA, was applied to intact plants with 1- to 2-mm-long flower buds. GA, may be horticulturally useful for Easter cactus crop scheduling.

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Thomas H. Boyle

Investigations were performed to determine the effects of timing of application and concentration of BA on the vegetative growth of Easter cactus [Rhipsalidopsis gaertneri (Regel) Moran `Crimson Giant']. BA was applied to rooted phylloclades at 27, 37, and/or 47 days after propagation (DAP) at 200 to 1000 mg·liter-1. At 80 DAP, the number and cumulative length of secondary (2°) phylloclades (those developing from the rooted phylloclade) of BA-treated plants exceeded those of the controls. Number and cumulative length of 2° phylloclades increased linearly with increasing BA concentration. At 316 DAP, there were no differences between BA-treated plants and controls in numbers of 2° and apical (terminal) phylloclades. BA also was applied to plants at either 95 or 187 DAP. Treatments included 10, 50, 100, and 200 mg BA/liter and an unsprayed control. Number of new phylloclades (those developing after treatments) and percentage of old phylloclades with new phylloclades increased linearly in response to increasing BA concentration. Relative to the controls, one application of BA at 50, 100, or 200 mg·liter-1 resulted in a ≈50% to 400% increase in total dry weight of new phylloclades accompanied by a ≈4% to 30% decrease in total dry weight of old phylloclades. Branching of mature plants, i.e., with three to five tiers of phylloclades, was significantly affected by timing of application and concentration of BA. BA may be useful for modifying plant architecture of Easter cactus to increase flowering and product marketability. Chemical name used: N- (phenylmethyl) -1H- purine-6-amine[benzyladenine (BA)].

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Thomas H. Boyle, Fabian D. Menalled, and Maureen C. O'Leary

The existence of self-incompatibility (SI) was demonstrated in `Britton' and `Rose' Easter cactus (Rhipsalidopsis). In a full diallel cross among five clones, 18 out of 20 outcrosses resulted in 68% to 100% fruit set, whereas reciprocal crosses between two of the clones and all five self-pollinations failed to set fruit. Pollen tube growth was greatly inhibited in styles of selfed pistils, but there was no evidence of pollen tube inhibition in compatibly crossed pistils. Easter cactus exhibited characteristics typically found in sporophytic SI systems (trinucleate pollen, papillate stigmas, and scant stigmatic exudate) together with those associated with gametophytic SI systems (stylar inhibition of pollen tube growth and absence of reciprocal differences in outcrosses). Additional experiments were performed to determine the effects of bud pollinations, growth regulators (BA, GA3, and NAAm), and high temperatures (0- to 48-h exposure at 40C) on the SI response. Heat treatments were more effective than either bud pollinations or growth regulators in overcoming SI, and yielded an average of 7.2 viable seeds per treated flower when plants were incubated for 12 h at 40C and selfed immediately after incubation. Isozyme analysis of the S0 parent and putative S1 progeny confirmed that selfing had occurred following heat treatments. Using S1 progeny in breeding programs may extend the flower color range and lead to a greater diversity in other plant characteristics than presently exists in cultivated germplasm. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine [benzyladenine (BA)], gibberellic acid (GA3), and α-naphthaleneacetamide (NAAm).

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Hiroaki Ito, Takahiro Hayashi, Masaki Hashimoto, Katsuro Miyagawa, Saori Nakamura, Youichi Mizuta, and Susumu Yazawa

) cockscomb ( Celosia cristata ), (I) bougainvillea ( Bougainvillea spectabilis ), (J) easter cactus ( Rhipsalidopsis gaertneri ), (K) portulaca ( Portulaca grandiflora ), (L) four o'clock ( Mirabilis jalapa ), (M) snapdragon ( Antirrhinum majus ), (N

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Charles L. Rohwer and Royal D. Heins

.J. Stimart, D.P. 1988 Influence of photoperiod and growth regulators on flowering of Rhipsalidopsis gaertneri J. Amer. Soc. Hort. Sci. 113 75 78 Boyle, T.H. Marcotrigiano, M. Hamlin, S.M. 1994