Photoperiod, Irradiance, and Temperature Affect Echinopsis ‘Rose Quartz’ Flowering

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  • 1 Department of Horticultural Science, Controlled Environment Agriculture Physiology and Extension, University of Minnesota, 305 Alderman Hall, 1970 Folwell Avenue, Saint Paul, MN 55108
  • | 2 Altman Plants, Inc., 3742 Blue Bird Canyon Road, Vista, CA 92084

Photoperiod, irradiance, cool temperature (5 °C), and benzyladenine (BA) application effects on Echinopsis ‘Rose Quartz’ flowering were examined. Plants were placed in a 5 °C greenhouse under natural daylight (DL) for 0, 4, 8, or 12 weeks, then moved to a 22/18 °C (day/night temperature) greenhouse under short days (SD, 8-hour DL) plus 0, 25, 45, or 75 μmol·m−2·s−1 supplemental lighting (0800–1600 hr; 8-hour photoperiod), long days (LD) delivered with DL plus night-interruption lighting (NI) (2200–0200 hr), or DL plus 25, 45, or 75 μmol·m−2·s−1 supplemental lighting (0800–0200 hr) for 6 weeks. Plants were then grown under DL only. Percent flowering plants increased as irradiance increased from 0–25 to +75 μmol·m−2·s−1 on uncooled plants, from 0% to 100% as 5 °C exposure increased from 0 to 8 weeks under subsequent SD and from 25% to 100% as 5 °C exposure increased from 0 to 4 weeks under subsequent LD. As 5 °C exposure duration increased from 0 to 12 weeks (SD-grown) and from 0 to 8 weeks (LD-grown), flower number increased from 0 to 11 and from 5 to 21 flowers per plant across irradiance treatments, respectively. Total production time ranged from 123 to 147 days on plants cooled from 8 to 12 weeks (SD-grown) and from 52 to 94 days on plants cooled for 0–4 weeks to 119–153 days on plants cooled for 8–12 weeks (LD-grown). Flower life varied from 1 to 3 days. BA spray application (10–40 mg·L−1) once or twice after a 12-week 5 °C exposure reduced flower number. Flower development was not photoperiodic. High flower number (17–21 flowers/plant) and short production time (including cooling time, 120–122 days) occurred when plants were grown at 5 °C for 8 weeks, then grown under LD + 45–75 μmol·m−2·s−1 for 6 weeks (16 hours; 10.9–12.8 mol·m−2·d−1) at a 22/18 °C day/night temperature. Taken together, Echinopsis ‘Rose Quartz’ exhibited a facultative cool temperature and facultative LD requirement for flowering.

Abstract

Photoperiod, irradiance, cool temperature (5 °C), and benzyladenine (BA) application effects on Echinopsis ‘Rose Quartz’ flowering were examined. Plants were placed in a 5 °C greenhouse under natural daylight (DL) for 0, 4, 8, or 12 weeks, then moved to a 22/18 °C (day/night temperature) greenhouse under short days (SD, 8-hour DL) plus 0, 25, 45, or 75 μmol·m−2·s−1 supplemental lighting (0800–1600 hr; 8-hour photoperiod), long days (LD) delivered with DL plus night-interruption lighting (NI) (2200–0200 hr), or DL plus 25, 45, or 75 μmol·m−2·s−1 supplemental lighting (0800–0200 hr) for 6 weeks. Plants were then grown under DL only. Percent flowering plants increased as irradiance increased from 0–25 to +75 μmol·m−2·s−1 on uncooled plants, from 0% to 100% as 5 °C exposure increased from 0 to 8 weeks under subsequent SD and from 25% to 100% as 5 °C exposure increased from 0 to 4 weeks under subsequent LD. As 5 °C exposure duration increased from 0 to 12 weeks (SD-grown) and from 0 to 8 weeks (LD-grown), flower number increased from 0 to 11 and from 5 to 21 flowers per plant across irradiance treatments, respectively. Total production time ranged from 123 to 147 days on plants cooled from 8 to 12 weeks (SD-grown) and from 52 to 94 days on plants cooled for 0–4 weeks to 119–153 days on plants cooled for 8–12 weeks (LD-grown). Flower life varied from 1 to 3 days. BA spray application (10–40 mg·L−1) once or twice after a 12-week 5 °C exposure reduced flower number. Flower development was not photoperiodic. High flower number (17–21 flowers/plant) and short production time (including cooling time, 120–122 days) occurred when plants were grown at 5 °C for 8 weeks, then grown under LD + 45–75 μmol·m−2·s−1 for 6 weeks (16 hours; 10.9–12.8 mol·m−2·d−1) at a 22/18 °C day/night temperature. Taken together, Echinopsis ‘Rose Quartz’ exhibited a facultative cool temperature and facultative LD requirement for flowering.

Cacti have potential as new floriculture and landscape crops. Cacti can have ornamental spines, unique forms, and occasionally showy flowers and can often survive dry conditions. The epiphytic cacti Schlumbergera, Hatoria, and Rhipsalidopsis have been commercialized as flowering potted plants (Boyle, 1990, 1991; Meier, 1995; O’Leary and Boyle, 1999, 2000). Subsequent work on Schlumbergera and Hatoria showed BA spray application during flower initiation increased flower number (Boyle, 1995; Heins et al., 1981; Ho et al., 1985). In other work, Japanese and Korean scientists facilitated the development of a grafted cactus industry (primarily Gymnocalycium and Echinopsis grafted on Hylocereus) where plants are grown for colorful and/or uniquely shaped scions as potted plants (Kim and Kim, 2006). Erwin (1996) subsequently researched temperature and photoperiod effects on grafted cacti growth to decrease scion losses.

Little recent work has focused on desert cacti flowering physiology. Work by Runger on temperature and photoperiod effects on Mammillaria zeilmanniana (Runger, 1967), Mammillaria longicoma (Runger, 1968a), Notocactus tabularis (Runger, 1971), Rebutia marsoneri (Runger, 1968b), and Rebutia violaciflora flowering (Runger, 1973) showed cool temperature (5–17 °C) and photoperiod interacted to affect flowering, and species varied in temperature and photoperiod requirements for flower induction and development. Research here examined irradiance, photoperiod, and cool-temperature effects on flowering of the desert cactus hybrid Echinopsis ‘Rose Quartz’.

‘Rose Quartz’ is cross between Echinopsis silvestrii and another Echinopsis species (parent not reported, R. O’Connell) that is asexually propagated. Echinopsis silvestrii is indigenous to the Tucuman and Salta regions of northern Argentina where it is often solitary, with white, nonfragrant, 2–5 cm long flowers (Anderson, 2001; Hunt et al., 2006). Other Echinopsis species are indigenous to northern Argentina, northeastern Chile, and northwestern Brazil, and Bolivia, and have large white, yellow, red, or orange flowers that can be fragrant (Anderson, 2001; Hunt et al., 2006). ‘Rose Quartz’ has large red flowers, blooms repeatedly, is large stemmed, and branches readily (personal observation). The habit and prolific flowering of this cultivar make it a potential new ornamental crop. Research objectives here were to 1) determine whether photoperiod, irradiance, and/or a 5 °C exposure affected Echinopsis ‘Rose Quartz’ flowering, and to 2) determine whether BA spray application affected Echinopsis ‘Rose Quartz’ flowering.

Materials and Methods

Two hundred 3-year-old multistemmed Echinopsis ‘Rose Quartz’ plants in 10-cm diameter plastic pots were received from Altman Plants, Inc. (Vista, CA), on Sept. 1 and were grown in a greenhouse under natural DL(7–16 mol·m−2·d−1) with a decreasing photoperiod (13:15–9:06 h) under 26/18 ± 2 °C day/night temperatures.

Expt. 1: Flowering responses to environment.

One hundred twenty-eight plants were selected for uniformity (based on size and branch number) and placed in a cool greenhouse (5 ± 2 °C; DL) on Nov. 28. After a 0-, 4-, 8-, or 12-week 5 °C exposure, plants were moved to a lighting treatment greenhouse (22/18 °C day/night temperature) for 6 weeks. A 5 °C cooling treatment temperature is in the optimal range (4–6 °C) for vernalization and overcoming dormancy, and 12 weeks is the maximum time many species require to complete vernalization or overcome dormancy (Lang, 1959; Padhye et al., 2006). Six weeks was selected as a lighting treatment length because previous research on a number of herbaceous species showed that 3–5 weeks was required for complete flower induction at 20–25 °C (Mattson and Erwin, 2005). Lighting treatments were SD (8-h DL) +0, +25, +45, or +75 μmol·m−2·s−1 supplemental high-pressure sodium lighting (0800–1600 hr; LucoLux LU400, General Electric, Cleveland, OH), or LD treatments [DL plus NI (2200–0200 hr; 2 μmol·m−2·s−1 from incandescent lamps)], +25, +45, or +75 μmol·m−2·s−1 supplemental lighting from high-pressure sodium lamps (0800–0200 hr; 18-h photoperiod; 0800–0200 hr). SD was achieved by pulling an opaque cloth over plants from 1600 to 0800 hr. After lighting treatments, plants were placed in a 22/18 ± 1 °C day/night temperature greenhouse (DL only) and data were collected for 85 d.

Mean daily light integral (DLI) in the 5 °C greenhouse was 4.0 ± 2.0 mol·m−2·d−1 (12 weeks). Mean DLI on plants grown under SD, SD + 25, SD + 45, and SD + 75 μmol·m−2·s−1 (after a 12-week 5 °C exposure) were 8.2 ± 4.6, 8.9 ± 4.6, 9.5 ± 4.6, and 10.4 ± 4.6 mol·m−2·d−1, respectively. Mean DLI on plants grown under NI, LD + 25, LD + 45, and LD + 75 μmol·m−2·s−1 environments (after a 12-week 5 °C exposure) were 8.3 ± 4.6, 9.5 ± 4.6, 10.9 ± 4.6, and 12.8 ± 4.6 mol·m−2·d−1, respectively.

In the 5 °C greenhouse, plants were watered lightly every other week. Thereafter, plants were fertilized weekly with 14.3 mm N, 0.72 mm P, 6.5 mm K, 1.67 mm Ca, and 1.1 mm Mg, plus micronutrients in the irrigation water (Miracle-Gro 15N–2.2P–12.5K Cal–Mg, The Scotts Co., Marysville, OH). The date each flower opened, how many flowers bloomed per plant, and how long each of the first three flowers per plant stayed open were collected. The experiment was organized in a completely randomized statistical design in a factorial arrangement. Main factors were photoperiod, irradiance, and 5 °C exposure duration. Analysis of variance (ANOVA) (P = 0.05) and mean separation [Tukey’s honestly significant difference (hsd) (α = 0.05)] were conducted. Percent data were arcsine transformed before ANOVA.

Expt. 2: BA effects on flower number.

Thirty-two plants were selected for uniformity and grown as in Expt. 1, except plants were grown at 5 °C for 12 weeks then under LD (DL ± 45 μmol·m−2·s−1; 22/18 °C) for 12 weeks. Plants were sprayed with a solution containing 0 (distilled water only), 10, 20, or 40 mg·L−1 BA (wet, but not dripping; Sigma-Aldrich Inc., St. Louis, MO) 1 week after removal from 5 °C. Half of plants received a second application (same concentration) 1 week later. Application timing and concentrations were based on effective timing and rates identified on epiphytic cacti (Boyle, 1995; Heins et al., 1981; Ho et al., 1985). Data collection and analysis were as in Expt. 1. The experiment was organized in a completely randomized statistical design.

Expt 3: LD effects on early flower development.

Sixteen plants were selected for uniformity and grown as in Expt. 1, except plants were grown at 5 °C for 12 weeks and then 22/18 °C under LD (DL ± 45 μmol·m−2·s−1; 0800–0200 hr) for 0, 2, 4, 6, or 8 weeks. Plants were then moved to SD (DL ± 45 μmol·m−2·s−1; 0800–1600 hr) for 12 weeks. Data were collected as in Expt 1. The experiment was organized in a completely randomized statistical design.

Results

Expt 1.

SD-grown plants cooled for 0 or 4 weeks did not flower, but all SD-grown plants flowered when cooled for 8–12 weeks (Table 1). In contrast, 25% to 100% of uncooled LD-grown plants flowered, and all cooled (>4 weeks) LD-grown plants flowered (Table 1). Percent uncooled LD-grown plants that flowered increased from 25%–50% to 100% as supplemental irradiance increased from 0–25 to 75 μmol·m−2·s−1 (Table 1).

Table 1.

Effect of 5 °C exposure, photoperiod, and irradiance on percent Echinopsis ‘Rose Quartz’ percent flowering (PF), days to first open flower (DTF) from the end of cooling, flower number per plant (FN), and total production time (PT; cooling time + DTF). Plants were placed in a 5 °C greenhouse under natural daylight (DL) for 0, 4, 8, or 12 weeks, and were then moved to a 22/18 °C (day/night temperature) greenhouse under short days (SD, 8-h DL) plus 0, 25, 45, or 75 μmol·m−2·s−1 supplemental lighting, or long days (LD) provided as DL plus night-interruption lighting (NI; 2200–0200 hr), or DL plus 25, 45, or 75 μmol·m−2·s−1 supplemental lighting (0800–0200 hr; 18 h) for 6 weeks after which plants were grown under DL only. Percent data were arcsine transformed before analysis of variance. Lowercase letters represent mean separation (Tukey’s hsd(0.05)) across cooling time. Uppercase letters represent mean separation across light treatments.

Table 1.

Days to first flower (DTF) from the end of cooling decreased when plants were cooled for 12 vs. 8 weeks on SD-grown plants under 0 and SD + 25 μmol·m−2·s−1 lighting treatments (Table 1). DTF of LD-grown plants (0 and LD+25 μmol·m−2·s−1) increased from 52 to 64 to 66 d as 5 °C duration increased from 0 to 4 weeks (Table 1). DTF was greatest on SD + 25 μmol·m−2·s−1 (75 d), and least (56–64 d across cooling treatments) when grown under the LD + 45 to 75 μmol·m−2·s−1 lighting treatments (Table 1).

As 5 °C exposure duration increased from 0 to 12 weeks, flower number increased from 0 to 11 flowers per plant on SD-grown plants across irradiance treatments (Table 1). In contrast, as 5 °C duration increased from 0 to 8 weeks on LD-grown plants, flower number per plant increased from 5 to 21 flowers per plant across irradiance treatments (Table 1).

Total production time among SD-grown plants that flowered ranged from 123 to 147 d across irradiance treatments. Among LD-grown plants, production time ranged from 52 to 94 d on plants cooled for 0–4 weeks, to 119–153 d on plants cooled for 8–12 weeks (Table 1). We note that those differences were more related to cooling time, rather than forcing time, as the DTF was unchanged in most treatments (Table 1). Flower life varied from 1 to 3 d across all treatments (data not presented).

Expts. 2 and 3.

BA concentration interacted with application number (*; P = 0.05) to affect flower number. One BA application (across concentrations) decreased flower number from 16 (water only) to 15 flowers per plant. There were 11 flowers on plants that received two BA applications.

Moving plants from LD to SD after a 12-week 5 °C exposure, affected DTF (*; P = 0.05), but not flower number per plant (P = nonsignificant.). DTF were 61 (b), 59 (ab), 54 (a), 58 (ab), and 61 (b) d for plants moved from LD to SD after 0, 2, 4, 6, or 8 weeks, respectively (letters in parenthesis denote mean separation using Tukey’s hsd). Plants moved from LD to SD after 4 weeks had a lower DTF than plants moved after 0 or 8 weeks (see Tukey’s mean separation above).

Discussion

Classification of flowering response groups involves comparison of node number below the first flower on plants grown under different environments (Thomas and Vince-Prue, 1997). Node counting is difficult on cacti as they have areoles (specialized axillary or lateral buds) often arranged in whorls (Mauseth, 1983). Because node number is not easily quantified, DTF and flower number per plant were considered. Of these, we focused on flower number as it quantifies the “degree” of induction to classify plants into photoperiodic/cool-temperature response groups here.

‘Rose Quartz’ can be classified as a facultative LD plant with a facultative cool-temperature requirement for flowering. Determination of whether the cool-temperature requirement resulted from vernalization or overcoming flower bud dormancy would require areole dissection before cooling to determine whether flower buds were present.

Our results are consistent with conclusions that can be drawn from previous work on desert cacti flowering (personal interpretation of data). Runger’s (1967) data suggested M. zeilmanniana had a facultative cool-temperature and facultative SD requirement for flowering. Similarly, N. tabularis flowering data suggested this species had a facultative cool-temperature and facultative irradiance requirement for flowering (Runger, 1971). In contrast, R. marsoneri (Runger, 1968b) and R. violaciflora (Runger, 1973) data suggested plants had a facultative cool-temperature and facultative SD requirement for flowering.

Data here suggested ‘Rose Quartz’ had an optimal cooling duration of 8 weeks (56 d) for maximum flowering. Runger (1968a, 1968b, 1971, 1973) suggested that optimal cooling duration for cacti he studied was 60–70 d. However, cacti in Runger’s work were cooled at 10–15 °C rather than at 5 °C as here. Runger acknowledged cooling at 5–10 °C vs. 10–15 °C reduced the duration of cooling required for full induction (1967, 1968a, 1968b, 1971).

Both cool temperature and LD promoted ‘Rose Quartz’ flowering (Table 1). Similar cool temperature and LD promotion of flowering occurs with Easter lily (Lilium longiflorum; Waters and Wilkins, 1967) and other herbaceous perennials (Padhye et al., 2006). Runger (1967) showed that M. zeilmanniana flowering was promoted by 5–7 °C and photoperiod was irrelevant during cooling; however, photoperiod was increasingly important as temperature increased from 5 to 17 °C. In contrast, N. tabularis flowering was promoted by a 5–15 °C exposure and photoperiod was irrelevant (Runger, 1971).

BA application after a 5 °C exposure did not increase ‘Rose Quartz’ flower number. In fact, BA application decreased ‘Rose Quartz’ flower number. Increased flower number resulting from a spray application of 20–40 mg·L−1 BA to Schlumbergera and Hatoria required synchronization of that application with flower induction (Boyle, 1995; Heins et al., 1981; Ho et al., 1985). We do not know when desert cacti initiate flowers. Therefore, the lack of response (increased flower number) to a BA spray application may be a result of inappropriate spray timing.

Flower development on ‘Rose Quartz’ was photoperiod independent. Photoperiod independence of cacti flower development may be species specific as Runger (1967) reported an LD requirement for flower development with M. zeilmanniana, but not N. tabularis (Runger, 1971).

Literature Cited

  • Anderson, E.F. 2001 The cactus family. Timber Press, Portland, OR

  • Boyle, T.H. 1990 Flowering of Rhipsalidopsis rosea in response to temperature and photoperiod HortScience 25 217 219

  • Boyle, T.H. 1991 Temperature and photoperiodic regulation of flowering in ‘Crimson Giant’ Easter cactus J. Amer. Soc. Hort. Sci. 116 618 622

    • Search Google Scholar
    • Export Citation
  • Boyle, T.H. 1995 BA influences flowering and dry-matter partitioning in shoots of ‘Crimson Giant’ Easter cactus HortScience 30 289 291

  • Erwin, J.E. 1996 Temperature and photoperiod affect grafted cactus scion necrosis HortTechnology 6 393 396

  • Heins, R.D., Armitage, A.M. & Carlson, W.H. 1981 Influence of temperature, water stress and BA on vegetative and reproductive growth of Schlumbergera truncata HortScience 16 679 680

    • Search Google Scholar
    • Export Citation
  • Ho, Y.S., Sanderson, K.C. & Williams, J.C. 1985 Effect of chemical and photoperiod on the growth and flowering of Thanksgiving cactus J. Amer. Soc. Hort. Sci. 110 658 662

    • Search Google Scholar
    • Export Citation
  • Hunt, D.R., Taylor, N. & Charles, G. 2006 The new cactus lexicon. DH Books, Milborne Court, UK

  • Kim, K.S. & Kim, Y.J. 2006 Floricultural production in Korea Chron. Hort. 46 20 23

  • Lang, A. 1959 Physiology of flowering Annu. Rev. Plant Physiol. 3 265 306

  • Mattson, N.S. & Erwin, J.E. 2005 The impact of photoperiod and irradiance on flowering of several herbaceous annuals Scientia Hort. 104 275 292

  • Mauseth, J.D. 1983 Introduction to cactus anatomy. Part 6. Areoles and spines Cact. Succ. J. 55 272 276

  • Meier, E. 1995 Easter cactus (Rhipsalidopsis; Cactaceae) Haseltonia 3 10 24

  • O’Leary, M.C. & Boyle, T. 1999 Cultivar identification and genetic diversity within Hatoria (Cactaceae) clonal germplasm collection J. Amer. Soc. Hort. Sci. 124 373 376

    • Search Google Scholar
    • Export Citation
  • O’Leary, M.C. & Boyle, T. 2000 Diversity and distribution of isozymes in a Schlumbergera (Cactaceae) clonal germplasm collection J. Amer. Soc. Hort. Sci. 125 81 85

    • Search Google Scholar
    • Export Citation
  • Padhye, S., Fausey, B., Runkle, E. & Cameron, A. 2006 Day-neutral vernalization. Greenhouse Grower. March, p. 38–40

  • Runger, W. 1967 Uber die blutenbildung von Mammillaria zeilmanniana Gartenbauwissenschaft 32 19 25

  • Runger, W. 1968a Uber die blutenbildung von Mammillaria longicoma Gartenbauwissenschaft 33 463 468

  • Runger, W. 1968b Uber die blutenbildung von Rebutia marsoneri Gartenbauwissenschaft 34 511 515

  • Runger, W. 1971 Uber die blutenbildung von Notocactus tabularis Gartenbauwissenschaft 36 223 228

  • Runger, W. 1973 Bluhreaktion von Rebutia violaciflora auf temperature und tageslange Gartenbauwissenschaft 38 349 352

  • Thomas, B. & Vince-Prue, D. 1997 Photoperiodism in plants, p. 1–26. 2nd ed. Academic Press, New York, NY

  • Waters, W.E. & Wilkins, H.F. 1967 Influence of intensity, duration and date of light on growth and flowering of uncooled Easter lily (Lilium longiflorum Thunb.‘Georgia’). Proc. Amer. Soc. Hort. Sci. 90:433–439

Contributor Notes

We thank Fran Esqueda, Esther Gesick, and Ben Dill for their advice and work on this project. We also acknowledge the USDA–ARS NRFI, the Floriculture Research Alliance, and the Minnesota Agriculture Experiment Station for their financial support.

Professor.

Plant breeder.

President.

Corresponding author. E-mail: erwin001@umn.edu.

  • Anderson, E.F. 2001 The cactus family. Timber Press, Portland, OR

  • Boyle, T.H. 1990 Flowering of Rhipsalidopsis rosea in response to temperature and photoperiod HortScience 25 217 219

  • Boyle, T.H. 1991 Temperature and photoperiodic regulation of flowering in ‘Crimson Giant’ Easter cactus J. Amer. Soc. Hort. Sci. 116 618 622

    • Search Google Scholar
    • Export Citation
  • Boyle, T.H. 1995 BA influences flowering and dry-matter partitioning in shoots of ‘Crimson Giant’ Easter cactus HortScience 30 289 291

  • Erwin, J.E. 1996 Temperature and photoperiod affect grafted cactus scion necrosis HortTechnology 6 393 396

  • Heins, R.D., Armitage, A.M. & Carlson, W.H. 1981 Influence of temperature, water stress and BA on vegetative and reproductive growth of Schlumbergera truncata HortScience 16 679 680

    • Search Google Scholar
    • Export Citation
  • Ho, Y.S., Sanderson, K.C. & Williams, J.C. 1985 Effect of chemical and photoperiod on the growth and flowering of Thanksgiving cactus J. Amer. Soc. Hort. Sci. 110 658 662

    • Search Google Scholar
    • Export Citation
  • Hunt, D.R., Taylor, N. & Charles, G. 2006 The new cactus lexicon. DH Books, Milborne Court, UK

  • Kim, K.S. & Kim, Y.J. 2006 Floricultural production in Korea Chron. Hort. 46 20 23

  • Lang, A. 1959 Physiology of flowering Annu. Rev. Plant Physiol. 3 265 306

  • Mattson, N.S. & Erwin, J.E. 2005 The impact of photoperiod and irradiance on flowering of several herbaceous annuals Scientia Hort. 104 275 292

  • Mauseth, J.D. 1983 Introduction to cactus anatomy. Part 6. Areoles and spines Cact. Succ. J. 55 272 276

  • Meier, E. 1995 Easter cactus (Rhipsalidopsis; Cactaceae) Haseltonia 3 10 24

  • O’Leary, M.C. & Boyle, T. 1999 Cultivar identification and genetic diversity within Hatoria (Cactaceae) clonal germplasm collection J. Amer. Soc. Hort. Sci. 124 373 376

    • Search Google Scholar
    • Export Citation
  • O’Leary, M.C. & Boyle, T. 2000 Diversity and distribution of isozymes in a Schlumbergera (Cactaceae) clonal germplasm collection J. Amer. Soc. Hort. Sci. 125 81 85

    • Search Google Scholar
    • Export Citation
  • Padhye, S., Fausey, B., Runkle, E. & Cameron, A. 2006 Day-neutral vernalization. Greenhouse Grower. March, p. 38–40

  • Runger, W. 1967 Uber die blutenbildung von Mammillaria zeilmanniana Gartenbauwissenschaft 32 19 25

  • Runger, W. 1968a Uber die blutenbildung von Mammillaria longicoma Gartenbauwissenschaft 33 463 468

  • Runger, W. 1968b Uber die blutenbildung von Rebutia marsoneri Gartenbauwissenschaft 34 511 515

  • Runger, W. 1971 Uber die blutenbildung von Notocactus tabularis Gartenbauwissenschaft 36 223 228

  • Runger, W. 1973 Bluhreaktion von Rebutia violaciflora auf temperature und tageslange Gartenbauwissenschaft 38 349 352

  • Thomas, B. & Vince-Prue, D. 1997 Photoperiodism in plants, p. 1–26. 2nd ed. Academic Press, New York, NY

  • Waters, W.E. & Wilkins, H.F. 1967 Influence of intensity, duration and date of light on growth and flowering of uncooled Easter lily (Lilium longiflorum Thunb.‘Georgia’). Proc. Amer. Soc. Hort. Sci. 90:433–439

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