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Mark W. Farnham and Thomas Björkman

. In general, cool conditions are required both to induce and maintain vernalization and to allow normal floral development to proceed. If vernalization fails, no head is formed ( Wurr et al., 1995 ). If the coordination of floral development is

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Christopher J. D’Angelo and Irwin L. Goldman

longevity and sprout suppression, but can also delay growth when it is desired. Dormancy release, along with vernalization, are key processes for seed production during which rapid, uniform growth and development are valuable. There is great economic

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Catherine M. Whitman and Erik S. Runkle

perennials, revealing that vernalization and photoperiod can induce or hasten flowering and that seedlings of several species must complete a juvenile phase before they can respond to inductive conditions ( Runkle et al., 2001 ). Aquilegia includes ≈65

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Sonali Padhye, Erik S. Runkle and Arthur C. Cameron

Two experiments were conducted to quantify the effect of vernalization temperature and duration on flowering of Dianthusgratianopolitanus `Bath's Pink'. In Expt. 1, plants were vernalized at 5 °C for 0, 3, 6, 9, 12, or 15 weeks and in Expt. 2, plants were vernalized at 0, 5 or 10 °C for 0, 2, 4, 6 or 8 weeks. After treatments, plants were forced in a greenhouse at 20 °C. Node development, days to first visible bud (DVB), days to first open flower (DFLW), number of buds and height at FLW were recorded. In Expt. 1, 10% of nonvernalized plants flowered and 100% of vernalized plants flowered. As vernalization duration increased from 3 to 15 weeks, DTVB decreased from 24 to 13. Average DFLW were 114, 41, 34, 33, 33, and 28 for 0-, 3-, 6-, 9-, 12-, and 15-week treatments, respectively. In Expt. 2, 40% of plants flowered without vernalization. Following 2 weeks of vernalization at 0 °C, 80% of plants flowered and as the duration of vernalization increased to ≥4 weeks, all plants flowered. Average DFLW decreased from 38 to 28 following 2 or 4 weeks of vernalization at 0 °C. Longer vernalization did not further reduce DFLW. All plants cooled at 5 °C flowered and vernalization duration did not affect DFLW. Percent flowering after vernalization at 10 °C for 2, 4, 6, and 8 weeks was 20%, 60%, 90%, and 100%, respectively, and average DFLW were 46, 45, 35, and 33, respectively. In conclusion, vernalization is required to force D.`Bath's Pink'. To achieve complete flowering, plants should be vernalized at 5 °C for ≥2 weeks or at 0 °C for 4 weeks or at 10 °C for 8 weeks. Qualitative effects of vernalization such as node development and number of buds and height at FLW will be discussed.

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Anusuya Rangarajan, Betsy A. Ingall and Victoria C. Zeppelin

Annual production of globe artichokes (Cynara scolymus L.) requires vernalization of the plants, either through cold treatment of transplants or from natural temperature conditions in the spring. Studies were conducted in upstate New York, to determine if artificial vernalization treatments could be achieved by earlier planting dates. Initial trials evaluated two varieties used for annual production in other parts of the country—`Imperial Star' and `Green Globe' Improved. Transplants were set in the field with or without a vernalizing cool treatment, to determine the extent of natural vernalization achieved under New York conditions. `Imperial Star' produced slightly higher marketable yields than `Green Globe Improved' in 2 years of trials. Vernalization treatment increased the number of plants producing buds and the marketable yields, when transplants were set after 15 May. Natural vernalization was achieved and cold treatment before transplanting did not improve yields of plants established in early May. At later planting dates, vernalizing transplants increased the number of plants producing apical buds (largest) by about 20%, yet over 57% of nonvernalized plants of each variety produced buds within the season. Average bud sizes did not vary with vernalization treatment. A similar number of days from transplanting to first bud harvest (69 to 75 days) was noted regardless of planting date and size of tran.

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Gregory E. Welbaum

The globe artichoke (Cynara scolymus L.) is usually propagated vegetatively because plants grown from seed lack uniformity. Furthermore, in much of the United States, only a small percentage of plants grown from seed flower during the first season due to insufficient chilling for vernalization. Artichokes cannot be grown reliably as perennials without winter protection where temperatures are consistently below -10C. The new cultivars Imperial Star (IS) and Talpiot (TP) reportedly produce uniform plants from seed and a high percentage of flower heads (capitulum) the first year with minimal chilling. `Imperial Star' and TP were compared with the standard seed-propagated cultivars `Green Globe Improved' (GG) and `Grande Buerre' (GB). Plants of each cultivar were tested over a 3-year period in Blacksburg, Va., or for 1year in three other locations. Essentially all IS and GG plants flowered after receiving 1356 h of chilling at <10C. With 205 h of chilling, 83% of IS plants flowered compared to 25% for GG. No TP or GB plants flowered after receiving as much as 528 h of chilling. In the mountains of western Virginia, only IS plants established in the field in early May received sufficient chilling to produce flower heads during the late summer and early fall. June transplants did not flower because sufficient chilling was not obtained for vernalization. In warmer areas of central and eastern Virginia, fall establishment for spring harvest may yield a higher percentage of flowering plants compared to spring planting and summer harvest.

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Ariningsun P. Cinantya, Fure-Chyi Chen and Yao-Chien Alex Chang

complete vernalization on D. Sea Mary ‘Snow King’ and D. Love Memory ‘Fizz’. However, no research was found in the literature regarding the effect of long-term dark shipping on photosynthesis of nobile-type dendrobiums. Therefore, this research examined

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Genhua Niu, Royal Heins, Arthur Cameron and William Carlson

The influence of daily light integral (DLI) before vernalization and vernalization temperature and duration on growth and flower development was determined for seed-propagated perennials Aquilegia ×hybrida Sims `Remembrance', Coreopsis grandiflora Hogg ex Sweet `Sunray', and Lavandula angustifolia Mill. `Hidcote Blue'. Seedlings were grown under two DLIs (4 or 14 mol·m-2·d-l) for 5 weeks before being vernalized at -2.5, 0, 2.5, or 5 °C for 2,4,5, or 8 weeks. `Remembrance' and `Sunray' plants were vernalized in the dark, while `Hidcote Blue' plants were vernalized in light at 5 to 10 μmol·m-2·s-l for 9 hourslday. After vernalization, plants were forced under a 16-h photoperiod in the greenhouse at 20±2 °C. `Remembrance' plants flowered uniformly when vernalized at 0 to 2.5 °C for 2 weeks or longer, and flower number, plant height, time to visible bud or to flower were generally not influenced by vernalization temperature or duration. No `Sunray' plants flowered without vernalization, and only a low percentage flowered with 4-week vernalization. Compared with low DLI, a 14 mol·m-2·d-1 before vernalization delayed flowering by 7 to 20 days in `Remembrance', but there were no substantial differences in flowering characteristics of `Sunray'. `Hidcote Blue' plants were best vernalized in the light at 5 °C for 8 weeks to obtain rapid and uniform flowering and the highest number of inflorescences. Flowering and survival percentages of `Hidcote Blue' were much lower for plants at 14 mol·m-2·d-l DLI compared to 4 mol·m-2·d-1.

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Ayumi Suzuki and James D. Metzger

The effect of cool temperature treatments on flowering of Osteospermum ecklonis Norl. cv. Nairobi was evaluated. Plants vernalized at temperatures from 4 to 15 °C for 4 to 6 weeks exhibited increased flower numbers, more synchronized flower development among individual plants, and reduced forcing times. Part of the increased flower number observed in the vernalized plants could be attributed to a small increase in branch numbers from 2 to 3. However, a longer period of vernalization slowed flower development, and therefore increased overall production times. Vernalization also reduced stem growth, primarily through a reduction in the number of nodes produced by each branch.

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Genhua Niu, Royal Heins, Arthur Cameron and William Carlson

The influence of vernalization temperature and duration and devernalization treatments on subsequent growth and flower development of Campanula `Birch Hybrid' and Leucanthemum ×superbum Bergman ex J. Ingram `Snow Cap' was determined. In the vernalization experiment, plants of `Birch Hybrid' were vernalized at 0, 2.5, 5, 7.5, or 10 °C for 2, 4, 6, or 8 weeks. `Snow Cap' was vernalized at 0, 2.5, 5, or 10 °C for 2, 4, 6, or 8 weeks. In another devernalization experiment, plants of both species were moved to a high temperature (30/10 °C, day/night) growth chamber for 2 or 4 days at various times during or after the 6-week vernalization period. A 6-week vernalization was necessary to obtain 100% flowering in `Birch Hybrid', and 8 weeks of vernalization decreased time to flower by 7 to 10 days compared with 6-week vernalization. Exposure to high temperature for 2 days during or immediately after vernalization did not devernalize `Birch Hybrid' plants, while a 4-day exposure decreased flowering percentage in some treatments and delayed flowering by 7 to 10 days. There were no significant differences in flowering characteristics of `Snow Cap' plants vernalized at 0 to 5 °C for 4 to 8 weeks. A 2-week vernalization at 0, 2.5, 5, or 10 °C or 4 to 8 week vernalization at 10 °C delayed flowering by 5 to 10 days compared with those vernalized at 0 to 5 °C for 4 to 8 weeks. Exposure to high temperature for 2 d did not devernalize `Snow Cap' plants regardless of exposure times, but a 4-day exposure delayed flowering by 4 to 5 days in some treatments. Combined, the data indicate that `Birch Hybrid' has an obligate 6-week vernalization requirement and `Snow Cap' has a facultative 4-week vernalization requirement that can be fulfilled in the 0 to 10 °C range. Exposure to temperatures of 30 °C (9 h·d-1) for 12 out of 42 days did not devernalize either species but in some cases caused a small delay in time to flower.