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Effect of Low Temperatures Applied to Seeds and Seedlings on Flowering of Lathyrus latifolius L
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Phlox paniculata Lyon ex Pursh `Eva Cullum' plants were grown under seven photoperiods following 0 or 15 weeks of 5 °C to determine the effects of photoperiod and cold treatment on flowering. Photoperiods were a 9-hour day extended with incandescent lamps to 10, 12, 13, 14, 16, or 24 hours; an additional treatment was a 9-hour day with a 4-hour night interruption (NI). Noncooled plants remained vegetative under photoperiods ≤13 hours; as the photoperiod increased from 14 to 24 hours, flowering percentage increased from 20 to 89. Flowering of noncooled plants took 73 to 93 days. Flowering percentage was 19, 50, or 100 when cooled plants were held under photoperiods of 10, 12, or ≥13 hours or NI, respectively. Time to flower in cooled plants progressively decreased from 114 to 64 days as the photoperiod increased from 10 to 24 hours. Reproductive cooled plants had at least three times more flowers, were at least 50% taller, were more vigorous, and developed seven or eight more nodes than did noncooled plants. Photoperiod had no effect on height of flowering plants.
A renewed interest in perennial garden plants occurred during the 1980s. The need for more information on how to force the plants for flower-show exhibition prompted this research. Experiments were designed that combined the effects of cold storage, daylength, and greenhouse temperature on the development of perennials. The six species and cultivars studied were categorized by the interaction of cold and daylength on their growth and flowering strategy.
The effect of photoperiod on the flowering of Lathyrus latifolius L,. was studied by using 'Pink Pearl','Red Pearl' and 'White pearl'. Plants were exposed to an 8-hr photoperiod under natural daylight. The photoperiod was extended with 60W incandescent lamps to give an 8- to 24-hrs day. Under photoperiods at and above 14-hr, flower buds were initiated; the days from bud formation to flowering were shortened in plants grown under a 16-hr photoperiod or if the night was interrupted for 2 hr beginning at midnight. Earlier sowing resulted in earlier flowering, if the plants were subjected to a 16- hr photoperiod.
Seed-propagated annual dianthuses, D. x Mikadonadeshiko, D. barbalus, D. superbus var longicalicinus, and D. japonicus, are grown for cut flowers in Japan. Investigations on the flowering behavior in responses to chilling and to day length in these dianthuses were carried out. D. x Mikadonadeshiko and D. barbatus have a cold requirement for flowering as their representative cultivars Miss Biwako and Kurokawawase, and required exposure to natural chilling till mid December for flower bud formation and stem clongation. Plants grown above 14 °C remained vegetative, exhibiting no vernalizing effect. Long day length (LD) promoted flowering and stem clongation for the suboptimally or optimally vernalized plants, LD had no effect on flower bud initiation in non-vernalized plants. Non vernalized plants initiated flower buds under natural short days during the winter. On the other hand, D. superbus var longicalicinus and D. japonicus showed no cold requirement and were day neutral for flowering. Rosetted growth in winter was caused simply by low temperature which regresses stem elongation. Dianthus spp. which require low temperature possess a juvenile phase lasting 9 weeks from seeding by which time 9 to 10 leaf pairs are produced on the main stem. Seed vernalization was ineffective for these cultivars. In the youngest plants capable of being stimulated by low temperature, only the main stem bolted, the lateral shoots which were immature during vernalization remained vegetative even after vernalization. This demonstrated that the action of cold on flowering was limited to mature shoots. The differences in cold requirement among the six D. barbatus cultivars was also observed. The ever flowering cv Kyakko required no chilling, whereas others, such as cv Arima, required 9 or more weeks of chilling at 5°C to flower.
Statice (Limonium sinuatumi Mill. =Statice sinuata L.) is one of perennials, and has a low temperature requirement for bolting and flowering. It is generally stated that in perennials and biennials the low temperature requirement is satisfied when growing plants are chilled in winter, but not when germinating seeds are chilled. In this study, the effect of chilling of germinating seeds on bolting and flowering of statice was investigated. Three cultivars, ‘Early Blue’ (early flowering), ‘Midnight Blue’ (medium flowering), and ‘Super Blue’ (late flowering) were used.
1. The statice plants sown in autumn developed flower stalks and formed flower buds in the following spring only when they experienced a certain amount of low temperature in winter.
2. The plants from seeds vernalized by chilling at 2-3°C for 30 days flowered earlier with a smaller number of foliage leaves than those from non-vernalized seeds. The vernalized plants produced a greater number of cut flowers in early crop season, that is, until the following March. Although L. sinuatum is perennial, it proves to be a plant of seed vernalization type.
3. The most effective temperature for seed vernalization was 2°C. The temperature of 5°C had less effect. Early and medium flowering cultivars were vernalized sufficiently by 2°C for 20 days, while late flowering cultivar for 40 days.
4. When the vernalized seedlings were transferred directly to high temperature conditions (constant temperature of 30°C), and grown there for 5 days or more, the vernalization effect was nullified completely. Under field conditions, daily mean temperatures higher than 25°C caused the devernalization.
フウリンソウの開花調節に関する研究(第1報)
- 植松盾次郎 石坂 宏
- 開花に及ぼす播種期
- 加温開始時期
- 日長の影響 加温程度
- 埼玉園試研報
スイートピーの開花促進について(第1報).低温および長日処理が
- 治 並河
- 井上知昭