シュッコンカスミソウの低温要求性に関する研究
スポンサーリンク
概要
- 論文の詳細を見る
Gypsophisa has recently received considerable attention as a commercially produced cut flower in Japan, as well as in European countries and United State. However, non-uniformity of growth and failure to bloom have been serious problems in early forcing from autumn to winter. Although long-day is considered the primary environmental factor required to induce flowering, plants grow vigorously after exposure to winter chilling. This study was commenced to examine the difference in chilling requirement among 'Bristol Fairy' and how temperature govern the growth and flowering of gypsophila. 1. Flower bud initiation and development of Gypsophila paniculata L. 'Bristol Fairy' grown under field conditions were observed by means of a scanning electron microscope. In plants which were exposed to a sufficient amount of chilling during the previous winter, flower bud initiation took place when the average stem length was 18cm. Subsequently, differentiation of sepals and petals occurred. Stamen primordia in the terminal floret were initiated around 30 April. Between 5 and 10 May, when shoots were in the visible bud stage, the pistil primordium appeared in the terminal floret. Following differentiation of floral organs, the style elongated and the petaloid stamens appeared. The petals and petaloid stamens expanded in succession which led to the dehiscing of the sepals, resulting in anthesis of the terminal floret on 30 May. In plants which were exposed to a limited amount of chilling, the flower bud initiation was delayed. It did not take place in buds located from middle to basal nodes on the main stem. However, after the apical meristem enlarged, differentiation and development of the floral organs in the terminal floret progressed at the same rate irrespective of the amount of exposure to previous chilling. 2. Twenty eight plants of 'Bristol Fairy' which showed different growth and flowering behavior, were selected. The influences of exposure to chilling on growth and flowering of these vegetative lines and cultivars were compared, by exposing them to different durations of natural chilling in winter. Flowering responses widely varied among selections. Some lines, such as line 11 and 20, hardly bloomed even when plants were exposed to natural chilling until 1 February. Each vegetative line responded to chilling similarly throughout three years. The non-uniformity of growth and failure to bloom in early forcing seem to be the result of these differences in chilling requirements among vegetive lines. The growth characteristics without exposure to previous chilling also varied among vegetative lines. The chilling requirements of cultivars became less in the following order, > 'Diamond' and 'Bristol Fairy' > 'Flamingo' and 'Red Sea'. From the results of statistical analysis, it was evaluated that range from 0℃ to 10℃ is most effective as chilling and high temperature above 15℃ nullifies chilling effects. Consequently, the differince in durations of chilling exposure required for flowering under natural conditions may be strongly influenced not only by the amount of chilling but also by the amount of high temperature above 15℃ to which plants were exposed during day time. 3. Application of 300 ppm 6-benzylaminopurine (BA) promoted flower initiation and advanced blooming by about half a month in a heated plastic house under long-day conditions in 'Bristol Fairy' line 04, 08 and 13, but not in line 20. BA treatment also promoted flowering in line 08 and 13 even when grown in an unheated plastic house under natural daylength. However, this promotive effect of BA was not obvious when it was applied to the plants which were exposed to a sufficient chilling. BA seems to mostly substitute for chilling for the induction of flowering, and consequently plants treated with BA overcame unfavorable growing conditions. Gibberellic acid (GA_3) did not promote flower initiation in any lines. 4. To determine effects of high temperature on rosette formation and flower malformation, plants at different developmental stages were exposed to high temperatures after exposure to previous winter chilling. Initial exposure of vegetative shoots to high temperature (30℃ from 600 to 1800 and 25℃ at night) from 31 March to 10 April resulted in resette formation in those plants which require long durations of winter chilling such as 'Perfecta' and 'Bristol Fairy' line 20. Rosette formation occurred even when these plants were grown under optimum conditions. About 50% of the 'Diamond' and 'Bristol Fdairy' line 03 shoots formed resettes after exposure to the high temperature; these cultivars require a relatively lengthy exposure to winter chilling to satisfy their rest requirements. Conversely, 'Flamingo', 'Red Sea' and 'Bristol Fairy' line 08 which require a little chilling did not form rosettes but bloomed. Exposure to the high temperature immediately after the onset of flower bud initiation resulted in shorter flower stalks and fewer nodes with inflorescences on the main stem. Flower malformation was induced when shoots were exposed to the high temperature around 30 April when stamen initiation in the terminal floret was occurring. Anatomical studies revealed that the flower malformation was related to an abnormally extended period of transformation of stamens to petaloid structures prior to anthesis. Meristematic activities of the stamen primordia were prolonged after an exposure to high temperature at this stage of floret formation. Consequently, cluster-like petaloid stamens formed around the meristematic tissue that resulted in increased number of petals. Malformed flowers occurred more frequently in cultivars and vegetative lines which require longer durations of chiling. These results show that the exposure to high temperature neutralizes the chilling effects for reproductive growth and induces the formation of rosette. Both rosettes and malformed flowers may be expressions of the transition from the reproductive growth (anther) to a vegetative growth (petal) at the meristematic level, as a result of exposure to high temperature. Prolonged vegetative growth was observed when plants were exposed to chilling in combination with high day temperature at 15℃ or 25℃. Therefore, high temperature above 15℃ during chilling exposure also nullifies its promotive effects for flowering. 5. Four vegetative lines of 'Bristol Fairy' were grown under natural conditions in autumn. Shoots of line 09 and 13 initiated flower bud. In contrast, shoots of line 04 and 20 formed resette. However, rosette formation was not accompanied by decreased new root growth. Line 13 and 20 were grafted on their own root and reciprocally, produced the scion/stock combinations of 13/13, 13/20, 20/13 and 20/20. The grafted plants were then exposed to chilling which was sufficient to promote flowering for ungrafted line 13 rooted cuttings but insufficient for those of line 20. The onset of shoot elongation was delayed and the percentage of blooming plants was decreased on 13/20, 20/13 and 20/20 graft combinations. Shoot elongation of 13/20 combinations was delayed nearly 6 weeks as compared with that of 13/13 plants. Plants of line 04 showed rapid growth after their shoot and root were chilled. All the plants with their shoot unchilled and root chilled bloomed during the chilling treatment. In this case, removal of the flower stalks after the chilling treatment resulted in rapid growth and high percentage of blooming in lateral shoots which had not been chilled. This suggests that the chilling effects were translocated from root to shoot and retained in basal nodes. These results indicate that the chilling roots have the great influence on shoot growth and consequent flowering in gypsophila. 6. In order to construct a forcing schedule with three floral flushes, effects of chilling exposure and BA application on the flowering were investigated, using 'Red Sea' and 'Bristol Fairy' selections. For the 1st flush in November, foliar spray of 100-300 ppm BA was effective for advancing flowering time in 'Bristol Fairy'. Although the percentage of blooming in line 13 gradually decreased as the final pinching became later, plants treated with BA before 30 September showed 100% blooming. However earlier flowering accompanied the occurrence of flower malformation. Cut flowers obtained from BA applied plants were shorter and less in volume. Exposure of rooted cuttings to chilling at 2℃ for 40 or 55 days before planting reduced days to bloom and improved cut flower quality. When rooted cuttings previously exposed to chiling for 40 days were planted on 15 September and applied 100 ppm BA on 30 September, cut flowers with sufficient length and volume were harvested in the mid to late November. Duration of exposure to natural chilling for more than 50 days (800 hr below 10℃) after the lst flush was required for vigorous shoot growth in line 09. Application of 300 ppm BA in combination with natural chilling also promoted the flowering. The 2 nd flush was harvested in mid April. The 3 rd flush was harvested from late June to early July, being 1 month later than natural flowering time. On the basis of these data, a forcing schedule with three floral flushes per one year was constructed by selecting vegetative lines with less chilling requirements, such as 'Red Sea' and 'Bristol Fairy' line 09 and 13, and by applying previous chilling exposure and foliar spray of BA.
- 大阪府立大学の論文
- 1993-03-31