Effects of temperature and photoperiod on floral bud formation of Fragaria ×ananassa Duch. ‘Taoyuan No. 3’
Date Issued
2010
Date
2010
Author(s)
Lee, Peng-Han
Abstract
Fragaria ×ananassa Duch. cv. ‘Taoyuan No. 1’and F. ×ananassa Duch. cv. ‘Taoyuan No. 3’are the main strawberry cultivar planted in Taiwan. ‘Taoyuan No. 1’ (‘Toyonoka’) was introduced from Japan, which had been accumulated a lot of studies. However, as the first cultivar that had been bred in Taiwan, there is not much information about flowering of ‘Taoyuan No. 3’. Therefore, by treating different temperature and photoperiod combinations, this study aims to figure out suitable and unsuitable conditions on floral bud formation of ‘Taoyuan No. 3’. We want to review current cultivation pattern, and discuss economical ways to adjust the harvest.
In the temperature experiments, ‘Taoyuan No. 3 was able to form and sprout floral bud under 13.5-hour-daylength with 25/20℃. This behavior is meet to the term of infra short-day strawberry. Excessively strict daylength and cool temperature are not necessary for floral bud formation. 25/20℃ treatment sprouts the inflorescences in growth chamber earlier than 20/15℃ and 15/10℃. It shows that vegetative growth state affects the ability to sprout inflorescences. Since the plants gradually went into dormancy under 20/15℃ and 15/10℃, with smaller leaf area, shorter petiole, and clustered appearance. Although root growth was relatively better in the cooler temperature, but shoot growth activity was greatly reduced, especially 15/10℃ treatment had significantly less number of leaves, leading to postpone the sprouting of inflorescences. After the treatment, eventually the total inflorescence number of 20/15℃ and 15/10℃ were not as much as 25/20℃. Even the total inflorescence number of 15/10℃ was less than the outdoor control. Therefore, it is not lower the temperature, the better to promote flower bud formation.
The treatment of increase the illumination, whether to prolong the daylength, or use night break methods, was able to promote the existing inflorescence sprout uniformly, as well as the germination of runners, the prolongation of petiole, and the extension of leaf area. Using incandescent filaments as major light source of night break, it was able to inhibit the later floral bud differentiation efficiently in the field. After the night break, plants could sprout the inflorescences about 2 months later. Thus we must consider the form of light source that involving the details about wavelength, light intensity, frequency etc., and treat processing timing with an appropriate length. In addition, the treatment of daylength, the floral bud formation could not be suppressed completely under 20/15℃ with the 16-hour-daylength. It indicates the critical short day of ‘Taoyuan No. 3’ will change with temperature.
Integrating the results of temperature and photoperiod treatments, we can propagate strawberry runner plants earlier by increasing light. The earlier we propagate the easier to improve the quality of runner plants. And then we could harvest strawberries earlier by low temperature and short day treatments (about 20/15℃, less than 13.5-hour was recommended). Also, the strawberries could be forced go into dormancy by low temperature, or inhibited the floral buds by increasing light. Considering the actual situation with the cost, it would be advantageous to delay the harvest by these ways. In the future, the harvest season of strawberry would not be definitely limited form November to April in Taiwan.
Subjects
strawberry
temperature
photoperiod
floral bud
Type
thesis
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