Effect of Temperature and Light on Floral Initiation of Broccoli
Date Issued
2015
Date
2015
Author(s)
Chang, Ya-Ching
Abstract
The cool and dry weather in winter of southern Taiwan provides a good condition for broccoli (Brassica oleracea L. var. italica) seed production. To broaden the seed market to temperate countries, it’s necessary to introduce some cold-tolerance germplasm into the breeding program. However, such plant materials often accompany the character of late and/or very late maturity having strong cold requirement for flowering. Therefore, flower inducing in late and/or very late maturity cultivars or varieties become an important issue in southern Taiwan. The objective of this study is to evaluate the effect of seedling photoperiod and light quality on the floral initiation of broccoli. The vernalization requirement of early maturity ‘TSS AVRDC No.2’ and medium maturity ‘B75’ was significantly higher with seedling nursing photoperiod 14/10 h than with 12/12 h. Therefore, the nursing photoperiod 14/10 h was choosing for following studies. Ten days of vernalization treatment (15/10oC) significantly shortened the days from sowing to apex transition (DTAT) and the shorten effect was more significant as temperature increased. Without vernalization treatment, the delay of DTAT increased as temperature increased in ‘TSS AVRDC No.2’ and ‘B75’ tended to remain in vegetative growth till the end of experiment in higher temperature. The DTAT also shortened while grown under HR (High red light proportion light source, R/FR=13.0, red light proportion 42%) than LR (Low red light proportion light source, R/FR=2.6, red light proportion 34%) light source, and the shorten effect was more significant while ambient temperature elevated. In ‘TSS AVRDC No.2’, the vernalization, light quality and obligate temperature were interacting between each other. The DTAT shorten effect (DSE) of HR under vernalization (DSE-HRV) and the DSE of vernalization under HR (DSE-VHR) was similar. A possible explanation of the similarity was that these two factors have interaction and might be replaced between each other. Therefore, we concluded that the controlling of broccoli flowering can be more promising if a combination treatment of vernalization and HR light quality can be applied. However, the effect on cultivars of late and very late maturity should be tested.
Subjects
Vernalization
Light quality
Photoperiod
Type
thesis
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