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atures near optimal for vegetative growth. This lack of heat tolerance restricts broccoli production to maritime High temperature causes unevenly-sized flower buds climates lacking extreme temperatures. The alteration in on broccoli inflorescences. This deformity limits pro- the inflorescence structure has been described primarily duction of broccoli to areas where summer temper- in terms of the marketability of the commercial product atures rarely exceed 30°C. The stage of development (Heather et al., 1992). sensitive to heat was determined by exposing plants Inflorescence development in broccoli involves prolifof ‘Galaxy’ broccoli at varying developmental stages eration of the meristem to make a highly ramified inflorto 35°C day temperature for 1 week, and subsequently escence. Developmental arrest occurs during floral bud analysing the head structure. During the high temper- development and internode elongation (Carr and Irish, ature exposure, the development of certain flower 1997). In contrast, cauliflower has greater meristem prolifbuds was arrested. There was no corresponding ces- eration and is arrested earlier, after the first florallysation of bud initiation at the apex. No injury resulted determined gene expression but before any bud developif heat was applied before the reproductive induction, ment (Carr and Irish, 1997). Exposure to high tempernor was there injury to differentiated flower buds. ature during a time window several weeks before harvest |
