General Introduction to the study of flowering time
The transition from vegetative to reproductive development represents one of the major phase changes during the life cycle of a plant. This transition is initiated by both endogenous (e.g. age and developmental phase) and environmental signals. The most important environmental signals that affect flowering time are those associated with the changing seasons; temperature and photoperiod, although other external stimuli such as light quality and nutrition can also play a role in particular locations. The complex interactions of endogenous and environmental stimuli act to maximise the reproductive success of a plant, by ensuring that flowering occurs only under conditions and at the time, that are favourable for fertilisation and seed formation (Coupland, 1995b) .
Investigation of flowering time
both enhances our knowledge of plant biology and potentially provides commercial benefits in increasing the yield of crop plants. In many crop species optimal yield is dependent upon the time of flowering, and the manipulation of this trait can provide commercial advantages. For example, loss of the flowering time associated photoperiod response in maize and winter wheat varieties are beneficial traits as they increase the range in which plants are able to grow (Paulsen, 1987; Paterson, 1995; Streck et al., 2003) .
During the floral transition, major changes occur at the shoot apical meristem (SAM). The SAM is a group of stem cells formed during embryogenesis. All aerial tissues of a plant, such as stems, leaves and flowers are derived from the SAM (Weigel and Jurgens, 2002) . The floral transition can be considered as a reprogramming of the meristem so that it forms flowers and reproductive organs rather than vegetative organs such as leaves (Howell, 1998).
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