ABSTRACT
Photosynthesis and nutrition were formerly assigned a supportive role for floral induction and evocation. A most significant fact to recognize is that the stimulus coming from the leaves cannot be separated readily, by physiological means, from bulk assimilate transport. Essentially all physiological systems must be considered if one is dealing with "energetics". Regardless of species or other environmental requirements for flower initiation, it is widely observed that flower initiation has a higher-photon flux requirement than continued vegetative development. Photon flux somewhat above the compensation points is often sufficient for floral initiation, but both "qualitative" as well as "quantitative" measures of reproductive development change as light intensity increases. The hypothesis that energy flux through tissues represents an important component of the floral stimulus suggests a strategic role for nutrient diversion or resource allocation in reproductive development. In several plants, highphoton flux densities in the photosynthetically active region override and/or replace photoperiodic requirements.
