Levels and Ultrastructural Localization of Calcium in <italic>Sinapis alba</italic> during the Floral Transition

Abstract

Atomic absorption spectrophotometry was used to determine the total amount of Ca in the leaves and apical bud of the long-day plant Sinapis alba during the floral transition induced by a single long day. The level of Ca increased in the apical bud but did not change significantly in the leaves. Ca was further localized cytochemically and measured in the meristem cells by X-ray microprobe analysis. In the meristem, the level of Ca was found to increase in all cellular compartments, but mainly in the nucleolus. The results are discussed in relation to other events that are known to occur in the meristem during the floral transition.