
Abstract The floral nectary of the foxglove (Digitalis purpureaL.), located at the base of the ovary, was examined by: scanning electron microscopy; quantitative bright-field microscopy via computer-aided 3-D reconstruction from serial sections; morphometric procedures; transmission electron microscopy and measurement of nectar efflux under different experimental conditions. Time-lapse video recording via a microscope with incident light clearly showed that the nectar escaped from the apertures of modified stomata. The volume flux via individual stomatal apertures was 0.31±0.1 nl min-1; therefore only a fraction of the total number of stomata per nectary (115±8) would be sufficient to discharge the amount of nectar reported in previous publications. The stomatal apertures are continuous with intercellular spaces traversing the small-celled nectariferous tissue. The latter is vascularized only by phloem, whose termini consists of rows of slender cells. These sieve-like cells are surrounded by more or less isodiametrical sheath cells with dimensions similar to the secretory cells. Details of nectary functioning are based on enhanced structural information, complementary data on nectar discharge after experimental manipulations and the nature of the effluence.
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