Developmental evidence for stamen number reductionin populations of Hibbertia fasciculata (Dilleniaceae)

Discrete Australian populations of Hibbertia fasciculata R. Br. ex DC. differ in stamen number per flower: three to four in isolated, northeastern coastal populations in New South Wales vs. 10–12 in southeastern Australian populations. In all populations, the stamen bases are attached to three broad flat pedestals regardless of number of stamens present. In certain other Hibbertia species, each pedestal results from initiation via a common stamen primordium that usually produces at least 3–4 stamens per common primordium. In H. fasciculata, each of the three pedestals is associated with three to four stamens in flowers of southeastern populations, but with only one stamen per pedestal in the coastal populations of New South Wales. Because the pedestals (remnants of common primordia) have persisted, the evolutionary trend probably has been one of reduction in stamen number. General observations and comparative studies suggest that this population-based reduction series in stamen number (as well as reduced plant size and flower size) reflects a locally successful trend towards smaller organs throughout the plant body together with a shift in pollination ecology.     

The diversity of stamen structures and dehiscence patterns among Magnoliidae

ENDRESS, P. K. & HUFFORD, L. D., 1989. The diversity of stamen structures and dehiscence patterns among Magnoliidae . Structure of stamens, particularly the patterns of anther dehiscence were studied over a wide range of families of the Magnoliidae with emphasis on the Magnoliales and Laurales as the most conservative orders of the angiosperms. Valvate dehiscence by proximal and distal stomial bifurcation was found (in addition to the already known Sarcandra and Polyalthia) for the first time in Degeneriaceae, Himantandraceae, Eupomatiaceae, in some additional Annonaceae, and in Peumus of the Monimioideae sensu lata. At least proximal bifurcations of the stomia occur in some Magnoliaceae and Ranunculaceae. An endothecial-like connective hypodermis was found (in addition to the already known Chloranthaceae and Magnoliaceae) in some Annonaceae, in Pseudowintera (Winteraceae), and in Thalictrum (Ranunculaceae). In the Annonaceae an endothecial-like connective hypodermis is partly correlated with valvate dehiscence by stomial bifurcations (as in many Hamamelididae). However, in many Magnoliidae stamens with this valvate pattern the anther is massive, especially in ‘laminar’ stamens, and the counterforce to the opening valves is therefore provided on the morphological and not on the histological level. Concomitant with valvate dehiscence by circular or elliptic flaps in the Laurales is often structural and functional dissocation of the two pollen sacs of a thcca, which is expressed by: (1) independent opening of each pollen sac, (2) lack of disruption of the interlocular zone of a theca, (3) frequent occurrence of asymmetry of the two pollen sacs of the theca, (4) frequent loss of one pollen sac per theca. In Berberidaceae with similar flaps asymmetry of the two pollen sacs of a theca is also common. These finds, together with the detection by paleobotanists of valvate anthers from the Lower Cretaceous, point to the probability that valvate anthers were more common in primitive angiosperms than previously thought.     

Systematic chemical analysis of flavonoids in the Nelumbinis stamen

The stamen of lotus, known as Nelumbinis stamen, has been used as the folk medicine and functional food for a long time, which showed good activities of anti-ulcer, anti-thrombosis, analgesic, anti-diarrhea, strengthen uterine contraction. The bioactivities of Nelumbinis stamen were attributed to the existence of flavonoids, its characteristic chemical constituents. A reliable method for comprehensive chemical analysis of flavonoids in Nelumbinis stamen by HPLC–DAD–MS was developed for the first time. The extraction protocol of flavonoids from Nelumbinis stamen was optimized by an orthogonal design. The chromatographic conditions were optimized, which exhibited similar level than that of the UHPLC platform allowing target compound identification in a shorter time with little solvent consumption. Moreover, similarity analysis, hierarchical clustering analysis and principal components analysis were successfully applied to demonstrate the variability of these Nelumbinis stamen samples.