Stamen increase

In belladonna plants deuteration had a drastic effect on flower development (25). The number of calyx lobes, corolla lobes, and stamens, while invariably 5 in control flowers, increased to as many as 9 or 10 in plants grown in 70 percent D2O medium. Abnormally shaped berries formed in plants grown in heavy water. The extent of malformation depended,on the D2O content of the medium and how late in the life cycle of the plant that the berry formed. The shapes ranged from pear-shaped to dumbbell-shaped to cylindrical. The misshapened berries resulted from the tenacity with which the corolla remained attached to the ripening berry in deuterated plants. As the berry enlarged, a constriction developed where the corolla was attached to the berry. The size and number of seeds were severely reduced in deuterated berries with only a few rudimentary seeds apparent in the 70 percent berries. 

Livia Wanntorp and co-workers (Chapter 9) study the variation in merism in Conostegia (Melastomataceae) and explore how changes in petal and stamen numbers correlate with increases in carpel numbers. 

The contribution of Gerhard Prenner (Chapter 11) studies a special case of high stamen and carpel numbers in Acacia celastrifolia and how this appears to be a concerted increase, linked with specific pollination strategies. 

Based on our data set, there are no unequivocal changes in floral characters on the line from the base of the mesangiosperms to the common ancestor of Canellales and Piperales. If mesangiosperms originally had a trimerous androe-cium, as inferred when phyllotaxis and merism are treated as separate characters, there was an increase in the number of stamens per whorl in Canellales (i.e. the androecium became polymerous), followed by connation of the stamens into... 

Increase in stamen number appears to have occurred in different ways and perhaps in response to different factors in different groups of palms. 

This occurs only in species where the number of stamens is higher than ten. The number of stamens varies considerably due to a secondary increase of the androe-cium. We observed that the increase of the stamens in the species of Conostegia examined could at least follow two different staminal developmental patterns ... 

In flowers of Conostegia rhodopetala, C. off. montana, C. xalapensis and Clidemia octona, the secondary increase of the stamens can also occur by a clear process of dedoublement, a phenomenon implying that each or most of the stamens in a flower splits into two parts. Paired stamens are closely adjacent, occasionally laterally fused and occur in antepetalous positions. 

In flowers with a secondary increase of the androecium, the respective positions of petals, stamens and carpels tend to be less clear and any relationship between parts seems to be lost. In Conostegia macrantha (Fig 9.3E), carpels tend to be opposite the alternipetalous stamens, but the different numbers of stamens and carpels blur any general pattern. Within Conostegia the number of carpels varies between 4 and 22 (25 according to Schnell, 1996). In most of the species the number of carpels (nearly) equals the number of petals, although there are some species, such as C. macrantha, which have many more carpels than petals. 

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