Dédoublement revisited: towards a renewed interpretation of the androecium of the Magnoliophytina

Abstract

DCdoublement revisited: towards a renewed interpretation of the androecium of the Magnoliophytina. There has been much controversy about didoublement in the past. DCdoublement was originally described as a process of doubling of a (stamen) prirnordium up to two equivalent primordia. Later, i t was extended to explain occurrences of higher stamen numbers, even without evidence of a division. Different interpretations from both opponents and protagonists of dkdoublement are critically examined and concepts such as negative, positive, serial, lateral and congenital dkdoublement are discussed. Some case studies are presented to evaluate the concept of dkdoublement. Paired stamens are not necessarily the result of splitting; they can also arise by a spatial shift, connected with the cyclization of a spiral flower. Two smaller stamen primordia replacing a stamen without visible splitting and a primordium dividing ontogenetically into a stamen pair are essentially similar. The morphological difference between both configurations can be explained by the principle of variable proportions. Radial dkdoublement and stamen-petal complexes are examples of meristem fusion (absorption) and may be defined by the term 'negative dkdoublement' in the sense of Celakovsky (1894). A distinction between 'dkdoublement' sensu stl-icto and 'polygenesis' is proposed.

Evolutionary diversification of the flowers in angiosperms

“…In basal eudicots, they characterize Papaveraceae, e.g., Eschscholzia (androecium) ( Endress, 1987a ); Berberidaceae, Podophyllum , (androecium) ( deMaggio and Wilson, 1986 ;Ronse De Craene, 2010 ); Ranunculaceae (androecium) ( Sch ö ffel, 1932 ); Buxaceae (androecium) ( von Balthazar and Endress, 2002a , b); and Tetracentron (gynoecium) ( Endress, 1986a ;Chen et al, 2007 ). In core eudicots, they have a scattered occurrence ( Ronse Decraene and Smets, 1993aSmets, , b , 1996Smets, , 1998. Examples are Brassicaceae and Cleomaceae (perianth and androecium) ( Endress, 1992 ), Apodanthaceae (perianth) ( Blarer et al, 2004 ) or Fouquieriaceae (androecium) ( Sch ö nenberger, 2009 ).…”

The floral development ofNeurada procumbensL. (Neuradaceae)

“…As for stamens, paired 0 1996 Royal Botanical Society of The Netherlands, Acta Bot. Need 45, [229][230][231][232][233][234][235][236][237][238][239][240][241] structures may arise by the division of a complex primordium, or they may arise independently and be at the same time connected (see Ronse Decraene & Smets 1993). In Grielum there are 5-10 carpels (Focke 1894).…”