Multiple origin of congested inflorescences in Cyperus s.s.: developmental and structural evidence

GUARISE, N. J.; VEGETTI, A.; POZNER, R.

AMERICAN JOURNAL OF BOTANY

BOTANICAL SOC AMER INC

Lugar: St. Louis; Año: 2012 vol. 99 p. 1276 - 1288

0002-9122

Premise of the study: Cyperus is taxonomically subdivided into two units, characterized either by the alternative states of the Kranz anatomy (C3 or C4) or the inflorescence shape (condensed or lax). This classification is not completely congruent, because at least one or perhaps both of these presumed character states has or have evolved several times. Considering that a multiple origin of the condensed type of inflorescence is much more probable, we focused a SEM study on the development of inflorescences in species of Cyperus with C3 and C4 anatomy. Methods: Freshly collected inflorescence of C. entrerianus Boeck., C. eragrostis Boeck., C. oxylepis Nees ex Steud. and C. incomtus were studied using stereoscopic and scanning electron microscope. Key results: Both structural and developmental results in Cyperus inflorescence aredescribed. The inflorescences of species with C3 and C4 anatomy showed differences mainly in the: (1) mature structure, (2) position of second-order branching initiation in the first developmental state of the inflorescence, (3) development and elongation of the main axis and branching development, (4) types of ramifications, (5) phyllotaxis and symmetry. Conclusions: Results support the multiple origin of congested inflorescences based especially on heterochrony in the development and elongation of the main axis and branches, branching pattern and phyllotaxis.