Anther and gynoecium structure and development of male and female gametophytes of Koelreuteria elegans subsp. formosana (Sapindaceae): Phylogenetic implications

FERRUCCI M.S.; ZINI, L. M.; ZINI, L. M.; AVALOS A.A.; LATTAR E.C.; AVALOS A.A.; LATTAR E.C.; FERRUCCI M.S.

FLORA

ELSEVIER GMBH

Año: 2019 vol. 255 p. 98 - 109

0367-2530

Anther and gynoecium structure and embryologicalinformation in Koelreuteria and Sapindaceae as a whole remain understudied, aswell as the evolution of imperfect flowers in the latter. The aims of thisstudy were to analys in K. elegans subsp. formosana the anther and gynoeciumstructure and the development of male and female gametophytes in the two floralmorphs of putatively imperfect flowers. Standard techniques were applied for LMand SEM. Compared to the normal anther development in staminate flowers, adelayed programmed cell death of tapetum, septum and middle layers on the onsetof microspore stage result in indehiscent anthers in the functionallypistillate flowers. Orbicules are reported for the first time in Sapindaceae.Gynoecium development in functionally pistillate flowers is normal, whereas infunctionally staminate ones a pistillode with degenerated ovules at the tetradstage is formed. The pollen tube transmitting tract consists of one layer ofepithelial cells with a small lumen in the style and ovary. The anatomy of thelatter revealed an axile placentation and complete septum. Reproductivecharacters of Koelreuteria shared with other Sapindaceae taxa are a secretorybinucleate tapetum, simultaneous cytokinesis, unicellular stigmatic papillae,Polygonum type megagametophyte with ephemeral antipodals, and ovulescampylotropous, with funicular obturator and amphistomic micropyle. Imperfect flowersin the family are triggered by defective sporophytic tissues impacting on thenormal development of microspores and megaspores, disrupting embryologicalevents in staminate and pistillate organs at different developmental stages.Reconstructing ancestral character state under parsimony revealed that two ovulesper locule, absence of obturator, presence of hypostase, and binucleate tapetummay be regarded as plesiomorphic for Sapindaceae. These analyses have providedinformation on the evolution of embryological characters in the family and itsphylogenetic significance.