Developmental and Structural Section
Strittmatter, Lara , Negrón-Ortiz, Vivian , Hickey, R. James .
Heterochrony and its role in sex determination of cryptically dioecious Consolea (Cactaceae) staminate flowers.
OVULE development, megasporogenesis, and megagametogenesis were studied in six cryptically dioecious species of Consolea. All species showed uniform development typical for the Opuntioideae. Ovule development proceeds acropetally but is asynchronous across floral morphs. At anthesis, female morph ovules are functional and available for fertilization, whereas staminate flower ovules are senescing and incapable of being fertilized. In occasional plants of some species, staminate flowers may reach anthesis with a few functional apical ovules capable of seed formation. Such plants are described as inconstant/leaky males. Ovule fertility differences across morphs are interpreted as resulting from heterochronic ovule development and senescence, although variation in embryo sac longevity cannot be ruled out. Significantly, ovule abortion follows a common pattern and timing in staminate flowers of both male morphs in all species, thus based on this uniformity we hypothesize a common origin for the cryptically dioecious breeding system in Consolea. Furthermore, staminate expression in Consolea appears to be controlled by a common, genetically determined heterochronic ovule developmental program affecting the relative timing of ovule receptivity and flower opening. Heterochrony, in this context, represents a novel mechanism of male sex determination.[c.e.:srb]
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1 - Miami University, Department of Botany, Oxford, Ohio, 45056, USA
Presentation Type: Oral Paper:Papers for Sections
Location: 312/Bell Memorial Union
Date: Tuesday, August 1st, 2006
Time: 8:30 AM