Developmental events associated with the critical stage for sex determination in wild-rice florets

The developmental events of florets and a critical stage for sex determinat ion in two wild-rice populations (Zizania palustris cv. Franklin and Zizani a palustris cv. K-2Pi) have been identified. Formation of bisexual florets precedes the development of both male and female florets. Developmental ind icators, established by measuring the length of florets and panicles, indic ate that the critical stage for sex determination occurs when floret and pa nicle lengths are 1-2 mm and 3 cm., respectively. The stage of floret devel opment at which sex determination occurs is the same in the two investigate d wild-rice populations. Organ suppression in bisexual florets is an essent ial step for sex determination during the formation of unisexual florets. H istological examination of suppressed stamens or pistils in unisexual flore ts of wild-rice indicates that cell death does not occur during sex determi nation. In addition, the length of anthers and pistils in bisexual florets indicates that floral development in the transition zone is normal when com pared with the male, florets in the male spikelets and female florets in th e female spikelets.