Dioecy and wind pollination in Pernettya rigida (Ericaceae) of the Juan Fernández Islands

Abstract

Reched June 1999; accepkd for publication 3ub I999Pemet&a r g & is endemic to the Juan Fernhndez archipelago. Although all flowers are complete, with seemingly fertile stamens and pistils, differences in fruit production and detailed field, anatomical, and morphological studies indicate they are functionally unisexual, and the species is consequently dioecious. A comparison of 15 features demonstrated sigdicant differences between the sexes. The populational sex ratio is 1 : 1. Nectaries located between the filaments produce small amounts of floral nectar with similar sugar composition in both sexes. There are ~= 3 3 , 3 5 7 (or ~=133,429) pollen tetrads (or pollen grains)/male flower and X = 109 ovules/female flower. No tetrads in either hand self-pollinated or open pollinated male flowers showed any pollen germination. Tetrads on open-and handpollinated female flowers germinate. Female flowers do not show autogamy or apomixis. During more than 80 hours of field observation, we recorded only seven floral visitors (representing three insect species).

Protogynous, pollen limitation and low seed production reasoned for the dieback of Spartina anglica in coastal China

“…Pollen viability at the shedding stage was estimated using a microscope [15,36]. The pollens of ten inflorescences (n = 10) from field and greenhouse experiments were measured in July and May, respectively, when the pollens began shedding.…”

Heterochrony and its role in sex determination of cryptically dioecious Consolea (Cactaceae) staminate flowers

“…spp. and Pernettya rigida D.C. show a well-developed gynoecium that is completely empty (Motley & Carr, 1998;Anderson et al, 2000). When well-developed ovules are present in functionally staminate flowers, the reason for their nonfunctionality may be related to abnormal callose deposition, as in Rauvolfia sellowii Müll.…”

Subdioecy in Consolea spinosissima (Cactaceae): breeding system and embryological studies

“…The phylogenetic distribution of this mating system provides evidence that dioecy arose independently many times from hermaphroditic lineages (Anderson et al, 2000). Despite its broad taxonomic range, dioecy is relatively rare, being found in only 4% of all angiosperm species (Yampolsky and Yampolsky, 1922).…”