Aims Within inflorescences of sexually reproducing hermaphrodites,the production of ovules,fruits and seeds commonly declines from basal(early-opening)to distal(late-opening)flowers,while pol-len production remains co...Aims Within inflorescences of sexually reproducing hermaphrodites,the production of ovules,fruits and seeds commonly declines from basal(early-opening)to distal(late-opening)flowers,while pol-len production remains constant or only changes slightly,with the result that distal(late-opening)flowers become functionally male.However,few empirical studies have specifically examined whether or not changes in allocation to pollen production actually lead to changes in the number of seeds sired,a more direct measure of male fitness.in pseudogamous apomicts,fitness depends on the number of seeds produced;thus,a contrasting pattern of variation in the pollen-to-ovule(P/o)ratio within inflorescences might be expected.Methods We investigated floral sex allocation and reproductive success within racemes of Hosta ventricosa,a pseudogamous apomictic hermaphrodite possessing flowers that open acropetally.We quan-tified variations in pollen number,ovule number,the P/o ratio and fruit and seed production,from 2007 to 2011,among flowers within racemes of four populations of H.ventricosa in southwest China.Ecological causes for fruit and seed production were evaluated by observing patterns of pollen deposition,flower removal and sup-plemental pollination.Important Findings Pollen number,ovule number and the P/o ratio declined from basal-to-distal positions in all sampled populations(years).Fruit and seed production decreased distally in most populations(years).low fruit and seed set of distal flowers was not due to pollen limitation because pollen deposition never declined distally and the low fruit and seed set of distal flowers remained even after supplementary pollination was provided.The flower-removal experiment indicated that inter-fruit competition for resources among flowers was common.The low P/o ratio of distal flowers in H.ventricosa might be favored because they were unable to obtain fitness by donat-ing pollen and siring seeds on other plants.our study may help to understand the adaptive significance of sex allocation a展开更多
Inflorescences structures in context of their evolution have been conducted for 60 genera and 170 species of Celastrales （according to APG （Angiosperm Phylogeny Group） III 2009, almost 60% of genera and 15% of spec...Inflorescences structures in context of their evolution have been conducted for 60 genera and 170 species of Celastrales （according to APG （Angiosperm Phylogeny Group） III 2009, almost 60% of genera and 15% of species from this taxon of the world flora）. There are two big groups of inflorescences in Celastrales-intercalary （more often） and terminal. For many genera of Celastrales both types of inflorescences can be observed, although the frequency of their occurrence varies. There is an important difference between two types of inflorescences： character of completion of the main axis （the terminal flower present or absent）. Flower opening can be in basipetal （Celastraceae, Brexia） or acropetal （Stackhousiaceae） order. Partial inflorescence types included： simple, compound or umbrellate dichasia, spike, raceme, thyrse. Simple flowers of Parnassia are large, nested on long reproductive shoots, emerging from a rosette, with amplexicaule leaf.展开更多
基金National Natural Science Foundation of China(30870388,31370436).
文摘Aims Within inflorescences of sexually reproducing hermaphrodites,the production of ovules,fruits and seeds commonly declines from basal(early-opening)to distal(late-opening)flowers,while pol-len production remains constant or only changes slightly,with the result that distal(late-opening)flowers become functionally male.However,few empirical studies have specifically examined whether or not changes in allocation to pollen production actually lead to changes in the number of seeds sired,a more direct measure of male fitness.in pseudogamous apomicts,fitness depends on the number of seeds produced;thus,a contrasting pattern of variation in the pollen-to-ovule(P/o)ratio within inflorescences might be expected.Methods We investigated floral sex allocation and reproductive success within racemes of Hosta ventricosa,a pseudogamous apomictic hermaphrodite possessing flowers that open acropetally.We quan-tified variations in pollen number,ovule number,the P/o ratio and fruit and seed production,from 2007 to 2011,among flowers within racemes of four populations of H.ventricosa in southwest China.Ecological causes for fruit and seed production were evaluated by observing patterns of pollen deposition,flower removal and sup-plemental pollination.Important Findings Pollen number,ovule number and the P/o ratio declined from basal-to-distal positions in all sampled populations(years).Fruit and seed production decreased distally in most populations(years).low fruit and seed set of distal flowers was not due to pollen limitation because pollen deposition never declined distally and the low fruit and seed set of distal flowers remained even after supplementary pollination was provided.The flower-removal experiment indicated that inter-fruit competition for resources among flowers was common.The low P/o ratio of distal flowers in H.ventricosa might be favored because they were unable to obtain fitness by donat-ing pollen and siring seeds on other plants.our study may help to understand the adaptive significance of sex allocation a
文摘Inflorescences structures in context of their evolution have been conducted for 60 genera and 170 species of Celastrales （according to APG （Angiosperm Phylogeny Group） III 2009, almost 60% of genera and 15% of species from this taxon of the world flora）. There are two big groups of inflorescences in Celastrales-intercalary （more often） and terminal. For many genera of Celastrales both types of inflorescences can be observed, although the frequency of their occurrence varies. There is an important difference between two types of inflorescences： character of completion of the main axis （the terminal flower present or absent）. Flower opening can be in basipetal （Celastraceae, Brexia） or acropetal （Stackhousiaceae） order. Partial inflorescence types included： simple, compound or umbrellate dichasia, spike, raceme, thyrse. Simple flowers of Parnassia are large, nested on long reproductive shoots, emerging from a rosette, with amplexicaule leaf.
