Size Dependent Sex Expression In Nomochars And Lloydia Oxycarpa (Liliaceae)

Reproduction is the key process of the species evolution. Flowering plants haveevolved into a great variety of stratergies to achieve only one primarypurpose---reproductive success. And the diversity of stratergies attracted manyevolutionary biologists. Understanding the sexual system diversity of flowering plantsand its adaptive significance has being one of the important issues of plantevolutionary biology. The unparalleled diversity of plant’ sexual systems, in nature, isthe result of the separation and combination of male and female function in time andspace. The sex expression are controlled mainly by genetic but sometimes influencedby non-genetic factors, such as resource availability. Besides, some plants also canchange their sexual expression in different stages in lifetime, to probe into whichfactors caused such sexual expression transforming have being concerned byevolutionary ecologists. In the course of the sexual system from combination toseparation, it is very rare that plants with male flowers intrude into the population ofhermaphrodite flowers though female abortion, however, such phenomenon occursfrequently in Liliaceae. The dissertation selected genus Nomocharis and speciesLloydia oxycarpa of Liliaceae to studies sexual system of Nomocharis by usingherbaria specimens, and the patterns of sexual expression of Lloydia oxycarpa in timeand space and its adaptive significance, furthermore to explore the relation of plantsize and sexual expression of the these plants, and to discuss significance of the maleflowers existing in the populations. Studied on the size-dependent sex expression inLloydia oxycarpa (Liliaceae): spatial and temporal patterns and their implications, atthe same time, we discuss the significance of that the precent of male flowers in apoputation.Firstly, By means of observing and measuring most specimens of Nomocharis (Liliaceae) from several herbaria (PE, KUN, HITBC CDBI) in China, we data of theflower sex phenotypes, flower size, plant height and altitude to determine the sexdistribution and to analyze the relationship between plant size and flower size, sexexpression of the most specimens N. aperata, N. saluenensis, N. meleagrina,N.pardanthina. We found that (1) male flowers occur in all the studied species anddifferent combinations of hermaphroditic and male flowers at plant level, resulting incomplex sex expression. Individual level, plants generally divided to malehermaphroditic and andromonoecy individuals.(2) Of four further studies species N.aperata, N. saluenensis, N. meleagrina, N.pardanthina, male plants were significantlysmaller than plants with hermaphroditic flowers in three species, besidesN.saluenensis. Not sex phenotype but plant size, which was not related to altitude, hassignificant effects on flower size of three of them.(3) The number of total flowers andhermaphroditic flowers each plant increased with plant size. However, the number ofmale flowers was independently of size. Our study suggested resources availability(i.e. plant size) determined the sex phenotypes of individual flowers. We highlightedthe occurrence of male flowers in genus Nomocharis and suggested further field studyare absolutely necessary. Furthermore, this study provides a case study to better useherbarium specimens as prerequisites for field researches of floral sexual diversity.Secondly, studied on the perennial herb Lloydia oxycarpa, we got the followingresults.(1) most of the plants produce only one flower per year, either hermaphroditicor male.(2) Among the117individuals that produce hermaphroditic flowers(hereafter perfect flowers) last year,35.9%of them changed to male plants in currentyear,34.2%remained as hermaphroditism,26.5%did not flower and3.4%produceboth male and perfect flowers.(3) Large plants tended to produce perfect flowers andsmall plants tended to only produce male ones. Among predictors that indicate plantsize, plant dry weight was the best one to predict the plants’ sex expressing (whetherproduced a perfect flower).(4) when pollen from male and perfect flowers were pollinated on perfect flowers, they performed similar in terms of seeds number perfruit.(5) perfect flowers has auto-selfing mechanism, induced high fruit set in naturalcondition. Sum these results up, we conclude that Lloydia oxycarpa is a sequentialandromoniecious species, in which the sex expression largely depended on the plantsize. The presence of male flowers in this system implied a flexibility of sexualallocation in space and time, which may increase plants mating opportunities inlifetime.