Effects Of Pestle And Plant Phenotype On Behavior And Reproductive Success

Reproduction is a fundamental feature of all known life and one of key events in plant life history. Plant sexual reproduction is the process by which plants generate new individuals, or offspring(fruits and seeds) by the fusion of gametes. Q uantity and quality of fruits and seeds(reproductive success) determined directly maintenance of populations and survival of species. Reproductive success of flowering plants was affected by many biological and abiological factors. In the present study, effects of nectar robbing and phenotypic traits on reproductive success in a facultative selfing annual, Incarvillea sinensis var. sinensis, were discussed by manipulating experiments and field investigation.Nectar robbing is very common among flowering plants; nectar robbers are some flower visitors that remove floral nectar by biting or piercing holes in flowers, without contacting the anthers and/or stigma. Some plants benefit from self- fertilization for reproductive assurance, and thus might experience little effect of nectar robbing on fruit production. In facultative selfing plants which involve both outcrossing by pollinators and se lfing when pollinators are scarce or not available, nectar robbing is expected to have no influence on fruit set, but may affect pollinator- mediated fruit set. In order to test this prediction, we manipulated robbing(open to be robbed or excluding nectar robbers by caging flowers) in an annual facultative selfing plant Invarvillea sinensis and quantified fruit set, seed number and weight per fruit. Pollinator- mediated fruit set was evaluated on the basis of the closure of stigmatic lobes, which generally occurs after pollinator visiting. The height of flowers was measured to test whether nectar robbers have a visiting preference for specific floral traits. Bumble bees, workers of Bombus patagiatus, were the primary pollinators of I. sinensis and some of them were also nectar robbers. Robbers stole nectar from both open flowers and flower buds. Averaged frequency of nectar robbing was 20.24%, ranging from 0 to 51.43%. Experiments excluding nectar robbers showed that nectar robbing did not have significant effects on proportion of fruit set, seed number per fruit and seed mass per fruit. However, the proportion of stigmatic lobes closed was significantly higher in robbed flowers than in unrobbed flowers, suggesting that robbing influences pollinator- mediated fruit set. Height of robbed flowers was significantly higher than that of unrobbed flowers, suggesting that nectar robbers prefer robbing from larger and higher flowers. These results provide insight into the effects of nectar robbing on the reproduction of plants.In order to estimate effects of flowering phenological and floral traits on reproductive success, we observed flowering phenology and measured phenotypic traits and fruit and seed production of I. sinensis. The results showed that the flowering period of the studied population lasted from late June to early September, about 80 days, while individual flowering duration sustained 22 days(ranging from 1–55 days), with a peak flowering for July 30. Univariate linear regression showed flowering time was significantly negatively correlated with reproductive success(measured by fruit number, seed number and seed weight), indicating early flowering plants were favoured; whereas plant size(plant height and flower number per plant) and flower size(tube length) were significantly positively correlated with reproductive success, indicating higher plants with more flowers had reproductive advantages. Importantly, among all five traits, only flower size(tube length) was significantly positively correlated w ith pollinator visitation rates and proportion of pollinator- mediated fruit and seed production, indicating the potential reason for this facultative selfing plant produces showy floral display. These results provided insights into understanding the adaptive(reproductive) strategy of this facultative selfing plant in harsh environments(half desert).