Effects of floral sexual investment and dichogamy on floral longevity

Aims Floral longevity,the duration that a flower remains open and func-tional,varies greatly among species.Variation in floral longevity has been considered to be optimal strategy for resource allocation under different ecological conditions,mainly determined by the rates of pollination and cost of flower maintenance.However,it is unclear whether an intrinsic factor,floral sexual investment,con-strains evolution of floral longevity.The theoretical model also pre-dicts that dichogamy favors long-lived flowers,but empirical studies to test this prediction remain unexplored.Methods To examine the effect of floral sexual investment on floral longevity,we measured flower size together with pollen and ovule production in 37 sympatric flowering plants in a natural community.The duration of the female and male phase in 21 protandrous species and floral longevity of the other 16 adichogamous species were documented in the field.Important Findings Floral longevity varied from 1 day to 15 days,while pollen num-ber per flower varied from 643 to 710880 and ovule number per flower from 1 to 426 in the 37 species.Flower size was corre-lated with pollen production as well as ovule production.Floral longevity was positively related to pollen production but not to ovule production.Consistent with the prediction that dichogamy favors long-lived flowers,we found the floral longevity of pro-tandrous species was significantly longer than that of adichoga-mous species.in the protandrous species,pollen production per flower was observed to be positively related to male duration,while ovule production was not related to female duration.our analyses of variation in floral longevity and sexual investment among different species suggest that the floral sexual investment could be an intrinsic factor contributing to the selected floral longevity,particularly the male phase,and that high pollen pro-duction could potentially increase pollen removal,i.e.male pro-ductive success.

Convergent relationships between flower economics and hydraulic traits across aquatic and terrestrial herbaceous plants

Maintaining open flowers is critical for successful pollination and depends on long-term water and carbon balance.Yet the relationship between how flower hydraulic traits are coordinated in different habitats is poorly understood.Here,we hypothesize that the coordination and trade-offs between floral hydraulics and economics traits are independent of environmental conditions.To test this hypothesis,we investigated a total of 27 flower economics and hydraulic traits in six aquatic and six terrestrial herbaceous species grown in a tropical botanical garden.We found that although there were a few significant differences,most flower hydraulics and economics traits did not differ significantly between aquatic and terrestrial herbaceous plants.Both flower mass per area and floral longevity were significantly positively correlated with the time required for drying full-hydrated flowers to 70%relative water content.Flower dry matter content was strongly and positively related to drought tolerance of the flowers as indicated by flower water potential at the turgor loss point.In addition,there was a trade-off between hydraulic efficiency and the construction cost of a flower across species.Our results show that flowers of aquatic and terrestrial plants follow the same economics spectrum pattern.These results suggest a convergent flower economics design across terrestrial and aquatic plants,providing new insights into the mechanisms by which floral organs adapt to aquatic and terrestrial habitats.