Abstract
In estuarine wetlands, the daily periodic tidal activity has a profound effect on plant growth and reproduction. We studied the effects of tidal action on pollination and reproductive allocation of Sagittaria graminea. Results showed that the species had very different reproductive allocation in tidal and non-tidal habitats. In the tidal area, seed production was only 9.7% of that in non-tidal habitat, however, plants produced more male flowers and nearly twice the corms compared to those in non-tidal habitat. An experiment showed that the time available for effective pollination determined the pollination rate and pollen deposition in the tidal area. A control experiment suggested that low pollen deposition from low visitation frequency is not the main cause of very low seed sets or seed production in this plant in tidal habitat. The negative effects of tides (water) on pollen germination may surpass the influence of low pollen deposition from low visitation frequency. The length of time from pollen deposition to flower being submerged by water affected pollen germination rate on stigmas; more than three hours is necessary to allow pollen germination and complete fertilization to eliminate the risk of pollen grains being washed away by tidal water.
Highlights
Most perennial flowering plants combine sexual reproduction with some form of clonal reproduction [1,2]
Sexual reproduction through seeds is considered advantageous in a heterogeneous environment or with pathogens, and clonal reproduction via bulbils, corms or rhizomes is considered more successful in stable habitats [3,4]
This suggests that the plasticity of life history traits in clonal plants may be an adaptative strategy for life in different environments [2,13]
Summary
Most perennial flowering plants combine sexual reproduction with some form of clonal reproduction [1,2]. Few studies have focused on the plants living in complex habitat, for example, living in tidal habitat, where their growth and reproduction are affected by the matrix of conditions and population density, and by tidal activity. These plants experience extreme water level changes twice a day, and may be completely submerged, including during the flowering season. We addressed the following questions: 1) how does reproductive allocation differ between both reproductive patterns in the tidal and non-tidal habitats? 2) how does reproductive allocation differ between sexual and asexual reproduction in tidal and non-tidal habitats? 3) how does water affect pollen germination and stigma receptivity? is there a trade-off relationship between the two reproductive patterns?
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