Flower closure in the field bindweed (Convolvulus arvensis): a field test of the pollination hypothesis

Although the behavioral plasticity of flower traits has received considerable attention, its adaptive value is not thoroughly understood. We experimentally examined flower opening/closure in field bindweed (Convolvulus arvensis), a species with short flower persistence (1 day) in which adaptive responses to pollination were not previously expected. In line with the pollination hypothesis we suggested that flower exposure in this species should respond to pollination. More specifically, we predicted that flower closure in the pollinated flowers would be quicker than that in unpollinated flowers. As predicted, the unpollinated flowers were open for a longer time than the pollinated flowers. There was no difference, however, between the self- and cross-pollinated flowers in terms of flower longevity. There was an inverse relationship between flower longevity and fertility, which also suggests that pollination leads to reduced flower longevity. Collectively, our results suggest that field bindweed flowers respond to pollination adaptively, because prolonged flower longevity may increase the likelihood of successful pollination and flower closure reduces energy spent on flower maintenance and/or intraspecific competition with genetically familiar flowers. The behavioral plasticity of flower closure does not seem to be restricted only to plants with high flower longevity.