Meeting Abstract
Plants with indeterminate inflorescences require sustained rates of photosynthesis to support continued flower production and thus increased fitness. In dioecious species, flower size and number tradeoffs may also favor a greater number of smaller flowers in males to increase overall pollen production, but genes expressed during development affect both leaves and floral organs, resulting in a potential conflict between photosynthetic rate and flower number. We investigated the quantitative genetic and functional architecture among leaf, physiological, and flower traits in Silene latifolia in an effort to determine whether functional tradeoffs reflect constraint in underlying genetic correlations, and whether the net functional relationship between performance variables is similar to the tradeoff between performance traits. We grew 595 plants of known pedigree in a greenhouse and measured flower size and number, leaf size and thickness, photosynthetic rate, and transpiration. We found a weak negative functional correlation between photosynthetic rate and flower number in both sexes, and a stronger negative genetic correlation between these performance traits in males but not females. Thicker leaves resulted in increased photosynthetic rate but reduced flower number in performance gradients in males, and the underlying genetic correlations for these traits mirrored this pattern. However, the net functional relationship between performance variables was close to 0. Integration among the measured traits may mitigate the constraints of this functional tradeoff.
