The carbon balance of flowers of Diplacus aurantiacus (Scrophulariaceae)

Measurements and modeling of photosynthesis, respiration and growth in flowers of Diplacus aurantiacus, a semidrought-deciduous shrub, indicate that they can provide 18%-25% of their total carbon requirements through photosynthesis of flower parts. Daily photosynthetic carbon fixation exceeds daily respiratory CO₂ loss during most non-fruiting stages of development. However, this carbon gain fails to meet the requirements for new biomass construction during bud growth and corolla expansion. During fruiting stages, insufficient carbon is fixed to fully supply either respiration or growth. The calyx performs most of the flower's photosynthesis throughout the life of the flower. However, during stages of fruit development, the contribution of the ovary to flower photosynthesis may equal that of the calyx.