Determining the Water Dynamics of Flowering Using Miniature Sap Flow Sensors

Angiosperms dominate almost every ecosystem globally, and for the vast majority, flowering is vital to successful reproduction, yet little work has characterized the dynamics of water use during flowering and its impacts on the reproductive biology of wild plants. Here we demonstrate a new implementation of the heat ratio method to measure sap flow dynamics of leaves and flowers. We employed this new method to estimate the water requirements of flowering in four tropical species: the understory tree, Hybanthus prunifolius (Violaceae), the liana Clitoria javitensis (Fabaceae), the canopy tree Cordia alliodora (Boraginaceae), the shrub Annona acuminata (Annonaceae). Our results suggest that there is substantial diversity in the timing and magnitude of water transport to flowers. Some species show almost no water flow to flowers, while flowers of other species show sap velocities approximately 30-50% that of nearby leaves. This variability is likely related to the pathway and mechanism of water transport to flowers, to floral morphology, and to evaporative demand in the floral microenvironment.