Abstract
'Bridal Pink' roses (Rosa hybrida L.), with their cut stems in deionized water, were held at 20°C in a glass tank in which the vapor pressure was maintained at 2.3 kPa (high vapor pressure : HVP) or 1.4 kPa (intermediate vapor pressure : IVP). Large, heavy cut roses with high initial water potentials retained water longer in HVP than in IVP. Transpiration and water uptake rates of cut roses placed in HVP were markedly lower than those in IVP. Transpiration and water uptake rates of individual organs, and defoliated, disbudded, and intact cut roses revealed that water losses from leaves and/or flower buds were closely correlated to water uptake by intact cut roses. The low water potential of flower buds, which occurred earlier and severer in IVP than in HVP, is attributed to : 1) the initial increase in petal volume ; 2) the following decrease in water uptake capacity of leaves and flower buds, and 3) competition for water between leaves and a flower bud.
