Competitive Water Relations between Leaves and Flower Bud during Transport of Cut Roses

Abstract

Cut roses (Rosa hybrida L. 'Bridal Pink') were subjected to wet- or dry-transport at 5°C for 24 to 72 hr and the resulting competition for water between leaves and a flower bud was studied. Water loss during the dry-transport was closely related to the decrease in water potential. Bent neck was observed in 50% of cut flowers when petal and leaf water potentials became -0.9 and -1.2 MPa, respectively. Stomatal conductance decreased throughout the 72 hr dry-transport period. Rehydration did not restore completely the conductance. The hydraulic conductance of basal stem segments decreased with an increase in the duration of dry- and wet-transport, but that of the upper segments decreased only in the dry-transport. No significant difference existed between conductance measured acropetally and basipetally in the uppermost stem segment. Consequently, the water potential of leaves was higher than that of petals, which suggests that when a strong competition for water develops between these two organs during the dry-transport period, water flows from the petals to the leaves. A comparison between water loss from the individual organs and that of the intact cut flowers revealed that 19% of the initial fresh weight was lost from the intact cut flowers after 72 hr dry-transport; 1/3 of the water lost was translocated to the leaves from the flower bud.