Flowers with solid or woody stems will survive longer when damaged than other stems. The vascular bundles, which serve much the same purpose as blood vessels in people, exist throughout these stems. When one section of the stem is damaged, the intact vascular bundles can still take food and water to the flower. If the injury is small, the plant may still be able to keep the flower alive for its normal lifecycle. If most of the stem is damaged, it may still take days for the flower to run out of food and water, giving the gardener time to try to repair the damage.
Soft stems may look larger than solid stems, but they contain fewer vascular bundles. This makes it more difficult for soft-stemmed flowers to keep enough food and water flowing to the flower around the injured area. When soft stems are damaged, they have fewer food and water reserves to rely on than solid- stemmed flowers. Even slight splits could cause a flower to wilt within a day, and major damage must be repaired quickly or the flower will die.
A flower with stems that are hollow in the center will quickly run out of water. Once a stem is cut or split, the water seeps out of the stem and the plant can no longer move water above the split. If the gardener can repair the damage, the plant still has to fill the stem completely with water before the flower has the moisture it needs to survive. Hollow stemmed flowers often die of dehydration within 24 hours of being damaged.
If the flower has a milky sap it can also die quickly when damaged. The sap leaks out of the damaged vascular bundles, much like blood from a wound, taking nutrients and water with it. Unless the split is repaired quickly all the sap above the split can drain out of the stem. Once this happens the flower will not have enough water to survive and will wilt within hours. Even if the damage can be repaired in time the flower may die if the plant is unable to produce enough sap to replace, and quickly enough, the water and nutrients that were lost.