Changes in temperature, humidity, and other factors can alter this balance. The rose structure is a complex mix of vessels, leaves, and petals, which must be handled with care. Roses are sensitive to gases in the atmosphere. Some flowers are more sensitive than others. Water is an integral part of the life support system.
Leaves decay if continually kept underwater.
Generally, leaves should not remain continually underwater. They can get slimy and deteriorate from bacteria and other tiny organisms living in vase water. Stem ends can become blocked. They dry out and heal over after being cut and kept dry. Bacteria and other organisms clog stem ends as well.