Roses, carnations, chrysanthemums and other cut flowers from the florist often can be made to last much longer than they do.

Even after being cut, the flowers are still living things. They need water, food, cool temperatures and anti-aging compounds if they are to remain beautiful for long.

Lack of water often is the main reason for a short life. This can happen when they are standing in a vase full of water.The stems cannot absorb the moisture. Bacteria or bubbles of air can block the end of the stem and prevent movement of water upward.

Cutting about one-half inch off the end of the stem can remove the block. It is best if the cut is made with the stem in water.

Use a sharp knife or pruning shears when cutting flowers. Do not use household shears which may mash the stem and close some of the tubes which are needed to absorb water.

Once the cut is made under water, a small droplet of water hangs on the cut and you can then safely move the stem to the vase where it will be displayed. Make the move rather fast so the end of the stem won't dry off before it reaches its new water supply.

Occasionally a rose will wilt, or develop a weak stem just below the bud, causing the bloom to tip over. Remove that bloom from the arrangement, recut about one inch from the base of the stem (under water, of course), then submerge the entire bloom, stem and foilage under water for 20 minutes or so. Usually the flower revives nicely and can be replaced in the arrangement.

It is best to use water at about 100 degrees F. to revive the rose. Be sure to straighten the angle of the head or it will revive with bent neck. For long stem roses, a couple of inches of water in the bottom of the bathtub works well.

High temperature speeds up the life process of cut flowers, and this means rapid respiration and utilization of food and a shorter lasting quality. A common method of slowing down growth activities of a flower or plant is to keep it at a low temperature.

The rate of respiration is reduced as temperatures are lowered; it essentially is stopped at 32 degrees. Respiration rates increase rapidly as the temperature increases; at 50 degrees F. it is about twice as rapid as at 32 degrees and at 65 degrees twice again as rapid.

The vase life of your roses can be increased 30 to 50 per cent by using a floral preservative. The preservative provides food, eliminates bacteria which might clog the stems and helps prevent the early termination of the flower's life by preventing ethylene buildup, a natural by-product of plant respiration.

Research at Michigan State University has shown that either Sprite of 7-Up can do the trick. Mix one part water with each part soft drink and add a half teaspoon of chlorine bleach to each quart of the solution. The bleach cuts bacterial growth. The sugar in the soft drinks sustains life.