Ribonuclease in senescing morning glory: purification and demonstration of de novo synthesis.

Isolated flower buds and flowers of Ipomoea tricolor went through the same stages of development as those attached to the plant. Ribonuclease activity increased sharply in both cases during the time of flower fading and aging. Affinity chromatography using guanosine diphosphate-Sepharose was employed for fast and efficient purification of ribonuclease. Flowers which were kept on D(2)O during the senescence phase incorporated deuterium into ribonuclease as shown by isopycnic density gradient centrifugation in CsCl, suggesting that ribonuclease was de novo synthesized during aging of the flower.