Relative Changes in Polyamines during Citrus Flower Development

Several stages of citrus (Citrus sinensis L. Osbeck. cv. Valencia) flowers, from very small bud (stage 1) to anthesis (stage 6), were evaluated for free and conjugated polyamines. The concentration of putrescine and spermidine synthesis increased markedly during the early stages, and then declined as the flower buds grew. At anthesis, putrescine and spermidine concentrations had increased significantly. Spermine concentration was very low and showed no significant change during the first three floral developmental stages; however, by stages 5 and 6, spermine concentration showed a slight but significant increase. Eighty percent of the total polyamine content in fully developed flowers is localized in the reproductive organs and only 20% is localized in the petals and the calyx. This study relates changes in conjugated and free polyamines to citrus flower growth.