Nutrient remobilization during pollination-induced corolla senescence in petunia

Senescence represents the last stage of flower development. The premature senescence of flowers caused by environmental stresses during shipping, storage or retailing reduces the salability of ornamentals. Delaying flower senescence increases shelf life and post production quality, thereby increasing the value of ornamental plants. Corolla senescence is accompanied by increased activity of proteases and nucleases. These enzymes are believed to function in the large-scale degradation of proteins and nucleic acids, which allows the plant to salvage essential nutrients from dying petals before they are shed. Pollination accelerates corolla senescence in many species. Similar changes in nucleases and proteases are detected in petunia corollas during the age-related senescence of unpollinated flowers and the accelerated senescence of pollinated flowers, but it is unclear whether nutrient remobilization is similar. The objective of this research was to investigate the nutrient changes during pollination-induced corolla senescence. Plant macronutrients, micronutrients and additional elements were measured from nonsenescing corollas on the day of flower opening and compared to levels in corollas at the advanced stage of senescence. Nutrient levels were also measured at various times after pollination. Carbon, nitrogen, phosphorus, potassium, sulfur, iron, molybdenum, and zinc were reduced during pollination-induced senescence. In contrast, only carbon, nitrogen, phosphorus and copper were found to be reduced in corollas during the senescence of unpollinated flowers. These studies suggest that a different nutrient remobilization program is occurring during pollination-induced senescence and this may be due to the different sink tissues and how the nutrients are transported. Nutrients in pollinated flowers are likely being remobilized to the developing ovary, while in unpollinated flowers they are being transported to sink tissues outside of the flower. In order to understand the senescence program in flowers it is necessary to study the process in unpollinated and pollinated flowers.