Soluble proteins were extracted from the leaves of Petunia hybrida when flower differentiation was induced. The results showed that 4 special proteins, with molecular weight of 49.45 kD (a), 35.45 kD (b), 17.98 kD (c) and 11.74 kD(d), are related to blossoming of flowers after photoperiod induction. Without proteins a and d only floral buds were formed which were never blossomed. There were flowers when all the 4 special proteins appeared together. Proteins c and d disappeared after blossoming. Proteins in different tissues were different when the plant was induced to blossom. Thus, for example, protein c and d were absent from stem throughout the process.