SUMMARY

Three proteins specific to the flowering state were found in Sinapis by immunological techniques. Two of these are specific to the stamen and one to the pistil. By the use of a histoimmunofluorescence technique their localization in the developing flower primordia and in the apex was examined during the transition to flowering. These proteins are not detected in the apex at evocation. They all appear at a relatively late stage of stamen or pistil maturation. The stamen proteins are localized in both the intine and exine layers of pollen grains in stamens 2-3 mm long; at anthesis they are essentially in the exine. The pistil protein is found in the stigma and in the transmitting tissue of the style. All these proteins contain sugar residues. A possible implication of these proteins in the process of male-female recognition is discussed