Certain Factors Influencing Expression of the Flowering Stimulus in Xanthium. Part I. Translocation and Inhibition of the Flowering Stimulus

Abstract

1. Inhibition of flowering in the receptor branch (or long-day branch) of a two-branched Xanthium plant is quantitatively related to the leaf area exposed to long day. An inverse relationship exists between the amount of mature long-day leaf tissue present and the magnitude of the flowering response of the receptor branch. 2. When a carbohydrate-deficient condition is created in the receptor branch by subjecting the branch to deep shade during the day, the inhibition of the mature long-day leaves is overcome and the receptor flowers. Presumably, carbohydrates move from the donor to the receptor branch, and this greater translocation of carbohydrates is apparently accompanied by movement of the stimulus to the receptor buds in spite of the presence of mature long-day leaves. Conversely, shading the donor branch, which presumably would result in a flow of carbohydrates from the receptor to the donor, results in less movement of the stimulus to the receptor branch, as is indicated by a lower flowering respon...