The Relative Sensitivity of Xanthium Leaves of Different Ages to Photoperiodic Induction.

Publisher Website
Google Scholar
Abstract
The photoperiodic sensitivity of Xanthium leaves of different ages was compared, and the rate of movement of the flowering stimulus out of the leaves was detd. Young terminal leaves 1/2 to 2/3 expanded were found to be the most sensitive to one photoinductive cycle, based on the rate of morph. development of the terminal inflorescence. Defoliation expts. showed that the stimulus begins to move out of the leaf within 4 hours after the end of a 15 hour dark period and is essentially complete within 24 hours. Expts. with lateral buds demonstrated that the increasing sensitivity of the young leaves is a function of the physiological age of the leaf rather than the quantity of leaf tissue. The greatest sensitivity of both types of leaves occurred at about 5 to 7 days old, even though the leaf area differed by a factor of more than 20.