Mobility of Boron in Several Dicotyledonous Species

The translocation of dialyzable (soluble) boron from mature leaves of plants deprived of an external supply of this element was determined for several dicotyledonous species including bean, chard, cocklebur, cotton, cucumber, sunflower, tobacco, tomato, and turnip. Although a significantly lower dialyzable-boron concentration was found in all species showing deficiency symptoms except cocklebur and cucumber, this reduction was caused primarily by an increased fresh weight of the leaves and not by a change in absolute quantities of boron. The total dialyzable boron per leaf was significantly lower only in cotton and turnip. It was concluded that cotton and turnip were the only species showing a high degree of boron mobility under the experimental conditions used in this investigation.