Experimental Studies on Leafy Spurge (Euphorbia Esula L.). II. Starch Distribution and Vasculature in Relation to Apical Dominance

Abstract

Analyses of the distribution of starch and of the inception of vascular connections in decapitated and nondecapitated seedlings of leafy spurge show that starch grains are randomly distributed in the cortical cells of the hypocotyl, indicating continuous protoplasmic streaming in cells. However, the starch grains tend to aggregate in large masses in cells immediately after decapitation, which may have resulted from stoppage of protoplasmic streaming. Starch confined to certain regions of the cell can also be observed in older nondecapitated seedlings. Decapitation of seedlings also produces vascular connections between the hypocotylary axis and the shoots, and this process may be mediated by auxin. Two stages of shoot development can be distinguished. The initial growth is independent of vascular connections; the second stage of growth comes after the establishment of vascular connections and is produced by substances moving from the root through the hypocotylary axis. The importance of vascular connectio...