Changes in Auxin and Cytokinin Activity in Roots of Red Oak, Quercus rubra, Seedlings during Lateral Root Formation

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Abstract
Quercus rubra L. seedlings were partially root pruned to induce formation of new laterals. Auxins in root extract fractions that cochromatographed with IAA, and cytokinins in root xylem sap fractions that cochromatographed with zeatin and zeatin riboside, were quantified by bioassays at 24 h intervals after pruning. Auxin activity sharply increased in the first 24 h and then decreased to prepruning levels. Cytokinin activity also increased during the first 24 h. New laterals appeared 4 to 5 days after pruning. The possible sources and role of these two hormones in root initiation are discussed.