APOLAR MOVEMENT OF ZEATIN THROUGH COLEUS PETIOLES AND PISUM ROOTS AS ESTIMATED BY BIOASSAY AND RADIOACTIVE LABELLING

The movement and polarity of zeatin, a highly active, endogenous cytokinin, through petioles and roots were tested in the classical experimental arrangement using excised 5-mm sections. Zeatin in the receiver cylinders of agar was measured by soybean callus bioassay and by liquid scintillation counting of ¹⁴C that had been added in the donor cylinders as 8-¹⁴C] zeatin. Both methods agreed in showing movement, but there was no polarity in Coleus #5 petioles. The amounts moved were about one-tenth of the GA-3 movement through petioles of the third pair of leaves of the same clone. Movement of ¹⁴C-zeatin through Pisum roots was similarly statistically significant but non-polar; the amounts moved were similar to those previously observed for polar GA-3 movement through Zea roots.