IN-VITRO ADVENTITIOUS SHOOT PRODUCTION IN PAULOWNIA

In vitro adventitious shoot formation was examined in petioles and lam inae of Paulownia elongata, P. fortunei, and P. 'Henan 1'. Fully expan ded, dark green, thick, older leaves were healthier and exhibited grea ter callus and shoot production than did young leaves. The ten clones used varied greatly in adventitious shoot formation. When single expla nts from the center of each lamina were cultured, P. 'Henan 1' and P. elongata exhibited similar shoot production, and both were more prolif ic than P. fortunei. Shoot production per leaf from P. elongata and P. 'Henan 1' could be greatly increased if petioles were cut in half and leaf laminae were cut into three strips, rather than leaving petiole and laminae explants intact. The growth regulator concentrations requi red for maximal shoot production differed among clones, but all requir ed 0.2 or 0.5 mg/l naphthaleneacetic acid and 5.0 or 7.0 mg/l benzylad enine. The average adventitious shoot production after 4 weeks in cult ure for the two most prolific genotypes was 63 shoots per leaf from P. 'Henan 1' and 48 shoots per leaf from P. elongata.