In vitro adventitious shoot formation was examined in petioles and laminae ofPaulownia elongata, P. fortunei, andP. 'Henan 1'. Fully expanded, dark green, thick, older leaves were healthier and exhibited greater callus and shoot production than did young leaves. The ten clones used varied greatly in adventitious shoot formation. When single explants from the center of each lamina were cultured,P. 'Henan 1' andP. elongata exhibited similar shoot production, and both were more prolific thanP. fortunei. Shoot production per leaf fromP. elongata andP. '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 required for maximal shoot production differed among clones, but all required 0.2 or 0.5 mg/l naphthaleneacetic acid and 5.0 or 7.0 mg/l benzyladenine. The average adventitious shoot production after 4 weeks in culture for the two most prolific genotypes was 63 shoots per leaf fromP. 'Henan 1' and 48 shoots per leaf fromP. elongata.
Keywords: Adventitious Shoot; Growth Regulator; Regulator Concentration; Shoot Formation; Young Leaf.