Young leaves were washed with tap water followed by 10 min in a 0.5% active sodium hypochlorite solution containing 0.1% Tween-20. The leaves were rinsed three times with sterilized distilledwater and cut into 0.5 cm×0.5 cmsegments. Leaf segments were cultured on MS medium containing Fe-EDTA (Murashige and Skoog, 1962) supplemented with
vitamins (Ringe and Nitsch, 1968), 20 g l−1 sucrose and 8 g l−1 agar (Wako Pure Chemical Industries).