IN-VITRO PROPAGATION OF SALIX-TARRACONENSIS PAU-EX-FONT-QUER, AN ENDEMIC AND THREATENED PLANT

Salix tarraconensis Pau ex Font Quer, an endemic willow species from n ortheast Spain, was micropropagated with nodal segments. Shoot multipl ication was obtained with different cytokinins, either on Murashige an d Skoog medium or woody plant medium. Best results for shoot formation were obtained on Murashige and Skoog medium containing 4.9 mu M of 6- gamma-gamma-dimethylallylaminopurine. Shoots showed strong apical domi nance, and some cultures displayed apical necrosis. Benzyladenine gave the worst results; shoots displayed very slow growth, deformed leaves , and hyperhydricity. Good rooting of shoots was obtained with differe nt auxins or without plant growth regulators on woody plant medium. Th e best results (90-100%) were obtained within 20 d. On rooting media w ith indole-3-butyric acid or indoleacetic acid, shoot elongation was g ood (35-40 mm length). Apical necrosis was observed in elongating shoo ts on rooting medium, but this disturbance favored axillary bud sprout ing and formation of new shoots. Shoot length and quality of roots dec reased gradually as the concentration of naphthaleneacetic acid increa sed. Plant survival was 90% 4 weeks after removal from in vitro condit ions.